Internet Engineering Task Force S. Sivabalan Internet-Draft J. Medved Intended status: Standards Track Cisco Systems, Inc. Expires: February 01, 2014 July 31, 2013 IGP Extensions for Segment Routing Capable PCE Discovery draft-sivabalan-pce-disco-segment-routing-00.txt Abstract When a PCE is a Label Switching Router (LSR) participating in Interior Gateway Protocol (IGP), or a server participating in IGP, its presence and path computation capabilities can be advertised using IGP flooding. Such IGP extensions exist for OSPF and ISIS to advertise several such capabilities. Segment Routing (SR) leverages the source routing and tunneling pardigms in which a node steers a packet through the network using segments. A segment can be an MPLS label or IPv6 header with a new extension. In SR networks, a PCE can be used to compute paths using SR PCEP extension. This document specifies additional capability to advertise a PCE that supports the new SR PCEP extension. 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 February 01, 2014. Copyright Notice Copyright (c) 2013 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 Sivabalan & Medved Expires February 01, 2014 [Page 1] Internet-Draft Segment Routing capable PCE Discovery July 2013 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 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. IGP Extensions for SR Capability . . . . . . . . . . . . . . 3 4. Backward Compatibility . . . . . . . . . . . . . . . . . . . 4 5. Management Considerations . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 8.1. Normative References . . . . . . . . . . . . . . . . . . 4 8.2. Informative References . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction [RFC5440] describes the Path Computation Element Protocol (PCEP), which defines the communication between a Path Computation Client (PCC) and a Path Control Element (PCE), or between PCE and PCE, enabling computation of Multiprotocol Label Switching (MPLS) for Traffic Engineering Label Switched Path (TE LSP) characteristics. [I-D.ietf-pce-stateful-pce] specifies a set of extensions to PCEP to enable stateful control of TE LSPs between and across PCEP sessions in compliance with [RFC4657]. SR technology leverages the source routing and tunneling paradigms. A node steers a packet through a controlled set of instructions, called segments, by prepending the packet with an SR header. This technology enables any head-end node to select any path without relying on hop-by-hop signaling technique (e.g., LDP or RSVP-TE). It depends only on segments that are advertised by IGPs. SR architecture is described in [SR-ARCH]. A SR path can be derived with an aid of a PCE. Extension to PCE Protocol (PCEP) to support SR Traffic Engineering (SR-TE) path computation functionality is specified in [SR-PCEP]. Sivabalan & Medved Expires February 01, 2014 [Page 2] Internet-Draft Segment Routing capable PCE Discovery July 2013 When PCCs are LSRs participating in the IGP (OSPF or IS-IS), and PCEs are either LSRs or servers also participating in the IGP, an effective mechanism for PCE discovery within an IGP routing domain consists of utilizing IGP advertisements. Such extension to OSPF and IS-IS exists in [RFC5088] and [RFC5089], respectively. Currently, the IGP PCE capability does not indicate whether the advertised PCE is capabable of supporting SR PCEP extension specified in [SR-PCEP]. Advertising such capability would facilitate a PCC to learn about available SR capable PCEs. A PCC could listen to IGP updates, or use other mechanisms that carry IGP information to interested clients, such as BGP-LS ([I-D.ietf-idr-ls-distribution]). This document extends the IGP capability advertisement mechanism to include SR capability. 1.1. 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] 2. Terminology The following terminology is used in this document: IGP: Interior Gateway Protocol IS-IS: Intermediate System to Intermediate System LSR: Label Switching Router OSPF: Open Shortest Path First PCC: Path Computation Client PCE: Path Computation Element PCEP: Path Computation Element Protocol SR: Segment Routing SR-TE: Segment Routed Traffic Engineering 3. IGP Extensions for SR Capability The PCE-CAP-FLAGS sub-TLV is an optional sub-TLV used to advertise PCE capabilities. It MAY be present within the PCED sub-TLV carried by OSPF or IS-IS. [RFC5088] and [RFC5089] provide the description and processing rules for this sub-TLV when carried within OSPF and IS-IS respectively. The PCE-CAP-FLAGS sub-TLV has the following format: o TYPE: 5 o LENGTH: Multiple of 4 Sivabalan & Medved Expires February 01, 2014 [Page 3] Internet-Draft Segment Routing capable PCE Discovery July 2013 o VALUE: This contains an array of units of 32 bit flags with the most significant bit as 0. Each bit represents one PCE capability PCE capability bits are defined in [RFC5088]. This document defines new capability bits for the SR capable PCE as follows: Bit Capability 13 Segment Routing PCE capability 4. Backward Compatibility An LSR that does not support the new IGP PCE capability bits specified in this document silently ignores those bits. IGP extensions defined in this document do not introduce any new interoperability issues. 5. Management Considerations A configuration option may be provided for advertising and withdrawing SR capability on a PCE. 6. Security Considerations Security considerations described in [RFC5088] are applicable to stateful PCE capabilities. No additional security measures are required. 7. IANA Considerations IANA is requested to allocate a new bit in "PCE Capability Flags" registry for SR PCE capability as follows: Bit Meaning Reference 13 SR PCE capability This document Table 1 8. References 8.1. 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-02 (work in progress), February 2013. Sivabalan & Medved Expires February 01, 2014 [Page 4] Internet-Draft Segment Routing capable PCE Discovery July 2013 [I-D.ietf-pce-stateful-pce] Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP Extensions for Stateful PCE", draft-ietf-pce-stateful- pce-03 (work in progress), March 2013. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [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. [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009. [SR-ARCH] Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Litkowski, S., and M. Horneffer, "Segment Routing Architecture", draft-filsfils-rtgwg-segment-routing-00.txt (work in progress), June 2013. [SR-PCEP] Sivabalan, S., Filsfils, C., Medved, J., Crabbe, E., and R. Raszuk, "PCEP Extensions for Segment Routing", draft- sivabalan-pce-segment-routing-00.txt (work in progress), June 2013. 8.2. Informative References [RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE) Communication Protocol Generic Requirements", RFC 4657, September 2006. Authors' Addresses Siva Sivabalan Cisco Systems, Inc. 2000 Innovation Drive Kanata, Ontario K2K 3E8 Canada Email: msiva@cisco.com Sivabalan & Medved Expires February 01, 2014 [Page 5] Internet-Draft Segment Routing capable PCE Discovery July 2013 Jan Medved Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134 USA Email: jmedved@cisco.com Sivabalan & Medved Expires February 01, 2014 [Page 6]