Network Working Group J. Dong Internet-Draft M. Chen Intended status: Standards Track D. Dhody Expires: March 4, 2016 Huawei Technologies J. Tantsura Ericsson September 1, 2015 BGP Extensions for Path Computation Element (PCE) Discovery draft-dong-pce-discovery-proto-bgp-03 Abstract In networks where Path Computation Element (PCE) is used for centralized path computation, it is desirable for Path Computation Clients (PCCs) to automatically discover a set of PCEs and select the suitable ones to establish the PCEP session. RFC 5088 and RFC 5089 define the PCE discovery mechanisms based on Interior Gateway Protocols (IGP). This document describes several scenarios in which the IGP based PCE discovery mechanisms cannot be used directly. This document specifies the BGP extensions for PCE discovery in these scenarios. The BGP based PCE discovery mechanism is complementary to the existing IGP based mechanisms. Requirements Language 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 [RFC2119]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on March 4, 2016. Dong, et al. Expires March 4, 2016 [Page 1] Internet-Draft BGP Extensions for PCE Discovery September 2015 Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Carrying PCE Discovery Information in BGP . . . . . . . . . . 4 2.1. PCE Address Information . . . . . . . . . . . . . . . . . 4 2.2. PCE Discovery TLVs . . . . . . . . . . . . . . . . . . . 5 3. Operational Considerations . . . . . . . . . . . . . . . . . 6 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 7.1. Normative References . . . . . . . . . . . . . . . . . . 7 7.2. Informative References . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction In network scenarios where Path Computation Element (PCE) is used for centralized path computation, it is desirable for Path Computation Clients (PCCs) to automatically discover a set of PCEs and select the suitable ones to establish the PCEP session. [RFC5088] and [RFC5089] define the PCE discovery mechanisms based on Interior Gateway Protocols (IGP). Those IGP based mechanisms may not work in several scenarios where the PCEs do not participate in the IGP, and it is difficult for PCEs to participate in multiple IGP domains where PCE discovery is needed. In some scenarios, Backward Recursive Path Computation (BRPC) [RFC5441] can be used by cooperating PCEs to compute inter-domain path, in which case these cooperating PCEs should be known to each other in advance. In case of inter-AS networks where the PCEs do not participate in a common IGP, the existing IGP discovery mechanism cannot be used to discover the PCEs in other domains. Dong, et al. Expires March 4, 2016 [Page 2] Internet-Draft BGP Extensions for PCE Discovery September 2015 In the Hierarchical PCE scenario [RFC6805], the child PCEs need to know the address of the parent PCEs. This cannot be achieved through IGP based discovery, as normally the child PCEs and the parent PCE are under different administration and reside in different domains. Besides, as BGP could be used for north-bound distribution of routing and Label Switched Path (LSP) information to PCE as described in [I-D.ietf-idr-ls-distribution] [I-D.ietf-idr-te-lsp-distribution] and [I-D.ietf-idr-te-pm-bgp], PCEs can obtain the routing information without participating in IGP. In this scenario, some other PCE discovery mechanism is needed. A detailed set of requirements for a PCE discovery mechanism are provided in [RFC4674]. This document proposes to extend BGP for PCE discovery in the above scenarios. In networks where BGP-LS is used for the north-bound routing information distribution to PCE, the BGP based PCE discovery can reuse the existing BGP sessions and mechanisms to achieve PCE discovery. It should be noted that in each IGP domain, the IGP based PCE discovery mechanism may be used in conjunction with the BGP based PCE discovery. Thus the BGP based PCE discovery is complementary to the existing IGP based mechanisms. Dong, et al. Expires March 4, 2016 [Page 3] Internet-Draft BGP Extensions for PCE Discovery September 2015 +-----------+ | PCE | +-----------+ | v +-----------+ | BGP | +-----------+ | Speaker | | PCE | +-----------+ +-----------+ | | | | | | | | +---------------+ | +-------------------+ | v v v v +-----------+ +-----------+ +-----------+ | BGP | | BGP | | BGP | | Speaker | | Speaker | . . . | Speaker | | & PCC | | & PCC | | | +-----------+ +-----------+ +-----------+ | | via | IGP v +-----------+ | PCC | +-----------+ Figure 1: BGP for PCE discovery As shown in the network architecture in Figure 1, BGP is used for both routing information distribution and PCE information discovery. The routing information is collected from the network elements and distributed to PCE, while the PCE discovery information is advertised from PCE to PCCs, or between different PCEs. The PCCs maybe co- located with the BGP speakers as shown in Figure 1. The IGP based PCE discovery mechanism may be used for the distribution of PCE discovery information in IGP domain. 2. Carrying PCE Discovery Information in BGP 2.1. PCE Address Information The PCE discovery information is advertised in BGP UPDATE messages using the MP_REACH_NLRI and MP_UNREACH_NLRI attributes [RFC4760]. The AFI and SAFI defined in [I-D.ietf-idr-ls-distribution] are re- used, and a new NLRI Type is defined for PCE discovery information as below: Dong, et al. Expires March 4, 2016 [Page 4] Internet-Draft BGP Extensions for PCE Discovery September 2015 o Type = TBD: PCE Discovery NLRI The format of PCE Discovery NLRI is shown in the following figure: 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 +-+-+-+-+-+-+-+-+ | Protocol-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | | (64 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ PCE-Address (4 or 16 octets) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2. PCE Discovery NLRI The 'Protocol-ID' field SHOULD be set to a new value which indicates the information source protocol is PCE. +-------------+----------------------------------+ | Protocol-ID | NLRI information source protocol | +-------------+----------------------------------+ | TBD | PCE | +-------------+----------------------------------+ As defined in [I-D.ietf-idr-ls-distribution], the 64-Bit 'Identifier' field is used to identify the "routing universe" where the PCE belongs. 2.2. PCE Discovery TLVs The detailed PCE discovery information is carried in the BGP-LS attribute [I-D.ietf-idr-ls-distribution] with a new "PCE Discovery TLV", which contains a set of sub-TLVs for specific PCE discovery information. The PCE Discovery TLV and sub-TLVs SHOULD only be used with the PCE Discovery NLRI. The format of the PCE Discovery TLV is shown as below: Dong, et al. Expires March 4, 2016 [Page 5] Internet-Draft BGP Extensions for PCE Discovery September 2015 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ PCE Discovery Sub-TLVs (variable) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3. PCE Discovery TLV The PCE Discovery sub-TLVs are listed as below. The format of the PCE Discovery sub-TLVs are consistent with the IGP PCED sub-TLVs as defined in [RFC5088] and [RFC5089]. The PATH-SCOPE sub-TLV MUST always be carried in the PCE Discovery TLV. Other PCE Discovery sub- TLVs are optional and may facilitate the PCE selection process on the PCCs. Type | Length | Name ------+------------+-------------------------------- TBD | 3 | PATH-SCOPE sub-TLV TBD | variable | PCE-CAP-FLAGS sub-TLV TBD | variable | OSPF-PCE-DOMAIN sub-TLV TBD | variable | IS-IS-PCE-DOMAIN sub-TLV TBD | variable | OSPF-NEIG-PCE-DOMAIN sub-TLV TBD | variable | IS-IS-NEIG-PCE-DOMAIN sub-TLV More PCE Discovery sub-TLVs may be defined in future and the format SHOULD be in line with the new sub-TLVs defined for IGP based PCE discovery. 3. Operational Considerations Existing BGP operational procedures apply to the advertisement of PCE discovery information. This information is treated as pure application level data which has no immediate impact on forwarding states. Normal BGP path selection can be applied to PCE Discovery NLRI only for the information propagation in the network, while the PCE selection on the PCCs would be based on the information carried in the PCE Discovery TLV. The PCE discovery information is considered relatively stable and does not change frequently, thus this information will not bring significant impact on the amount of BGP updates in the network. Dong, et al. Expires March 4, 2016 [Page 6] Internet-Draft BGP Extensions for PCE Discovery September 2015 4. IANA Considerations IANA needs to assign a new NLRI Type for 'PCE Discovery NLRI' from the "BGP-LS NLRI-Types" registry. IANA needs to assign a new Protocol-ID for "PCE" from the "BGP-LS Protocol-IDs" registry. IANA needs to assign a new TLV code point for 'PCE Discovery TLV' from the "node anchor, link descriptor and link attribute TLVs" registry. IANA needs to create a new registry for "PCE Discovery Sub-TLVs". The registry will be initialized as shown in section 2.2 of this document. 5. Security Considerations Procedures and protocol extensions defined in this document do not affect the BGP security model. See the 'Security Considerations' section of [RFC4271] for a discussion of BGP security. Also refer to [RFC4272] and [RFC6952] for analysis of security issues for BGP. 6. Acknowledgements The authors would like to thank Zhenbin Li and Hannes Gredler for their discussion and comments. 7. References 7.1. Normative References [I-D.ietf-idr-ls-distribution] Gredler, H., Medved, J., Previdi, S., Farrel, A., and S. Ray, "North-Bound Distribution of Link-State and TE Information using BGP", draft-ietf-idr-ls-distribution-11 (work in progress), June 2015. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, January 2006, . Dong, et al. Expires March 4, 2016 [Page 7] Internet-Draft BGP Extensions for PCE Discovery September 2015 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, DOI 10.17487/RFC4760, January 2007, . [RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R. Zhang, "OSPF Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5088, DOI 10.17487/RFC5088, January 2008, . [RFC5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R. Zhang, "IS-IS Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5089, DOI 10.17487/RFC5089, January 2008, . 7.2. Informative References [I-D.ietf-idr-te-lsp-distribution] Dong, J., Chen, M., Gredler, H., Previdi, S., and J. Tantsura, "Distribution of MPLS Traffic Engineering (TE) LSP State using BGP", draft-ietf-idr-te-lsp- distribution-03 (work in progress), May 2015. [I-D.ietf-idr-te-pm-bgp] Wu, Q., Previdi, S., Gredler, H., Ray, S., and J. Tantsura, "BGP attribute for North-Bound Distribution of Traffic Engineering (TE) performance Metrics", draft-ietf- idr-te-pm-bgp-02 (work in progress), January 2015. [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", RFC 4272, DOI 10.17487/RFC4272, January 2006, . [RFC4674] Le Roux, J., Ed., "Requirements for Path Computation Element (PCE) Discovery", RFC 4674, DOI 10.17487/RFC4674, October 2006, . [RFC5441] Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux, "A Backward-Recursive PCE-Based Computation (BRPC) Procedure to Compute Shortest Constrained Inter-Domain Traffic Engineering Label Switched Paths", RFC 5441, DOI 10.17487/RFC5441, April 2009, . Dong, et al. Expires March 4, 2016 [Page 8] Internet-Draft BGP Extensions for PCE Discovery September 2015 [RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the Path Computation Element Architecture to the Determination of a Sequence of Domains in MPLS and GMPLS", RFC 6805, DOI 10.17487/RFC6805, November 2012, . [RFC6952] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of BGP, LDP, PCEP, and MSDP Issues According to the Keying and Authentication for Routing Protocols (KARP) Design Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013, . Authors' Addresses Jie Dong Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: jie.dong@huawei.com Mach(Guoyi) Chen Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: mach.chen@huawei.com Dhruv Dhody Huawei Technologies Leela Palace Bangalore, Karnataka 560008 India Email: dhruv.ietf@gmail.com Jeff Tantsura Ericsson 300 Holger Way San Jose, CA 95134 US Email: jeff.tantsura@ericsson.com Dong, et al. Expires March 4, 2016 [Page 9]