PANA Working Group D. Forsberg Internet-Draft Nokia Expires: April 20, 2005 Y. Ohba (Ed.) Toshiba B. Patil Nokia H. Tschofenig Siemens A. Yegin Samsung October 20, 2004 Protocol for Carrying Authentication for Network Access (PANA) draft-ietf-pana-pana-06 Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 20, 2005. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract Extensible Authentication Protocol (EAP) defines a number of authentication schemes. Network access authentication requires a Forsberg, et al. Expires April 20, 2005 [Page 1] Internet-Draft PANA October 2004 host to authenticate itself before being authorized for sending and receiving packets. The Protocol for Carrying Authentication for Network Access (PANA) is defined in this document. PANA is a link-layer agnostic carrier for EAP. PANA specifies the client-to-network access authentication within the scope of an overall secure network access framework. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1 Specification of Requirements . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . 8 4. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 10 4.1 Discovery and Handshake Phase . . . . . . . . . . . . . . 10 4.2 Authentication Phase . . . . . . . . . . . . . . . . . . . 13 4.3 Authorization Phase . . . . . . . . . . . . . . . . . . . 15 4.4 Re-authentication Phase . . . . . . . . . . . . . . . . . 15 4.5 Termination Phase . . . . . . . . . . . . . . . . . . . . 17 5. Protocol Design Details and Processing Rules . . . . . . . . 19 5.1 Payload Encoding . . . . . . . . . . . . . . . . . . . . . 19 5.2 Transport Layer . . . . . . . . . . . . . . . . . . . . . 20 5.2.1 Fragmentation . . . . . . . . . . . . . . . . . . . . 20 5.3 Sequence Number and Retransmission . . . . . . . . . . . . 20 5.4 Message Authentication Code . . . . . . . . . . . . . . . 21 5.5 Message Validity Check . . . . . . . . . . . . . . . . . . 21 5.6 PANA Security Association . . . . . . . . . . . . . . . . 23 5.7 Error Handling . . . . . . . . . . . . . . . . . . . . . . 25 5.8 Device ID Choice . . . . . . . . . . . . . . . . . . . . . 25 5.9 Updating PaC' Address . . . . . . . . . . . . . . . . . . 26 5.10 Session Lifetime . . . . . . . . . . . . . . . . . . . . 26 5.11 Network Selection . . . . . . . . . . . . . . . . . . . 27 5.12 Separate NAP and ISP Authentication . . . . . . . . . . 27 5.12.1 Negotiating Separate NAP and ISP Authentication . . 28 5.12.2 Execution of Separate NAP and ISP Authentication . . 28 5.12.3 AAA-Key Calculation . . . . . . . . . . . . . . . . 29 5.12.4 Re-authentication . . . . . . . . . . . . . . . . . 30 5.12.5 Example Sequence . . . . . . . . . . . . . . . . . . 30 6. Security and Mobility . . . . . . . . . . . . . . . . . . . 32 6.1 PANA Security Association Establishment . . . . . . . . . 32 6.2 Mobility . . . . . . . . . . . . . . . . . . . . . . . . . 32 7. PANA Headers and Formats . . . . . . . . . . . . . . . . . . 35 7.1 IP and UDP Headers . . . . . . . . . . . . . . . . . . . . 35 7.2 PANA Header . . . . . . . . . . . . . . . . . . . . . . . 35 7.3 AVP Header . . . . . . . . . . . . . . . . . . . . . . . . 37 8. PANA Messages, Message Specifications and AVPs . . . . . . . 40 8.1 PANA Messages . . . . . . . . . . . . . . . . . . . . . . 40 8.2 Message Specifications . . . . . . . . . . . . . . . . . . 40 Forsberg, et al. Expires April 20, 2005 [Page 2] Internet-Draft PANA October 2004 8.2.1 PANA-PAA-Discover (PDI) . . . . . . . . . . . . . . . 41 8.2.2 PANA-Start-Request (PSR) . . . . . . . . . . . . . . . 41 8.2.3 PANA-Start-Answer (PSA) . . . . . . . . . . . . . . . 41 8.2.4 PANA-Auth-Request (PAR) . . . . . . . . . . . . . . . 41 8.2.5 PANA-Auth-Answer (PAN) . . . . . . . . . . . . . . . . 42 8.2.6 PANA-Reauth-Request (PRAR) . . . . . . . . . . . . . . 42 8.2.7 PANA-Reauth-Answer (PRAA) . . . . . . . . . . . . . . 42 8.2.8 PANA-Bind-Request (PBR) . . . . . . . . . . . . . . . 42 8.2.9 PANA-Bind-Answer (PBA) . . . . . . . . . . . . . . . . 43 8.2.10 PANA-Ping-Request (PPR) . . . . . . . . . . . . . . 43 8.2.11 PANA-Ping-Answer (PPA) . . . . . . . . . . . . . . . 43 8.2.12 PANA-Termination-Request (PTR) . . . . . . . . . . . 43 8.2.13 PANA-Termination-Answer (PTA) . . . . . . . . . . . 44 8.2.14 PANA-Error-Request (PER) . . . . . . . . . . . . . . 44 8.2.15 PANA-Error-Answer (PEA) . . . . . . . . . . . . . . 44 8.2.16 PANA-FirstAuth-End-Request (PFER) . . . . . . . . . 44 8.2.17 PANA-FirstAuth-End-Answer (PFEA) . . . . . . . . . . 45 8.2.18 PANA-Update-Request (PUR) . . . . . . . . . . . . . 45 8.2.19 PANA-Update-Answer (PUA) . . . . . . . . . . . . . . 45 8.3 AVPs in PANA . . . . . . . . . . . . . . . . . . . . . . . 45 8.3.1 MAC AVP . . . . . . . . . . . . . . . . . . . . . . . 48 8.3.2 Device-Id AVP . . . . . . . . . . . . . . . . . . . . 49 8.3.3 Session-Id AVP . . . . . . . . . . . . . . . . . . . . 49 8.3.4 Cookie AVP . . . . . . . . . . . . . . . . . . . . . . 49 8.3.5 Protection-Capability AVP . . . . . . . . . . . . . . 49 8.3.6 Termination-Cause AVP . . . . . . . . . . . . . . . . 49 8.3.7 Result-Code AVP . . . . . . . . . . . . . . . . . . . 50 8.3.8 EAP-Payload AVP . . . . . . . . . . . . . . . . . . . 54 8.3.9 Session-Lifetime AVP . . . . . . . . . . . . . . . . . 54 8.3.10 Failed-AVP AVP . . . . . . . . . . . . . . . . . . . 54 8.3.11 NAP-Information AVP . . . . . . . . . . . . . . . . 54 8.3.12 ISP-Information AVP . . . . . . . . . . . . . . . . 54 8.3.13 Provider-Identifier AVP . . . . . . . . . . . . . . 54 8.3.14 Provider-Name AVP . . . . . . . . . . . . . . . . . 55 8.3.15 Key-Id AVP . . . . . . . . . . . . . . . . . . . . . 55 8.3.16 Post-PANA-Address-Configuration (PPAC) AVP . . . . . 55 8.3.17 Nonce AVP . . . . . . . . . . . . . . . . . . . . . 56 8.3.18 IP-Address AVP . . . . . . . . . . . . . . . . . . . 56 9. PANA Protocol Message Retransmissions . . . . . . . . . . . 57 9.1 Transmission and Retransmission Parameters . . . . . . . . 58 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 60 10.1 PANA UDP Port Number . . . . . . . . . . . . . . . . . . 60 10.2 PANA Multicast Address . . . . . . . . . . . . . . . . . 60 10.3 PANA Header . . . . . . . . . . . . . . . . . . . . . . 60 10.3.1 Message Type . . . . . . . . . . . . . . . . . . . . 60 10.3.2 Flags . . . . . . . . . . . . . . . . . . . . . . . 61 10.4 AVP Header . . . . . . . . . . . . . . . . . . . . . . . 61 10.4.1 AVP Code . . . . . . . . . . . . . . . . . . . . . . 61 Forsberg, et al. Expires April 20, 2005 [Page 3] Internet-Draft PANA October 2004 10.4.2 Flags . . . . . . . . . . . . . . . . . . . . . . . 62 10.5 AVP Values . . . . . . . . . . . . . . . . . . . . . . . 62 10.5.1 Algorithm Values of MAC AVP . . . . . . . . . . . . 62 10.5.2 Protection-Capability AVP Values . . . . . . . . . . 62 10.5.3 Termination-Cause AVP Values . . . . . . . . . . . . 62 10.5.4 Result-Code AVP Values . . . . . . . . . . . . . . . 62 10.5.5 Post-PANA-Address-Configuration AVP Values . . . . . 63 11. Security Considerations . . . . . . . . . . . . . . . . . . 64 11.1 General Security Measures . . . . . . . . . . . . . . . 64 11.2 Discovery . . . . . . . . . . . . . . . . . . . . . . . 65 11.3 EAP Methods . . . . . . . . . . . . . . . . . . . . . . 66 11.4 Separate NAP and ISP Authentication . . . . . . . . . . 66 11.5 Cryptographic Keys . . . . . . . . . . . . . . . . . . . 66 11.6 Per-packet Ciphering . . . . . . . . . . . . . . . . . . 67 11.7 PAA-to-EP Communication . . . . . . . . . . . . . . . . 67 11.8 Livenes Test . . . . . . . . . . . . . . . . . . . . . . 68 11.9 Mobility Optimization . . . . . . . . . . . . . . . . . 68 11.10 Updating PaC's IP Address . . . . . . . . . . . . . . . 68 11.11 Early Termination of a Session . . . . . . . . . . . . . 69 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 70 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 71 13.1 Normative References . . . . . . . . . . . . . . . . . . . 71 13.2 Informative References . . . . . . . . . . . . . . . . . . 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 73 Intellectual Property and Copyright Statements . . . . . . . 75 Forsberg, et al. Expires April 20, 2005 [Page 4] Internet-Draft PANA October 2004 1. Introduction Network access authentication has traditionally been a layer 2 function. This document specifies a protocol that enables EAP to be transported above the IP layer. As a result, network access authentication can be made a function of the network layer thereby achieving link-layer independence for the process of authenticating a client seeking access to a network. At the present time, there are no standardized solutions for authenticating a host for network access at the network layer. The problem statement for which the PANA protocol is a solution can be found in Appendix A of [I-D.ietf-pana-requirements]. PANA relies on EAP for the actual authentication of a client. It does not define any new authentication protocols or schemes. It enables EAP messages to be carried between the client and the network. The actual choice of a specific EAP method to be run over PANA is dependent on the underlying access network technology. The key factor in the choice of the EAP method is the determination of whether the lower layer (link/physical) provides security for the PANA messages. A secure network access authentication framework goes beyond just authenticating the client to the network. Other aspects such as address configuration, data traffic security, access control filters and separation of the enforcement point from the protocol end-point are documented in [I-D.ietf-pana-framework] and [I-D.ietf-pana-snmp]. This document specifies the client-network interaction and the messages defined for this purpose. 1.1 Specification of Requirements In this document, several words are used to signify the requirements of the specification. These words are often capitalized. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Forsberg, et al. Expires April 20, 2005 [Page 5] Internet-Draft PANA October 2004 2. Terminology PANA Client (PaC): The client side of the protocol that resides in the host device. It is responsible for providing the credentials in order to prove its identity for network access authorization. PANA Authentication Agent (PAA): The protocol entity in the access network whose responsibility is to verify the credentials provided by a PANA client (PaC) and authorize network access to the device associated with the client and identified by a Device Identifier (DI). Note the authentication and authorization procedure can, according to the EAP model, be also offloaded to the backend AAA infrastructure. PANA Session: A PANA session begins with the handshake between the PANA Client (PaC) and the PANA Authentication Agent (PAA), and terminates as a result of an authentication failure, a timeout, or an explicit termination message. A fixed session identifier is maintained throughout a session. A session cannot be shared across multiple network interfaces. Session Identifier: This identifier is used to uniquely identify a PANA session on the PAA and PaC. It includes an identifier of the PAA, therefore it cannot be shared across multiple PAAs. It is included in PANA messages to bind the message to a specific PANA session. This bidirectional identifier is allocated by the PAA following the handshake and freed when the session terminates. PANA Security Association (PANA SA): A PANA security association is a relationship between the PaC and PAA, formed by the sharing of cryptographic keying material and associated context. Security associations are duplex. That is, one security association is needed to protect the bidirectional traffic between the PaC and the PAA. Device Identifier (DI): Forsberg, et al. Expires April 20, 2005 [Page 6] Internet-Draft PANA October 2004 The identifier used by the network as a handle to control and police the network access of a client. Depending on the access technology, this identifier may contain an address that is carried in protocol headers (e.g., IP or link-layer address), or a locally significant identifier that is made available by the local protocol stack (e.g., circuit id, PPP interface id) of a connected device. Enforcement Point (EP): A node on the access network where per-packet enforcement policies (i.e., filters) are applied on the inbound and outbound traffic of client devices. Information such as the DI and (optionally) cryptographic keys are provided by the PAA per client for generating filters on the EP. Network Access Provider (NAP): A service provider that provides physical and link-layer connectivity to an access network it manages. AAA-Key: A key derived by the EAP peer and EAP server and transported to the authenticator [I-D.ietf-eap-keying]. Forsberg, et al. Expires April 20, 2005 [Page 7] Internet-Draft PANA October 2004 3. Protocol Overview The PANA protocol is run between a client (PaC) and a server (PAA) in order to perform authentication and authorization for the network access service. The protocol messaging consists of a series of request and responses, some of which may be initiated by either ends. Each message can carry zero or more AVPs as payload. The main payload of PANA is EAP which performs authentication. PANA helps PaC and PAA establish an EAP session. PANA is a UDP-based protocol. It has its own retransmission mechanism to reliably deliver messages. PANA messages are sent between a PaC and PAA as part of a PANA session. A PANA session consists of distinct phases: o Discovery and handshake phase: This is the phase that initiates a new PANA session. The PaC discovers the PAA(s) by either explicitly soliciting advertisements for them or receiving unsolicited advertisements. The PaC's answer sent in response to an advertisement starts a new session. o Authentication phase: Immediately following the handshake phase is the EAP execution between the PAA and PaC. The EAP payloads (which carry an EAP method inside) is what is used for authentication. Authentication phase may involve execution of two EAP sessions back-to-back, one for the NAP and one for the ISP. o Authorization phase: Following a successful PANA authentication phase, the PaC gains access to the network and can send and receive IP data traffic through EP. During this phase, the PaC and PAA may optionally ping each other to test liveness of the PANA session on each end. o Re-authentication phase: Following an authorization phase, the PAA must initiate re-authentication before the PANA session lifetime expires. Again EAP is carried by PANA to perform authentication. This phase may be optionally triggered by both the PaC and the PAA without any respect to the session lifetime. The session moves to this phase from authorized phase, and returns back there upon successful re-authentication. o Termination phase: The PaC or PAA may choose to discontinue the access service at any time. An explicit disconnect message can be sent by either end. If either the PaC or the PAA disconnects without engaging in termination messaging, it is expected that Forsberg, et al. Expires April 20, 2005 [Page 8] Internet-Draft PANA October 2004 either the expiration of a finite session lifetime or failed liveness tests would do the job. PaC PAA Message[AVPs] ----------------------------------------------------- // Discovery and handshake phase -----> PANA-PAA-Discover <----- PANA-Start-Request -----> PANA-Start-Answer // Authentication phase <----- PANA-Auth-Request /* EAP Request */ -----> PANA-Auth-Answer -----> PANA-Auth-Request /* EAP Response */ <----- PANA-Auth-Answer <----- PANA-Bind-Request /* EAP Success */ -----> PANA-Bind-Answer // Authorization phase (IP data traffic allowed) <----- PANA-Ping-Request -----> PANA-Ping-Answer // Termination phase -----> PANA-Termination-Request <----- PANA-Termination-Answer Figure 1: Illustration of PANA Messages in a Session Cryptographic protection of messages between the PaC and PAA is possible as soon as EAP in conjunction with the EAP method exports a shared key. That shared key is used to create a PANA SA. The PANA SA helps generating per-message authentication codes that provide integrity protection and authentication. PANA also allows creation of a new PANA session with a new PAA out of an existing session with another PAA. This optimization allows PaC achieve quicker authorization without having to run EAP upon movement (changing PAAs). Throughout the lifetime of a session, various problems found with the incoming messages can generate a PANA error message sent in response. Forsberg, et al. Expires April 20, 2005 [Page 9] Internet-Draft PANA October 2004 4. Protocol Details The following sections explain in detail the various phases of a PANA session. 4.1 Discovery and Handshake Phase When a PaC attaches to a network, and knows that it has to discover a PAA, it SHOULD send a PANA-PAA-Discover message to a well-known link local multicast address (TBD) and UDP port (TBD). The PANA PAA discovery assumes that the PaC and the PAA are one hop away from each other. If the PaC knows the IP address of the PAA (based on pre-configuration), it MAY unicast the PANA-PAA-Discover message to that address. When the PAA receives a PANA-PAA-Discover message from a PaC, the PAA SHOULD unicast a PANA-Start-Request message to the PaC. The PaC MAY also choose to start sending packets before getting authenticated. In that case, the network may detect this and the PAA MAY send an unsolicited PANA-Start-Request message to the PaC in addition to filtering the unauthorized traffic. The EP is the node that can detect such activity. The PAA-to-EP protocol MAY be used for this purpose. When a PaC receives a PANA-Start-Request message from a PAA, it responds with a PANA-Start-Answer message if it wishes to enter an authentication phase. The answer message copies the sequence number. There can be multiple PAAs on the link and a PaC may receive multiple PANA-Start-Request messages from those PAAs. The authentication and authorization result does not depend on which PAA is chosen by the PaC. By default the PaC MAY choose the PAA that sent the first response. A PANA-Start-Request message MAY carry a Cookie AVP that contains a cookie. The sequence number is set to a randomly picked initial sequence number. The cookie is used for preventing the PAA from resource consumption DoS attacks by blind attackers. The cookie is computed in such a way that it does not require any per-session state maintenance on the PAA in order to verify the cookie returned in a PANA-Start-Answer message. The exact algorithms and syntax used for generating cookies does not affect interoperability and hence is not specified here. An example algorithm is described below. Cookie = | HMAC_SHA1( , ) Forsberg, et al. Expires April 20, 2005 [Page 10] Internet-Draft PANA October 2004 where is a randomly generated secret known only to the PAA, is an index used for choosing the secret for generating the cookie and '|' indicates concatenation. The secret-version should be changed frequently enough to prevent replay attacks. The secret key is valid for a certain time frame. When the PaC sends a PANA-Start-Answer message in response to a PANA-Start-Request containing a Cookie AVP, the answer MUST contain a Cookie AVP with the cookie value copied from the request. When the PAA receives the PANA-Start-Answer message from the PaC, it verifies the cookie. The cookie is considered as valid if the received cookie has the expected value. If the computed cookie is valid, the protocol enters an authentication phase. Otherwise, it MUST silently discard the received message. Initial EAP Request MAY be optionally carried by the PANA-Start-Request (as opposed to by a later PANA-Auth-Request) message in order to reduce the number of round-trips. This optimization SHOULD NOT be used if the PAA discovery is desired to be stateless. A Protection-Capability AVP and a Post-PANA-Address-Configuration (PPAC) AVP MAY be included in the PANA-Start-Request in order to indicate required and available capabilities for the network access. These AVPs MAY be used by the PaC for assessing the capability match even before the authentication takes place. But these AVPs are provided during the insecure discovery and handshake phase, there are certain security risks involved in using the provided information. See Section 11 for further discussion on this. If the initial EAP Request message is carried in the PANA-Start-Request message, an EAP Response message MUST be carried in the PANA-Start-Answer message returned to the PAA. In any case, PANA MUST NOT generate an EAP message on behalf of EAP peer or EAP (pass-through) authenticator. The PANA-Start-Request/Answer exchange is needed before entering an authentication phase even when the PaC is pre-configured with PAAs IP address and the PANA-PAA-Discover message is unicast. A Nonce AVP MUST be included in PANA-Start-Request and PANA-Start-Answer messages. The nonces are used to establish a PANA SA. A PANA-Start-Request message that carries a Cookie AVP is never retransmitted. A PANA-Start-Request message that does not carry a Forsberg, et al. Expires April 20, 2005 [Page 11] Internet-Draft PANA October 2004 Cookie AVP is retransmitted based on timer. A PANA-Start-Answer message that carries a Cookie AVP is retransmitted based on timer. A PANA-Start-Answer message that does not carry a Cookie AVP is never retransmitted based on timer. It is possible that both the PAA and the PaC initiate the discovery and handshake procedure at the same time, i.e., the PAA sends a PANA-Start-Request message while the PaC sends a PANA-PAA-Discover message. To resolve the race condition, the PAA SHOULD silently discard the PANA-PAA-Discover message received from the PaC after it has sent a PANA-Start-Request message with creating a state (i.e., no Cookie AVP is included in the message) for the PaC. In this case PAA will retransmit PANA-Start-Request based on a timer, if PaC doesn't respond in time (message was lost for example). If the PAA had sent a PANA-Start-Request message without creating a state for the PaC (i.e., a Cookie AVP was included in the message), then it SHOULD answer to the PANA-PAA-Discover message. Figure 2 shows an example sequence for the discovery and handshake phase when a PANA-PAA-Discover message is sent by the PaC. Figure 3 shows an example sequence for the discovery and handshake phase that is triggered by data traffic. PaC PAA Message(seqno)[AVPs] ------------------------------------------------------ -----> PANA-PAA-Discover(0) <----- PANA-Start-Request(x)[Nonce, Cookie] -----> PANA-Start-Answer(x)[Nonce, Cookie] (continued to authentication phase) Figure 2: Example Sequence for Discovery and Handshake Phase when PANA-PAA-Discover is sent by PaC PaC EP PAA Message(seqno)[AVPs] ------------------------------------------------------ ---->o (Data packet arrival or L2 trigger) ------> PAA-to-EP protocol, or another mechanism <------------ PANA-Start-Request(x)[Nonce, Cookie] ------------> PANA-Start-Answer(x)[Nonce, Cookie] (continued to authentication phase) Figure 3: Example Sequence for Discovery and Handshake when discovery is triggered by data traffic Forsberg, et al. Expires April 20, 2005 [Page 12] Internet-Draft PANA October 2004 4.2 Authentication Phase The main task in authentication phase is to carry EAP messages between the PaC and the PAA. EAP Request and Response messages are carried in PANA-Auth-Request messages. PANA-Auth-Answer messages are simply used to acknowledge receipt of the requests. As an optimization, a PANA-Auth-Answer message MAY include the EAP Response. Another optimization allows optionally carrying the first EAP Request/Response in PANA-Start-Request/Answer message as described in Section 4.1 When an EAP Success/Failure message is sent from a PAA, the message is carried in a PANA-Bind-Request (PBR) message. The PANA-Bind-Request messages MUST be acknowledged with a PANA-Bind-Answer (PBA) message. Figure 4 shows an example sequence in an authentication phase. PaC PAA Message(seqno)[AVPs] -------------------------------------------------------------------- (continued from discovery and handshake phase) <----- PANA-Auth-Request(x+1) [Session-Id, EAP{Request}] -----> PANA-Auth-Answer(x+1) // No piggybacking EAP-Response [Session-Id] -----> PANA-Auth-Request(y) [Session-Id, EAP{Response}] <----- PANA-Auth-Answer(y) [Session-Id] <----- PANA-Auth-Request(x+2) [Session-Id, EAP{Request}] -----> PANA-Auth-Answer(x+2) // Piggybacking EAP-Response [Session-Id, EAP{Response}] <----- PANA-Bind-Request(x+3) [Session-Id, EAP{Success}, Device-Id, IP-Address, Lifetime, Protection-Cap., PPAC, MAC] -----> PANA-Bind-Answer(x+3) [Session-Id, Device-Id, PPAC, MAC] Figure 4: Example Sequence in Authentication Phase When an EAP method that is capable of deriving keys is used during the authentication phase and the keys are successfully derived, the PANA-FirstAuth-End-Request and PANA-FirstAuth-End-Answer and/or PANA-Bind-Request and PANA-Bind-Answer messages, and all subsequent PANA messages MUST contain a MAC AVP. The PANA-Bind-Request and the PANA-Bind-Answer message exchange is also used for binding device identifiers of the PaC and EP(s), and Forsberg, et al. Expires April 20, 2005 [Page 13] Internet-Draft PANA October 2004 the IP address of the PAA to the PANA SA. To achieve this, the PANA-Bind-Request SHOULD contain the device identifier(s) of the EP(s) in Device-Id AVP(s) when they are either MAC or IP address(es), and the IP address of the PAA in an IP-Address AVP. PANA-Bind-Answer SHOULD contain PaC's device identifier in a Device-Id AVP when it is already presented with that of EP(s). The PaC MUST use the same type of device identifier as contained in the PANA-Bind-Request message. This exchange when protected by a MAC AVP prevents man-in-the-middle attacks. The PANA-Bind-Request message MAY also contain a Protection-Capability AVP to indicate if link-layer or network-layer ciphering should be initiated after PANA. No link layer or network layer specific information is included in the Protection-Capability AVP. When the information is preconfigured on the PaC and the PAA this AVP can be omitted. It is assumed that at least PAA is aware of the security capabilities of the access network. The PANA protocol does not specify how the PANA SA and the Protection-Capability AVP will be used to provide per-packet protection for data traffic. Additionally, PANA-Bind-Request MUST include a Post-PANA-Address-Configuration AVP, which helps PAA to inform PaC about whether a new IP address MUST be configured and the available methods to do so. PaC MUST include a PPAC AVP in order to indicate its choice of method when there is a match between the methods offered by the PAA and the methods available on the PaC. When there is no match, a PPAC AVP MUST NOT be included and the Result-Code AVP MUST be set to PANA_PPAC_CAPABILITY_UNSUPPORTED in the PANA-Bind-Answer message. PANA-Bind-Request and PANA-Bind-Answer messages MUST be retransmitted based on the retransmission rule described in Section 5.3. EAP authentication can fail at a pass-through authenticator without sending an EAP-Failure message [I-D.ietf-eap-statemachine]. When this occurs, the PAA SHOULD send a PANA-Error-Request message to the PaC with using PANA_UNABLE_TO_COMPLY result code. The PaC SHOULD not change its state unless the error message is secured by PANA or lower layer. In any case, a more appropriate way is to rely on a timeout on the PaC. There is a case where EAP authentication succeeds with producing an EAP-Success message but network access authorization fails due to, e.g., authorization rejected by a AAA proxy or authorization locally rejected by the PAA. When this occurs, the PAA MUST send PANA-Bind-Request with a result code PANA_AUTHORIZATION_REJECTED. If a AAA-Key is established between PaC and PAA by the time when the EAP-Success is generated by the EAP server (this is the case when the EAP method provides protected success indication), this PANA-Bind message exchange MUST be protected with a MAC AVP and with carrying a Forsberg, et al. Expires April 20, 2005 [Page 14] Internet-Draft PANA October 2004 Key-Id AVP. The AAA-Key and the PANA session MUST be deleted after the PANA-Bind message exchange. 4.3 Authorization Phase Once an authentication phase or a re-authentication phase successfully completes, the PaC gains access to the network and can send and receive IP data traffic through EP and the PANA session enters an authorization phase. In this phase, PANA-Ping-Request and PANA-Ping-Answer messages are used for testing the liveness of the PANA session on the PANA peer. Both the PaC and the PAA are allowed to send a PANA-Ping-Request message to the communicating peer whenever they need to make sure the availability of the session on the peer and expect the peer to return a PANA-Ping-Answer message. Both PANA-Ping-Request and PANA-Ping-Answer messages MUST be protected with a MAC AVP when a PANA SA is available. Implementations MUST limit the rate of performing this test. The PaC and the PAA can handle rate limitation on their own, they do not have to perform any coordination with each other. There is no negotiation of timers for this purpose. Figure 5 and Figure 6 show liveness tests as they are initiated by the PaC and the PAA respectively. PaC PAA Message(seqno)[AVPs] ------------------------------------------------------ -----> PANA-Ping-Request(q)[Session-Id, MAC] <----- PANA-Ping-Answer(q)[Session-Id, MAC] Figure 5: Example Sequence for PaC-initiated liveness test PaC PAA Message(seqno)[AVPs] ------------------------------------------------------ <----- PANA-Ping-Request(p)[Session-Id, MAC] -----> PANA-Ping-Answer(p)[Session-Id, MAC] Figure 6: Example Sequence for PAA-initiated liveness test 4.4 Re-authentication Phase A PANA session in an authorization phase can enter a re-authentication phase to extend the current session lifetime by re-executing EAP. Once the re-authentication phase successfully completes, the session re-enters the authorization phase. Otherwise, Forsberg, et al. Expires April 20, 2005 [Page 15] Internet-Draft PANA October 2004 the session is deleted. When a PaC wants to initiate re-authentication, it sends a PANA-Reauth-Request message to the PAA. This message MUST contain a Session-Id AVP which is used for identifying the PANA session on the PAA. If the PAA already has an established PANA session for the PaC with the matching identifier, it MUST first respond with a PANA-Reauth-Answer, followed by a PANA-Auth-Request that starts a new EAP authentication. If PAA cannot identify the session, it MUST respond with a PANA-Error-Request with the error code PANA_UNKNOWN_SESSION_ID. PANA-Reauth-Request/Answer messages MUST contain a MAC AVP when PANA SA is available. PaC may receive a PANA-Auth-Request before receiving the answer to its outstanding PANA-Reauth-Request. This condition can arise due to packet re-ordering or a race condition between the PaC and PAA when they both attempt to engage in re-authentication. PaC MUST keep discarding the received PANA-Auth-Requests until it receives the answer to its request. When the PAA initiates re-authentication, it sends a PANA-Auth-Request message containing the session identifier for the PaC to enter an authentication phase. PAA SHOULD initiate EAP authentication before the current session lifetime expires. Re-authentication of an on-going PANA session MUST maintain the existing sequence numbers. For any re-authentication, if there is an established PANA SA, PANA-Auth-Request and PANA-Auth-Answer messages MUST be protected by adding a MAC AVP to each message. Any subsequent EAP-based authentication MUST be performed with the same ISP and NAP that was selected during the initial authentication. An example sequence for a re-authentication initiated by a PaC is shown in Figure 7. Forsberg, et al. Expires April 20, 2005 [Page 16] Internet-Draft PANA October 2004 PaC PAA Message(seqno)[AVPs] ------------------------------------------------------ -----> PANA-Reauth-Request(q) [Session-Id, MAC] <----- PANA-Reauth-Answer(q) [Session-Id, MAC] <----- PANA-Auth-Request(p) [Session-Id, EAP{Request}, MAC] -----> PANA-Auth-Answer(p) // No piggybacking EAP-Response [Session-Id, MAC] -----> PANA-Auth-Request(q+1) [Session-Id, EAP{Response}, MAC] <----- PANA-Auth-Answer(q+1) // No piggybacking EAP-Response [Session-Id, MAC] <----- PANA-Auth-Request(p+1) [Session-Id, EAP{Request}, MAC] -----> PANA-Auth-Answer(p+1) // Piggybacking EAP-Response [Session-Id, EAP{Response}, MAC] <----- PANA-Bind-Request(p+2) [Session-Id, EAP{Success}, Device-Id, IP-Address, Key-Id, Lifetime, Protection-Cap., PPAC, MAC] -----> PANA-Bind-Answer(p+2) [Session-Id, Device-Id, Key-Id, PPAC, MAC] Figure 7: Example Sequence for re-authentication initiated by PaC 4.5 Termination Phase A procedure for explicitly terminating a PANA session can be initiated either from the PaC (i.e., disconnect indication) or from the PAA (i.e., session revocation). The PANA-Termination-Request and the PANA-Termination-Answer message exchanges are used for disconnect indication and session revocation procedures. The reason for termination is indicated in the Termination-Cause AVP. When there is an established PANA SA established between the PaC and the PAA, all messages exchanged during the termination phase MUST be protected with a MAC AVP. When the sender of the PANA-Termination-Request receives a valid acknowledgment, all states maintained for the PANA session MUST be deleted immediately. Forsberg, et al. Expires April 20, 2005 [Page 17] Internet-Draft PANA October 2004 PaC PAA Message(seqno)[AVPs] ------------------------------------------------------ -----> PANA-Termination-Request(q)[Session-Id, MAC] <----- PANA-Termination-Answer(q)[Session-Id, MAC] Figure 8: Example Sequence for Session Termination Forsberg, et al. Expires April 20, 2005 [Page 18] Internet-Draft PANA October 2004 5. Protocol Design Details and Processing Rules 5.1 Payload Encoding The payload of any PANA message consists of zero or more AVPs (Attribute Value Pairs). A brief description of the AVPs defined in this document is listed below: o Cookie AVP: contains a random value that is used for making handshake robust against blind resource consumption DoS attacks. o Protection-Capability AVP: contains information which protection should be initiated after the PANA exchange (e.g., link-layer or network layer protection). o Device-Id AVP: contains a device identifier of the PaC or an EP. A device identifier is represented as a pair of device identifier type and device identifier value. Either a layer-2 address or an IP address is used for the device identifier value when this AVP is present. o EAP AVP: contains an EAP PDU. o MAC AVP: contains a Message Authentication Code that protects a PANA message PDU. o Termination-Cause AVP: contains the reason of session termination. o Result-Code AVP: contains information about the protocol execution results. o Session-Id AVP: contains the session identifier value. o Session-Lifetime AVP: contains the duration of authorized access. o Failed-AVP: contains the offending AVP that caused a failure. o NAP-Information AVP, ISP-Information AVP: contains the information on a NAP and an ISP, respectively. o Key-Id AVP: contains a AAA-Key identifier. o PPAC AVP: Post-PANA-Address-Configuration AVP. Conveys the list of IP address configuration methods available when sent by the PAA, and the chosen method when sent by the PaC. o Nonce AVP: contains a randomly chosen value. Forsberg, et al. Expires April 20, 2005 [Page 19] Internet-Draft PANA October 2004 o IP-Address AVP: contains an IP Address of a PaC. 5.2 Transport Layer PANA uses UDP as its transport layer protocol. The UDP port number is TBD. All messages except for PANA-PAA-Discover are always unicast. PANA-PAA-Discover MAY be unicast when the PaC knows the IP address of the PAA. 5.2.1 Fragmentation PANA does not provide fragmentation of PANA messages. Instead, it relies on fragmentation provided by EAP methods and IP layer when needed. 5.3 Sequence Number and Retransmission PANA uses sequence numbers to provide ordered and reliable delivery of messages. PaC and PAA maintain two sequence numbers: the next one to be used for a request it initiates and the next one it expects to see in a request from the other end. These sequence numbers are 32-bit unsigned numbers. They are monotonically incremented by 1 as new requests are generated and received, and wrapped to zero on the next message after 2^32-1. Answers always contain the same sequence number as the corresponding request. Retransmissions maintain the same sequence number. The initial sequence numbers (ISN) are randomly picked by PaC and PAA as they send their very first request messages. PANA-PAA-Discover message carries sequence number 0. When a request message is received, it is considered valid in terms of sequence numbers if and only if its sequence number matches the expected value. This check does not apply to PANA-PAA-Discover, and the very first request messages. When an answer message is received, it is considered valid in terms of sequence numbers if and only if its sequence number matches that of the currently outstanding request. A peer can only have one outstanding request at a time. PANA messages are retransmitted based on timer at until a response is received (in which case the retransmission timer is stopped) or the number of retransmission reaches the maximum value (in which case the PANA session MUST be deleted immediately). The retransmission timer SHOULD be calculated as described in [RFC2988] to provide congestion Forsberg, et al. Expires April 20, 2005 [Page 20] Internet-Draft PANA October 2004 control. See Section 9 for default timer and maximum retransmission count parameters. PaC and PAA MUST respond to duplicate requests. Last transmitted PANA answer MAY be cached in case it is not received by the peer and that generates a retransmission of the last request. When available, a cached answer can be used instead of fully processing the retransmitted request and forming a new answer from scratch. PANA MUST NOT generate EAP message duplication. EAP payload of a retransmitted PANA message MUST NOT be passed to the EAP layer. 5.4 Message Authentication Code A PANA message can contain a MAC (Message Authentication Code) AVP for cryptographically protecting the message. When a MAC AVP is included in a PANA message, the value field of the MAC AVP is calculated by using the PANA_MAC_KEY in the following way: MAC AVP value = PANA_MAC_PRF(PANA_MAC_KEY, PANA_PDU) where PANA_PDU is the PANA message including the PANA header, with the MAC AVP value field first initialized to 0. PANA_MAC_PRF represents the pseudo random function corresponding to the MAC algorithm specified in the MAC AVP. In this version of draft, PANA_MAC_PRF is HMAC-SHA1. The PaC and PAA MUST use the same algorithm to calculate a MAC AVP they originate and receive. The algorithm is determined by the PAA when a PANA-Bind-Request with a MAC AVP is sent. When the PaC does not support the MAC algorithm specified in the PANA-Bind-Request message, it MUST silently discard the message. The PAA MUST NOT change the MAC algorithm throughout the continuation of the PANA session. 5.5 Message Validity Check When a PANA message is received, the message is considered to be invalid at least when one of the following conditions are not met: o The IP Hop Limit (or TTL) field has a value of 255, i.e., the packet could not possibly have been forwarded by a router. o Each field in the message header contains a valid value including sequence number, message length, message type, version number, flags, etc. o When a device identifier of the PaC is bound to the PANA session, it matches the device identifier carried in MAC or or IP header, Forsberg, et al. Expires April 20, 2005 [Page 21] Internet-Draft PANA October 2004 or other locally-significant identifier provided by the lower-layers (e.g., circuit ID) unless the message is a PANA-Update-Request with an IP-Address AVP. o The message type is one of the expected types in the current state. Specifically the following messages are unexpected and invalid: * In discovery and handshake phase: + PANA-Termination-Request and PANA-Ping-Request. + PANA-Bind-Request. + PANA-Update-Request. * In authentication phase: + PANA-PAA-Discover. + PANA-Update-Request. + PANA-Start-Request after a PaC receives the first valid PANA-Auth-Request. + PANA-Termination-Request before the PaC receives the first successful PANA-Bind-Request. * After successful PANA authentication: + PANA-Start-Request as well as a non-duplicate PANA-Bind-Request. + PANA-PAA-Discover. * In termination phase: + PANA-PAA-Discover. + All requests but PANA-Termination-Request. o The message payload contains a valid set of AVPs allowed for the message type and there is no missing AVP that needs to be included in the payload. o Each AVP is decoded correctly. Forsberg, et al. Expires April 20, 2005 [Page 22] Internet-Draft PANA October 2004 o When a MAC AVP is included, the AVP value matches the MAC value computed against the received message. o When a Device-Id AVP is included, the AVP is valid if the device identifier type contained in the AVP is supported (check performed by both PaC and PAA) and is the requested one (check performed by PAA only) and the device identifier value contained in the AVP matches the value extracted from the lower-layer encapsulation header corresponding to the device identifier type contained in the AVP (check performed by PAA only). Note that a Device-Id AVP carries the PaC's device identifier in messages from PaC to PAA and EP(s)' device identifier in messages from PAA to PaC. o When an IP-Address AVP is received in a message, the AVP is valid if the IP address matches the source address in the IP header. Invalid messages MUST be discarded in order to provide robustness against DoS attacks. In addition, an error notification message MAY be returned to the sender. See Section 5.7 for details. 5.6 PANA Security Association A PANA SA is created as an attribute of a PANA session when EAP authentication succeeds with a creation of a AAA-Key. A PANA SA is not created when the PANA authentication fails or no AAA-Key is produced by any EAP authentication method. In the case where two EAP authentications are performed in sequence in a single PANA authentication phase, it is possible that two AAA-Keys are derived. If this happens, the PANA SA MUST be generated from both AAA-Keys. When a new AAA-Key is derived as a result of EAP-based re-authentication, any key derived from the old AAA-Key MUST be updated to a new one that is derived from the new AAA-Key. In order to distinguish the new AAA-Key from old ones, one Key-Id AVP MUST be carried in PANA-Bind-Request and PANA-Bind-Answer messages or PANA-FirstAuth-End-Request and PANA-FirstAuth-End-Answer messages at the end of the EAP authentication which resulted in deriving a new AAA-Key. The Key-Id AVP is of type Unsigned32 and MUST contain a value that uniquely identifies the AAA-Key within the PANA session. The PANA-Bind-Answer message (or the PANA-FirstAuth-End-Answer message) sent in response to a PANA-Bind-Request message (or a PANA-FirstAuth-End-Request message) with a Key-Id AVP MUST contain a Key-Id AVP with the same AAA-Key identifier carried in the request. PANA-Bind-Request, PANA-Bind-Answer, PANA-FirstAuth-End-Request and PANA-FirstAuth-End-Answer messages with a Key-Id AVP MUST also carry a MAC AVP whose value is computed by using the new PANA-MAC-KEY derived from the new AAA-Key (or the new pair of AAA-Keys when the PANA_MAC_KEY is derived from two AAA-Keys). Although the specification does not mandate a particular method for calculation of Forsberg, et al. Expires April 20, 2005 [Page 23] Internet-Draft PANA October 2004 Key-Id AVP value, a simple method is to use monotonically increasing numbers. The created PANA SA is deleted when the corresponding PANA session is deleted. The lifetime of the PANA SA is the same as the lifetime of the PANA session for simplicity. PANA SA attributes as well as PANA session attributes are listed below: PANA Session attributes: * Session-Id * Device-Id of PaC * IP address of PaC (may be the same as the Device-Id of PaC) * IP address of PAA * List of device identifiers of EPs * Sequence number of the last transmitted request * Sequence number of the last received request * Last transmitted message payload * Retransmission interval * Session lifetime * Protection-Capability * PANA SA attributes: + Nonce generated by PaC (PaC_nonce) + Nonce generated by PAA (PAA_nonce) + AAA-Key + AAA-Key Identifier + PANA_MAC_KEY The PANA_MAC_KEY is used to integrity protect PANA messages and derived from AAA-Key(s). When two AAA-Keys (AAA-Key1 and AAA-Key2) Forsberg, et al. Expires April 20, 2005 [Page 24] Internet-Draft PANA October 2004 are generated as a result of double EAP authentication (see Section 4.2) the compound AAA-Key can be computed as follows ('|' indicates concatenation): AAA-Key = AAA-Key1 | AAA-Key2 The PANA_MAC_KEY is computed in the following way: PANA_MAC_KEY = The first N bits of HMAC_SHA1(AAA-Key, PaC_nonce | PAA_nonce | Session-ID) where the value of N depends on the integrity protection algorithm in use, i.e., N=160 for HMAC-SHA1. The length of AAA-Key MUST be N bits or longer. See Section Section 5.4 for the detailed usage of the PANA_MAC_KEY. 5.7 Error Handling A PANA-Error-Request message MAY be sent by either the PaC or the PAA when a badly formed PANA message is received or in case of other errors. The receiver of this request MUST respond with a PANA-Error-Answer message. If the cause of this error message was a request message (e.g., PANA-PAA-Discover or *-Request), then the request MAY be retransmitted immediately without waiting for its retransmission timer to go off. If the cause of the error was a response message, the receiver of the PANA-Error-Request message SHOULD NOT resend the same response until it receives the next request. To defend against DoS attacks a timer MAY be used. One (1) error notification is sent to each different sender each N seconds. N is a configurable parameter. When an error message is sent unprotected with a MAC AVP and the lower-layer is insecure, the error message is treated as an informational message. The receiver of such an error message MUST NOT change its state unless the error persists and the PANA session is not making any progress. 5.8 Device ID Choice The device identifier used in the context of PANA can be an IP address, a MAC address, or an identifier that is not carried in data packets but has local significance in identifying a connected host (e.g., circuit id, PPP interface id). The last type of identifiers are commonly used in point-to-point links where MAC addresses are not available and lower-layers are already physically or Forsberg, et al. Expires April 20, 2005 [Page 25] Internet-Draft PANA October 2004 cryptographically secured. It is assumed that the PAA knows the link type and the security mechanisms being provided or required on the access network (e.g., based on physical security, link-layer ciphers enabled before or after PANA, or IPsec). Based on that information, the PAA can decide what type of EP device id will be used when running PANA with the client. When IPsec-based security [I-D.ietf-pana-ipsec] is the choice of access control, the PAA SHOULD provide IP address(es) as EP(s)' device ID, and expect the PaC to provide its IP address in return. In case IPsec is not used, MAC addresses are used as device IDs when available. If non-IPsec access control is enabled, and a MAC address is not available, device ID exchange does not occur within PANA. Instead, peers rely on lower-layers to provide locally-significant identifiers along with received PANA packets. 5.9 Updating PaC' Address A PaC's IP address can change in certain situations. For example, the PANA framework [I-D.ietf-pana-framework] describes a case in which a PaC replaces a pre-PANA address (PRPA) with a post-PANA address (POPA), and the PaC and PAA create host routes to each other in order to maintain on-link communication based on the POPA. The PAA needs to be notified about the change of PaC address. After the PaC has changed its address, it MUST send a PANA-Update-Request message to the PAA. The message MUST carry the new PaC address in an IP-Address AVP. If the address contained in the request is invalid, the PAA MUST send a PANA-Error message with the result code PANA_INVALID_IP_ADDRESS. Otherwise, the PAA MUST update the PANA session with the new PaC address and return a PANA-Update-Answer message. If there is an established PANA SA, both PANA-Update-Request and PANA-Update-Answer messages MUST be protected with a MAC AVP. 5.10 Session Lifetime The authentication phase determines the PANA session lifetime when the network access authorization succeeds. The Session-Lifetime AVP MAY be optionally included in the PANA-Bind-Request message to inform PaC about the valid lifetime of the PANA session. It MUST be ignored when included in other PANA messages. When there are multiple EAP authentication taking place, this AVP SHOULD be included after the final authentication. The lifetime is a non-negotiable parameter that can be used by PaC to manage PANA-related state. PaC does not have to perform any actions when the lifetime expires, other than optionally purging local state. Forsberg, et al. Expires April 20, 2005 [Page 26] Internet-Draft PANA October 2004 PAA SHOULD initiate EAP authentication before the current session lifetime expires. PaC and PAA MAY optionally rely on lower-layer indications to expedite the detection of a disconnected peer. Availability and reliability of such indications depend on the specific access technologies. PANA peer can use PANA-Ping-Request message to verify the disconnection before taking an action. The session lifetime parameter is not related to the transmission of PANA-Ping-Request messages. These messages can be used for asynchronously verifying the liveness of the peer. The decision to send PANA-Ping-Request message is taken locally and does not require coordination between the peers. 5.11 Network Selection In a discovery and handshake phase, a PANA-Start-Request message sent from the PAA MAY contain zero or one NAP-Information AVP and zero or more ISP-Information AVPs to advertise the information on the NAP and/or ISPs. The PaC MAY indicate its choice of ISP by including an ISP-Information AVP in the PANA-Start-Answer message. When a AAA backend is used, the identity of the destination AAA server or realm MUST be determined based on the explicitly chosen ISP. When the ISP-Information AVP is not present, the access network MAY rely on the client identifier carried in the EAP authentication method to make this determination. The PaC can choose an ISP and contain an ISP-Information AVP for the chosen ISP in a PANA-Start-Answer message even when there is no ISP-Information AVP contained in the PANA-Start-Request message. 5.12 Separate NAP and ISP Authentication PANA allows running at most two EAP sessions in sequence in an authentication phase to support separate NAP and ISP authentication as described in next sections. Currently, running multiple EAP sessions in sequence in an authentication phase is designed only for separate NAP and ISP authentication. It is not for running arbitrary number of EAP sessions in sequence, or giving the PaC another chance to try another EAP authentication method within an integrated NAP and ISP authentication when an EAP authentication method fails. Within separate NAP and ISP authentication, the NAP authentication and the ISP authentication are considered completely independent. Presence or success of one should not effect the other. Making a network access authorization decision based on the success or failure of each authentication is a network policy issue. Forsberg, et al. Expires April 20, 2005 [Page 27] Internet-Draft PANA October 2004 5.12.1 Negotiating Separate NAP and ISP Authentication When the PaC and PAA negotiates in the discovery and handshake phase to perform separate NAP and ISP authentication, the PaC and the PAA operate in the following way in addition to the behavior defined in Section 4.1 In the discovery and handshake phase, the PAA MAY enable separate NAP and ISP authentication ([I-D.ietf-pana-framework]) by setting the S-flag of the message header of the PANA-Start-Request. If the S-flag of the received PANA-Start-Request message is not set, the PaC MUST NOT set the S-flag in the PANA-Start-Answer message sent back to the PAA. If the S-flag of the received PANA-Start-Request message is set, the PaC can indicate its desire to perform separate NAP and ISP authentication by setting the S-flag in the PANA-Start-Answer message. If the S-flag in the PANA-Start-Answer message is not set, only one authentication is performed and the processing occurs as described in Section 4.1. If the S-flag in the PANA-Start-Answer message is set, the determination of the destination AAA server or realm for ISP authentication is performed as described in Section 5.11. In addition, where backend AAA servers are used for NAP authentication, the NAP is considered the ultimate AAA realm, and the destination AAA server for this authentication is determined entirely by the local configuration on the access server hosting the PAA (NAS). When the S-flag is set in a PANA-Start-Request message, the initial EAP Request MUST NOT be carried in the PANA-Start-Request message. (If the initial EAP Request were contained in the PANA-Start-Request message during the S-flag negotiation, the PaC cannot tell whether the EAP Request is for NAP authentication or ISP authentication.) 5.12.2 Execution of Separate NAP and ISP Authentication When the PaC and PAA have negotiated in the discovery and handshake phase to perform separate NAP and ISP authentication, the PaC and the PAA operate in the following way in addition to the behavior defined in Section 4.2 o The S-flag of PANA-Auth-Request and PANA-Auth-Answer messages MUST be set. o An EAP Success/Failure message is carried in a PANA-FirstAuth-End-Request (PFER) message as well as a Forsberg, et al. Expires April 20, 2005 [Page 28] Internet-Draft PANA October 2004 PANA-Bind-Request (PBR) message. The PANA-FirstAuth-End-Request message MUST be used at the end of the first EAP authentication and the PANA-Bind-Request MUST be used for the second EAP authentication. The PANA-FirstAuth-End-Request messages MUST be acknowledged with a PANA-FirstAuth-End-Answer (PFEA) message. o If the first EAP authentication has failed, the PAA can choose not to perform the second EAP authentication by clearing the S-flag of the PANA-FirstAuth-End-Request message. In this case, the S-flag of the PANA-FirstAuth-End-Answer message sent by the PaC MUST be cleared. If the S-flag of the PANA-FirstAuth-End-Request message is set when the first EAP authentication has failed, the PaC can choose not to perform the second EAP authentication by clearing the S-flag of the PANA-FirstAuth-End-Answer message. If the first EAP authentication failed and the S-flag is not set in the PANA-FirstAuth-End-Answer message as a result of those operations, the PANA session MUST be immediately deleted. Otherwise, the second EAP authentication MUST be performed. o The PAA determines the execution order of NAP authentication and ISP authentication. In this case, the PAA can indicate which authentication (NAP authentication or ISP authentication) is currently occurring by using N-flag in the PANA message header. When NAP authentication is being performed, the N-flag MUST be set. When ISP authentication is being performed, the N-flag MUST NOT be set. The N-flag MUST NOT be set when S-flag is not set. 5.12.3 AAA-Key Calculation When the PaC and PAA have negotiated in the discovery and handshake phase to perform separate NAP and ISP authentication, if the lower-layer is insecure, the two EAP authentication methods used in the separate authentication MUST be capable of deriving keys. In this case, if the first EAP authentication is successful, the PANA-FirstAuth-End-Request and PANA-FirstAuth-End-Answer messages as well as PANA-Auth-Request and PANA-Auth-Answer messages in the second EAP authentication MUST be protected with the key derived from the AAA-Key for the first EAP authentication. The PANA-Bind-Request and PANA-Bind-Answer messages and all subsequent PANA messages exchanged in authorized phase, re-authentication phase and termination phase MUST be protected either with the AAA-Key for the first EAP authentication if the first EAP authentication succeeds and the second EAP authentication fails, or with the AAA-Key for the second EAP authentication if the first EAP authentication fails and the second EAP authentication succeeds, or with the compound AAA-Key derived from the two AAA-Keys, one for the first EAP authentication and the other from the second EAP authentication, if both the first and second EAP authentications succeed. Forsberg, et al. Expires April 20, 2005 [Page 29] Internet-Draft PANA October 2004 5.12.4 Re-authentication When separate ISP and NAP authentication is performed, it is possible that different authorization lifetime values are associated with the two authentications. In this case, the smaller authorization lifetime value MUST be used for calculating the PANA Session-Lifetime value. As a result, when entering a re-authentication phase, both NAP and ISP authentication will be performed in the same re-authentication phase. 5.12.5 Example Sequence A PANA message sequence with separate NAP and ISP authentication is illustrated in Figure 9. The example assumes the following scenario: o The PaC initiates the discovery and handshake phase. o The PAA offers separate NAP and ISP authentication, as well as a choice of ISP from "ISP1" and "ISP2". The PaC accepts the offer from PAA, with choosing "ISP1" as the ISP. o NAP authentication and ISP authentication is performed in this order in authentication phase. o An EAP authentication method with a single round trip is used in each EAP sequence. o After a PANA SA is established, all messages are integrity and replay protected with MAC AVPs. o Authorization, re-authentication and termination phases are not shown. PaC PAA Message(seqno)[AVPs] ----------------------------------------------------- // Discovery and handshake phase -----> PANA-PAA-Discover(0) <----- PANA-Start-Request(x) // S-flag set [Nonce, Cookie, ISP-Information("ISP1"), ISP-Information("ISP2"), NAP-Information("MyNAP")] -----> PANA-Start-Answer(x) // S-flag set [Nonce, Cookie, // PaC chooses "ISP1" ISP-Information("ISP1")] // Authentication phase Forsberg, et al. Expires April 20, 2005 [Page 30] Internet-Draft PANA October 2004 <----- PANA-Auth-Request(x+1) // NAP authentication [Session-Id, EAP{Request}] // S- and N-flags set -----> PANA-Auth-Answer(x+1) // S- and N-flags set [Session-Id] // No piggybacking -----> PANA-Auth-Request(y) // S- and N-flags set [Session-Id, EAP{Response}] <----- PANA-Auth-Answer(y)[Session-Id] // S- and N-flags set <----- PANA-Auth-Request(x+2) // S- and N-flags set [Session-Id, EAP{Request}] -----> PANA-Auth-Answer(x+2) // S- and N-flags set [Session-Id, EAP{Response}] // Piggybacking <----- PANA-FirstAuth-End-Request(x+3) // S- and N-flags set [Session-Id, EAP{Success}, Key-Id, MAC] -----> PANA-FirstAuth-End-Answer(x+3) // S- and N-flags set [Session-Id, Key-Id, MAC] <----- PANA-Auth-Request(x+4) // ISP authentication [Session-Id, EAP{Request}, MAC] // S-flag set -----> PANA-Auth-Answer(x+4) // S-flag set [Session-Id, MAC] // No piggybacking -----> PANA-Auth-Request(y+1) // S-flag set [Session-Id, EAP{Response}, MAC] <----- PANA-Auth-Answer(y+1) // S-flag set [Session-Id, MAC] <----- PANA-Auth-Request(x+5) // S-flag set [Session-Id, EAP{Request}, MAC] -----> PANA-Auth-Answer(x+5) // S-flag set [Session-Id, EAP{Response}, MAC] // Piggybacking <----- PANA-Bind-Request(x+6) // S-flag set [Session-Id, EAP{Success}, Device-Id, IP-Address, Key-Id, Lifetime, Protection-Cap., PPAC, MAC] -----> PANA-Bind-Answer(x+6) // S-flag set [Session-Id, Device-Id, Key-Id, PPAC, MAC] Figure 9: A Complete Message Sequence for Separate NAP and ISP Authentication Forsberg, et al. Expires April 20, 2005 [Page 31] Internet-Draft PANA October 2004 6. Security and Mobility 6.1 PANA Security Association Establishment When PANA is used over an already established secure channel, such as physically secured wires or ciphered link-layers, we can reasonably assume that man-in-the-middle attacks or service theft is not possible. See [I-D.ietf-pana-threats-eval] for a detailed discussion. In environments where no secure channel prior to the PANA execution is available, PANA needs to protect itself against a number of attacks. The device identifier that is used during the authentication needs to be verified at the end of the authentication to prevent service theft and DoS attacks. Additionally, a free loader should be prevented from spoofing data packets by using the device identifier of an already authorized legitimate client. Both of these requirements necessitate generation of a security association between the PaC and the PAA at the end of the authentication. This can only be done when the authentication method used can generate session keys. Use of session keys can prevent attacks which would otherwise be very easy to launch by eavesdropping on and spoofing traffic over an insecure link. The EAP method provided session key is transported to the PAA (if necessary) and is subsequently input to the creation of the PANA SA. Applying the PANA SA to the messages exchanged during the final PANA handshake provides implicit key confirmation to both the PAA and the PaC. Implicit key confirmation shows both, the PaC and the PAA, that they possess the unique and fresh session key. Protecting the final PANA handshake also ensures that the device identifier (and other information) cannot be modified by an adversary. Further usage of the keying material is discussed in [I-D.ietf-pana-framework]. 6.2 Mobility A mobile PaC's network access authentication performance can be enhanced by deploying a context-transfer-based mechanism, where some session attributes are transferred from the previous PAA to the new one in order to avoid performing a full EAP authentication (reactive approach). Additional mechanisms that are based on the proactive AAA state establishment at one or more candidate PAAs may be developed in the future [I-D.irtf-aaaarch-handoff]. The details of a context-transfer-based mechanism is provided in this section. Upon changing its point of attachment, a PaC that wants to quickly Forsberg, et al. Expires April 20, 2005 [Page 32] Internet-Draft PANA October 2004 resume its ongoing PANA session without running EAP MAY send its unexpired PANA session identifier in its PANA-Start-Answer message. Along with the Session-Id AVP, a MAC AVP MUST be included in this message. The MAC AVP is computed by using the PANA_MAC_KEY shared between the PaC and its previous PAA that has an unexpired PANA session with the PaC. This action signals PaC's desire to perform the mobility optimization. In the absence of a Session-Id AVP in this message, the PANA session takes its usual course (i.e., EAP-based authentication is performed). If a PAA receives a session identifier in the PANA-Start-Answer message, and it is configured to enable this optimization, it SHOULD retrieve the PANA session attributes from the previous PAA. Current PAA determines the identity of the previous PAA by looking at the DiameterIdentity part of the PANA session identifier. The MAC AVP can only be verified by the previous PAA, therefore a copy of the PANA message SHOULD be provided to the previous PAA. The mechanism required to send a copy of the PANA-Start-Answer message from current PAA to the previous PAA, and retrieve the session attributes is outside the scope of PANA protocol. The Context Transfer Protocol [I-D.ietf-seamoby-ctp] might be useful for this purpose. When the previous or current PAA is not configured to enable this optimization, the current PAA can not retrieve the PANA session attributes, or the PANA session has already expired (i.e., session lifetime is zero), the PAA MUST send the PANA-Auth-Request message with a new session identifier and let the PANA exchange take its usual course. This action will engage EAP-based authentication and create a fresh PANA session from scratch. In case the current PAA can retrieve the on-going PANA session attributes from the previous PAA, the PANA session continues with a PANA-Bind exchange. As part of the context transfer, an intermediate AAA-Key material is provided by the previous PAA to the current PAA. AAA-Key-int = The first N bits of HMAC-SHA1(AAA-Key, DiameterIdentity | Session-ID) The value of N depends on the integrity protection algorithm in use, i.e., N=160 for HMAC-SHA1. DiameterIdentity is the identifier of the current PAA. Session-ID is the identifier of the PaC's PANA session with the previous PAA. The current PAA and PaC compute the new AAA-Key by using the nonce values and the AAA-Key-int. Forsberg, et al. Expires April 20, 2005 [Page 33] Internet-Draft PANA October 2004 AAA-Key-new = The first N bits of HMAC-SHA1(AAA-Key-int, PaC_nonce | PAA_nonce) New PANA_MAC_KEY is computed based on the algorithm described in Section 5.6, by using the new AAA-Key and the new Session-ID assigned by the current PAA. The MAC AVP contained in the PANA-Bind-Request and PANA-Bind-Answer messages MUST be generated and verified by using the new PANA_MAC_KEY. The Session-ID AVP MUST include a new session identifier assigned by the current PAA. A new PANA session is created upon successful completion of this exchange. Note that correct operation of this optimization relies on many factors, including applicability of authorization state from one network attachment to another. [I-D.ietf-eap-keying] identifies this operation as "fast handoff" and provides deployment considerations. Operators are recommended to take those guidelines into account when using this optimization in their networks. Forsberg, et al. Expires April 20, 2005 [Page 34] Internet-Draft PANA October 2004 7. PANA Headers and Formats This section defines message formats for PANA protocol. 7.1 IP and UDP Headers The Hop Limit (or TTL) field of the IP header MUST be set to 255. When a PANA-PAA-Discover message is multicast, IP destination address of the message is set to a well-known link-local multicast address (TBD). A PANA-PAA-Discover message MAY be unicast in some cases as specified in Section 4.1. Any other PANA packet is unicast between the PaC and the PAA. The source and destination addresses SHOULD be set to the addresses on the interfaces from which the message will be sent and received, respectively. When the PANA packet is sent in response to a request, the UDP source and destination ports of the response packet MUST be copied from the destination and source ports of the request packet, respectively. The destination port of an unsolicited PANA packet MUST be set to an assigned value (TBD), and the source port MUST be set to a value chosen by the sender. 7.2 PANA Header A summary of the PANA header format is shown below. The fields are transmitted in network byte order. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Version | Reserved | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | Message Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVPs ... +-+-+-+-+-+-+-+-+-+-+-+-+- Version This Version field MUST be set to 1 to indicate PANA Version 1. Forsberg, et al. Expires April 20, 2005 [Page 35] Internet-Draft PANA October 2004 Reserved This 8-bit field is reserved for future use, and MUST be set to zero, and ignored by the receiver. Message Length The Message Length field is three octets and indicates the length of the PANA message including the header fields. Flags The Flags field is eight bits. The following bits are assigned: 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |R S N r r r r r r r r r r r r r| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ R(equest) If set, the message is a request. If cleared, the message is an answer. S(eparate) When the S-flag is set in a PANA-Start-Request message it indicates that PAA is willing to offer separate NAP and ISP authentication. When the S-flag is set in a PANA-Start-Answer message it indicates that the PaC accepts on performing separate NAP and ISP authentication. When the S-flag is set in a PANA-Auth-Request/Answer, PANA-FirstAuth-End-Request/Answer and PANA-Bind-Request/Answer messages it indicates that separate NAP and ISP authentication is being performed in the authentication phase. For other cases, S-flag MUST NOT be set. N(AP authentication) When the N-flag is set in a PANA-Auth-Request message, it indicates that the current EAP authentication is for NAP authentication. When the N-flag is unset in a PANA-Auth-Request message, it indicates that the current EAP authentication is for ISP authentication. The PaC MUST copy the value of the flag in its requests from the last received request of the PAA. The value of the flag on an answer MUST be copied from the request. The N-flag MUST NOT be set when Forsberg, et al. Expires April 20, 2005 [Page 36] Internet-Draft PANA October 2004 S-flag is not set. r(eserved) these flag bits are reserved for future use, and MUST be set to zero, and ignored by the receiver. Message Type The Message Type field is two octets, and is used in order to communicate the message type with the message. The 16-bit address space is managed by IANA [ianaweb]. PANA uses its own address space for this field. Sequence Number The Sequence Number field contains a 32 bit value. AVPs AVPs are a method of encapsulating information relevant to the PANA message. See section Section 7.3 for more information on AVPs. 7.3 AVP Header Each AVP of type OctetString MUST be padded to align on a 32-bit boundary, while other AVP types align naturally. A number of zero-valued bytes are added to the end of the AVP Data field till a word boundary is reached. The length of the padding is not reflected in the AVP Length field [RFC3588]. The fields in the AVP header MUST be sent in network byte order. The format of the header is: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVP Code | AVP Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVP Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vendor-Id (opt) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+-+-+-+-+ Forsberg, et al. Expires April 20, 2005 [Page 37] Internet-Draft PANA October 2004 AVP Code The AVP Code, combined with the Vendor-Id field, identifies the attribute uniquely. AVP numbers are allocated by IANA [ianaweb]. PANA uses its own address space for this field although some of the AVP formats are borrowed from Diameter protocol [RFC3588]. AVP Flags The AVP Flags field is two octets. The following bits are assigned: 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |V M r r r r r r r r r r r r r r| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ M(andatory) The 'M' Bit, known as the Mandatory bit, indicates whether support of the AVP is required. V(endor) The 'V' bit, known as the Vendor-Specific bit, indicates whether the optional Vendor-Id field is present in the AVP header. r(eserved) These flag bits are reserved for future use, and MUST be set to zero, and ignored by the receiver. AVP Length The AVP Length field is four octets, and indicates the number of octets in this AVP including the AVP Code, AVP Length, AVP Flags, and the AVP data. Reserved This two-octet field is reserved for future use, and MUST be set to zero, and ignored by the receiver. Forsberg, et al. Expires April 20, 2005 [Page 38] Internet-Draft PANA October 2004 Vendor-Id The Vendor-Id field is present if the 'V' bit is set in the AVP Flags field. The optional four-octet Vendor-Id field contains the IANA assigned "SMI Network Management Private Enterprise Codes" [ianaweb] value, encoded in network byte order. Any vendor wishing to implement a vendor-specific PANA AVP MUST use their own Vendor-Id along with their privately managed AVP address space, guaranteeing that they will not collide with any other vendor's vendor-specific AVP(s), nor with future IETF applications. Data The Data field is zero or more octets and contains information specific to the Attribute. The format and length of the Data field is determined by the AVP Code and AVP Length fields. Forsberg, et al. Expires April 20, 2005 [Page 39] Internet-Draft PANA October 2004 8. PANA Messages, Message Specifications and AVPs 8.1 PANA Messages Figure 10 lists all PANA messages defined in this document. Message Direction: PaC---PAA ---------------------------------------- PANA-PAA-Discover --------> PANA-Start-Request <-------- PANA-Start-Answer --------> PANA-Auth-Request <-------> PANA-Auth-Answer <-------> PANA-Reauth-Request --------> PANA-Reauth-Answer <-------- PANA-FirstAuth-End-Request <-------- PANA-FirstAuth-End-Answer --------> PANA-Bind-Request <-------- PANA-Bind-Answer --------> PANA-Ping-Request <-------> PANA-Ping-Answer <-------> PANA-Termination-Request <-------> PANA-Termination-Answer <-------> PANA-Update-Request --------> PANA-Update-Answer <-------- PANA-Error-Request <-------> PANA-Error-Answer <-------> Figure 10: PANA Message Overview 8.2 Message Specifications Every PANA message MUST include a corresponding ABNF [RFC2234] specification found in [RFC3588]. Example: message ::= < PANA-Header: , [REQ] [SEP] > Forsberg, et al. Expires April 20, 2005 [Page 40] Internet-Draft PANA October 2004 * [ AVP ] 8.2.1 PANA-PAA-Discover (PDI) The PANA-PAA-Discover (PDI) message is used to discover the address of PAA(s). Both sequence numbers in this message are set to zero (0). PANA-PAA-Discover ::= < PANA-Header: 1 > * [ AVP ] 8.2.2 PANA-Start-Request (PSR) PANA-Start-Request (PSR) is sent by the PAA to the PaC. The PAA sets the sequence number to an initial random value. PANA-Start-Request ::= < PANA-Header: 2, REQ [SEP] > { Nonce } [ Cookie ] [ EAP-Payload ] [ NAP-Information ] * [ ISP-Information ] [ Protection-Capability] [ PPAC ] * [ AVP ] 8.2.3 PANA-Start-Answer (PSA) PANA-Start-Answer (PSA) is sent by the PaC to the PAA in response to a PANA-Start-Request message. PANA-Start-Answer ::= < PANA-Header: 2 [SEP] > { Nonce } [ Session-Id ] [ Cookie ] [ EAP-Payload ] [ ISP-Information ] * [ AVP ] 0*1 < MAC > 8.2.4 PANA-Auth-Request (PAR) PANA-Auth-Request (PAR) is sent by the PAA to the PaC. Forsberg, et al. Expires April 20, 2005 [Page 41] Internet-Draft PANA October 2004 PANA-Auth-Request ::= < PANA-Header: 3, REQ [SEP] [NAP] > < Session-Id > < EAP-Payload > * [ AVP ] 0*1 < MAC > 8.2.5 PANA-Auth-Answer (PAN) PANA-Auth-Answer (PAN) is sent by the PaC to the PAA in response to a PANA-Auth-Request message. PANA-Auth-Answer ::= < PANA-Header: 3 [SEP] [NAP] > < Session-Id > < EAP-Payload > * [ AVP ] 0*1 < MAC > 8.2.6 PANA-Reauth-Request (PRAR) PANA-Reauth-Request (PRAR) is sent by the PaC to the PAA. PANA-Reauth-Request ::= < PANA-Header: 4, REQ > < Session-Id > * [ AVP ] 0*1 < MAC > 8.2.7 PANA-Reauth-Answer (PRAA) PANA-Reauth-Answer (PRAA) is sent by the PAA to the PaC in response to a PANA-Reauth-Request message. PANA-Reauth-Answer ::= < PANA-Header: 4 > < Session-Id > * [ AVP ] 0*1 < MAC > 8.2.8 PANA-Bind-Request (PBR) PANA-Bind-Request (PBR) is sent by the PAA to the PaC. PANA-Bind-Request ::= < PANA-Header: 5, REQ [SEP] [NAP] > < Session-Id > { Result-Code } { PPAC } Forsberg, et al. Expires April 20, 2005 [Page 42] Internet-Draft PANA October 2004 { IP-Address } [ EAP-Payload ] [ Session-Lifetime ] [ Protection-Capability ] [ Key-Id ] * [ Device-Id ] * [ AVP ] 0*1 < MAC > 8.2.9 PANA-Bind-Answer (PBA) PANA-Bind-Answer (PBA) is sent by the PaC to the PAA in response to a PANA-Result-Request message. PANA-Bind-Answer ::= < PANA-Header: 5 [,SEP] [NAP] > < Session-Id > { Result-Code } [ PPAC ] [ Device-Id ] [ Key-Id ] * [ AVP ] 0*1 < MAC > 8.2.10 PANA-Ping-Request (PPR) PANA-Ping-Request (PPR) is either sent by the PaC or the PAA. PANA-Ping-Request ::= < PANA-Header: 6, REQ > < Session-Id > * [ AVP ] 0*1 < MAC > 8.2.11 PANA-Ping-Answer (PPA) PANA-Ping-Answer (PPA) is sent in response to a PANA-Ping-Request. PANA-Ping-Answer ::= < PANA-Header: 6 > < Session-Id > * [ AVP ] 0*1 < MAC > 8.2.12 PANA-Termination-Request (PTR) PANA-Termination-Request (PTR) is sent either by the PaC or the PAA. Forsberg, et al. Expires April 20, 2005 [Page 43] Internet-Draft PANA October 2004 PANA-Termination-Request ::= < PANA-Header: 7, REQ > < Session-Id > < Termination-Cause > * [ AVP ] 0*1 < MAC > 8.2.13 PANA-Termination-Answer (PTA) PANA-Termination-Answer (PTA) is sent either by the PaC or the PAA in response to PANA-Termination-Request. PANA-Termination-Answer ::= < PANA-Header: 7 > < Session-Id > * [ AVP ] 0*1 < MAC > 8.2.14 PANA-Error-Request (PER) PANA-Error is sent either by the PaC or the PAA. PANA-Error-Request ::= < PANA-Header: 8 REQ > < Session-Id > < Result-Code > { Failed-AVP } * [ AVP ] 0*1 < MAC > 8.2.15 PANA-Error-Answer (PEA) PANA-Error-Answer is sent in response to a PANA-Error-Request. PANA-Error-Answer ::= < PANA-Header: 8 > < Session-Id > * [ AVP ] 0*1 < MAC > 8.2.16 PANA-FirstAuth-End-Request (PFER) PANA-FirstAuth-End-Request (PFER) is sent by the PAA to the PaC. PANA-FirstAuth-End-Request ::= < PANA-Header: 9, REQ [SEP] [NAP] > < Session-Id > { EAP-Payload } { Result-Code } Forsberg, et al. Expires April 20, 2005 [Page 44] Internet-Draft PANA October 2004 [ Key-Id ] * [ AVP ] 0*1 < MAC > 8.2.17 PANA-FirstAuth-End-Answer (PFEA) PANA-FirstAuth-End-Answer (PFEA) is sent by the PaC to the PAA in response to a PANA-FirstAuth-End-Request message. PANA-FirstAuth-End-Answer ::= < PANA-Header: 9, REQ [SEP] [NAP] > < Session-Id > [ Key-Id ] * [ AVP ] 0*1 < MAC > 8.2.18 PANA-Update-Request (PUR) PANA-Update-Request (PUR) is sent by the PaC to the PAA. PANA-Update-Request ::= < PANA-Header: 10, REQ > < Session-Id > < IP-Address > * [ AVP ] 0*1 < MAC > 8.2.19 PANA-Update-Answer (PUA) PANA-Update-Answer (PUA) is sent by the PAA to the PaC in response to a PANA-Update-Request. PANA-Update-Answer ::= < PANA-Header: 10 > < Session-Id > * [ AVP ] 0*1 < MAC > 8.3 AVPs in PANA PANA defines several AVPs that are specific to the protocol. A number of others AVPs are reused. These are specified in other documents such as [RFC3588]. The following tables lists the AVPs used in this document, and specifies in which PANA messages they MAY, or MAY NOT be present. Forsberg, et al. Expires April 20, 2005 [Page 45] Internet-Draft PANA October 2004 The table uses the following symbols: 0 The AVP MUST NOT be present in the message. 0+ Zero or more instances of the AVP MAY be present in the message. 0-1 Zero or one instance of the AVP MAY be present in the message. It is considered an error if there are more than one instance of the AVP. 1 One instance of the AVP MUST be present in the message. 1+ At least one instance of the AVP MUST be present in the message. +-----------------------------------------+ | Message | | Type | +-----+-----+-----+-----+-----+-----+-----+ Attribute Name | PSR | PSA | PAR | PAN | PBR | PBA | PDI | --------------------+-----+-----+-----+-----+-----+-----+-----+ Result-Code | 0 | 0 | 0 | 0 | 1 | 1 | 0 | Session-Id | 0 | 0-1 | 1 | 1 | 1 | 1 | 0 | Termination-Cause | 0 | 0 | 0 | 0 | 0 | 0 | 0 | EAP-Payload | 0-1 | 0-1 | 1 | 0-1 | 0-1 | 0 | 0 | MAC | 0 | 0-1 | 0-1 | 0-1 | 0-1 | 0-1 | 0 | Nonce | 1 | 1 | 0 | 0 | 0 | 0 | 0 | Device-Id | 0 | 0 | 0 | 0 | 0+ | 0-1 | 0 | Cookie | 0-1 | 0-1 | 0 | 0 | 0 | 0 | 0 | Protection-Cap. | 0-1 | 0 | 0 | 0 | 0-1 | 0 | 0 | PPAC | 0-1 | 0 | 0 | 0 | 1 | 0-1 | 0 | Session-Lifetime | 0 | 0 | 0 | 0 | 0-1 | 0 | 0 | Failed-AVP | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ISP-Information | 0+ | 0-1 | 0 | 0 | 0 | 0 | 0 | NAP-Information | 0-1 | 0 | 0 | 0 | 0 | 0 | 0 | Key-Id | 0 | 0 | 0 | 0 | 0-1 | 0-1 | 0 | IP-Address | 0 | 0 | 0 | 0 | 0 | 0 | 0 | --------------------+-----+-----+-----+-----+-----+-----+-----+ Figure 11: AVP Occurrence Table (1/3) Forsberg, et al. Expires April 20, 2005 [Page 46] Internet-Draft PANA October 2004 +-------------------------------------+ | Message | | Type | +-----+-----+-----+-----+------+------+ Attribute Name | PPR | PPA | PTR | PTA | PFER | PFEA | --------------------+-----+-----+-----+-----+------+------+ Result-Code | 0 | 0 | 0 | 0 | 1 | 0 | Session-Id | 1 | 1 | 1 | 1 | 1 | 1 | Termination-Cause | 0 | 0 | 1 | 0 | 0 | 0 | EAP-Payload | 0 | 0 | 0 | 0 | 1 | 0 | MAC | 0-1 | 0-1 | 0-1 | 0-1 | 0-1 | 0-1 | Nonce | 0 | 0 | 0 | 0 | 0 | 0 | Device-Id | 0 | 0 | 0 | 0 | 0 | 0 | Cookie | 0 | 0 | 0 | 0 | 0 | 0 | Protection-Cap. | 0 | 0 | 0 | 0 | 0 | 0 | PPAC | 0 | 0 | 0 | 0 | 0 | 0 | Session-Lifetime | 0 | 0 | 0 | 0 | 0 | 0 | Failed-AVP | 0 | 0 | 0 | 0 | 0 | 0 | ISP-Information | 0 | 0 | 0 | 0 | 0 | 0 | NAP-Information | 0 | 0 | 0 | 0 | 0 | 0 | Key-Id | 0 | 0 | 0 | 0 | 0-1 | 0-1 | IP-Address | 0 | 0 | 0 | 0 | 0 | 0 | --------------------+-----+-----+-----+-----+------+------+ Figure 12: AVP Occurrence Table (2/3) Forsberg, et al. Expires April 20, 2005 [Page 47] Internet-Draft PANA October 2004 +-------------------------------------+ | Message | | Type | +-----+-----+-----+-----+------+------+ Attribute Name | PUR | PUA | PER | PEA | PRAR | PRAA | --------------------+-----+-----+-----+-----+------+------+ Result-Code | 0 | 0 | 1 | 0 | 0 | 0 | Session-Id | 1 | 1 | 1 | 1 | 1 | 1 | Termination-Cause | 0 | 0 | 0 | 0 | 0 | 0 | EAP-Payload | 0 | 0 | 0 | 0 | 0 | 0 | MAC | 0-1 | 0-1 | 0-1 | 0-1 | 0-1 | 0-1 | Nonce | 0 | 0 | 0 | 0 | 0 | 0 | Device-Id | 0 | 0 | 0 | 0 | 0 | 0 | Cookie | 0 | 0 | 0 | 0 | 0 | 0 | Protection-Cap. | 0 | 0 | 0 | 0 | 0 | 0 | PPAC | 0 | 0 | 0 | 0 | 0 | 0 | Session-Lifetime | 0 | 0 | 0 | 0 | 0 | 0 | Failed-AVP | 0 | 0 | 1 | 0 | 0 | 0 | ISP-Information | 0 | 0 | 0 | 0 | 0 | 0 | NAP-Information | 0 | 0 | 0 | 0 | 0 | 0 | Key-Id | 0 | 0 | 0 | 0 | 0 | 0 | IP-Address | 1 | 0 | 0 | 0 | 0 | 0 | --------------------+-----+-----+-----+-----+------+------+ Figure 13: AVP Occurrence Table (3/3) 8.3.1 MAC AVP The first octet (8 bits) of the MAC (AVP Code 1) AVP data contains the MAC algorithm type. Rest of the AVP data payload contains the MAC encoded in network byte order. The 8-bit Algorithm name space is managed by IANA [ianaweb]. The AVP length varies depending on the used algorithm. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Algorithm | MAC... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Algorithm 1 HMAC-SHA1 (20 bytes) Forsberg, et al. Expires April 20, 2005 [Page 48] Internet-Draft PANA October 2004 MAC The Message Authentication Code is encoded in network byte order. 8.3.2 Device-Id AVP The Device-Id AVP (AVP Code 2) is of Address type [RFC3588]. IPv4 and IPv6 addresses are encoded as specified in [RFC3588]. The content and format of data (including byte and bit ordering) for link-layer addresses is expected to be specified in specific documents that describe how IP operates over different link-layers. For instance, [RFC2464]. Address families other than that are defined for link-layer or IP addresses MUST NOT be used for this AVP. 8.3.3 Session-Id AVP All messages pertaining to a specific PANA session MUST include a Session-Id AVP (AVP Code 3) which carries a PAA-assigned fix value throughout the lifetime of a session. When present, the Session-Id SHOULD appear immediately following the PANA header. The Session-Id MUST be globally and eternally unique, as it is meant to identify a PANA Session without reference to any other information, and may be needed to correlate historical authentication information with accounting information. The PANA Session-Id AVP has the same format as the Diameter Session-Id AVP [RFC3588]. 8.3.4 Cookie AVP The Cookie AVP (AVP Code 4) is of type OctetString. The data is opaque and the exact content is outside the scope of this protocol. 8.3.5 Protection-Capability AVP The Protection-Capability AVP (AVP Code 5) is of type Unsigned32. The AVP data indicates the cryptographic data protection capability supported by the EPs. Below is a list of specified data protection capabilities: 0 L2_PROTECTION 1 IPSEC_PROTECTION 8.3.6 Termination-Cause AVP The Termination-Cause AVP (AVP Code 6) is of type of type Enumerated, and is used to indicate the reason why a session was terminated on the access device. The AVP data is used as a collection of flags The Forsberg, et al. Expires April 20, 2005 [Page 49] Internet-Draft PANA October 2004 following Termination-Cause AVP defined in [RFC3588] are used for PANA. LOGOUT 1 (PaC -> PAA) The client initiated a disconnect ADMINISTRATIVE 4 (PAA -> PaC) The client was not granted access, or was disconnected, due to administrative reasons, such as the receipt of a Abort-Session-Request message. SESSION_TIMEOUT 8 (PAA -> PaC) The session has timed out, and service has been terminated. 8.3.7 Result-Code AVP The Result-Code AVP (AVP Code 7) is of type Unsigned32 and indicates whether an EAP authentication was completed successfully or whether an error occurred. Here are Result-Code AVP values taken from [RFC3588] and adapted for PANA. 8.3.7.1 Authentication Results Codes These result code values inform the PaC about the authentication and authorization result. The authentication result and authorization result can be different as described below, but only one result that corresponds to the one detected first is returned. PANA_SUCCESS 2001 Both the authentication and authorization processes are successful. PANA_AUTHENTICATION_REJECTED 4001 The authentication process failed. When this error is returned, the authorization process also fails. PANA_AUTHORIZATION_REJECTED 5003 The authorization process failed. This error could occur when authorization is rejected by a AAA proxy or rejected locally by a PAA, even if the authentication procedure succeeds. Forsberg, et al. Expires April 20, 2005 [Page 50] Internet-Draft PANA October 2004 8.3.7.2 Protocol Error Result Codes Protocol error result code values. PANA_MESSAGE_UNSUPPORTED 3001 Error code from PAA to PaC or from PaC to PAA. Message type not recognized or supported. PANA_UNABLE_TO_DELIVER 3002 Error code from PAA to PaC. PAA was unable to deliver the EAP payload to the authentication server. PANA_INVALID_HDR_BITS 3008 Error code from PAA to PaC or from PaC to PAA. A message was received whose bits in the PANA header were either set to an invalid combination, or to a value that is inconsistent with the message type's definition. PANA_INVALID_AVP_BITS 3009 Error code from PAA to PaC or from PaC to PAA. A message was received that included an AVP whose flag bits are set to an unrecognized value, or that is inconsistent with the AVP's definition. PANA_AVP_UNSUPPORTED 5001 Error code from PAA to PaC or from PaC to PAA. The received message contained an AVP that is not recognized or supported and was marked with the Mandatory bit. A PANA message with this error MUST contain one or more Failed-AVP AVP containing the AVPs that caused the failure. PANA_UNKNOWN_SESSION_ID 5002 Error code from PAA to PaC or from PaC to PAA. The message contained an unknown Session-Id. PAA MUST NOT send this error result code value to PaC if PaC sent an unknown Session-Id in the PANA-Start-Answer message (session resumption). PANA_INVALID_AVP_VALUE 5004 Forsberg, et al. Expires April 20, 2005 [Page 51] Internet-Draft PANA October 2004 Error code from PAA to PaC or from PaC to PAA. The message contained an AVP with an invalid value in its data portion. A PANA message indicating this error MUST include the offending AVPs within a Failed-AVP AVP. PANA_MISSING_AVP 5005 Error code from PAA to PaC or from PaC to PAA. The message did not contain an AVP that is required by the message type definition. If this value is sent in the Result-Code AVP, a Failed-AVP AVP SHOULD be included in the message. The Failed-AVP AVP MUST contain an example of the missing AVP complete with the Vendor-Id if applicable. The value field of the missing AVP should be of correct minimum length and contain zeroes. PANA_RESOURCES_EXCEEDED 5006 Error code from PAA to PaC. A message was received that cannot be authorized because the client has already expended allowed resources. An example of this error condition is a client that is restricted to one PANA session and attempts to establish a second session. PANA_CONTRADICTING_AVPS 5007 Error code from PAA to PaC. The PAA has detected AVPs in the message that contradicted each other, and is not willing to provide service to the client. One or more Failed-AVP AVPs MUST be present, containing the AVPs that contradicted each other. PANA_AVP_NOT_ALLOWED 5008 Error code from PAA to PaC or from PaC to PAA. A message was received with an AVP that MUST NOT be present. The Failed-AVP AVP MUST be included and contain a copy of the offending AVP. PANA_AVP_OCCURS_TOO_MANY_TIMES 5009 Error code from PAA to PaC or from PaC to PAA. A message was received that included an AVP that appeared more often than permitted in the message definition. The Failed-AVP AVP MUST be included and contain a copy of the first instance of the offending AVP that exceeded the maximum number of occurrences. PANA_UNSUPPORTED_VERSION 5011 Forsberg, et al. Expires April 20, 2005 [Page 52] Internet-Draft PANA October 2004 Error code from PAA to PaC or from PaC to PAA. This error is returned when a message was received, whose version number is unsupported. PANA_UNABLE_TO_COMPLY 5012 This error is returned when a request is rejected for unspecified reasons. For example, when an EAP authentication fails at an EAP pass-through authenticator without passing an EAP-Failure message to the PAA, a Result-Code AVP with this error code is carried in PANA-Error-Request message. PANA_INVALID_AVP_LENGTH 5014 Error code from PAA to PaC or from PaC to PAA. The message contained an AVP with an invalid length. The PANA-Error message indicating this error MUST include the offending AVPs within a Failed-AVP AVP. PANA_INVALID_MESSAGE_LENGTH 5015 Error code from PAA to PaC or from PaC to PAA. This error is returned when a message is received with an invalid message length. PANA_PROTECTION_CAPABILITY_UNSUPPORTED 5016 Error code from PaC to PAA. This error is returned when the PaC receives a PANA-Bind-Request with a Protection-Capability AVP and a valid MAC AVP but does not support the protection capability specified in the Protection-Capability AVP. PANA_PPAC_CAPABILITY_UNSUPPORTED 5017 Error code from PaC to PAA. This error is returned in a PANA-Bind-Answer message when there is no match between the list of PPAC methods offered by the PAA and the ones available on the PaC. PANA_INVALID_IP_ADDRESS 5018 Error code from PAA to PaC. This error is returned in a PANA-Error-Request message when the IP-Address AVP in the received PANA-Update-Request message is invalid (e.g., a non-unicast address). Forsberg, et al. Expires April 20, 2005 [Page 53] Internet-Draft PANA October 2004 8.3.8 EAP-Payload AVP The EAP-Payload AVP (AVP Code 8) is of type OctetString and is used to encapsulate the actual EAP packet that is being exchanged between the EAP peer and the EAP authenticator. 8.3.9 Session-Lifetime AVP The Session-Lifetime AVP (AVP Code 9) data is of type Unsigned32. It contains the number of seconds remaining before the current session is considered expired. 8.3.10 Failed-AVP AVP The Failed-AVP AVP (AVP Code 10) is of type Grouped and provides debugging information in cases where a request is rejected or not fully processed due to erroneous information in a specific AVP. The format of the Failed-AVP AVP is defined in [RFC3588]. 8.3.11 NAP-Information AVP The NAP-Information AVP (AVP Code 11) is of type Grouped, and contains zero or one Provider-Identifier AVP which carries the identifier of the NAP and one Provider-Name AVP which carries the name of the NAP. Its Data field has the following ABNF grammar: NAP-Information ::= < AVP Header: 11 > 0*1 { Provider-Identifier } { Provider-Name } * [ AVP ] 8.3.12 ISP-Information AVP The ISP-Information AVP (AVP Code 12) is of type Grouped, and contains zero or one Provider-Identifier AVP which carries the identifier of the ISP and one Provider-Name AVP which carries the name of the ISP. Its Data field has the following ABNF grammar: ISP-Information ::= < AVP Header: 12 > 0*1 { Provider-Identifier } { Provider-Name } * [ AVP ] 8.3.13 Provider-Identifier AVP The Provider-Identifier AVP (AVP Code 13) is of type Unsigned32, and Forsberg, et al. Expires April 20, 2005 [Page 54] Internet-Draft PANA October 2004 contains an IANA assigned "SMI Network Management Private Enterprise Codes" [ianaweb] value, encoded in network byte order. 8.3.14 Provider-Name AVP The Provider-Name AVP (AVP Code 14) is of type UTF8String, and contains the UTF8-encoded name of the provider. 8.3.15 Key-Id AVP The Key-Id AVP (AVP Code 15) is of type Integer32, and contains an AAA-Key identifier. The AAA-Key identifier is assigned by PAA and MUST be unique within the PANA session. 8.3.16 Post-PANA-Address-Configuration (PPAC) AVP The data field of PPAC AVP (AVP Code 16) is of type Unsigned32. The AVP data is used to carry a set of flags which maps to various IP address configuration methods. When sent by the PAA, the AVP MUST have at least one of the flags set, and MAY have more than one set. When sent by the PaC, only one of the flags MUST be set. The format of the AVP data is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |N|D|A|T|I| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ PPAC Flags N (No configuration) The PaC does not have to (if sent by PAA) or will not (if sent by PaC) configure a new IP address after PANA. D (DHCP) The PaC can (if sent by PAA) or will (if sent by PaC) use DHCP [RFC2131][RFC3315] to configure a new IP address after PANA. A (stateless autoconfiguration) The PaC can/will use stateless IPv6 address autoconfiguration [RFC2462] to configure a new IP address after PANA. Forsberg, et al. Expires April 20, 2005 [Page 55] Internet-Draft PANA October 2004 T (DHCP with IPsec tunnel mode) The PaC can/will use [RFC3456] to configure a new IP address after PANA. I (IKEv2) The PaC can/will use [I-D.ietf-ipsec-ikev2] to configure a new IP address after PANA. Reserved These flag bits are reserved for future use, and MUST be set to zero, and ignored by the receiver. Unless the N-flag is set, the PaC MUST configure a new IP address using one of the methods indicated by the other flags. Refer to [I-D.ietf-pana-framework] for a detailed discussion on when these methods can be used. 8.3.17 Nonce AVP The Nonce AVP (AVP Code 17) is of type OctetString. The data contains a randomly generated value in opaque format. The data length MUST be between 8 and 256 bytes inclusive. 8.3.18 IP-Address AVP The IP-Address (AVP Code 18) contains an IP address of n a PaC or PAA. The payload format of the IP-Address AVP is the same as that of the Device-Id AVP (see See Section 8.3.2). Address families for IPv4 or IPv6 MUST be used for this AVP. Address families for IPv4 or IPv6 MUST be used for this AVP. Forsberg, et al. Expires April 20, 2005 [Page 56] Internet-Draft PANA October 2004 9. PANA Protocol Message Retransmissions The PANA protocol provides retransmissions for the PANA-PAA-Discover and request messages. The rule is that the sender of the request message retransmits the request if the corresponding answer is not received in time. Answer messages are sent as answers to the request messages, not based on a timer. PaC MUST retransmit PANA-PAA-Discover if a subsequent PANA-Start-Request is not received in time. Even though a PANA-Start-Request is received, PANA-PAA-Discover may still have to be retransmitted. This is because a stateless PANA handshake requires one time transmission of a PANA-Start-Request. PAA MUST NOT start a timer and retransmit the request if it wants to avoid state creation. If the received PANA-Start-Request included a Cookie AVP (an indication of stateless handshake), PaC MUST retransmit PANA-PAA-Discover until the first PANA-Auth-Request is received. PANA retransmission timers are based on the model used in DHCPv6 [RFC3315]. Variables used here are also borrowed from this specification. PANA is a request response like protocol. The message exchange terminates when either the request sender successfully receives the appropriate answer, or when the message exchange is considered to have failed according to the retransmission mechanism described below. The retransmission behavior is controlled and described by the following variables: RT Retransmission timeout IRT Initial retransmission time MRC Maximum retransmission count MRT Maximum retransmission time MRD Maximum retransmission duration RAND Randomization factor With each message transmission or retransmission, the sender sets RT according to the rules given below. If RT expires before the message exchange terminates, the sender recomputes RT and retransmits the message. Forsberg, et al. Expires April 20, 2005 [Page 57] Internet-Draft PANA October 2004 Each of the computations of a new RT include a randomization factor (RAND), which is a random number chosen with a uniform distribution between -0.1 and +0.1. The randomization factor is included to minimize synchronization of messages. The algorithm for choosing a random number does not need to be cryptographically sound. The algorithm SHOULD produce a different sequence of random numbers from each invocation. RT for the first message transmission is based on IRT: RT = IRT + RAND*IRT RT for each subsequent message transmission is based on the previous value of RT: RT = 2*RTprev + RAND*RTprev MRT specifies an upper bound on the value of RT (disregarding the randomization added by the use of RAND). If MRT has a value of 0, there is no upper limit on the value of RT. Otherwise: if (RT > MRT) RT = MRT + RAND*MRT MRC specifies an upper bound on the number of times a sender may retransmit a message. Unless MRC is zero, the message exchange fails once the sender has transmitted the message MRC times. MRD specifies an upper bound on the length of time a sender may retransmit a message. Unless MRD is zero, the message exchange fails once MRD seconds have elapsed since the client first transmitted the message. If both MRC and MRD are non-zero, the message exchange fails whenever either of the conditions specified in the previous two paragraphs are met. If both MRC and MRD are zero, the client continues to transmit the message until it receives a response. 9.1 Transmission and Retransmission Parameters This section presents a table of values used to describe the message retransmission behavior of PANA requests (REQ_*) and PANA-PAA-Discover message (PDI_*). The table shows default values. Parameter Default Description Forsberg, et al. Expires April 20, 2005 [Page 58] Internet-Draft PANA October 2004 ------------------------------------------------ PDI_IRT 1 sec Initial PDI timeout. PDI_MRT 120 secs Max PDI timeout value. PDI_MRC 0 Configurable. PDI_MRD 0 Configurable. REQ_IRT 1 sec Initial Request timeout. REQ_MRT 30 secs Max Request timeout value. REQ_MRC 10 Max Request retry attempts. REQ_MRD 0 Configurable. So for example the first RT for the PBR message is calculated using REQ_IRT as the IRT: RT = REQ_IRT + RAND*REQ_IRT Forsberg, et al. Expires April 20, 2005 [Page 59] Internet-Draft PANA October 2004 10. IANA Considerations This section provides guidance to the Internet Assigned Numbers Authority (IANA) regarding registration of values related to the PANA protocol, in accordance with BCP 26 [IANA]. The following policies are used here with the meanings defined in BCP 26: "Private Use", "First Come First Served", "Expert Review", "Specification Required", "IETF Consensus", "Standards Action". This section explains the criteria to be used by the IANA for assignment of numbers within namespaces defined within this document. For registration requests where a Designated Expert should be consulted, the responsible IESG area director should appoint the Designated Expert. For Designated Expert with Specification Required, the request is posted to the PANA WG mailing list (or, if it has been disbanded, a successor designated by the Area Director) for comment and review, and MUST include a pointer to a public specification. Before a period of 30 days has passed, the Designated Expert will either approve or deny the registration request and publish a notice of the decision to the PANA WG mailing list or its successor. A denial notice must be justified by an explanation and, in the cases where it is possible, concrete suggestions on how the request can be modified so as to become acceptable. 10.1 PANA UDP Port Number PANA uses one well-known UDP port number (Section 5.2, Section 4.1 and Section 7.1, which needs to be assigned by the IANA. 10.2 PANA Multicast Address PANA uses one well-known IPv4 multicast address for which the scope is limited to be link-local by setting the TTL field to 255, and one well-known IPv6 link-local scoped multicast address (Section 4.1 and Section 7.1), which need to be assigned by the IANA. 10.3 PANA Header As defined in Section 7.2, the PANA header contains two fields that requires IANA namespace management; the Message Type and Flags field. 10.3.1 Message Type The Message Type namespace is used to identify PANA messages. Values 0-65,533 are for permanent, standard message types, allocated by IETF Consensus [IANA]. This document defines the Message Types 1-10. See Section 8.2.1 through Section 8.2.19 for the assignment of the Forsberg, et al. Expires April 20, 2005 [Page 60] Internet-Draft PANA October 2004 namespace in this specification. The values 65,534 and 65,535 (hexadecimal values 0xfffe - 0xffff) are reserved for experimental messages. As these codes are only for experimental and testing purposes, no guarantee is made for interoperability between communicating PaC and PAA using experimental commands, as outlined in [IANA-EXP]. 10.3.2 Flags There are 16 bits in the Flags field of the PANA header. This document assigns bit 0 ('R'equest), bit 1 ('S'eparate) and bit 2 ('N'AP Authentication). The remaining bits MUST only be assigned via a Standards Action [IANA]. 10.4 AVP Header As defined in Section 7.3, the AVP header contains three fields that requires IANA namespace management; the AVP Code, AVP Flags and Vendor-Id fields where only the AVP Code and AVP Flags create new namespaces. 10.4.1 AVP Code The AVP Code namespace is used to identify attributes. There are multiple namespaces. Vendors can have their own AVP Codes namespace which will be identified by their Vendor-ID (also known as Enterprise-Number) and they control the assignments of their vendor-specific AVP codes within their own namespace. The absence of a Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA controlled AVP Codes namespace. The AVP Codes and sometimes also possible values in an AVP are controlled and maintained by IANA. AVP Code 0 is not used. This document defines the AVP Codes 1-18. See Section 8.3.1 through Section 8.3.18 for the assignment of the namespace in this specification. AVPs may be allocated following Designated Expert with Specification Required [IANA]. Release of blocks of AVPs (more than 3 at a time for a given purpose) should require IETF Consensus. Note that PANA defines a mechanism for Vendor-Specific AVPs, where the Vendor-Id field in the AVP header is set to a non-zero value. Vendor-Specific AVPs codes are for Private Use and should be encouraged instead of allocation of global attribute types, for functions specific only to one vendor's implementation of PANA, where no interoperability is deemed useful. Where a Vendor-Specific AVP is implemented by more than one vendor, allocation of global AVPs should Forsberg, et al. Expires April 20, 2005 [Page 61] Internet-Draft PANA October 2004 be encouraged instead. 10.4.2 Flags There are 16 bits in the AVP Flags field of the AVP header, defined in Section 7.3. This document assigns bit 0 ('V'endor Specific) and bit 1 ('M'andatory). The remaining bits should only be assigned via a Standards Action . 10.5 AVP Values Certain AVPs in PANA define a list of values with various meanings. For attributes other than those specified in this section, adding additional values to the list can be done on a First Come, First Served basis by IANA [IANA]. 10.5.1 Algorithm Values of MAC AVP As defined in Section 8.3.1, the Algorithm field of MAC AVP (AVP Code 1) defines the value of 1 (one) for HMAC-SHA1. All remaining values are available for assignment via IETF Consensus [IANA]. 10.5.2 Protection-Capability AVP Values As defined in Section 8.3.5, the Protection-Capability AVP (AVP Code 5) defines the values 0 and 1. All remaining values are available for assignment via a Standards Action [IANA]. 10.5.3 Termination-Cause AVP Values As defined in Section 8.3.6, the Termination-Cause AVP (AVP Code 6) defines the values 1, 4 and 8. All remaining values are available for assignment via IETF Consensus [IANA]. 10.5.4 Result-Code AVP Values As defined in Section 8.3.7.1 and Section 8.3.7.2 the Result-Code AVP (AVP Code 7) defines the values 2001, 3001-3002, 3008-3009, 4001, 5001-5009 and 5011-5019. All remaining values are available for assignment via IETF Consensus [IANA]. Forsberg, et al. Expires April 20, 2005 [Page 62] Internet-Draft PANA October 2004 10.5.5 Post-PANA-Address-Configuration AVP Values As defined in Section 8.3.16, the Post-PANA-Address-Configuration AVP (AVP Code 17) defines the bits 0 ('N': no configuration), 1 ('D': DHCP), 2 ('A' stateless autoconfiguration), 3 ('T': DHCP with IPsec tunnel mode) and 4 ('I': IKEv2). All remaining values are available for assignment via a Standards Action [IANA]. Forsberg, et al. Expires April 20, 2005 [Page 63] Internet-Draft PANA October 2004 11. Security Considerations The PANA protocol defines a UDP-based EAP encapsulation that runs between two IP-enabled nodes on the same IP link. Various security threats that are relevant to a protocol of this nature are outlined in [I-D.ietf-pana-threats-eval]. Security considerations stemming from the use of EAP and EAP methods are discussed in [RFC3748]. This section provides a discussion on the security-related issues that are related to PANA framework and protocol design. An important element in assessing security of PANA design and deployment in a network is the presence of lower-layer (physical and link-layer) security. In the context of this document, lower-layers are said to be secure if they can prevent eavesdropping and spoofing of packets. Examples of such networks are physically-secured DSL networks and 3GPP2 networks with crytographically-secured cdma2000 link-layer. In these examples, the lower-layer security is enabled even before running the first PANA-based authentication. In the absence of such a pre-established secure channel, one needs to be created in conjunction with PANA using a link-layer or network-layer cryptographic mechanism (e.g., IPsec). 11.1 General Security Measures PANA provides multiple mechanisms to secure a PANA session. Since PaC and PAA are on the same IP link, a simple TTL check on the received PANA messages prevents off-link attacks. PANA messages carry sequence numbers, which are monotonically incremented by 1 with every new request message. These numbers are randomly initialized at the beginning of the session, and verified against expected numbers upon receipt. A message whose sequence number is different than the expected one is silently discarded. In addition to accomplishing orderly delivery of EAP messages and duplicate elimination, this scheme also helps prevent an adversary spoof messages to disturb ongoing PANA and EAP sessions unless it can also eavesdrop to synchronize on the expected sequence number. The PANA framework defines EP which is ideally located on a network device that can filter traffic from the PaCs before the traffic enters the Internet. A set of filters can be used to discard unauthorized packets, such as a PANA-Start-Request message that is received from the segment of the access network where only PaCs are supposed to be connected. Forsberg, et al. Expires April 20, 2005 [Page 64] Internet-Draft PANA October 2004 The protocol also provides authentication and integrity protection to PANA messages when the used EAP method can generate cryptographic session keys. A PANA SA is generated based on the AAA-Key exported by the EAP method. This SA is used for generating per-packet MAC to protect the PANA header and payload (including the complete EAP message). The cryptographic protection prevents an adversary from acting as a man-in-the-middle, injecting messages, replaying messages and modifying the content of the exchanged messages. Any packet that fails to pass the MAC verification is silently discarded. The earliest this protection can be enabled is when the very first PANA-Bind-Request that signals a successful authentication is generated. Starting with the PANA-Bind-Request and PANA-Bind-Answer, any subsequent PANA message until the session gets torn down can be cryptographically protected. The PANA SA enables authenticated and integrity protected exchange of the device ID information between the PaC and PAA. This ensures there were no man-in-the-middle during the PANA authentication. The lifetime of the PANA SA is bounded by the AAA-authorized session lifetime with an additional tolerance period. Unless PANA state is updated by executing another EAP authentication, the PANA SA is removed when the current session expires. The ability to use cryptographic protection within PANA is determined by the used EAP method, which is generally dictated by the deployment environment. Insecure lower-layers necessitate use of key-generating EAP methods. In networks where lower-layers are already secured, cryptographic protection of PANA messages is not necessary. 11.2 Discovery The discovery and handshake phase is vulnerable to spoofing attacks as these messages are not authenticated and integrity protected. In order to prevent very basic denial-of service attacks an adversary should not be able to cause state creation by sending discovery messages to the PAA. This protection is achieved by using a cookie-based scheme (similar to [RFC2522] which allows the responder (PAA) to be stateless in the first round of message exchange. A return-routability test does not provide additional protection as PANA traffic is not routed but simply forwarded on-link. It is difficult to prevent this threat entirely. In networks where lower-layers are not secured prior to running PANA, the capability discovery enabled through inclusion of Protection-Capability and Post-PANA-Address-Configuration AVPs in a Forsberg, et al. Expires April 20, 2005 [Page 65] Internet-Draft PANA October 2004 PANA-Start-Request message is susceptible to spoofing leading to denial-of service attacks. Therefore, usage of these AVPs during the discovery and handshake phase in such insecure networks is NOT RECOMMENDED. The same AVPs are delivered via an integrity-protected PANA-Bind-Request upon successful authentication. 11.3 EAP Methods Eavesdropping EAP packets might cause problems when the EAP method is weak and enables dictionary or replay attacks or even allows an adversary to learn the long-term password directly. Furthermore, if the optional EAP Identity payload is used then it allows the adversary to learn the identity of the PaC. In such a case a privacy problem is prevalent. To prevent these threats, [I-D.ietf-pana-framework] suggests using proper EAP methods for particular environments. Depending on the deployment environment an EAP authentication which supports user identity confidentiality, protection against dictionary attacks and session key establishment must be used. It is therefore the responsibility of the network operators and users to choose a proper EAP method. 11.4 Separate NAP and ISP Authentication The PANA design allows running two separate EAP sessions for the same PaC in a single authentication phase: one with the NAP, and one with the ISP. The process of arriving at the resultant authorization, which is a combination of the individual authorizations obtained from respective service providers, is outside the scope of this protocol. In the absence of lower-layer security, both authentications MUST be able to generate a AAA-Key, leading to generation of a PANA SA. The resultant PANA SA cryptographically binds the two AAA-Keys together, hence it prevents man-in-the-middle attacks. 11.5 Cryptographic Keys When the EAP method exports a AAA-Key, this key is used to produce a PANA SA with PANA_MAC_KEY with a distinct key ID. The PANA_MAC_KEY is unique to the PANA session, and takes PANA-based nonce values into computation to cryptographically separate itself from the AAA-Key. The PANA_MAC_KEY is solely used for authentication and integrity protection of the PANA messages within the designated session. Two AAA-Keys may be generated as a result of separate NAP and ISP authentication. In that case, the AAA-Key used with the PANA SA is the combination of both keys. Forsberg, et al. Expires April 20, 2005 [Page 66] Internet-Draft PANA October 2004 The PANA SA lifetime is bounded by the AAA-Key lifetime. Another execution of EAP method yields in a new AAA-Key, and updates the PANA SA, PANA_MAC_KEY and key ID. Upon PaC's movement to a another PAA (new PAA) and request to perform a context transfer based optimization, the current PAA computes a AAA-Key-int based on the AAA-Key, ID of new PAA, and the session ID. This AAA-Key-int is delivered to the new PAA, and used in the computation of AAA-Key-new, which further takes a pair of nonce values into account. After this point on, the AAA-Key-new becomes the AAA-Key between the PaC and the new PAA. When link-layer or network-layer ciphering [I-D.ietf-pana-ipsec] is enabled as a result of successful PANA authentication, a separate master key is generated based on the AAA-Key, session ID, key ID, and EP ID. The lifetime of this key is bounded by the lifetime of the PANA SA. This key may be used with a secure association protocol [I-D.ietf-ipsec-ikev2] to produce further cipher-specific and transient keys. 11.6 Per-packet Ciphering Networks that are not secured at the lower-layers prior to running PANA can rely on enabling per-packet data traffic ciphering upon successful PANA session establishment. The PANA framework allows generation of a master key from AAA-Key for using with a per-packet protection mechanism, such as link-layer or IPsec-based ciphering [I-D.ietf-pana-ipsec]. In case the master key is not readily useful to the ciphering mechanism, an additional secure association protocol [I-D.ietf-ipsec-ikev2] may be needed to produce the required keying material. These mechanisms ultimately establish a cryptographic binding between the data traffic generated by and for a client and the authenticated identity of the client. Data traffic must be minimally data origin authenticated, replay and integrity protected, and optionally encrypted. 11.7 PAA-to-EP Communication The PANA framework allows separation of PAA from EP(s). SNMPv3 [I-D.ietf-pana-snmp] is used between the the PAA and EP for provisioning authorized PaC information on the EP. This exchange MUST be always physically or cryptographically protected for authentication, integrity and replay protection. It MUST also be privacy-protected when per-PaC master key for per-packet ciphering is transmitted to the EP. Forsberg, et al. Expires April 20, 2005 [Page 67] Internet-Draft PANA October 2004 The per-packet ciphering master key MUST be unique to the PaC and EP pair. The session ID and EP's device ID are taken into computation for achieving this effect [I-D.ietf-pana-ipsec]. Compromise of an EP does not automatically lead to compromise of another EP or the PAA. 11.8 Livenes Test A PANA session is associated with a session lifetime. The session is terminated unless it is refreshed by a new round of EAP authentication before it expires. Therefore, at the latest a disconnected client can be detected when its lifetime expires. A disconnect may also be detected earlier by using PANA ping messages. A request message can be generated by either PaC or PAA at any time and the peer must respond with an answer message. A successful round-trip of this exchange is a simple verification that the peer is alive. This test can be engaged when there is a possibility that the peer might have disconnected (e.g., after discontinuation of data traffic). Periodic use of this exchange as a keep-alive requires additional care as it might result in congestion and hence false alarms. This exchange is cryptographically protected when a PANA SA is available in order to prevent threats associated with the abuse of this functionality. 11.9 Mobility Optimization The mobility optimization described in Section 4.12 involves the previous PAA providing a AAA-Key to the current PAA of the PaC. There are security risks stemming from potential compromise of PAAs. Compromise of the current PAA does not yield compromise of the previous PAA, as AAA-Key cannot be computed from a compromised AAA-Key-new. But a compromised previous PAA along with the intercepted nonce values on the current link leads to the compromise of AAA-Key-new. Operators should be aware of the potential risk of using this optimization. An operator can reduce the risk exposure by forcing the PaC to perform an EAP-based authentication immediately after the PaC gains access to new link via the optimized PANA execution. 11.10 Updating PaC's IP Address Even though the IP-Address AVP in a PANA-Update-Request can be cryptographically protected by the MAC AVP, there is not way to prove the ownership of the IP address presented by the PaC. Hence an authorized PaC can launch a redirect attack by spoofing a victim's IP address. Forsberg, et al. Expires April 20, 2005 [Page 68] Internet-Draft PANA October 2004 11.11 Early Termination of a Session The PANA protocol supports the ability for both the PaC and the PAA to transmit a tear-down message before the session lifetime expires. This message causes state removal, a stop of the accounting procedure and removes the installed per-PaC state on the EP(s). This message is cryptographically protected when PANA SA is present. Forsberg, et al. Expires April 20, 2005 [Page 69] Internet-Draft PANA October 2004 12. Acknowledgments We would like to thank Jari Arkko, Mohan Parthasarathy, Julien Bournelle, Rafael Marin Lopez, Pasi Eronen, Randy Turner, Erik Nordmark and all members of the PANA working group for their valuable comments to this document. Forsberg, et al. Expires April 20, 2005 [Page 70] Internet-Draft PANA October 2004 13. References 13.1 Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [RFC2988] Paxson, V. and M. Allman, "Computing TCP's Retransmission Timer", RFC 2988, November 2000. [RFC2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G. and J. Arkko, "Diameter Base Protocol", RFC 3588, September 2003. [RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462, December 1998. [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet Networks", RFC 2464, December 1998. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [RFC3456] Patel, B., Aboba, B., Kelly, S. and V. Gupta, "Dynamic Host Configuration Protocol (DHCPv4) Configuration of IPsec Tunnel Mode", RFC 3456, January 2003. [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J. and H. Levkowetz, "Extensible Authentication Protocol (EAP)", RFC 3748, June 2004. [I-D.ietf-eap-keying] Aboba, B., "Extensible Authentication Protocol (EAP) Key Management Framework", draft-ietf-eap-keying-03 (work in progress), July 2004. [IANA] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. Forsberg, et al. Expires April 20, 2005 [Page 71] Internet-Draft PANA October 2004 13.2 Informative References [I-D.ietf-pana-requirements] Yegin, A. and Y. Ohba, "Protocol for Carrying Authentication for Network Access (PANA)Requirements", draft-ietf-pana-requirements-09 (work in progress), August 2004. [RFC2522] Karn, P. and W. Simpson, "Photuris: Session-Key Management Protocol", RFC 2522, March 1999. [I-D.ietf-pana-threats-eval] Parthasarathy, M., "Protocol for Carrying Authentication and Network Access Threat Analysis and Security Requirements", draft-ietf-pana-threats-eval-07 (work in progress), August 2004. [I-D.ietf-pana-ipsec] Parthasarathy, M., "PANA enabling IPsec based Access Control", draft-ietf-pana-ipsec-04 (work in progress), September 2004. [I-D.ietf-pana-framework] Jayaraman, P., "PANA Framework", draft-ietf-pana-framework-02 (work in progress), September 2004. [I-D.ietf-pana-snmp] Mghazli, Y., Ohba, Y. and J. Bournelle, "SNMP usage for PAA-2-EP interface", draft-ietf-pana-snmp-01 (work in progress), July 2004. [I-D.irtf-aaaarch-handoff] Arbaugh, W. and B. Aboba, "Experimental Handoff Extension to RADIUS", draft-irtf-aaaarch-handoff-04 (work in progress), November 2003. [I-D.ietf-eap-statemachine] Vollbrecht, J., Eronen, P., Petroni, N. and Y. Ohba, "State Machines for Extensible Authentication Protocol (EAP) Peer and Authenticator", draft-ietf-eap-statemachine-05 (work in progress), September 2004. [I-D.ietf-seamoby-ctp] Loughney, J., "Context Transfer Protocol", draft-ietf-seamoby-ctp-11 (work in progress), August 2004. Forsberg, et al. Expires April 20, 2005 [Page 72] Internet-Draft PANA October 2004 [I-D.ietf-ipsec-ikev2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", draft-ietf-ipsec-ikev2-17 (work in progress), October 2004. [ianaweb] IANA, "Number assignment", http://www.iana.org. [IANA-EXP] Narten, T., "Assigning Experimental and Testing Numbers Considered Useful", BCP 82, RFC 3692, January 2004. Authors' Addresses Dan Forsberg Nokia Research Center P.O. Box 407 FIN-00045 NOKIA GROUP Finland Phone: +358 50 4839470 EMail: dan.forsberg@nokia.com Yoshihiro Ohba Toshiba America Research, Inc. 1 Telcordia Drive Piscataway, NJ 08854 USA Phone: +1 732 699 5305 EMail: yohba@tari.toshiba.com Basavaraj Patil Nokia 6000 Connection Dr. Irving, TX 75039 USA Phone: +1 972-894-6709 EMail: Basavaraj.Patil@nokia.com Forsberg, et al. Expires April 20, 2005 [Page 73] Internet-Draft PANA October 2004 Hannes Tschofenig Siemens Corporate Technology Otto-Hahn-Ring 6 81739 Munich Germany EMail: Hannes.Tschofenig@siemens.com Alper E. Yegin Samsung Advanced Institute of Technology 75 West Plumeria Drive San Jose, CA 95134 USA Phone: +1 408 544 5656 EMail: alper.yegin@samsung.com Forsberg, et al. Expires April 20, 2005 [Page 74] Internet-Draft PANA October 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. 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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Forsberg, et al. Expires April 20, 2005 [Page 75]