Network Working Group A. Takacs, D. Caviglia Internet Draft Ericsson Document: draft-takacs-asym-bw-lsp-00.txt Don Fedyk Expires: August 2007 Nortel February 2007 GMPLS RSVP-TE extension in support of bidirectional LSPs with asymmetric bandwidth requirements 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. Abstract GMPLS provides general connection control functionality supporting different network technologies. This memo specifies a further generalization to support bidirectional LSPs with asymmetric requirements. The extension improves the flexibility of bidirectional LSP establishment and at the same time simplifies the control and management of asymmetric services. 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. Takacs et al Expires - August 2007 [Page 1] draft-takacs-asym-bw-lsp-00.txt February 2007 Table of Contents 1. Introduction...................................................2 2. Motivation for RSVP-TE extension...............................3 3. Protocol extension.............................................4 3.1 UPSTREAM_TSPEC object......................................6 Security Considerations...........................................6 IANA Considerations...............................................6 References........................................................6 Author's Addresses................................................7 1. Introduction RSVP-TE extensions [RFC3209] define the messages and procedures for unidirectional LSP establishment for MPLS networks. Per RFC3209 in order to establish a bidirectional data flow two separate RSVP-TE signaling message flows are needed to set up unidirectional LSPs, one in Upstream and one in Downstream direction. This procedure has a number of drawbacks that will be illustrated in more detail in the next section. GMPLS RSVP-TE [RFC3473] generalizes the MPLS concept to support connection control of other networking technologies, such as SDH/SONET [G.707], OTN [G.709], lambda/wavelength switching, etc. Since traditional connection oriented circuit switched (co-cs) transport technologies (SDH/SONET) generally assume bidirectional symmetrical connections, GMPLS RSVP-TE adds support for that kind of connections. Symmetrical bidirectional LSPs are supported if both directions have the same traffic engineering requirements including fate sharing, protection and restoration, and resource requirements (e.g., bandwidth). However, in connection oriented packet switched (co-ps) networks (e.g., ATM, IP/MPLS) resource availability and reservation (e.g., bandwidth) are more flexible than with some technologies supported by, e.g., Time-Division-Multiplexing, Lambda- Switching or Fiber-Switching. Moreover some emerging new services such as video applications are, with respect to bandwidth, asymmetrical in nature. To efficiently support bidirectional LSP establishment in resource flexible co-ps networks while maintaining the possibility to set-up LSPs in only one signaling session, the restriction of symmetrical traffic engineering requirements should be relaxed. Specifically, asymmetrical resource requirements (e.g., bandwidth) should be supported. Takacs et al Expires - August 2007 [Page 2] draft-takacs-asym-bw-lsp-00.txt February 2007 2. Motivation for RSVP-TE extension The limitation of symmetrical resource requirements may pose difficulties for operators to efficiently support the services foreseen for next generation networks. Examples of emerging service definitions are the various Ethernet Virtual Circuits (EVCs) defined by the Metro Ethernet Forum (MEF). Customers can specify arbitrary resource requirements between the UNIs of an EVC. For more detail see [MEF.6][ETH-PARAM]. Currently, when asymmetrical bandwidth resources are required operators are forced to use separate LSPs for each direction. This procedure implies all the disadvantages noted in [RFC3471], and restated here for the sake of clarity. 1) The latency to establish the bidirectional LSP is equal to one round trip signaling time plus one initiator-terminator signaling transit delay. This not only extends the setup latency for successful LSP establishment, but it extends the worst-case latency for discovering an unsuccessful LSP to as much as two times the initiator-terminator transit delay. These delays are particularly significant for LSPs that are established for restoration purposes. 2) The control overhead is twice that of a unidirectional LSP. This is because separate control messages (e.g., Path and Resv) must be generated for both segments of the bidirectional LSP. 3) Because the resources are established in separate segments, route selection is complicated. There is also additional potential race for conditions in assignment of resources, which decreases the overall probability of successfully establishing the bidirectional connection. 4) It is more difficult to provide a clean interface for SONET/SDH equipment that may rely on bidirectional hop-by-hop paths for protection switching. 5) Bidirectional optical LSPs (or lightpaths) are seen as a requirement for many optical networking service providers. The need for bidirectional LSPs were raised for non PSC networks, however especially the first three points are equally applicable for the bidirectional asymmetric bandwidth LSPs of PSC networks as well. Moreover, in cases where the two LSPs require symmetric routes (i.e., have to traverse the same nodes and links); it is not simple to assure it. One possible way to force the two LSPs to use the same path is to record the route of the first LSP using the Record Route Takacs et al Expires - August 2007 [Page 3] draft-takacs-asym-bw-lsp-00.txt February 2007 object (RRO) and then use the information contained therein to fill the Explicit Route object (ERO) for the second LSP. In general the use of separate sessions complicates the management and troubleshooting of the network. Means must be provided by higher layer entities, e.g., the network management system (NMS), to correlate the LSPs not just from RSVP-TE but also from an OAM point of view. Additionally, translation functionality may be required to provide operators with a service oriented bidirectional abstraction hiding the complex control plane operation. With the extension of bidirectional LSPs with support for asymmetrical resource requirements, the complexity of establishing and maintaining LSPs can be reduced and as a result network management, fault handling and OAM will be improved. All the above considerations do not imply that the support for the set-up of an asymmetrical bidirectional LSP with two separate LSPs is removed. Indeed, adding the possibility to set-up an asymmetrical LSP with a single RSVP-TE message set will give to the operator the maximum degree of flexibility in set-up options it can choose from for a bi-bidirectional service: A) Symmetrical case: Single RSVP-TE message set with Upstream Label as per RFC 3471 and RFC 3473; B) Asymmetrical with diverse routed Upstream and Downstream traffic: Two independent LSPs with two RSVP-TE message sets without Upstream Label C) Asymmetrical with co-routed Upstream and Downstream traffic flow: Single LSP set-up with RSVP-TE message set extended as per this memo. 3. Protocol extension Only a small extension is needed to GMPLS RSVP-TE [RFC3473] to support asymmetric resource requirements for bidirectional LSPs. The current specification of RSVP-TE already supports bidirectional LSPs, the fact that an LSP is bidirectional is encoded in the presence of the UPSTREAM_LABEL object in the Path message [RFC 3471, RFC3473]. A PATH message requesting a bidirectional LSP includes an UPSTREAM_LABEL object as part of the sender description. The message format according to RFC3473 is as follows. Takacs et al Expires - August 2007 [Page 4] draft-takacs-asym-bw-lsp-00.txt February 2007 ::= [ ] [ [ | ] ... ] [ ] [ ] [ ] [ ... ] [ ] [ ] [ ] [ ... ] ::= [ ] [ ] [ ] [ ] The SENDER_TSPEC object provides the description of the data flow for the downstream direction. In order to provide means to signal different traffic characteristics for the upstream direction a new UPSTREAM_TSPEC object is defined that is optionally included in a PATH message. If no UPSTREAM_TSPEC object is present but an UPSTREAM_LABEL is specified, symmetric resource reservation should be made according to the SENDER_TSPEC information following RSVP-TE specifications [RFC 3471, RFC3473] without this extension. The sender description is extended as follows. ::= [ ] [ ] [ ] [ ] [ ] For the ease of introduction into existing implementations no specific position of the UPSTREAM_TSPEC object is suggested. The extension does not pose any backward compatibility issue. Takacs et al Expires - August 2007 [Page 5] draft-takacs-asym-bw-lsp-00.txt February 2007 3.1 UPSTREAM_TSPEC object The UPSTREAM_TSPEC has Class-Number TBA by IANA, in the form of "0bbbbbbb". C-Types and formats should match the already defined C- Types and formats of the SENDER_TSPEC object. Security Considerations RSVP message security is described in [RFC2747] and provides message integrity and node authentication. This document introduces no other new security considerations. IANA Considerations TBA. References [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V. and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001. [RFC3473] L. Berger, Editor, "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions, " RFC 3471, January 2003. [RFC3471] Berger, L., Editor, "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003. [G.707] ITU-T Recommendation G.707/Y.1322 (2000), "Network node interface for the synchronous digital hierarchy (SDH)." [G.709] ITU-T Recommendation G.709/Y.1331 (2001), Interfaces for the optical transport network (OTN). [MEF.6] Metro Ethernet Forum, MEF 6, "Ethernet Services Definitions - Phase 1," June 2004. [ETH-PARAM] Dimitri Papadimitriou, "MEF Ethernet Traffic Parameters," , October 2006. [RFC2747] Baker, F., Lindell, B. and M. Talwar, "RSVP Cryptographic Authentication", RFC 2747, January 2000. Takacs et al Expires - August 2007 [Page 6] draft-takacs-asym-bw-lsp-00.txt February 2007 Author's Addresses Attila Takacs Ericsson 1. Laborc u. 1037 Budapest, Hungary Phone: +36-1-4377044 Email: attila.takacs@ericsson.com Diego Caviglia Ericsson Via A. Negrone 1/A Genova-Sestri Ponente, Italy Phone: +390106003738 Email: diego.caviglia@marconi.com Don Fedyk Nortel Networks 600 Technology Park Drive Billerica, MA, USA 01821 Phone: +1-978-288-3041 Email: dwfedyk@nortel.com Takacs et al Expires - August 2007 [Page 7] draft-takacs-asym-bw-lsp-00.txt 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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