--- 1/draft-ietf-idr-bgp-prefix-sid-22.txt 2018-06-14 07:14:10.496267132 -0700 +++ 2/draft-ietf-idr-bgp-prefix-sid-23.txt 2018-06-14 07:14:10.716272388 -0700 @@ -1,23 +1,23 @@ IDR S. Previdi, Ed. Internet-Draft C. Filsfils Intended status: Standards Track A. Lindem, Ed. -Expires: December 15, 2018 Cisco Systems +Expires: December 16, 2018 Cisco Systems A. Sreekantiah H. Gredler RtBrick Inc. - June 13, 2018 + June 14, 2018 Segment Routing Prefix SID extensions for BGP - draft-ietf-idr-bgp-prefix-sid-22 + draft-ietf-idr-bgp-prefix-sid-23 Abstract The 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. An SR domain is defined as a single administrative domain for global SID @@ -43,21 +43,21 @@ 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 December 15, 2018. + This Internet-Draft will expire on December 16, 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 @@ -67,31 +67,31 @@ the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. BGP-Prefix-SID . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. MPLS BGP Prefix SID . . . . . . . . . . . . . . . . . . . 4 3. BGP Prefix-SID Attribute . . . . . . . . . . . . . . . . . . 5 3.1. Label-Index TLV . . . . . . . . . . . . . . . . . . . . . 6 - 3.2. Originator SRGB TLV . . . . . . . . . . . . . . . . . . . 7 + 3.2. Originator SRGB TLV . . . . . . . . . . . . . . . . . . . 6 4. Receiving BGP Prefix-SID Attribute . . . . . . . . . . . . . 8 4.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 8 - 5. Advertising BGP Prefix-SID Attribute . . . . . . . . . . . . 10 + 5. Advertising BGP Prefix-SID Attribute . . . . . . . . . . . . 9 5.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 10 - 6. Error Handling of BGP Prefix-SID Attribute . . . . . . . . . 11 + 6. Error Handling of BGP Prefix-SID Attribute . . . . . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 8. Manageability Considerations . . . . . . . . . . . . . . . . 12 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 + 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 13 - 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 + 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 12.1. Normative References . . . . . . . . . . . . . . . . . . 14 12.2. Informative References . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 1. Introduction The 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 @@ -109,75 +109,73 @@ to the MPLS dataplane ([I-D.ietf-spring-segment-routing-mpls]), the SID consists of a label. [I-D.ietf-spring-segment-routing] also describes how segment routing can be applied to an IPv6 dataplane (SRv6) using an IPv6 routing header containing a stack of SR SIDs encoded as IPv6 addresses [I-D.ietf-6man-segment-routing-header]. The applicability and support for Segment Routing over IPv6 is beyond the scope of this document. - 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 Equal-Cost Multi-Path (ECMP) 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 by the BGP Prefix-SID. + A BGP-Prefix Segment is a BGP prefix with a Prefix-SID attached. A + BGP Prefix-SID is always a global SID + ([I-D.ietf-spring-segment-routing]) within the SR 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 Equal-Cost Multi-Path (ECMP) 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 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 Multiprotocol BGP labeled IPv4/IPv6 Unicast + to prefixes from Multiprotocol BGP IPv4/IPv6 Labeled Unicast ([RFC4760], [RFC8277]). Usage of the BGP Prefix-SID attribute for other Address Family Identifier (AFI)/ Subsequent Address Family Identifier (SAFI) combinations is not defined herein but may be specified in future specifications. [I-D.ietf-spring-segment-routing-msdc] describes example use cases where the BGP Prefix-SID is used for the above AFI/SAFI combinations. It should be noted that: - o A BGP Prefix-SID MAY be global between domains when the - interconnected domains agree on the SID allocation scheme. - Alternatively, when interconnecting domains, the ASBRs of each - domain will have to handle the advertisement of unique SIDs. The - mechanisms for such interconnection are outside the scope of the - protocol extensions defined in this document. + o A BGP Prefix-SID MAY be global across ASes when the interconnected + ASes agree on the SID allocation scheme. Alternatively, when + interconnecting ASes, the ASBRs of each domain will have to handle + the advertisement of unique SIDs. The mechanisms for such + interconnection are outside the scope of the protocol extensions + defined in this document. - o A BGP Prefix-SID MAY be attached to a prefix. In addition, each - prefix will likely have a different AS_PATH attribute. This - implies that each prefix is advertised individually, reducing the - ability to pack BGP advertisements (when sharing common - attributes). + o A BGP Prefix-SID MAY be attached to a prefix. This implies that + each prefix is advertised individually, reducing the ability to + pack BGP advertisements (when sharing common attributes). 2. BGP-Prefix-SID The BGP Prefix-SID advertised for BGP prefix P indicates that the segment routed path should be used (as described below) if the BGP best path selects the corresponding Network Layer Reachability Information (NLRI). 2.1. MPLS BGP Prefix SID 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. + locally originated 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 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]. @@ -197,42 +195,35 @@ This document 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 [I-D.ietf-idr-bgp-ls-segment-routing-ext]. However, as an optional alternative for the advertisement of the local SRGB without the topology nor the peer SIDs, hence without applicability for TE, the Originator SRGB TLV of the BGP Prefix- SID attribute is specified in Section 3.2 of this document. - As defined in [I-D.ietf-spring-segment-routing], the label index - L_I is an offset into 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. It should be noted that while SRGBs and - SIDs are advertised using 32-bit values, the derived label is - advertised in the 20 right-most bits. See Section 4.1 for more - details. + A BGP speaker will derive its local MPLS label L from the label + index L_I and its local SRGB as described in + [I-D.ietf-spring-segment-routing-mpls]. The BGP speaker then + programs the MPLS label L in its MPLS dataplane as its incoming/ + local label for the prefix. See Section 4.1 for more details. The outgoing label for the prefix is found in the NLRI of the - Multiprotocol BGP labeled IPv4/IPv6 Unicast prefix advertisement + Multiprotocol BGP IPv4/IPv6 Labeled Unicast prefix advertisement as defined in [RFC8277]. The label index L_I is only used as a hint to derive the local/incoming label. Section 3.1 of this document specifies the Label-Index TLV of the BGP Prefix-SID attribute; this TLV can be used to advertise the label index for a given prefix. - In order to advertise the label index of a given prefix P and, - optionally, the SRGB, an extension to BGP is needed: the BGP Prefix- - SID attribute. This extension is described in subsequent sections. - 3. BGP Prefix-SID Attribute The BGP Prefix-SID attribute is an optional, transitive BGP path attribute. The attribute type code 40 has been assigned by IANA (see Section 7). The BGP Prefix-SID attribute is defined here to be a set of elements encoded as "Type/Length/Value" tuples (i.e., a set of TLVs). All BGP Prefix-SID attribute TLVs will start with a 1-octet type and a 2-octet length. The following TLVs are defined in this document: @@ -233,31 +224,30 @@ Section 7). The BGP Prefix-SID attribute is defined here to be a set of elements encoded as "Type/Length/Value" tuples (i.e., a set of TLVs). All BGP Prefix-SID attribute TLVs will start with a 1-octet type and a 2-octet length. The following TLVs are defined in this document: o Label-Index TLV o Originator SRGB TLV - The Label-Index and Originator SRGB TLVs are used only when SR is applied to the MPLS dataplane. For future extensibility, 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 MUST + attached to IPv4/IPv6 Labeled 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -310,79 +300,65 @@ o Type is 3. o Length is the total length in octets of the value portion of the TLV: 2 + (non-zero 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 + o SRGB: 3 octets specifying the first label in the range followed by + 3 octets specifying the number of labels in the range. Note that the SRGB field MAY appear multiple times. If the SRGB field appears multiple times, the SRGB consists of multiple ranges that are concatenated. 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 + TLV MUST NOT be changed during the propagation of the BGP update. 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 receiving routers concatenate the ranges and build the Segment - Routing Global Block (SRGB) as follows: - - SRGB = [100, 199] - [1000, 1099] - [500, 599] - - The indexes span multiple ranges: - - index=0 means label 100 - ... - index 99 means label 199 - index 100 means label 1000 - index 199 means label 1099 - ... - index 200 means label 500 - ... + Examples of how the receiving routers concatenate the ranges and + build their neighbor's Segment Routing Global Block (SRGB) are + included in [I-D.ietf-spring-segment-routing-mpls]). The originator SRGB may only appear in a BGP Prefix-SID attribute - attached to Labeled IPv4/IPv6 unicast prefixes ([RFC8277]). It MUST + attached to IPv4/IPv6 Labeled Unicast prefixes ([RFC8277]). It MUST be ignored when received for other BGP AFI/SAFI combinations. Since the Label-Index TLV is required for IPv4/IPv6 prefix applicability, the originator SRGB will be ignored if it is not specified consistent with Section 6. 4. Receiving BGP Prefix-SID Attribute A BGP speaker receiving a BGP Prefix-SID attribute from an External BGP (EBGP) 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 SHOULD log an error for further analysis when discarding an attribute. 4.1. MPLS Dataplane: Labeled Unicast A BGP session supporting the Multiprotocol BGP labeled IPv4 or IPv6 Unicast ([RFC8277]) AFI/SAFI is required. - 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 "invalid" by the - receiving speaker. + When the BGP Prefix-SID attribute is attached to a BGP labeled IPv4 + or IPv6 Unicast [RFC8277] AFI/SAFI, it 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 + "invalid" by the receiving speaker. - The label index provides the receiving BGP speaker with guidance as - to the incoming label that SHOULD be assigned by that BGP speaker. + The label index provides guidance to the receiving BGP speaker as to + the incoming label that SHOULD be allocated to the prefix. 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. The mechanisms through which a given label index value is assigned to a given prefix are outside the scope of this document. 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 @@ -406,67 +382,67 @@ the best path, it SHOULD program the derived label as the label for the prefix in its local MPLS dataplane. When a BGP speaker receives a path from a neighbor with an "invalid" or "conflicting" BGP Prefix-SID attribute or when a BGP speaker receives a path from a neighbor with a BGP Prefix-SID attribute but is unable to process it (e.g., local policy disables the functionality), it MUST ignore the BGP Prefix-SID attribute. For the purposes of label allocation, a BGP speaker MUST assign a local (also called dynamic) label (non-SRGB) for such a prefix as per classic - Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]) operation. + Multiprotocol BGP IPv4/IPv6 Labeled Unicast ([RFC8277]) operation. In the case of an "invalid" BGP Prefix-SID attribute, a BGP speaker MUST follow the error handling rules specified in Section 6. A BGP speaker SHOULD log an error for further analysis. In the case of a "conflicting" BGP Prefix-SID attribute, a BGP speaker SHOULD NOT treat it as error and SHOULD propagate the attribute unchanged. A BGP Speaker SHOULD log a warning for further analysis, i.e., in the case the conflict is not due to a label index transition. When a BGP Prefix-SID attribute changes and transitions from "conflicting" to "acceptable", the BGP Prefix-SID attributes for other prefixes may also transition to "acceptable" as well. Implementations SHOULD assure all impacted prefixes revert to using the label indices corresponding to these newly "acceptable" BGP Prefix-SID attributes. The outgoing label is always programmed as per classic Multiprotocol - BGP labeled IPv4/IPv6 Unicast ([RFC8277]) operation. Specifically, a + BGP IPv4/IPv6 Labeled Unicast ([RFC8277]) operation. Specifically, a BGP speaker receiving a prefix with a BGP Prefix-SID attribute and a label NLRI field of Implicit NULL [RFC3032] from a neighbor 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. 5. Advertising BGP Prefix-SID Attribute - The BGP Prefix-SID attribute MAY be attached to labeled BGP prefixes - (IPv4/IPv6) [RFC8277]. In order to prevent distribution of the BGP - Prefix-SID attribute beyond its intended scope of applicability, + The BGP Prefix-SID attribute MAY be attached to BGP IPv4/IPv6 Label + Unicast prefixes [RFC8277]. In order to prevent distribution of the + BGP Prefix-SID attribute beyond its intended scope of applicability, attribute filtering SHOULD be deployed to remove the BGP Prefix-SID attribute at the administrative boundary of the segment routing domain. A BGP speaker that advertises a path received from one of its neighbors SHOULD advertise the BGP Prefix-SID received with the path without modification, as long as the BGP Prefix-SID was acceptable. If the path did not come with a BGP Prefix-SID attribute, the speaker MAY attach a BGP Prefix-SID to the path if configured to do so. The content of the TLVs present in the BGP Prefix-SID is determined by the configuration. 5.1. MPLS Dataplane: Labeled Unicast A BGP speaker that originates a prefix attaches the BGP Prefix-SID attribute when it advertises the prefix to its neighbors via - Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]). The value + Multiprotocol BGP IPv4/IPv6 Labeled Unicast ([RFC8277]). The value of the label index in the Label-Index TLV is determined by configuration. A BGP speaker that originates a BGP Prefix-SID attribute MAY optionally announce the Originator SRGB TLV along with the mandatory Label-Index TLV. The content of the Originator SRGB TLV is determined by configuration. Since the label index value must be unique within an SR domain, by default an implementation SHOULD NOT advertise the BGP Prefix-SID @@ -476,38 +452,41 @@ In all cases, the label field of the advertised NLRI ([RFC8277], [RFC4364]) MUST be set to the local/incoming label programmed in the MPLS dataplane for the given advertised prefix. If the prefix is associated with one of the BGP speaker's interfaces, this is the usual MPLS label (such as the Implicit or Explicit NULL label [RFC3032]). 6. Error Handling of BGP Prefix-SID Attribute When a BGP Speaker receives a BGP Update message containing a - malformed or invalid BGP Prefix-SID attribute attached to a Labeled - IPv4/IPv6 unicast prefix [RFC8277], it MUST ignore the received BGP + malformed or invalid BGP Prefix-SID attribute attached to a IPv4/IPv6 + Labeled Unicast prefix [RFC8277], it MUST ignore the received BGP Prefix-SID attributes and not advertise it to other BGP peers. In this context, a malformed BGP Prefix-SID attribute is one that cannot be parsed due to not meeting the minimum attribute length requirement, contains a TLV length that doesn't conform to the length constraints for the TLV, or a contains TLV length that would extend beyond the end of the attribute (as defined by the attribute length). This is equivalent to the "Attribute discard" action specified in + [RFC7606]. When discarding an attribute, 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. 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. + As per with [RFC7606], if the BGP Prefix-SID attribute appears more + than once in an UPDATE message, then all the occurrences of the + attribute other than the first one SHALL be discarded and the UPDATE + message will continue to be processed. Similarly, if a recognized + TLV appears more than once in an BGP Prefix-SID attribute while the + specification only allows for a single occurrence, then all the + occurrences of the TLV other than the first one SHALL be discarded + and the Prefix-SID attribute will continue to be processed. For future extensibility, 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) to the BGP Prefix-SID attribute from the BGP Path Attributes registry. @@ -530,28 +509,28 @@ 0 Reserved this document 1 Label-Index this document 2 Deprecated this document 3 Originator SRGB this document 4-254 Unassigned 255 Reserved this document This document also requests creation of the "BGP Prefix-SID Label- Index TLV Flags" registry under the "Border Gateway Protocol (BGP) Parameters" registry, Reference: draft-ietf-idr-bgp-prefix-sid. - Initially, this 16 bit flags registry will be empty. Flag bits will + Initially, this 16-bit flags registry will be empty. Flag bits will be allocated First Come First Served (FCFS) consistent with the BGP Prefix-SID TLV Types registry. Finally, this document requests creation of the "BGP Prefix-SID Originator SRGB TLV Flags" registry under the "Border Gateway Protocol (BGP) Parameters" registry, Reference: draft-ietf-idr-bgp- - prefix-sid. Initially, this 16 bit flags registry will be empty. + prefix-sid. Initially, this 16-bit flags registry will be empty. Flag bits will be allocated First Come First Served (FCFS) consistent with the BGP Prefix-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: @@ -590,22 +569,23 @@ doesn't want to leak any information related to internal prefixes and topology outside of the administrative domain. The internal information includes the BGP Prefix-SID. In order to prevent such leaking, the common BGP mechanisms (filters) are applied at the boundary of the SR/administrative domain. Local BGP attribute filtering policies and mechanisms are not standardized and, consequently, beyond the scope of this document. To prevent a Denial-of-Service (DoS) or Distributed-Denial-of-Service (DDoS) attack due to excessive BGP updates with an invalid or - conflicting BGP Prefix-SID attribute, message rate-limiting as well - as suppression of duplicate messages SHOULD be deployed. + conflicting BGP Prefix-SID attribute, error log message rate-limiting + as well as suppression of duplicate error log messages SHOULD be + deployed. 10. Contributors Keyur Patel Arrcus, Inc. US Email: Keyur@arrcus.com Saikat Ray @@ -615,20 +595,24 @@ Email: raysaikat@gmail.com 11. Acknowledgements 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 Bruno Decraene for substantive + comments and suggested text as part of the Routing Directorate + review. + The authors would like to thank Shyam Sethuram for comments and discussion of TLV processing and validation. The authors would like to thank Robert Raszuk for comments and suggestions regarding the MPLS data plane behavior. The authors would like to thank Krishna Deevi, Juan Alcaide, Howard Yang, and Jakob Heitz for discussions on conflicting BGP Prefix-SID label indices and BGP add paths.