--- 1/draft-ietf-idr-bgp-prefix-sid-01.txt 2015-12-21 08:15:29.004204214 -0800 +++ 2/draft-ietf-idr-bgp-prefix-sid-02.txt 2015-12-21 08:15:29.040205082 -0800 @@ -1,25 +1,25 @@ IDR S. Previdi Internet-Draft C. Filsfils Intended status: Standards Track A. Lindem -Expires: April 16, 2016 K. Patel +Expires: June 23, 2016 K. Patel A. Sreekantiah Cisco Systems S. Ray Unaffiliated H. Gredler - Juniper Networks - October 14, 2015 + Individual + December 21, 2015 Segment Routing Prefix SID extensions for BGP - draft-ietf-idr-bgp-prefix-sid-01 + draft-ietf-idr-bgp-prefix-sid-02 Abstract Segment Routing (SR) architecture allows a node to steer a packet flow through any topological path and service chain by leveraging source routing. The ingress node prepends a SR header to a packet containing a set of "segments". Each segment represents a topological or a service-based instruction. Per-flow state is maintained only at the ingress node of the SR domain. @@ -42,21 +42,21 @@ 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 April 16, 2016. + This Internet-Draft will expire on June 23, 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 publication of this document. Please review these documents @@ -74,40 +74,40 @@ 3.1. MPLS Prefix Segment . . . . . . . . . . . . . . . . . . . 4 3.2. IPv6 Prefix Segment . . . . . . . . . . . . . . . . . . . 5 4. BGP-Prefix-SID Attribute . . . . . . . . . . . . . . . . . . 5 4.1. Label-Index TLV . . . . . . . . . . . . . . . . . . . . . 6 4.2. IPv6 SID . . . . . . . . . . . . . . . . . . . . . . . . 7 4.3. Originator SRGB TLV . . . . . . . . . . . . . . . . . . . 8 5. Receiving BGP-Prefix-SID Attribute . . . . . . . . . . . . . 9 5.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 9 5.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 10 6. Announcing BGP-Prefix-SID Attribute . . . . . . . . . . . . . 10 - 6.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 10 + 6.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 11 6.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 11 - 7. Error Handling of BGP-Prefix-SID Attribute . . . . . . . . . 11 + 7. Error Handling of BGP-Prefix-SID Attribute . . . . . . . . . 12 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 - 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 - 11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 12 + 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 + 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 + 11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 13 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 12.1. Normative References . . . . . . . . . . . . . . . . . . 13 12.2. Informative References . . . . . . . . . . . . . . . . . 13 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 1. Segment Routing Documents The main references for this document are the SR architecture defined in [I-D.ietf-spring-segment-routing] and the related use case illustrated in [I-D.ietf-spring-segment-routing-msdc]. The Segment Routing Egress Peer Engineering architecture is described - in [I-D.filsfils-spring-segment-routing-central-epe]. + in [I-D.ietf-spring-segment-routing-central-epe]. The Segment Routing Egress Peer Engineering BGPLS extensions are described in [I-D.ietf-idr-bgpls-segment-routing-epe]. 2. Introduction Segment Routing (SR) architecture leverages the source routing paradigm. A group of inter-connected nodes that use SR forms a SR domain. The ingress node of the SR domain prepends a SR header containing "segments" to an incoming packet. Each segment represents @@ -115,21 +115,21 @@ path" or a service instruction (e.g.: "pass through deep packet inspection"). By inserting the desired sequence of instructions, the ingress node is able to steer a packet via any topological path and/ or service chain; per-flow state is maintained only at the ingress node of the SR domain. Each segment is identified by a Segment Identifier (SID). As described in [I-D.ietf-spring-segment-routing], when SR is applied to the MPLS dataplane the SID consists of a label while when SR is applied to the IPv6 dataplane the SID consists of an IPv6 prefix (see - [I-D.previdi-6man-segment-routing-header]). + [I-D.ietf-6man-segment-routing-header]). A BGP-Prefix Segment (aka BGP-Prefix-SID), is a BGP segment attached to a BGP prefix. A BGP-Prefix-SID is always global within the SR/BGP domain and identifies an instruction to forward the packet over the ECMP-aware best-path computed by BGP to the related prefix. The BGP- Prefix-SID is the identifier of the BGP prefix segment. This document describes the BGP extension to signal the BGP-Prefix- SID. Specifically, this document defines a new BGP attribute known as the BGP Prefix SID attribute and specifies the rules to originate, @@ -150,81 +150,82 @@ The BGP-Prefix-SID attached to a BGP prefix P represents the instruction "go to Prefix P" along its BGP bestpath (potentially ECMP-enabled). 3.1. MPLS Prefix Segment The BGP Prefix Segment is realized on the MPLS dataplane in the following way: - A Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC3107]) session - type is required. + As described in [I-D.ietf-spring-segment-routing-msdc] the + operator assigns a globally unique "index", L_I, to a locally + sourced prefix of a BGP speaker N which is advertised to all other + BGP speakers in the SR domain. According to [I-D.ietf-spring-segment-routing], each BGP speaker is configured with a label block called the Segment Routing Global Block (SRGB). While it is recommended to use the same SRGB across all the nodes within the SR domain, the SRGB of a node is a local property and could be different on different speakers. The drawbacks of the use case where BGP speakers have different SRGBs - are documented in [I-D.ietf-spring-segment-routing]. + are documented in [I-D.ietf-spring-segment-routing] and + [I-D.ietf-spring-segment-routing-msdc]. - As described in [I-D.ietf-spring-segment-routing-msdc] the - operator assigns a globally unique "index", L_I, to a locally - sourced prefix of a BGP speaker N which is advertised to all other - BGP speakers in the SR domain. + If traffic-engineering within the SR domain is required, each node + may also be required to advertise topological information and + Peering SID's for each of its links and peers. This informations + is required in order to perform the explicit path computation and + to express any explicit path into a list of segments. The + advertisement of topological information and Peer segments is + assumed to be done through + [I-D.ietf-idr-bgpls-segment-routing-epe]. + + If the BGP speakers are not all configured with the same SRGB, and + if traffic-engineering within the SR domain is required, each node + may be required to advertise its local SRGB in addition to the + topological information. + + This documents assumes that BGP-LS is the preferred method for + collecting both topological, peer segments and SRGB information + through [I-D.ietf-idr-ls-distribution], + [I-D.ietf-idr-bgpls-segment-routing-epe] and + + [I-D.gredler-idr-bgp-ls-segment-routing-ext]. However, as an + optional alternative for the advertisement of the local SRGB + without the topology nor the peer SID's, hence without + applicability for TE, the Originator SRGB TLV of the prefix-SID + attribute, is specified in Section 4.3 of this document. The index L_I is a 32 bit offset in the SRGB. Each BGP speaker derives its local MPLS label, L, by adding L_I to the start value of its own SRGB, and programs L in its MPLS dataplane as its - incoming/local label for the prefix. + incoming/local label for the prefix. See Section 5.1 for more + details. The outgoing label for the prefix is found in the NLRI of the Multiprotocol BGP labeled IPv4/IPv6 Unicast prefix advertisement. The index L_I is only used as a hint to derive the local/incoming label. - If the BGP speakers cannot be configured with the same SRGB and - traffic-engineering within the SR domain is required, each node - MAY be required to advertise its local SRGB. - - The preferred method leverages - [I-D.ietf-idr-bgpls-segment-routing-epe]. - - Indeed, in order to engineer traffic, it is important to have the - internal topology (BGP-LS extensions provide these), the peering - topology (BGP-LS-EPE extensions provide these), and the equivalent - of adjacency segments for each link in the topology (BGP-LS-EPE - extensions provide these through the PeerAdj segments). The first - two provide the topology input to the optimization process. The - latter provides a deterministic method to engineer a flow through - any desired path. - - In some very-simplified traffic-engineering context, it might not - be necessary to have either the topology or the adjacency - segments. In such simplified case, the BGP Prefix SID provides an - alternative method to distribute the SRGB of each node. - - If the BGP speakers cannot be configured with the same SRGB, the - proposed BGP Prefix-SID attribute allows the advertisement of the - SRGB so each node can advertise the SRGB it's configured with. The - drawbacks of the use case where BGP speakers have different SRGBs are - documented in [I-D.ietf-spring-segment-routing-msdc]. + Section 4.1 of this document specifies the Label-Index TLV of the + BGP Prefix-SID attribute; this TLV can be used to advertise the + label index of a given prefix. In order to advertise the label index of a given prefix P and, optionally, the SRGB, a new extension to BGP is needed: the BGP Prefix SID attribute. This extension is described in subsequent sections. 3.2. IPv6 Prefix Segment - As defined in [I-D.previdi-6man-segment-routing-header], and as + As defined in [I-D.ietf-6man-segment-routing-header], and as illustrated in [I-D.ietf-spring-segment-routing-msdc], when SR is used over an IPv6 dataplane, the BGP Prefix Segment is instantiated by an IPv6 prefix originated by the BGP speaker. Each node advertises a globally unique IPv6 address representing itself in the domain. This prefix (e.g.: its loopback interface address) is advertised to all other BGP speakers in the SR domain. Also, each node MUST advertise its support of Segment Routing for IPv6 dataplane. This is realized using the flags contained in the @@ -313,21 +314,21 @@ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |S| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: * S flag: if set then it means that the BGP speaker attaching the Prefix-SID Attribute to a prefix is capable of processing the IPv6 Segment Routing Header (SRH, - [I-D.previdi-6man-segment-routing-header]) for the segment + [I-D.ietf-6man-segment-routing-header]) for the segment corresponding to the originated IPv6 prefix. The use case leveraging the S flag is described in [I-D.ietf-spring-segment-routing-msdc]. The other bits of the flag field SHOULD be clear on transmission an MUST be ignored at reception. 4.3. Originator SRGB TLV The Originator SRGB TLV is an optional TLV and has the following @@ -358,21 +359,25 @@ o Type is 3. o Length is the total length of the value portion of the TLV: 2 + multiple of 6. o Flags: 16 bits of flags. None are defined in this document. Flags SHOULD be clear on transmission an MUST be ignored at reception. o SRGB: 3 octets of base followed by 3 octets of range. Note that - SRGB field MAY appear multiple times. + the SRGB field MAY appear multiple times. If the SRGB field + appears multiple times, the SRGB consists of multiple ranges. The + meaning of an SRGB with multiple ranges is explained in + Section 3.2 ("SID/Label Range TLV") of + [I-D.ietf-ospf-segment-routing-extensions]. The Originator SRGB TLV contains the SRGB of the router originating the prefix to which the BGP Prefix SID is attached and MUST be kept in the Prefix-SID Attribute unchanged during the propagation of the BGP update. The originator SRGB describes the SRGB of the node where the BGP Prefix Segment end. It is used to build SRTE policies when different SRGB's are used in the fabric ([I-D.ietf-spring-segment-routing-msdc]). @@ -515,60 +520,65 @@ 7. Error Handling of BGP-Prefix-SID Attribute When a BGP Speaker receives a BGP Update message containing a malformed BGP Prefix-SID attribute, it MUST ignore the received BGP Prefix-SID attributes and not pass it to other BGP peers. This is equivalent to the -attribute discard- action specified in [RFC7606]. When discarding an attribute, a BGP speaker MAY log an error for further analysis. If the BGP Prefix-SID attribute appears more than once in an BGP - Update message message, then, according to [RFC7606], all the - occurrences of the attribute other than the first one SHALL be - discarded and the BGP Update message shall continue to be processed. + Update message, then, according to [RFC7606], all the occurrences of + the attribute other than the first one SHALL be discarded and the BGP + Update message shall continue to be processed. When a BGP speaker receives an unacceptable Prefix-SID attribute, it MAY log an error for further analysis. 8. IANA Considerations This document defines a new BGP path attribute known as the BGP Prefix-SID attribute. This document requests IANA to assign a new attribute code type (suggested value: 40) for BGP the Prefix-SID attribute from the BGP Path Attributes registry. + Currently, IANA temporarily assigned the following: + + 40 BGP Prefix-SID (TEMPORARY - registered 2015-09-30, expires + 2016-09-30) [draft-ietf-idr-bgp-prefix-sid] + This document defines 3 new TLVs for BGP Prefix-SID attribute. These TLVs need to be registered with IANA. We request IANA to create a new registry for BGP Prefix-SID Attribute TLVs as follows: Under "Border Gateway Protocol (BGP) Parameters" registry, "BGP - Prefix SID attribute Types" Reference: draft-ietf-idr-bgp-prefix- - sid-00 Registration Procedure(s): Values 1-254 First Come, First - Served, Value 0 and 255 reserved + Prefix SID attribute Types" Reference: draft-ietf-idr-bgp-prefix-sid + Registration Procedure(s): Values 1-254 First Come, First Served, + Value 0 and 255 reserved Value Type Reference - 0 Reserved draft-ietf-idr-bgp-prefix-sid-00 - 1 Label-Index draft-ietf-idr-bgp-prefix-sid-00 - 2 IPv6 SID draft-ietf-idr-bgp-prefix-sid-00 - 3 Originator SRGB draft-ietf-idr-bgp-prefix-sid-00 + 0 Reserved this document + 1 Label-Index this document + 2 IPv6 SID this document + 3 Originator SRGB this document 4-254 Unassigned - 255 Reserved draft-ietf-idr-bgp-prefix-sid-00 + 255 Reserved this document 9. Security Considerations This document introduces no new security considerations above and beyond those already specified in [RFC4271] and [RFC3107]. 10. Acknowledgements - The authors would like to thanks Satya Mohanty and Acee Lindem for - their contribution to this document. + The authors would like to thanks Satya Mohanty for his contribution + to this document. 11. Change Log Initial Version: Sep 21 2014 12. References 12.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate @@ -589,50 +599,68 @@ Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 2006, . [RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K. Patel, "Revised Error Handling for BGP UPDATE Messages", RFC 7606, DOI 10.17487/RFC7606, August 2015, . 12.2. Informative References - [I-D.filsfils-spring-segment-routing-central-epe] - Filsfils, C., Previdi, S., Patel, K., Shaw, S., Ginsburg, - D., and D. Afanasiev, "Segment Routing Centralized Egress - Peer Engineering", draft-filsfils-spring-segment-routing- - central-epe-05 (work in progress), August 2015. + [I-D.gredler-idr-bgp-ls-segment-routing-ext] + Previdi, S., Psenak, P., Filsfils, C., Gredler, H., Chen, + M., and J. Tantsura, "BGP Link-State extensions for + Segment Routing", draft-gredler-idr-bgp-ls-segment- + routing-ext-01 (work in progress), December 2015. + + [I-D.ietf-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-ietf-6man-segment-routing- + header-00 (work in progress), December 2015. [I-D.ietf-idr-bgpls-segment-routing-epe] Previdi, S., Filsfils, C., Ray, S., Patel, K., Dong, J., and M. Chen, "Segment Routing Egress Peer Engineering BGP- LS Extensions", draft-ietf-idr-bgpls-segment-routing- - epe-00 (work in progress), June 2015. + epe-02 (work in progress), December 2015. + + [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-13 + (work in progress), October 2015. + + [I-D.ietf-ospf-segment-routing-extensions] + Psenak, P., Previdi, S., Filsfils, C., Gredler, H., + Shakir, R., Henderickx, W., and J. Tantsura, "OSPF + Extensions for Segment Routing", draft-ietf-ospf-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-05 (work in progress), - September 2015. + ietf-spring-segment-routing-07 (work in progress), + December 2015. + + [I-D.ietf-spring-segment-routing-central-epe] + Filsfils, C., Previdi, S., Ginsburg, D., and D. Afanasiev, + "Segment Routing Centralized Egress Peer Engineering", + draft-ietf-spring-segment-routing-central-epe-00 (work in + progress), October 2015. [I-D.ietf-spring-segment-routing-msdc] Filsfils, C., Previdi, S., Mitchell, J., and P. Lapukhov, "BGP-Prefix Segment in large-scale data centers", draft- ietf-spring-segment-routing-msdc-00 (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. - [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, DOI 10.17487/RFC4760, January 2007, . Authors' Addresses Stefano Previdi Cisco Systems Via Del Serafico, 200 @@ -663,20 +692,20 @@ Email: keyupate@cisco.com Arjun Sreekantiah Cisco Systems 170 W. Tasman Drive San Jose, CA 95124 95134 USA Email: asreekan@cisco.com - Saikat Ray Unaffiliated Email: raysaikat@gmail.com Hannes Gredler - Juniper Networks + Individual + AT - Email: hannes@juniper.net + Email: hannes@gredler.at