Network Working Group Internet Draft K. Kumaki, Ed. Category: standard track KDDI R&D Labs Created: April 18, 2008 T. Murai Expires: October 18, 2008 FURUKAWA NETWORK SOLUTION CORP. BGP protocol extensions for Path Computation Element (PCE) Discovery in a BGP/MPLS IP-VPN draft-kumaki-pce-bgp-disco-attribute-01.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. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract It is highly desirable for Path Computation Clients (PCCs) to be able to dynamically discover a set of Path Computation Elements (PCEs) when PCCs/PCEs request a path computation to PCEs within an AS and across ASs. In such a scenario, specifically BGP/MPLS IP-VPNs, it is advantageous to use BGP to distribute PCE information. This K.Kumaki, et al. [Page 1] draft-kumaki-pce-bgp-disco-attribute-01 April 2008 document defines a new attribute and describes how PCE information can be carried using BGP. Table of Contents 1. Introduction..................................................2 2. Terminology...................................................3 3. PCE Information...............................................4 3.1 BGP PCE Discovery Attribute..............................4 4. BGP Specific Procedure........................................5 5. Security Considerations.......................................5 6. IANA Considerations...........................................6 7. References....................................................6 7.1 Normative References.......................................6 7.2 Informative References.....................................6 8. Acknowledgments................................................6 9. Author's Addresses.............................................6 1. Introduction [RFC4655] describes the motivations and architecture for a Path Computation Element (PCE)-based path computation model for Multi Protocol Label Switching (MPLS) / Generalized MPLS (GMPLS) Traffic Engineering (TE) Label Switched Paths (LSPs). In this model, path computation requests are issued by a PCC to PCE that may be composite or external. In case the PCC and PCE are not composite, a request/response communication protocol is required to carry the request and return the response. The requirements for such a communication protocol are described in [RFC4657]. The communication protocol between PCC and PCE, and between PCEs, is defined in [PCEP]. In order for a PCC and PCE to communicate, the PCC must know the location of the PCE. Also, in order for PCEs to communicate, the PCE must know the location of another PCE as well. Actually, a number of PCEs can be contained in BGP/MPLS IP-VPNs, where it is assumed that a PCC will be CE and a PCE will be PE. Requirements for PCE in BGP/MPLS IP-VPN [E2E-RSVP-TE] are described. In that sense, it is highly desirable to have a mechanism for dynamic PCE discovery. Here, our aim is to discover PCEs selectively and automatically in BGP/MPLS IP- VPNs. The point here is that all PCEs are not necessarily discovered automatically and only specific PCEs that know VPN routes should be discovered automatically. However, if a PCE discovers other PCEs by IGP discovery [RFC5088] [RFC5089], the PCE establishes PCEP sessions for discovered PCEs. In a BGP/MPLS IP-VPN, PCEs should not establish full mesh PCEP sessions regardless of VPN routes. The disadvantage is a scalability of PCE based on the number of PCEP sessions. Therefore, in order to discover PCEs, BGP will be extended based on RFC4364 and needs to carry PCE information. Specifically, a PCE address for a VPNv4/VPNv6 tail-end address(es) (VPNv4/VPNv6 route(s)) is required. K.Kumaki, et al. [Page 2] draft-kumaki-pce-bgp-disco-attribute-01 April 2008 Afterwards, PCEs discover the PCE address or some PCE addresses automatically and establish PCEP session(s) for discovered PCE(s). As described in [PCE-DISCO-BGP], PCE discovery information consists of PCE location, PCE inter-domain functions, PCE domain visibility, PCE destination domains and a set of general PCECP capabilities. The PCE discovery information is described in [RFC5088] and [RFC5089], and the same TLVs can be used for BGP. Therefore, in order to establish a BGP session, a BGP speaker needs to have this capability. However, if RRs are deployed in BGP/MPLS IP-VPNs, service providers need to upgrade all RRs to recognize this capability. From the service provider perspective, it is not desirable to upgrade all RRs in order to add only one function (i.e., PCE function). Therefore, BGP PCE discovery attribute is defined in this document. In this case, needless to say, RRs are not required to upgrade and only PEs that speaks PCE protocol are required to upgrade. This document defines BGP PCE Discovery Attribute and describes how PCE information can be carried in the Path Attributes of the UPDATE message described in [RFC4271]. The BGP PCE discovery attribute is defined in section 3 and BGP specific procedure is described in section 4. 2. Terminology LSP: Label Switched Path TE LSP: Traffic Engineering Label Switched Path MPLS TE LSP: Multi Protocol Label Switching TE LSP AS: Autonomous System RR: Route Reflector IGP: Interior Gateway Protocol. Either of the two routing protocols Open Shortest Path First (OSPF) or Intermediate System to Intermediate System (ISIS). PCC: Path Computation Client: any client application requesting a path computation to be performed by a Path Computation Element. PCE: Path Computation Element: an entity (component, application or network node) that is capable of computing a network path or route based on a network graph and applying computational constraints. K.Kumaki, et al. [Page 3] draft-kumaki-pce-bgp-disco-attribute-01 April 2008 PE: Provider Edge: Provider Edge Equipment that has direct connections to CEs from the Layer3 point of view. 3. PCE Information The PCE discovery information as described in [PCE-DISCO-BGP] consists of PCE location, PCE inter-domain functions, PCE domain visibility, PCE destination domains and a set of general PCECP capabilities. The PCE discovery information is described in [RFC5088] and [RFC5089], and the same TLVs can be used for BGP. Here, the PCE discovery attribute for PCE in the Path Attributes of BGP is defined. 3.1 BGP PCE Discovery Attribute The PCE information is carried in the Path Attributes of the UPDATE message described in [RFC4271]. Here, the Transitive bit is defined as non-transitive. However, it is a future work though the transitive bit can be defined as 1 (transitive). The Attribute Flags will be set as follows: The Optional bit set to 1(optional). The Transitive bit set to 0(non-transitive). The Partial bit set to 0(complete). The Extended Length bit set to 1(2 octets). The Attribute Type will be set to some value. The Path Attributes will be encoded as < Length, List of TLV >. +---------------------------+ | Length (2 octets) | +---------------------------+ | List of TLVs(variable) | +---------------------------+ The meaning of the fields is described as follows: a) Length : The length in bytes of the list of TLVs carried in the Path Attribute. b) List of TLVs : This contains a list of TLVs each of which can be a PCE Discovery TLV. The encoding of the PCE discovery TLV and its sub-TLVs will be the K.Kumaki, et al. [Page 4] draft-kumaki-pce-bgp-disco-attribute-01 April 2008 same as that of the corresponding OSPF PCE TLVs described in [RFC5088] and [RFC5089]. 4. BGP Specific Procedure The PCE Discovery Attribute can be carried in the Path Attribute of BGP update messages. It can be handled regardless of IPv4/IPv6 and VPNv4/VPNv6 routes in BGP update message. Transmission processing: BGP speakers advertise the PCE address with routes. The PCE address is included in Path Attribute of BGP update message as BGP PCE Discovery attribute. It can be configurable whether to advertise the PCE address or not. PCE address decision: If a BGP speaker is PCE capable, the PCE address is the same as an assigned address for BGP speaker itself. It may be a vrf interface address or a loopback address. If a BGP speaker is not PCE capable, it is decided by configuration or another method. This method is out of scope of this document. receiving processing: BGP speakers that receive PCE Discovery Attributes register in their RIB with routes. procedure at path computation request: This part describes an inner process within a router between BGP process and path computation process. If the inquiry of a PCE address is received from path computation process, the BGP process retrieve the pertinent route of RIB, and returns the address of PCE Discovery Attribute. Path computation process transmits path computation request to this address. If this attribute is not in RIB, the BGP process notify path computation process error. If two or more PCE addresses of PCE Discovery Attribute exists, all the addresses are returned to path computation process. 5. Security Considerations This document defines BGP extensions for PCE discovery across an administrative domain. Hence the security of the PCE discovery relies on the security of BGP. The security issues are described in the existing BGP. [RFC2385] K.Kumaki, et al. [Page 5] draft-kumaki-pce-bgp-disco-attribute-01 April 2008 6. IANA Considerations IANA will assign BGP PCE Discovery Attribute type. 7. References 7.1 Normative References [RFC4271] Rekhter, Y. and Li, T., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5 Signature Option", RFC2385, August 1998. 7.2 Informative References [RFC4655] Farrel, A., Vasseur, J.-P., and Ash, J., "Path Computation Element (PCE) Architecture", RFC 4655, August 2006. [RFC4657] Ash, J., Le Roux, J.L., "PCE Communication Protocol Generic Requirements", RFC4657, September 2006. [PCEP] Vasseur, J.-P., et al., "Path Computation Element(PCE) communication Protocol (PCEP) - Version 1", Work in Progress, March 2008. [RFC5088] Le Roux, J.L., Vasseur, J.-P., Ikejiri, Y., Zhang, R., "OSPF protocol extensions for Path Computation Element (PCE) Discovery", RFC5088, January 2008. [RFC5089] Le Roux, J.L., Vasseur, J.-P., Ikejiri, Y., Zhang, R., "IS-IS protocol extensions for Path Computation Element (PCE) Discovery", RFC5089, January 2008. [E2E-RSVP-TE] Kumaki, K., Zhang, R. and Kamite, Y., "Requirements for supporting Customer RSVP and RSVP-TE over a BGP/MPLS IP-VPN", Work in Progress, April 2008. [PCE-DISCO-BGP] Vijayanand, C., Bhattacharya, S. and Kumar, P., "BGP Protocol extensions for PCE Discovery across Autonomous systems", Work in Progress, June 2007. 8. Acknowledgments The author would like to express thanks to Makoto Nakamura for his helpful and useful comments and feedback. 9. Author's Addresses K.Kumaki, et al. [Page 6] draft-kumaki-pce-bgp-disco-attribute-01 April 2008 Kenji Kumaki (Editor) KDDI R&D Laboratories, Inc. 2-1-15 Ohara Fujimino Saitama 356-8502, JAPAN Email: ke-kumaki@kddi.com Tomoki Murai FURUKAWA NETWORK SOLUTION CORP. 5-1-9, HIGASHI-YAWATA, HIRATSUKA Kanagawa 254-0016, JAPAN Email: murai@fnsc.co.jp Full Copyright Statement Copyright (C) The IETF Trust (2008). 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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