Network Working Group Renhai. Zhang Mach. Chen Internet Draft Huawei Technologies Co.,Ltd Expires: March 2007 October 12, 2006 Locate ASBR in PCE draft-zhang-pce-locate-asbr-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 April 12, 2007. Abstract The ability to compute constrained shortest Traffic Engineering (TE) Label Switched Paths (LSPs) in Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) networks across multiple domains has been identified as a key requirement. This document specifies a procedure for an inter-AS PCE to locate boundary node within its domain dynamically, which is used for path computation. Zhang & Chen Expires April 12, 2007 [Page 1] Internet-Draft draft-zhang-pce-locate-asbr-00.txt October 2006 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 RFC-2119 [1]. Table of Contents 1. Introduction................................................2 2. BGP extension...............................................3 2.1. EBGP Session Summary NLRI..............................3 2.2. ESSNP capability.......................................4 3. Procedure...................................................4 4. Example.....................................................5 5. Security Considerations.....................................6 6. IANA Considerations.........................................6 7. References..................................................6 7.1. Normative References...................................6 7.2. Informative References.................................6 Author's Addresses.............................................7 Intellectual Property Statement................................7 Disclaimer of Validity.........................................7 Copyright Statement............................................8 Acknowledgment.................................................8 1. Introduction The framework for inter-domain MPLS Traffic Engineering has been provided in [I-D.ietf-ccamp-inter-domain-framework]. An inter-AS PCE must have reachability information to the LSP tail- end and head-end. At minimum, this reachability information must include the AS path to the LSP tail-end, and the AS in which the tail-end and head-end of the LSP reside. Using this information, an inter-AS PCE can determine whether it can fully handle the path computation request by itself. PCE may obtain the reachability information using PCECP protocol extension, which is running between the ASBR and PCE. But this may increase the complexity of the ASBR. At the same time, PCE need make a selection among many ASBRs. So an IBGP session between an inter-AS PCE and each ASBR is a better choice. [BRPC] defines a PCE-based TE LSP computation method to compute optimal inter-domain constrained (G)MPLS TE LSPs. In this path Zhang & Chen Expires April 12, 2007 [Page 2] Internet-Draft draft-zhang-pce-locate-asbr-00.txt October 2006 computation method, an inter-AS PCE needs to locate ASBRs that provide connectivity from a specified AS. Network administrator could configure ASBRs information on the inter- AS PCE. But it may not be the best way. When the inter-AS link of an ASBR is down, the PCE may proceed the path computation without being aware of the situation.. Of course the result is that it can not get a successful path through this ASBR. In order to solve the problem, this document provides a method by which the PCE can dynamically obtain information on the ASBR and its interconnected AS. According to the above statement, MP-BGP is a good choice for an inter-AS PCE to achieve necessary information used in BRPC method. Thus, some extension to BGP is needed. 2. BGP extension EBGP speaker should report its connections to the inter-AS PCE. A new NLRI named EBGP Session Summary NLRI is introduced with extension to MP-BGP. 2.1. EBGP Session Summary NLRI The EBGP Session Summary NLRI is described below. A new AFI and SAFI need to be defined. +------------------------------------+ | Length (2 octets) | +------------------------------------+ | Router ID (4 octets) | +------------------------------------+ | AS Number (2 octets) | +------------------------------------+ / / / / / / +------------------------------------+ | Router ID (4 octets) | +------------------------------------+ | AS Number (2 octets) | +------------------------------------+ The use and the meaning of these fields are as follows: a) Length: Zhang & Chen Expires April 12, 2007 [Page 3] Internet-Draft draft-zhang-pce-locate-asbr-00.txt October 2006 The Length field indicates the length in bytes of the whole NLRI. b) Router ID: This field indicates the Router ID of the peer BGP speaker in the neighboring AS. c) AS Number: This field indicates the AS number of the BGP peer. The tuple of means an EBGP peer in a neighboring AS. It could appear more than once in the NLRI. With this information received from all EBGP speakers within its AS, an inter- AS PCE can have the knowledge of ASBRs in its AS and neighboring AS needed in path computation. 2.2. ESSNP capability New AFI and SAFI need to be defined and negotiated during BGP session establishment. It represents a capability to process EBGP Session Summary NLRI. We named this capability ESSNP (EBGP Session Summary NLRI Processing) here. As inter-AS PCE establish IBGP connections with all BGP speakers within its scope, with the ESSNP capability, it can have knowledge of the ASBRs within its domain and their corresponding interconnection of all neighboring ASes. Thus, when it computes using BRPC method, it can find appropriate ASBR. 3. Procedure When an ASBR establishes a new IBGP session with an inter-AS PCE, they SHOULD negotiate ESSNP capability firstly. Upon succeeding, the ASBR SHUOLD encapsulate each EBGP connection information in EBGP Session Summary NLRI, and send them to the PCE. When an EBGP speaker establishes a new EBGP connection, it SHUOLD encapsulate this connection information in EBGP Session Summary NLRI and send an update message to all the inter-AS PCEs that support ESSNP capability within the AS it resides in. When an EBGP connection of a speaker is down, it SHUOLD encapsulate this connection information in EBGP Session Summary NLRI and send a withdraw message to all the inter-AS PCEs that support ESSNP capability within the AS it resides in. Zhang & Chen Expires April 12, 2007 [Page 4] Internet-Draft draft-zhang-pce-locate-asbr-00.txt October 2006 4. Example An inter-AS PCE SHOULD build an EBGP Session Summary table to efficiently maintenance those information received from ASBR within its AS scope, using AS number or AS number combined with the Router ID of a neighboring ASBR as index to look up the local ASBR needed in computation. Let's see an example as follows: Inter-AS Inter-AS Inter-AS PCE1<---------->PCE2<--------------> PCE3 :: :: :: R1---ASBR1====ASBR3---R3---ASBR5====ASBR7---R5---R6 | | | | / | | | | | / | | | | | / | R2---ASBR2====ASBR4---R4---ASBR6 / R7 <==AS1=> <====AS2======> <=====AS3===> Figure 1 Inter-AS PCE Reference Model Assume that PCE1 received a computation request from R1 to R6. Then, this request is relayed to PCE3 eventually. The EBGP Session Summary table of PCE3 may be like this: AS number Router ID Local ASBR -------------------------------------------- AS2 ASBR5 ASBR7 AS2 ASBR6 ASBR7 Table 1: The EBGP Session Summary table for PCE3 PCE3 knows the request arriving from AS2. So it looks up Table 1 and finds the only ASBR connecting to AS2 is ASBR7. PCE3 computes and passes the result ASBR7-R5-R6-R7 to PCE2. The EBGP Session Summary table of PCE2 may be like this: AS number Router ID Local ASBR -------------------------------------------- AS1 ASBR1 ASBR3 AS1 ASBR2 ASBR4 AS3 ASBR7 ASBR5, ASBR6 Table 2: The EBGP Session Summary table for PCE2 Using AS3 and ASBR7 as index to look up Table 2, PCE2 will locate the ASBR in AS2 connecting to ASBR7 is ASBR5 and ASBR6. At the same time, PCE2 should locate ASBR connecting to AS1 because it should compute Zhang & Chen Expires April 12, 2007 [Page 5] Internet-Draft draft-zhang-pce-locate-asbr-00.txt October 2006 the path from those ASBRes to R7 and pass the partial result to PCE1. Using AS1 as index it will find ASBR3 and ASBR4. The computation continues as described in [BRPC]. 5. Security Considerations No new security issues are raised in this document. 6. IANA Considerations IANA is asked to allocate an AFI and SAFI for EBGP Statistic NLRI. 7. References 7.1. Normative References [BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, " A Backward Recursive PCE-based Computation (BRPC) procedure to compute shortest inter-domain Traffic Engineering Label Switched Paths ", draft-ietf-pce-brpc-00.txt, Work in Progress, August 2006. [RFC4655] A. Farrel, J.-P. Vasseur, J. Ash, " A Path Computation Element (PCE)-Based Architecture ", RFC 4655, August 2006. [BGP-MP] T. Bates, Y. Rekhter, R. Chandra, D. Katz, " Multiprotocol Extensions for BGP-4 ", RFC 2858, June 2000. 7.2. Informative References [2] Nabil Bitar, Jean-Louis Le Roux, Raymond Zhang, " Framework for PCE based inter-domain path computation ", draft-bitar-pce- inter-domain-frwk-00.txt, Work in Progress, June 2006. [BGP-CAP] R. Chandra, J. Scudder, " Capabilities Advertisement with BGP-4 ", RFC 3392, November 2002. Zhang & Chen Expires April 12, 2007 [Page 6] Internet-Draft draft-zhang-pce-locate-asbr-00.txt October 2006 Author's Addresses Renhai Zhang Huawei Technologies Co.,Ltd Email: zhangrenhai@huawei.com Mach chen Huawei Technologies Co.,Ltd Email: mach@huawei.com 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. 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. Disclaimer of Validity 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 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. Zhang & Chen Expires April 12, 2007 [Page 7] Internet-Draft draft-zhang-pce-locate-asbr-00.txt October 2006 Copyright Statement Copyright (C) The Internet Society (2006). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Zhang & Chen Expires April 12, 2007 [Page 8]