Network Working Group J. Dong Internet-Draft M. Chen Intended status: Standards Track Huawei Technologies Expires: January 1, 2015 June 30, 2014 BGP Extensions for Path Computation Element (PCE) Discovery draft-dong-pce-discovery-proto-bgp-00 Abstract 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 the set of PCEs. As BGP has been extended for north-bound distribution of routing and LSP path information to PCE, the PCEs may not participate in Interior Gateway Protocol (IGP) for collecting the routing information, thus the IGP based PCE discovery cannot be used directly in these scenarios. This document specifies the BGP extensions for PCE discovery. 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 January 1, 2015. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. Dong & Chen Expires January 1, 2015 [Page 1] Internet-Draft BGP Extensions for PCE Discovery June 2014 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 . . . . . . . . . . 3 2.1. PCE Address Information . . . . . . . . . . . . . . . . . 3 2.2. PCE Discovery Attribute . . . . . . . . . . . . . . . . . 4 3. Operational Considerations . . . . . . . . . . . . . . . . . 5 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 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 the set of PCEs. As BGP will be used for north-bound distribution of routing and Label Switched Path (LSP) information to PCE[I-D.ietf-idr-ls-distribution] [I-D.ietf-idr-te-lsp-distribution] [I-D.ietf-idr-te-pm-bgp], the PCEs may not participate in Interior Gateway Protocol (IGP) for collecting the routing information, thus the IGP based PCE discovery mechanisms defined in [RFC5088] [RFC5089] cannot be used directly. This document proposes to extend BGP for PCE discovery in such scenarios. While 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 complemental to the existing IGP based mechanisms. Dong & Chen Expires January 1, 2015 [Page 2] Internet-Draft BGP Extensions for PCE Discovery June 2014 +---------+ | PCE | +---------+ ^ | | | | V +---------+ +--------->| BGP |<---------+ | +----| Speaker |----+ | | | +---------+ | | | | ^ | | | | | | | | | | V | V V | +---------+ +---------+ +---------+ | BGP | | BGP | | BGP | | Speaker | | Speaker | | Speaker | +---------+ +---------+ +---------+ ^ ^ ^ IGP(optional) | | | V V V +---------+ +---------+ +---------+ | PCC | | PCC | | PCC | +---------+ +---------+ +---------+ Figure 1. BGP for routing collection and 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 distributed from the network elements up to PCE, while the PCE discovery information is advertised from PCE down to PCCs. IGP based PCE discovery mechanism may be used for the distribution of PCE discovery information in each 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]. A new NLRI called PCE_ADDR NLRI is defined for carrying the PCE address information which can be used to reach the PCE. The AFI/SAFI value for the PCE_ADDR NLRI is TBD. In order for two BGP speakers to exchange PCE_ADDR NLRI, they MUST use BGP Capabilities Advertisement [RFC4760] to ensure that both are capable of properly processing such NLRI. This is done by using Capability Code 1 (which indicates Multiprotocol Extensions capabilities), with the AFI/SAFI pair for the PCE_ADDR NLRI. Dong & Chen Expires January 1, 2015 [Page 3] Internet-Draft BGP Extensions for PCE Discovery June 2014 The format of PCE_ADDR NLRI is shown as below: 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-Address (4 or 16 octets) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2. PCE_ADDR NLRI For PCEs identified by IPv4 address, the Type field SHOULD be set to 1, and the Length field SHOULD be set to 4. For PCEs identified by IPv6 address, the Type field SHOULD be set to 2, and the Length field SHOULD be set to 16. 2.2. PCE Discovery Attribute The detailed PCE discovery information is carried in a new optional non-transitive BGP attribute called PCE_DISC Attribute, which consists of a series of PCE Discovery TLVs for specific PCE information. The PCE_DISC attribute SHOULD only be used with PCE_ADDR NLRI. The format of the PCE Discovery TLV is shown as below: 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 TLVs (variable) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3. PCE Discovery TLVs The Type code and format of the PCE Discovery TLVs are consistent with the IGP PCED Sub-TLVs defined in [RFC5088] [RFC5089]. Type 1 is reserved, which is used in IGP based PCE discovery mechanisms to carry PCE Address . Dong & Chen Expires January 1, 2015 [Page 4] Internet-Draft BGP Extensions for PCE Discovery June 2014 TLV-Type Length Name 2 3 PATH-SCOPE TLV 3 variable PCE-DOMAIN TLV 4 variable NEIG-PCE-DOMAIN TLV 5 variable PCE-CAP-FLAGS TLV The PATH-SCOPE TLV MUST always be carried in the PCE_DISC Attribute. Other TLVs are optional and may facilitate the PCE selection. More PCE Discovery TLVs may be defined in future. 3. Operational Considerations Existing BGP operational procedures apply to the advertisement of PCE discovery information. Such information is treated as pure application level data which has no immediate impact on forwarding states. 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. 4. IANA Considerations IANA needs to assign new AFI and SAFI codes for PCE_ADDR NLRI from "Address Family Numbers" and "Subsequent Address Family Identifiers" registry. IANA needs to assign a new type code for "PCE_DISC" attribute from "BGP Path Attributes" registry. 5. Security Considerations Procedures and protocol extensions defined in this document do not affect the BGP security model. See [RFC6952] for details. 6. Acknowledgements The authors would like to thank Zhenbin Li for the discussion and comments. 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Dong & Chen Expires January 1, 2015 [Page 5] Internet-Draft BGP Extensions for PCE Discovery June 2014 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, January 2007. [RFC5088] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang, "OSPF Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5088, January 2008. [RFC5089] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang, "IS-IS Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5089, January 2008. [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, May 2013. 7.2. Informative 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-05 (work in progress), May 2014. [I-D.ietf-idr-te-lsp-distribution] Dong, J., Chen, M., Gredler, H., and S. Previdi, "Distribution of MPLS Traffic Engineering (TE) LSP State using BGP", draft-ietf-idr-te-lsp-distribution-00 (work in progress), January 2014. [I-D.ietf-idr-te-pm-bgp] Wu, Q., Danhua, W., Previdi, S., Gredler, H., and S. Ray, "BGP attribute for North-Bound Distribution of Traffic Engineering (TE) performance Metrics", draft-ietf-idr-te- pm-bgp-00 (work in progress), January 2014. Authors' Addresses Jie Dong Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: jie.dong@huawei.com Dong & Chen Expires January 1, 2015 [Page 6] Internet-Draft BGP Extensions for PCE Discovery June 2014 Mach(Guoyi) Chen Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: mach.chen@huawei.com Dong & Chen Expires January 1, 2015 [Page 7]