--- 1/draft-ietf-idr-bgp-prefix-sid-10.txt 2018-01-31 15:13:13.649456142 -0800 +++ 2/draft-ietf-idr-bgp-prefix-sid-11.txt 2018-01-31 15:13:13.689457098 -0800 @@ -1,23 +1,23 @@ IDR S. Previdi, Ed. Internet-Draft C. Filsfils Intended status: Standards Track A. Lindem -Expires: July 20, 2018 Cisco Systems +Expires: August 4, 2018 Cisco Systems A. Sreekantiah H. Gredler RtBrick Inc. - January 16, 2018 + January 31, 2018 Segment Routing Prefix SID extensions for BGP - draft-ietf-idr-bgp-prefix-sid-10 + draft-ietf-idr-bgp-prefix-sid-11 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 an SR header to a packet containing a set of segment identifiers (SID). Each SID represents a topological or a service-based instruction. Per-flow state is maintained only on the ingress node of the SR domain. @@ -41,21 +41,21 @@ 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 July 20, 2018. + This Internet-Draft will expire on August 4, 2018. Copyright Notice Copyright (c) 2018 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 @@ -91,40 +91,40 @@ 12.1. Normative References . . . . . . . . . . . . . . . . . . 14 12.2. Informative References . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 1. Introduction Segment Routing (SR) architecture leverages the source routing paradigm. A group of inter-connected nodes that use SR forms an SR domain. A segment represents either a topological instruction such as "go to prefix P following shortest path" or a service instruction - (e.g.: "pass through deep packet inspection"). Other types of + (e.g., "pass through deep packet inspection"). Other types of segments may be defined in the future. A segment is identified through a Segment Identifier (SID). Typically, the ingress node of the SR domain prepends an SR header containing segments identifiers (SIDs) to an incoming packet. As described in [I-D.ietf-spring-segment-routing], when SR is applied - to the MPLS dataplane ([I-D.ietf-spring-segment-routing-mpls]) the + to the MPLS dataplane ([I-D.ietf-spring-segment-routing-mpls]), the SID consists of a label while when SR is applied to the IPv6 dataplane the SID consists of an IPv6 address. A BGP-Prefix Segment (and its BGP Prefix-SID), is a BGP segment attached to a BGP prefix. A BGP Prefix-SID is always a global SID ([I-D.ietf-spring-segment-routing]) within the SR/BGP domain (i.e., the set of Autonomous Systems under a common administration and control and where SR is used) 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. In this document, we always refer to the BGP Segment + prefix segment. In this document, we always refer to the BGP segment by the BGP Prefix-SID. This document describes the BGP extension to signal the BGP Prefix- SID. Specifically, this document defines a BGP attribute known as the BGP Prefix-SID attribute and specifies the rules to originate, receive, and handle error conditions for the attribute. The BGP Prefix-SID attribute defined in this document can be attached to prefixes from AFI/SAFI combinations: @@ -161,33 +161,33 @@ The BGP Prefix-SID is realized on the MPLS dataplane ([I-D.ietf-spring-segment-routing-mpls]) in the following way: The operator assigns a globally unique label 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 [I-D.ietf-spring-segment-routing] recommends - 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 + using 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] and [I-D.ietf-spring-segment-routing-msdc]. If traffic-engineering within the SR domain is required, each node may also be required to advertise topological information and Peering SIDs for each of its links and peers. This information is required to perform the explicit path computation and to express an explicit path as a list of SIDs. The advertisement of - topological information and Peer segments (Peer SIDs) is done + topological information and peer segments (Peer SIDs) is 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 peer segments (Peer SIDs) and SRGB information through [RFC7752], [I-D.ietf-idr-bgpls-segment-routing-epe], and @@ -239,27 +239,27 @@ o IPv6 SID TLV o Originator SRGB TLV The Label-Index and Originator SRGB TLVs are used only when SR is applied to the MPLS dataplane. The IPv6 SID TLV is used only when SR is applied to the IPv6 dataplane. - For future extendibility, unknown TLVs are ignored and propagated + For future extendibility, unknown TLVs MUST be ignored and propagated unmodified. 3.1. Label-Index TLV The Label-Index TLV MUST be present in the BGP Prefix-SID attribute - attached to Labeled IPv4/IPv6 unicast prefixes ([RFC8277]). It will + attached to Labeled IPv4/IPv6 unicast prefixes ([RFC8277]). It MUST be ignored when received for other BGP AFI/SAFI combinations. The Label-Index TLV has the following format: 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 | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | Label Index | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -280,21 +280,21 @@ flag field MUST be clear on transmission and MUST be ignored on reception. o Label Index: 32-bit value representing the index value in the SRGB space. 3.2. IPv6 SID The IPv6 SID TLV MAY be present in the BGP Prefix-SID attribute attached to MP-BGP unlabeled IPv6 unicast prefixes ([RFC4760]). It - will be ignored for other BGP AFI/SAFI combinations. The IPv6 SID + MUST be ignored for other BGP AFI/SAFI combinations. The IPv6 SID TLV has the following format: 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 | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RESERVED | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | @@ -339,65 +339,65 @@ | SRGB n (6 octets) | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: o Type is 3. o Length is the total length in octets of the value portion of the - TLV: 2 + multiple of 6. + TLV: 2 + (multiple of 6). o Flags: 16 bits of flags. None are defined in this document. Flags MUST be clear on transmission and MUST be ignored on reception. o SRGB: 3 octets of base followed by 3 octets of range. Note that the SRGB field MAY appear multiple times. If the SRGB field appears multiple times, the SRGB consists of multiple ranges. The Originator SRGB TLV contains the SRGB of the node originating the prefix to which the BGP Prefix-SID is attached. The Originator SRGB TLV MUST NOT be changed during the propagation of the BGP update. The originator SRGB describes the SRGB of the node where the BGP Prefix SID is attached. It is used to build segment routing policies when different SRGBs are used in the fabric, for example ([I-D.ietf-spring-segment-routing-msdc]). The originator SRGB may only appear in a BGP Prefix-SID attribute - attached to Labeled IPv4/IPv6 unicast prefixes ([RFC8277]). It will + attached to Labeled IPv4/IPv6 unicast prefixes ([RFC8277]). It MUST be ignored when received for other BGP AFI/SAFI combinations. 4. Receiving BGP Prefix-SID Attribute A BGP speaker receiving a BGP Prefix-SID attribute from an EBGP - neighbor residing outside the boundaries of the SR domain, MUST + neighbor residing outside the boundaries of the SR domain MUST discard the attribute unless it is configured to accept the attribute from the EBGP neighbor. A BGP speaker MAY log an error for further analysis when discarding an attribute. 4.1. MPLS Dataplane: Labeled Unicast A Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]) session type is required. A BGP speaker may be locally configured with an SRGB=[SRGB_Start, SRGB_End]. The preferred method for deriving the SRGB is a matter of local node configuration. - Given a label index L_I, we call L = L_I + SRGB_Start as the derived - label. A BGP Prefix-SID attribute is designated "unacceptable" for a - speaker M if the derived label value L lies outside the SRGB - configured on M. Otherwise the Label-Index TLV is designated - "acceptable" to speaker M. + Given a label index L_I, we refer to (L = L_I + SRGB_Start) as the + derived label. A BGP Prefix-SID attribute is designated + "unacceptable" for a speaker M if the derived label value L lies + outside the SRGB configured on M. Otherwise the Label-Index TLV is + designated "acceptable" to speaker M. The mechanisms through which a given label index value is assigned to a given prefix are outside the scope of this document. The label- index value associated with a prefix is locally configured at the BGP node originating the prefix. The BGP Prefix-SID attribute MUST contain the Label-Index TLV and MAY contain the Originator SRGB TLV. A BGP Prefix-SID attribute received without a Label-Index TLV MUST be considered as "unacceptable" by the receiving speaker. @@ -432,29 +432,29 @@ MUST adhere to standard behavior and program its MPLS dataplane to pop the top label when forwarding traffic to the prefix. The label NLRI defines the outbound label that MUST be used by the receiving node. The label index gives the information to the receiving node on which local/incoming label the BGP speaker SHOULD assign. 4.2. IPv6 Dataplane When an SR IPv6 BGP speaker receives an IPv6 Unicast BGP Update with a prefix having the BGP Prefix-SID attribute attached, it checks - whether the IPv6 SID TLV is present. If present and the chosen as - the best path, the prefix is installed into the Segment Routing IPv6 + whether the IPv6 SID TLV is present. If present and chosen as the + best path, the prefix is installed into the Segment Routing IPv6 dataplane as described in [I-D.ietf-spring-segment-routing]. The Label-Index and Originator SRGB TLVs MUST be ignored on reception. For future extendibility, no TLVs are required for the BGP IPv6 unicast address family. However, a BGP Prefix-SID attribute corresponding to the BGP IPv6 address family without an IPv6 SID TLV - will be ignored. + MUST be ignored. 5. Advertising BGP Prefix-SID Attribute The BGP Prefix-SID attribute MAY be attached to labeled BGP prefixes (IPv4/IPv6) [RFC8277] or to IPv6 unicast prefixes [RFC4760]. In order to prevent distribution of the BGP Prefix-SID attribute beyond its intended scope of applicability, attribute filtering SHOULD be deployed. A BGP speaker that advertises a path received from one of its @@ -509,66 +509,66 @@ unlabeled IPv6 unicast prefix [RFC4760], it MUST treat the advertisement as a withdrawal. This is equivalent to the "Treat-as- withdraw" action specified in [RFC7606]. This action is required since simply ignoring the BGP Prefix-SID attribute would modify the installed path and the "Attribute discard" option is not applicable in this case [RFC7606]. When withdrawing the prefix, a BGP speaker SHOULD log an error for further analysis. Consistent with [RFC7606], only the first occurrence of the BGP Prefix-SID attribute will be considered and subsequent occurrences - will be discarded. Similarily, only the first occurrence of a BGP + will be discarded. Similarly, only the first occurrence of a BGP Prefix-SID attribute TLV of a given TLV type will be considered unless the specification of that TLV type allows for multiple occurrences. - For future extendibility, unknown TLVs should be ignored and - propagated unmodified. + For future extendibility, unknown TLVs MUST be ignored and propagated + unmodified. 7. IANA Considerations This document defines a BGP path attribute known as the BGP Prefix- SID attribute. This document requests IANA to assign an attribute - code type (suggested value: 40) the BGP Prefix-SID attribute from the - BGP Path Attributes registry. + code type (suggested value: 40) to the BGP 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 TLVs for the BGP Prefix-SID attribute. These TLVs need to be registered with IANA. We request IANA to create a registry for BGP Prefix-SID Attribute TLVs as follows: Under "Border Gateway Protocol (BGP) Parameters" registry, "BGP Prefix-SID TLV Types" Reference: draft-ietf-idr-bgp-prefix-sid - Registration Procedure(s): Values 1-254 First Come, First Served, - Value 0 and 255 reserved + Registration Procedure(s): Values 1-254 First Come First Served + (FCFS), Value 0 and 255 reserved Value Type Reference 0 Reserved this document 1 Label-Index this document 2 IPv6 SID this document 3 Originator SRGB this document 4-254 Unassigned 255 Reserved this document This document also creates a registry for the 16 bits of flags in the Label-Index TLV. Initially, the registry will be empty. Flag bits - will be allocated First-Come, First Served consistent with the BGP- - SID TLV Types registry. + will be allocated First Come First Served (FCFS) consistent with the + BGP-SID TLV Types registry. Finally, this document creates a registry for the 16 bits of flags in the SRGB Originator TLV. Initially, the registry will be empty. - Flag bits will be allocated First-Come, First Served consistent with - the BGP-SID TLV Types registry. + Flag bits will be allocated First Come First Served (FCFS) consistent + with the BGP-SID TLV Types registry. 8. Manageability Considerations This document defines a BGP attribute to address use cases such as the one described in [I-D.ietf-spring-segment-routing-msdc]. It is assumed that advertisement of the BGP Prefix-SID attribute is controlled by the operator in order to: o Prevent undesired origination/advertisement of the BGP Prefix-SID attribute. By default, a BGP Prefix-SID attribute SHOULD NOT be @@ -620,29 +620,31 @@ The authors would like to thank Satya Mohanty for his contribution to this document. The authors would like to thank Alvaro Retana for substantive comments as part of the Routing AD review. The authors would like to thank Shyam Sethuram for comments and discussion of TLV processing and validation. + The authors would like to thank Peter Lee for IETF last call review. + 12. References 12.1. Normative References [I-D.ietf-spring-segment-routing] Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing - Architecture", draft-ietf-spring-segment-routing-14 (work - in progress), December 2017. + Architecture", draft-ietf-spring-segment-routing-15 (work + in progress), January 2018. [I-D.ietf-spring-segment-routing-mpls] Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing with MPLS data plane", draft-ietf-spring-segment-routing-mpls-11 (work in progress), October 2017. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8277] Rosen, E., "Using BGP to Bind MPLS Labels to Address Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017, . 12.2. Informative References [I-D.ietf-idr-bgp-ls-segment-routing-ext] - Previdi, S., Psenak, P., Filsfils, C., Gredler, H., and M. - Chen, "BGP Link-State extensions for Segment Routing", - draft-ietf-idr-bgp-ls-segment-routing-ext-03 (work in - progress), July 2017. + Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., + and M. Chen, "BGP Link-State extensions for Segment + Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-04 + (work in progress), January 2018. [I-D.ietf-idr-bgpls-segment-routing-epe] Previdi, S., Filsfils, C., Patel, K., Ray, S., and J. Dong, "BGP-LS extensions for Segment Routing BGP Egress Peer Engineering", draft-ietf-idr-bgpls-segment-routing- epe-14 (work in progress), December 2017. [I-D.ietf-spring-segment-routing-msdc] Filsfils, C., Previdi, S., Mitchell, J., Aries, E., and P. Lapukhov, "BGP-Prefix Segment in large-scale data