16ng Working Group J. Jee, Editor Internet-Draft ETRI Intended status: Informational S. Madanapalli Expires: May 21, 2008 LogicaCMG J. Mandin Runcom G. Montenegro Microsoft S. Park Samsung Electronics M. Riegel NSN November 18, 2007 IP over 802.16 Problem Statement and Goals draft-ietf-16ng-ps-goals-03.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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 May 21, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document specifies problems in running the IETF IP protocols Jee, Editor, et al. Expires May 21, 2008 [Page 1] Internet-Draft IP over 802.16 PS and Goals November 2007 over IEEE 802.16 networks by identifying specific gaps in the 802.16 MAC for IPv4 and IPv6 support. This document also provides an overview of IEEE 802.16 network characteristics and convergence sublayers. The common terminology to be used for the base guideline while defining the solution frameworks is also presented. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Overview of the IEEE 802.16-2004 MAC layer . . . . . . . . . . 5 3.1. Transport Connections . . . . . . . . . . . . . . . . . . 5 3.2. 802.16 PDU format . . . . . . . . . . . . . . . . . . . . 5 3.3. 802.16 Convergence Sublayer . . . . . . . . . . . . . . . 6 4. IP over IEEE 802.16 Problem Statement and Goals . . . . . . . 7 4.1. Root Problem . . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Point-to-Point Link model for IP CS: Problems . . . . . . 9 4.3. Ethernet like Link model for Ethernet CS: Problems . . . . 10 4.4. IP over IEEE 802.16 Goals . . . . . . . . . . . . . . . . 11 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 7. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Intellectual Property and Copyright Statements . . . . . . . . . . 14 Jee, Editor, et al. Expires May 21, 2008 [Page 2] Internet-Draft IP over 802.16 PS and Goals November 2007 1. Introduction Broadband Wireless Access networks address the inadequacies of low bandwidth wireless communication for user requirements such as high quality data/voice service, fast mobility, wide coverage, etc. The IEEE 802.16 Working Group on Broadband Wireless Access Standards develops standards and recommended practices to support the development and deployment of broadband Wireless Metropolitan Area Networks [IEEE802.16]. Recently, the WiMAX Forum, and, in particular, its NWG (Network Working Group) is defining the IEEE 802.16 network architecture (e.g., IPv4, IPv6, Mobility, Interworking with different networks, AAA, etc). The NWG is thus taking on work at layers above those defined by the IEEE 802 standards (typically limited to the physical and link layers only). Similarly, WiBro (Wireless Broadband), a Korean effort which focuses on the 2.3 GHz spectrum band, is also based on the IEEE 802.16 specification [IEEE802.16]. 802.16 [IEEE802.16] is point-to-point and connection-oriented at the MAC, physically arranged in a point-to-multipoint structure with the BS terminating one end of each connection and an individual SS terminating the other end of each connection. The 802.16 convergence sublayer (CS) is at the uppermost part of the MAC that is responsible for assigning transmit-direction Service Data Units (originating from a higher layer application - eg. an IP or Ethernet at the BS or SS) to a specific outbound transport connection. 802.16 defines two convergence sublayer types, the ATM CS and the Packet CS. The IP Specific Subpart (IP CS) and the 802.3 Ethernet Specific Subpart (Ethernet CS) of Packet CS is within the current 16ng WG scope. There exists complexity in configuring the IP Subnet over IEEE 802.16 network because of its point-to-point connection oriented feature and the existence of IP CS and Ethernet CS which assume different higher layer functionality. IP Subnet is a topological area that uses the same IP address prefix where that prefix is not further subdivided except into individual addresses as specified from [RFC4903]. The IP Subnet configuration is dependent on the underlying link layer's characteristic and decides the overall IP operation on the network. The IP CS and Ethernet CS of IEEE 802.16 assume different higher layer capability, like the IP routing functionality in case of IP CS and the bridging functionality in case of Ethernet CS. This means that underlying link layer's characteristics beneath IP can change according to the adopted convergence sublayers. This document provides the feasible IP Subnet model for each IP CS and Ethernet CS and specifies the problems in running IP protocols for each case. This document also presents an overview of 802.16 Jee, Editor, et al. Expires May 21, 2008 [Page 3] Internet-Draft IP over 802.16 PS and Goals November 2007 network characteristics specifically focusing on the convergence sublayers and the common terminology to be used for the base guideline while defining solution frameworks. 2. Terminology Subscriber Station (SS): An end-user equipment that provides connectivity to the 802.16 networks. It can be either fixed/nomadic or mobile equipment. In mobile environment, SS represents the Mobile Subscriber Station (MS) introduced in [IEEE802.16e]. Base Station (BS): A generalized equipment sets providing connectivity, management, and control between the subscriber station and the 802.16 networks. Access Router (AR): An entity that performs an IP routing function to provide IP connectivity for subscriber station (SS or MS). Protocol Data Unit (PDU): This refers to the data format passed from the lower edge of the 802.16 MAC to the 802.16 PHY, which typically contains Service Data Unit data after fragmentation, encryption, etc. Service Data Unit (SDU): This refers to the data format passed to the upper edge of the 802.16 MAC IP Subnet: Topological area that uses the same IP address prefix where that prefix is not further subdivided except into individual addresses as specified from [RFC4903]. Link: Topological area bounded by routers which decrement the IPv4 TTL or IPv6 Hop Limit when forwarding the packet as specified from [RFC4903]. Transport Connection: The MAC layer connection in 802.16 between a SS(MS) and BS with a specific QoS attributes. Several types of connections are defined and these include broadcast, unicast and multicast. Each transport connection is uniquely identified by a 16- bit connection identifier (CID). A transport connection is a unique connection intended for user traffic. The scope of the transport connection is between the SS(MS) and the BS. Connection Identifier (CID): A 16-bit value that identifies a connection to equivalent peers in the 802.16 MAC of the SS(MS) and BS. Ethernet CS: It means 802.3/Ethernet CS specific part of the Packet CS defined in 802.16 STD. Jee, Editor, et al. Expires May 21, 2008 [Page 4] Internet-Draft IP over 802.16 PS and Goals November 2007 802.1Q CS: It means 802.1Q (VLAN) specific part of the Packet CS defined in 802.16 STD. IP CS: It means IP specific subpart of the Packet CS defined in 802.16 STD. IPv4 CS: It means IP specific subpart of the Packet CS, Classifier 1 (Packet, IPv4) IPv6 CS: It means IP specific subpart of the Packet CS, Classifier 2 (Packet, IPv6). 3. Overview of the IEEE 802.16-2004 MAC layer 802.16 [IEEE802.16] is point-to-point and connection-oriented at the MAC, physically arranged in a point-to-multipoint structure with the BS terminating one end of each connection and an individual SS terminating the other end of each connection. Each node in the network possesses a 48-bit MAC address (though in the Base Station this 48-bit unique identifier is called "BSId"). The BS and SS learn each others' MAC Address/BSId during the SS's entry into the network. 3.1. Transport Connections User data traffic in both the BS-bound (uplink) and SS-bound (downlink) directions is carried on unidirectional "transport connections". Each transport connection has a particular set of associated parameters indicating characteristics such as cryptographic suite and quality-of-service. After successful entry of a SS to the 802.16 network, no data traffic is possible - as there are as yet no transport connections between the BS and SS. Transport connections are established by a 3-message signaling sequence within the MAC layer (usually initiated by the BS). A downlink-direction transport connection is regarded as "multicast" if it has been made available (via MAC signaling) to more than one SS. Uplink-direction connections are always unicast. 3.2. 802.16 PDU format An 802.16 PDU (ie. the format that is transmitted over the airlink) consists of a Generic MAC header, various optional subheaders, and a data payload. The 802.16 Generic MAC header carries the Connection Identifier (CID) Jee, Editor, et al. Expires May 21, 2008 [Page 5] Internet-Draft IP over 802.16 PS and Goals November 2007 of the connection with which the PDU is associated. We should observe that there is no source or destination address present in the raw 802.16 MAC header. 3.3. 802.16 Convergence Sublayer The 802.16 convergence sublayer (CS) is the component of the MAC that is responsible for mapping between the MAC service and the internal connection oriented service of the MAC CPS (Common Part Sublayer), through classification and encapsulation. The classification process assigns transmit-direction Service Data Units (originating from a higher layer application - eg. an IP stack at the BS or SS) to a specific outbound transport connection. The convergence sublayer maintains an ordered "classifier table". Each entry in the classifier table includes a classifier and a target CID. A classifier, in turn, consists of a conjunction of one or more subclassifiers - where each subclassifier specifies a packet field (eg. the destination MAC address in an Ethernet frame, or the TOS field of an IP datagram contained in an Ethernet frame) together with a particular value or range of values for the field. To perform classification on an outbound Service Data Unit, the convergence sublayer proceeds from the first entry of the classifier table to the last, and evaluates the fields of the Service Data Unit for a match with the table entry's classifier when a match is found, the convergence sublayer associates the Service Data Unit with the target CID (for eventual transmission), and the remainder of the 802.16 MAC and PHY processing can take place. 802.16 defines two convergence sublayer types, the ATM CS and the Packet CS. The ATM CS supports ATM directly. The Packet CS is subdivided into three specific subparts. o "The IP Specific Subpart" carries IP packets over a point-to-point connection. o "The 802.3 Ethernet Specific Subpart" carries packets encoded in the 802.3/Ethernet packet format with 802.3 style headers. o "The 802.1Q VLAN Specific Subpart" carries 802 style packets that contain 802.1Q VLAN Tags. Classifiers applied to connections at the time of connection establishment further classifies and subdivides the nature of the traffic over a connection. The classifications that apply to the Ethernet CS include packet over the 802.3/Ethernet CS, IPv4 over the 802.3/Ethernet CS, IPv6 over the 802.3/Ethernet CS, 802.3/Ethernet CS with ROHC header compression and Jee, Editor, et al. Expires May 21, 2008 [Page 6] Internet-Draft IP over 802.16 PS and Goals November 2007 802.3/Ethernet with ECRTP header compression. The classifications that apply to the 802.1Q/VLAN CS include IPv4 over 802.1Q/VLAN and IPv6 over 802.1Q/VLAN. It should be noted that while the 802.3/Ethernet CS has a packet classification that does not restrict the IP version (packet over the 802.3/Ethernet CS), the IP CS and 802.1Q/VLAN CS do. All the IP classifiers for those CSs are either IPv4 or IPv6. The classifiers enable the MAC to be sure of the presence of fields in the headers and so to be able to apply the payload header suppression (PHS) feature of 802.16 to those headers. For the sake of brevity in this document, the following naming conventions will be used for particular classifications of particular subparts of particular CSs. o IPv4 CS: Packet CS, IP Specific Subpart, Classifier 1 (Packet, IPv4) o IPv6 CS: Packet CS, IP Specific Subpart, Classifier 2 (Packet, IPv6) o Ethernet CS: Packet CS, 802.3/Ethernet Subpart, Classifier 3 (Packet, 802.3/Ethernet) An implementation of 802.16 can support multiple CS types. We can observe that the CS type, subpart and classification actually defines the type of data interface (eg. IPv4/IPv6 or 802.3) that is presented by 802.16 to the higher layer application. 4. IP over IEEE 802.16 Problem Statement and Goals 4.1. Root Problem The key issue when deploying IP over IEEE 802.16 network is how to configure an IP Subnet over that link which is connection-oriented and point-to-point in the MAC level. IP Subnet is a topological area that uses the same IP address prefix where that prefix is not further subdivided except into individual addresses. [RFC4903] There are three different IP Subnet models [RFC4968] that are possible for 802.16 network: 1) Point-to-point Link Model Jee, Editor, et al. Expires May 21, 2008 [Page 7] Internet-Draft IP over 802.16 PS and Goals November 2007 2) Ethernet like Link Model 3) Shared IPv6 Prefix Link Model The specific problems and issues when adopting the above IP Subnet models to the IEEE 802.16 network are like below: In the first point-to-point link model, each SS under a BS resides on the different IP Subnets. Therefore, only a certain SS and an AR exist under an IP Subnet and IP packets with destination address of link local scope are delivered only within the point-to-point link between a SS and an AR. The PPP [RFC1661] has been widely used for this kind of point-to-point link. However, the direct use of PPP is not possible on the 802.16 network because the 802.16 does not define a convergence sublayer which can encapsulate and decapsulate PPP frames. Therefore, there needs to be a mechanism to provide a point- to-point link between a SS and an AR in case of IP CS. The other alternative is to utilize the PPP over Ethernet by using the Ethernet CS. However, Ethernet CS assumes the upper layer's bridging functionality to realize the Ethernet like link model. In the second Ethernet like link model, all SSs under an AR reside on the same IP Subnet. This also applies when SSs are connected with different BSs. This Ethernet like link model assumes that underlying link layer provides the equivalent functionality like Ethernet, for example, native broadcast and multicast. It seems feasible to apply the 802.16's Ethernet CS to configure this link model. However, the 802.16's MAC feature is still connection-oriented not providing multicast and broadcast connection for IP packet transfer. There needs mechanisms like IEEE 802.1D to realize multicast and broadcast for Ethernet CS. Moreover, the frequent IP multicast and broadcast signaling within the IP subnet like Ethernet needs to be avoided not to wake up sleep/idle [IEEE802.16e] SSs. The last shared IPv6 prefix link model eventually results in multi- link subnet problems [RFC4903]. In 802.16, BS assigns separate 802.16 connections for SSs. Therefore, SSs are placed on the different links. In this situation, distributing shared IPv6 prefix for SSs which are placed on the different links causes the multi-link subnet problems. This is valid for IP CS and even to the Ethernet CS if any bridging functionality is not implemented on top of BS or between BS and AR. We identified the feasible IP Subnet models for IEEE 802.16 networks depending on the convergence sublayers. At the current stage, only the IP CS and Ethernet CS of IEEE 802.16 are within the 16ng scope. Followings are the feasible IP Subnet models for each convergence sublayer used. Jee, Editor, et al. Expires May 21, 2008 [Page 8] Internet-Draft IP over 802.16 PS and Goals November 2007 1. Point-to-Point Link model for IP CS. 2. Ethernet like Link Model for Ethernet CS. According to the point-to-point feature of 802.16's MAC, the Point- to-Point link model is the feasible IP Subnet model for IP CS under considering the multilink subnet problems. For the Ethernet CS, the Ethernet like link model is the feasible IP Subnet model. However, in this model unnecessary multicast and broadcast packets within an IP Subnet should be minimized. 4.2. Point-to-Point Link model for IP CS: Problems - Address Resolution: Address Resolution is the process by which IP nodes determine the link- layer address of a destination node on the same IP Subnet given only the destination's IP address. In case of IPCS, the ARP cache or Neighbor cache as 802.16 MAC address is never used as part of the 802.16 frame. Thus, performing the address resolution may be redundant in case of IPCS. For IPv4, blocking ARP needs to be implemented by SS itself in an implementation specific fashion not to send the unnecessary broadcast (Ethernet) frames over the air. For IPv6, address resolution is the function of IP layer and the IP reachability state is maintained through neighbor discovery packets. Therefore, blocking neighbor discovery packets would break the neighbor unreachability detection model. -Router Discovery: BS needs to send the RA with separate IP prefix in unicast manner for each SS explicitly to send periodic router advertisements in 802.16 Networks. - Prefix Assignment: Separate IP prefix should be distributed for each SS to locate them on different IP Subnets. When a SS moves between BSs under the same AR, the AR needs to redistribute the same IP Subnet prefix which the SS used at the previous BS. - Next-Hop: SS's next-hop always needs to be the AR which provides the IP connectivity at that access network. - Neighbor Unreachability Detection (NUD): Jee, Editor, et al. Expires May 21, 2008 [Page 9] Internet-Draft IP over 802.16 PS and Goals November 2007 Because SS always see an AR as the next hop, the NUD is required only for that AR. Also the requirement of NUD may depend on the existence of a connection to the BS for that particular destination. - Address Autoconfiguration: Because a unique prefix is assigned to each SS, the IP Subnet consists of only one SS and an AR. Therefore, duplicate address detection (DAD) is trivial. 4.3. Ethernet like Link model for Ethernet CS: Problems - Address Resolution: For Ethernet CS, sender needs to perform an address resolution to fill the destination Ethernet address field even though that address is not used for transmitting an 802.16 frame on the air. That Ethernet destination address is used for a BS or bridge to decide where to forward that Ethernet frame after decapsulating the 802.16 frame. When the destination's IP address has the same address prefix with its own, the sender should set the Ethernet frame's destination address as the destination itself. To acquire that address, the address resolution should be performed throughout conventional broadcast and multicast based ARP or NDP. However, if not filtered (e.g., [RFC4541]), these multicast and broadcast packets result in the problem of waking up the sleep/idle [IEEE802.16e] SSs. - Router Discovery: All SSs under the AR are located in the same broadcast domain in the Ethernet like link model. In this environment, sending periodic Router Advertisements with the destination of all-nodes multicast address results in the problem of waking up the sleep/idle [IEEE802.16e] SSs. - Prefix Assignment: Because the same IP prefix is shared with multiple SSs, an IP Subnet consists of multiple SSs and an AR. SS assumes that there exist on- link neighbors and tries to resolve the L2 address for the on-link prefixes. However, direct communication using link layer address between two SSs is not possible only with Ethernet CS without adding bridging functionality on top of BS or between BS and AR. - Next-Hop: When Ethernet CS is used and the accompanying Ethernet capability emulation is implemented, the next-hop for the destination IP with Jee, Editor, et al. Expires May 21, 2008 [Page 10] Internet-Draft IP over 802.16 PS and Goals November 2007 the same global prefix with the sender or link local address type should be the destination itself not an AR. - Neighbor Unreachability Detection (NUD): All SSs under the same AR are all the neighbors. Therefore, the NUD is required for all the SSs and AR. - Address Autoconfiguration: The duplicate address detection (DAD) should be performed among multiple SSs and an AR which are using the same IP prefix. The previous multicast based DAD cause the problem of waking up the sleep/idle [IEEE802.16e] SSs. 4.4. IP over IEEE 802.16 Goals The following are the goals in no particular order that point at relevant work to be done in IETF. Goal #1. Define the way to provide the point-to-point link model for IP CS. Goal #2. Reduce the power consumption caused by waking up sleep/idle [IEEE802.16e] terminals for Ethernet like link model. Goal #3. Do not cause multilink subnet problems. Goal #4. Provide the applicability of the previous security works like SEND [RFC3971]. Goal #5. Do not introduce any new security threats. 5. IANA Considerations This document does not require any actions from IANA. 6. Security Considerations This documents describes the problem statement and goals for IP over 802.16 networks and does not introduce any new security threats. 7. Acknowledgment The authors would like to express special thank to David Johnston for Jee, Editor, et al. Expires May 21, 2008 [Page 11] Internet-Draft IP over 802.16 PS and Goals November 2007 amending the section 4, "Overview of the IEEE 802.16-2006 MAC layer" and carefully reviewing the entire document and also to Phil Roberts for suggesting the reorganization of the document depending on the baseline IP subnet models. The authors also would like to express thank to Jari Arkko, HeeYoung Jung, Myung-Ki Shin, Eun-Kyoung Paik, Jaesun Cha and KWISF (Korea Wireless Internet Standardization Forum) for their comments and contributions. 8. References 8.1. Normative References [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, RFC 1661, July 1994. [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005. 8.2. Informative References [IEEE802.16] IEEE Std 802.16-2004, "IEEE Standard for Local and metropolitan area networks, Part 16: Air Interface for Fixed Broadband Wireless Access Systems", October 2004. [IEEE802.16e] IEEE Std 802.16e, "IEEE standard for Local and metropolitan area networks, Part 16:Air Interface for fixed and Mobile broadband wireless access systems", October 2005. [RFC4541] Christensen, M., Kimball, K., and F. Solensky, "Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches", RFC 4541, May 2006. [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, June 2007. [RFC4968] Madanapalli, S., "Analysis of IPv6 Link Models for 802.16 Based Networks", RFC 4968, August 2007. Jee, Editor, et al. Expires May 21, 2008 [Page 12] Internet-Draft IP over 802.16 PS and Goals November 2007 Authors' Addresses Junghoon Jee ETRI Email: jhjee@etri.re.kr Syam Madanapalli LogicaCMG Email: smadanapalli@gmail.com Jeff Mandin Runcom Email: jeff@streetwaves-networks.com gabriel_montenegro_2000@yahoo.com Microsoft Email: gabriel_montenegro_2000@yahoo.com Soohong Daniel Park Samsung Electronics Email: soohong.park@samsung.com Max Riegel Nokia Siemens Networks Email: maximilian.riegel@nsn.com Jee, Editor, et al. Expires May 21, 2008 [Page 13] Internet-Draft IP over 802.16 PS and Goals November 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property 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. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Jee, Editor, et al. Expires May 21, 2008 [Page 14]