TSVWG F. Le Faucheur Internet-Draft Cisco Intended status: Standards Track J. Manner Expires: August 28, 2007 University of Helsinki A. Narayanan Cisco February 24, 2007 RSVP Extensions for Path-Triggered RSVP Receiver Proxy draft-ietf-tsvwg-rsvp-proxy-proto-00.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 August 28, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Le Faucheur, et al. Expires August 28, 2007 [Page 1] Internet-Draft RSVP Receiver Proxy Extensions February 2007 Abstract RSVP signaling can be used to make end-to-end resource reservations in an IP network in order to guarantee the QoS required by certain flows. With conventional RSVP, both the data sender and receiver of a given flow take part in RSVP signaling. Yet, there are many use cases where resource reservation is required, but the receiver, the sender, or both, is not RSVP-capable. Where the receiver is not RSVP-capable, an RSVP router may behave as an RSVP Receiver Proxy thereby performing RSVP signaling on behalf of the receiver. This allows resource reservations to be established on the segment of the end-to-end path from the sender to the RSVP Receiver Proxy. However, as discussed in the companion document presenting RSVP Proxy Approaches, RSVP extensions are needed to facilitate operations with an RSVP Receiver Proxy whose signaling is triggered by receipt of RSVP Path messages from the sender. This document specifies these extensions. Le Faucheur, et al. Expires August 28, 2007 [Page 2] Internet-Draft RSVP Receiver Proxy Extensions February 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Conventions Used in This Document . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. RSVP Extensions for Sender Notification . . . . . . . . . . . 7 3.1. Sender Notification via PathErr Message . . . . . . . . . 9 3.1.1. Composition of SESSION and . . . . 12 3.1.2. Composition of ERROR_SPEC . . . . . . . . . . . . . . 12 4. Security Considerations . . . . . . . . . . . . . . . . . . . 14 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 7. Normative References . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 Intellectual Property and Copyright Statements . . . . . . . . . . 19 Le Faucheur, et al. Expires August 28, 2007 [Page 3] Internet-Draft RSVP Receiver Proxy Extensions February 2007 1. Introduction Guaranteed QoS for some applications with tight Qos requirements may be achieved by reserving resources in each node on the end-to-end path. The main IETF protocol for these resource reservations is RSVP specified in [RFC2205]. RSVP does not require that all intermediate nodes support RSVP, however it assumes that both the sender and the receiver of the data flow support RSVP. There are environments where it would be useful to be able to reserve resources for a flow on at least a subset of the flow path even when the sender or the receiver (or both) is not RSVP-capable. Since either the data sender or receiver may be unaware of RSVP, there are two distinct use cases. In the first case, an entity in the network must operate on behalf of the data sender, generate an RSVP Path message, and eventually receive, process and sink a Resv message. We refer to this entity as the RSVP Sender Proxy. In the latter case, an entity in the network must receive a Path message sent by a data sender (or by an RSVP Sender Proxy), and reply to it with a Resv message on behalf of the data receiver(s). We refer to this entity as the RSVP Receiver Proxy. RSVP Proxy approaches are presented in [I-D.ietf-tsvwg-rsvp-proxy-approaches]. That document also discusses, for each approach, how the reservations controlled by the RSVP Proxy can be synchronised with the application requirements (e.g. when to establish, maintain, tear down the RSVP reservation to satisfy application requirements). One RSVP Proxy approach is referred to as the Path-Triggered RSVP Receiver Proxy approach. With this approach, the RSVP Receiver Proxy uses the RSVP Path messages generated by the sender as the cue for establishing the RSVP reservation on behalf of the non-RSVP-capable receiver. The RSVP Receiver Proxy is effectively acting as a slave making reservations (on behalf of the receiver) under the sender's control. This changes somewhat the usual RSVP reservation model where reservations are normally controlled by receivers. Such a change greatly facilitates operations in the scenario of interest here, which is where the receiver is not RSVP-capable. Indeed it allows the RSVP Receiver Proxy to remain application unaware by taking advantage of the application awareness and RSVP awareness of the sender. Since the synchronisation between RSVP reservation and application requirement is now effectively performed by the sender, it is important that the sender is aware of the reservation state. However, as conventional RSVP assumes that the reservation is to be controlled by the receiver, some notifications about reservation Le Faucheur, et al. Expires August 28, 2007 [Page 4] Internet-Draft RSVP Receiver Proxy Extensions February 2007 state (notably the error message sent in case of admission control rejection of the reservation) are only sent to the receiver. This document specifies extension to RSVP procedures allowing such notifications to be also conveyed to the sender. This facilitates synchronization by the sender between RSVP reservation and application requirements in scenarios involving a Path-Triggered RSVP receiver Proxy. 1.1. Conventions Used in This Document 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]. Le Faucheur, et al. Expires August 28, 2007 [Page 5] Internet-Draft RSVP Receiver Proxy Extensions February 2007 2. Terminology RSVP-capable (or RSVP-aware): which supports the RSVP protocol as per [RFC2205] RSVP Receiver Proxy: an RSVP-capable router performing, on behalf of a receiver, the RSVP operations which would normally be performed by an RSVP-capable receiver if end-to-end RSVP signaling was used. Note that while RSVP is used upstream of the RSVP Receiver Proxy, RSVP is not used downstream of the RSVP Receiver Proxy. RSVP Sender Proxy: an RSVP-capable router performing, on behalf of a sender, the RSVP operations which would normally be performed by an RSVP-capable sender if end-to-end RSVP signaling was used. Note that while RSVP is used downstream of the RSVP Sender Proxy, RSVP is not used upstream of the RSVP Sender Proxy. Regular RSVP Router: an RSVP-capable router which is not behaving as a RSVP Receiver Proxy nor as a RSVP Sender Proxy. Note that the roles of RSVP Receiver Proxy, RSVP Sender Proxy, Regular RSVP Router are all relative to one unidirectional flow. A given router may act as the RSVP Receiver Proxy for a flow, as the RSVP Sender Proxy for another flow and as a Regular RSVP router for yet another flow. Le Faucheur, et al. Expires August 28, 2007 [Page 6] Internet-Draft RSVP Receiver Proxy Extensions February 2007 3. RSVP Extensions for Sender Notification This section defines extensions to RSVP procedures allowing notification of the sender of reservation failure. This facilitates synchronization by the sender between RSVP reservation and application requirements in scenarios involving a Path-Triggered RSVP receiver Proxy. As discussed in [I-D.ietf-tsvwg-rsvp-proxy-approaches], with the Path-Triggered RSVP Receiver Proxy approach, the RSVP router may be configured to use receipt of a regular RSVP Path message as the trigger for RSVP Receiver Proxy behavior. On receipt of the RSVP Path message, the RSVP Receiver Proxy: 1. establishes the RSVP Path state as per regular RSVP processing 2. identifies the downstream interface towards the receiver 3. sinks the Path message 4. behaves as if a Resv message (whose details are discussed below) was received on the downstream interface. This includes performing admission control on the downstream interface, establishing a Resv state (in case of successful admission control) and forwarding the Resv message upstream, sending periodic refreshes of the Resv message and tearing down the reservation if the Path state is torn down. Operation of the Path-Triggered Receiver Proxy in the case of a successful reservation is illustrated in Figure 1. Le Faucheur, et al. Expires August 28, 2007 [Page 7] Internet-Draft RSVP Receiver Proxy Extensions February 2007 |----| *** *** |----------| |----| | S |---------*r*----------*r*---------| RSVP |----------| R | |----| *** *** | Receiver | |----| | Proxy | |----------| *************************************************************> ===================RSVP======================> ---Path---> ----Path----> ---Path----> <--Resv---> <---Resv----- <--Resv---- |----| RSVP-capable |----| Non-RSCP-capable *** | S | Sender | R | Receiver *r* regular RSVP |----| |----| *** router ***> media flow ==> segment of flow path protected by RSVP reservation Figure 1: Successful Reservation We observe that, in the case of successful reservation, conventional RSVP procedures ensure that the sender is notified of the successful reservation establishment. Thus, no extensions are required in the presence of a Path-Triggered RSVP Receiver Proxy in the case of succesful reservation establishment. However, in case of reservation failure, conventional RSVP procedures only ensure that the receiver (or the RSVP Receiver Proxy) is notified of the reservation failure. Specifically, in case of an admission control rejection on a regular RSVP router, a ResvErr message is sent downstream towards the receiver. In the presence of an RSVP Receiver Proxy, if we simply follow conventional RSVP procedures, this means that the RSVP Receiver Proxy is notified of the reservation failure, but the sender does not. Operation of the Path-Triggered RSVP Receiver Proxy in the case of an admission control failure, assuming conventional RSVP procedures, is illustrated in Figure 2. Le Faucheur, et al. Expires August 28, 2007 [Page 8] Internet-Draft RSVP Receiver Proxy Extensions February 2007 |----| *** *** |----------| |----| | S |---------*r*----------*r*---------| RSVP |----------| R | |----| *** *** | Receiver | |----| | Proxy | |----------| *************************************************************> ===================RSVP======================> ---Path---> ----Path----> ---Path----> <---Resv----- <--Resv------ ---ResvErr---> --ResvErr---> |----| |----| *** | S | Sender | R | Receiver *r* regular RSVP |----| |----| *** router ***> media flow ==> segment of flow path protected by RSVP reservation Figure 2: Reservation Failure With Conventional RSVP While the sender could infer reservation failure from the fact that it has not received a Resv message after a certain time, there are clear benefits in ensuring that the sender gets a prompt explicit notification in case of reservation failure. Section 3.1 defines a method which can be used to achieve sender notification of reservation failure. An implementation of this document MUST support the method defined in Section 3.1. 3.1. Sender Notification via PathErr Message With this method, the RSVP Receiver Proxy MUST generate a PathErr message whenever the two following conditions are met: 1. The reservation establishment has failed (or the previously established reservation has been torn down) 2. The RSVP Receiver Proxy determines that it cannot re-establish the reservation (e.g. by adapting its reservation request in Le Faucheur, et al. Expires August 28, 2007 [Page 9] Internet-Draft RSVP Receiver Proxy Extensions February 2007 reaction to the error code provided in the received ResvErr in accordance with local policy) Operation of the Path-Triggered RSVP Receiver Proxy in the case of an admission control failure, using sender notification via PathErr Message, is illustrated in Figure 3. |----| *** *** |----------| |----| | S |---------*r*----------*r*---------| RSVP |----------| R | |----| *** *** | Receiver | |----| | Proxy | |----------| *************************************************************> ===================RSVP======================> ---Path---> ----Path----> ---Path----> <---Resv----- <--Resv------ ---ResvErr---> --ResvErr---> <--PathErr- <--PathErr--- <--PathErr--- |----| |----| *** | S | Sender | R | Receiver *r* regular RSVP |----| |----| *** router ***> media flow ==> segment of flow path protected by RSVP reservation Figure 3: Reservation Failure With Sender Notification The role of this PathErr is to notify the sender that the reservation was not established or was torn down. This may be in the case of receipt of a ResvErr, or because of local failure on the Receiver Proxy. On receipt of a ResvErr, in all situations where the reservation cannot be installed, the Receiver Proxy MUST generate a PathErr towards the sender. For local failures on the Receiver Proxy node, if a similar failure on an RSVP midpoint would cause the generation of a ResvErr (for example, CAC failure), the Receiver Proxy MUST generate a PathErr towards the sender. The Receiver Proxy Le Faucheur, et al. Expires August 28, 2007 [Page 10] Internet-Draft RSVP Receiver Proxy Extensions February 2007 MAY additionally generate a PathErr upon local failures which would not ordinarily cause generation of a ResvErr message, such as described in Appendix B of [RFC2205]. The PathErr generated by the Receiver Proxy corresponds to the sender(s) which triggered generation of Resv messages that failed. For Fixed-Filter (FF) style reservations, the Receiver Proxy sends a PathErr towards the (single) sender matching the failed reservation. For Shared-Explicit (SE) style reservations, the Receiver Proxy sends the PathErr(s) towards the set of senders which triggered reservations that failed. This may be a subset of senders sharing the same reservation, in which case the remaining senders would have their reservation intact and would not receive a PathErr. In both cases, the rules described in Section 3.1.8 of [RFC2205] for generating flow descriptors in ResvErrs, also apply for generating sender descriptors in PathErrs. For Wildcard-Filter (WF) style reservations, it is not possible for the receiver to know which sender caused the reservation failure. Therefore, the procedures described in this section do not apply to WF-style reservations. The procedures described in this section apply to both unicast and multicast sessions. However, for a multicast session, it is possible that reservation failure (e.g. admission control failure) in a node close to a sender may cause ResvErr messages to be sent to a large group of receivers. These receivers would, in turn, all send PathErr messages back to the same sender, which could cause a scalability issue in some environments. From the perspective of the sender, errors that prevent a reservation from being set up can be classified in two ways: 1. Errors which the sender can attempt to correct. The error code for those errors should explicitly be communicated back to the sender. An examples of this is "Class 1: Admission Control Failure", because the sender could potentially resend a Path with smaller traffic parameters. 2. Errors which the sender has no control over. For these errors, it is sufficient to notify the sender that the reservation was not set up successfully. An example of this is "Class 13: Unknown Object", because the sender has no control over the objects inserted into the reservation by the Receiver Proxy. The PathErr message generated by the Receiver Proxy has the same format as regular PathErr messages defined in [RFC2205]. The SESSION, ERROR_SPEC and sender descriptor are composed by the Receiver Proxy as specified in the following subsections. The Receiver Proxy MAY reflect back to the sender in the PathErr any POLICY_DATA objects received in the ResvErr. Le Faucheur, et al. Expires August 28, 2007 [Page 11] Internet-Draft RSVP Receiver Proxy Extensions February 2007 3.1.1. Composition of SESSION and The Receiver Proxy MUST insert the SESSION object corresponding to the failed reservation, into the PathErr. For Fixed-Filter (FF) style reservations, the Receiver Proxy MUST insert a corresponding to the failed reservation, into the PathErr. This is equal to the in the ResvErr received by the Receiver Proxy. For Shared-Explicit (SE) style reservations, the Receiver Proxy MUST insert a corresponding to the sender triggering the failed reservation, into the PathErr. This is equal to the in the ResvErr received by the Receiver Proxy. If multiple could not be admitted at a midpoint node, that node would generate multiple ResvErrs towards the receiver as per Section 3.1.8 of [RFC2205]. Each ResvErr would contain a that matches a specific sender. The Receiver Proxy MUST generate a PathErr for each ResvErr received, towards the corresponding sender. 3.1.2. Composition of ERROR_SPEC The Receiver Proxy MUST compose the ERROR_SPEC to be inserted into the PathErr as follows: 1. If the Receiver Proxy receives a ResvErr with any of these error codes: "Code 1 - Admission Control Failure" or "Code 2 - Policy Control Failure" then the Receiver Proxy copies the error code and value from the ERROR_SPEC in the ResvErr, into the ERROR_SPEC of the PathErr message. The error node in the PathErr MUST be set to the address of the Receiver Proxy. This procedure MUST also be followed for a local error on the Receiver Proxy that would ordinarily cause a midpoint to generate a ResvErr with one of the above codes. 2. If the Receiver Proxy receives a ResvErr with any error code other than the ones listed in 1. above, it composes a new ERROR_SPEC with error code ": Unrecoverable Receiver Proxy error" and error value "". The error node in the PathErr MUST be set to the address of the Receiver Proxy. This procedure MUST also be followed for a local error on the Receiver Proxy that would ordinarily cause a midpoint to generate a ResvErr with any error code except in 1) above, or if the Receiver Proxy generates a PathErr for a local error which ordinarily would not cause generation of a ResvErr. In some cases it may be predetermined that the PathErr will not reach the sender. For example, a node receiving a ResvErr with "Code 3: No Path for Resv", knows a priori that the PathErr message it generates cannot be forwarded by the same node which could not process the Resv. Nevertheless, the procedures above MUST be followed. Use Le Faucheur, et al. Expires August 28, 2007 [Page 12] Internet-Draft RSVP Receiver Proxy Extensions February 2007 of extensions such as the Notify message defined in [RFC3473] may be investigated in the future to address this issue. Le Faucheur, et al. Expires August 28, 2007 [Page 13] Internet-Draft RSVP Receiver Proxy Extensions February 2007 4. Security Considerations To be added. Le Faucheur, et al. Expires August 28, 2007 [Page 14] Internet-Draft RSVP Receiver Proxy Extensions February 2007 5. IANA Considerations This document requires that IANA allocates a new RSVP Error Code ": Unrecoverable Receiver Proxy error" as discussed in Section 3.1.2. Le Faucheur, et al. Expires August 28, 2007 [Page 15] Internet-Draft RSVP Receiver Proxy Extensions February 2007 6. Acknowledgments This document benefited from discussions with Carol Iturralde and Amca Zamfir. Le Faucheur, et al. Expires August 28, 2007 [Page 16] Internet-Draft RSVP Receiver Proxy Extensions February 2007 7. Normative References [I-D.ietf-tsvwg-rsvp-proxy-approaches] Le Faucheur, L., "RSVP Proxy Approaches", February 2007. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, September 1997. [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. Le Faucheur, et al. Expires August 28, 2007 [Page 17] Internet-Draft RSVP Receiver Proxy Extensions February 2007 Authors' Addresses Francois Le Faucheur Cisco Systems Greenside, 400 Avenue de Roumanille Sophia Antipolis 06410 France Phone: +33 4 97 23 26 19 Email: flefauch@cisco.com Jukka Manner University of Helsinki P.O. Box 68 University of Helsinki FIN-00014 University of Helsinki Finland Phone: +358 9 191 51298 Email: jmanner@cs.helsinki.fi URI: http://www.cs.helsinki.fi/u/jmanner/ Ashok Narayan Cisco Systems 300 Beaver Brook Road Boxborough, MAS 01719 United States Email: ashokn@cisco.com Le Faucheur, et al. Expires August 28, 2007 [Page 18] Internet-Draft RSVP Receiver Proxy Extensions February 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. 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