Network Working Group S. Previdi, Ed. Internet-Draft L. Ginsberg Intended status: Standards Track C. Filsfils Expires: May 21, 2016 Cisco Systems, Inc. November 18, 2015 Segment Routing IPv6 Prefix-SID draft-previdi-isis-ipv6-prefix-sid-00 Abstract This document defines the Segment Routing IPv6 Prefix-SID in the IPv4/IPv6 Extended Reachability Attribute Flags TLV. The new flag is used for advertising the capability to handle the IPv6 Segment Routing header for the prefix that has the flag attached. 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 May 21, 2016. 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 Previdi, et al. Expires May 21, 2016 [Page 1] Internet-Draft SRv6 Prefix-SID November 2015 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. SRv6 Prefix SID . . . . . . . . . . . . . . . . . . . . . . . 2 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 4. Security Considerations . . . . . . . . . . . . . . . . . . . 3 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 3 6.1. Normative References . . . . . . . . . . . . . . . . . . 3 6.2. Informative References . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction With Segment Routing (SR)[I-D.ietf-spring-segment-routing], a node steers a packet through an ordered list of instructions, called segments. Segments are identified through Segment Identifiers (SIDs) that are advertised by routing protocols. The IS-IS extensions for SR information advertisement are defined in [I-D.ietf-isis-segment-routing-extensions]. Segment Routing can be directly applied to the IPv6 dataplane through the use of the Segment Routing Header defined in [I-D.previdi-6man-segment-routing-header]. 2. SRv6 Prefix SID When SR is applied to the IPv6 dataplane, Segment Identifiers (SIDs) are regular IPv6 addresses that are advertised in routing protocols. When SR is used over IPv6 dataplane, it is desirable to identify which of the prefixes originated by a node can be used as SIDs compared to any other prefix that the node advertises. [I-D.ietf-isis-prefix-attributes], defines the IPv4/IPv6 Extended Reachability Attribute Flags TLV. This document defines the following new flag: S6-Flag (bit 3). SRv6 Prefix-SID flag: when set, the router indicates that the prefix this flag is attached to can be used as an IPv6 Prefix-SID. Previdi, et al. Expires May 21, 2016 [Page 2] Internet-Draft SRv6 Prefix-SID November 2015 The S6-Flag may also be set in conjunction with the Node-Flag (Bit 2) if the prefix does also identifies the node in the topology. In the case where the prefix has a shorter mask-length than 128 or when the prefix does not identify the node (e.g.: assigned to a physical interface instead of a loopback) the S6-Flag MAY be set and the N-flag MUST NOT be set. When a prefix is flagged as a SRv6-Prefix-SID, the originating router MUST support the IPv6 Segment Routing Header (SRH) and its procedures described in [I-D.previdi-6man-segment-routing-header]. Therefore the originating router MUST set the H-flag in the SR-Capability SubTLV as defined in [I-D.ietf-isis-segment-routing-extensions]. A router receiving the advertisement of the IPv6 prefix with the S6-Flag set MUST check whether the originator has set the H-flag in its SR-Capability SubTLV if present in the receiving router link state database. The S6-Flag has relevance only for IPv6 prefixes. When processing IPv4 prefixes, the S6-Flag MUST be ignored. 3. IANA Considerations This document introduces the SRv6-Prefix-SID flag in the Prefix Attribute Flags sub-TLV: Name Bit # ------- ----- S6-Flag 3 (suggested value, to be assigned by IANA) 4. Security Considerations This document doesn't introduce new security considerations. 5. Acknowledgements The authors would like to thank Nagendra Kumar for his review of this document. 6. References 6.1. Normative References Previdi, et al. Expires May 21, 2016 [Page 3] Internet-Draft SRv6 Prefix-SID November 2015 [I-D.ietf-isis-prefix-attributes] Ginsberg, L., Decraene, B., Filsfils, C., Litkowski, S., Previdi, S., Xu, X., and U. Chunduri, "IS-IS Prefix Attributes for Extended IP and IPv6 Reachability", draft- ietf-isis-prefix-attributes-01 (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, . 6.2. Informative References [I-D.ietf-isis-segment-routing-extensions] Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS Extensions for Segment Routing", draft-ietf-isis-segment- routing-extensions-05 (work in progress), June 2015. [I-D.ietf-spring-segment-routing] Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., and r. rjs@rob.sh, "Segment Routing Architecture", draft- ietf-spring-segment-routing-06 (work in progress), October 2015. [I-D.previdi-6man-segment-routing-header] Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova, J., Kosugi, T., Vyncke, E., and D. Lebrun, "IPv6 Segment Routing Header (SRH)", draft-previdi-6man-segment-routing- header-08 (work in progress), October 2015. Authors' Addresses Stefano Previdi (editor) Cisco Systems, Inc. Via Del Serafico, 200 Rome 00142 Italy Email: sprevidi@cisco.com Les Ginsberg Cisco Systems, Inc. US Email: ginsberg@cisco.com Previdi, et al. Expires May 21, 2016 [Page 4] Internet-Draft SRv6 Prefix-SID November 2015 Clarence Filsfils Cisco Systems, Inc. Brussels BE Email: cfilsfil@cisco.com Previdi, et al. Expires May 21, 2016 [Page 5]