| draft-ietf-idr-bgp-prefix-sid-11.txt | draft-ietf-idr-bgp-prefix-sid-12.txt | |||
|---|---|---|---|---|
| IDR S. Previdi, Ed. | IDR S. Previdi, Ed. | |||
| Internet-Draft C. Filsfils | Internet-Draft C. Filsfils | |||
| Intended status: Standards Track A. Lindem | Intended status: Standards Track A. Lindem | |||
| Expires: August 4, 2018 Cisco Systems | Expires: August 8, 2018 Cisco Systems | |||
| A. Sreekantiah | A. Sreekantiah | |||
| H. Gredler | H. Gredler | |||
| RtBrick Inc. | RtBrick Inc. | |||
| January 31, 2018 | February 4, 2018 | |||
| Segment Routing Prefix SID extensions for BGP | Segment Routing Prefix SID extensions for BGP | |||
| draft-ietf-idr-bgp-prefix-sid-11 | draft-ietf-idr-bgp-prefix-sid-12 | |||
| Abstract | Abstract | |||
| Segment Routing (SR) architecture allows a node to steer a packet | Segment Routing (SR) architecture allows a node to steer a packet | |||
| flow through any topological path and service chain by leveraging | flow through any topological path and service chain by leveraging | |||
| source routing. The ingress node prepends an SR header to a packet | source routing. The ingress node prepends an SR header to a packet | |||
| containing a set of segment identifiers (SID). Each SID represents a | containing a set of segment identifiers (SID). Each SID represents a | |||
| topological or a service-based instruction. Per-flow state is | topological or a service-based instruction. Per-flow state is | |||
| maintained only on the ingress node of the SR domain. | maintained only on the ingress node of the SR domain. | |||
| skipping to change at page 2, line 7 ¶ | skipping to change at page 2, line 7 ¶ | |||
| Internet-Drafts are working documents of the Internet Engineering | Internet-Drafts are working documents of the Internet Engineering | |||
| Task Force (IETF). Note that other groups may also distribute | Task Force (IETF). Note that other groups may also distribute | |||
| working documents as Internet-Drafts. The list of current Internet- | working documents as Internet-Drafts. The list of current Internet- | |||
| Drafts is at http://datatracker.ietf.org/drafts/current/. | Drafts is at http://datatracker.ietf.org/drafts/current/. | |||
| Internet-Drafts are draft documents valid for a maximum of six months | Internet-Drafts are draft documents valid for a maximum of six months | |||
| and may be updated, replaced, or obsoleted by other documents at any | and may be updated, replaced, or obsoleted by other documents at any | |||
| time. It is inappropriate to use Internet-Drafts as reference | time. It is inappropriate to use Internet-Drafts as reference | |||
| material or to cite them other than as "work in progress." | material or to cite them other than as "work in progress." | |||
| This Internet-Draft will expire on August 4, 2018. | This Internet-Draft will expire on August 8, 2018. | |||
| Copyright Notice | Copyright Notice | |||
| Copyright (c) 2018 IETF Trust and the persons identified as the | Copyright (c) 2018 IETF Trust and the persons identified as the | |||
| document authors. All rights reserved. | document authors. All rights reserved. | |||
| This document is subject to BCP 78 and the IETF Trust's Legal | This document is subject to BCP 78 and the IETF Trust's Legal | |||
| Provisions Relating to IETF Documents | Provisions Relating to IETF Documents | |||
| (http://trustee.ietf.org/license-info) in effect on the date of | (http://trustee.ietf.org/license-info) in effect on the date of | |||
| publication of this document. Please review these documents | publication of this document. Please review these documents | |||
| skipping to change at page 2, line 37 ¶ | skipping to change at page 2, line 37 ¶ | |||
| 2. BGP-Prefix-SID . . . . . . . . . . . . . . . . . . . . . . . 4 | 2. BGP-Prefix-SID . . . . . . . . . . . . . . . . . . . . . . . 4 | |||
| 2.1. MPLS BGP Prefix SID . . . . . . . . . . . . . . . . . . . 4 | 2.1. MPLS BGP Prefix SID . . . . . . . . . . . . . . . . . . . 4 | |||
| 2.2. IPv6 Prefix Segment . . . . . . . . . . . . . . . . . . . 5 | 2.2. IPv6 Prefix Segment . . . . . . . . . . . . . . . . . . . 5 | |||
| 3. BGP Prefix-SID Attribute . . . . . . . . . . . . . . . . . . 5 | 3. BGP Prefix-SID Attribute . . . . . . . . . . . . . . . . . . 5 | |||
| 3.1. Label-Index TLV . . . . . . . . . . . . . . . . . . . . . 6 | 3.1. Label-Index TLV . . . . . . . . . . . . . . . . . . . . . 6 | |||
| 3.2. IPv6 SID . . . . . . . . . . . . . . . . . . . . . . . . 7 | 3.2. IPv6 SID . . . . . . . . . . . . . . . . . . . . . . . . 7 | |||
| 3.3. Originator SRGB TLV . . . . . . . . . . . . . . . . . . . 7 | 3.3. Originator SRGB TLV . . . . . . . . . . . . . . . . . . . 7 | |||
| 4. Receiving BGP Prefix-SID Attribute . . . . . . . . . . . . . 9 | 4. Receiving BGP Prefix-SID Attribute . . . . . . . . . . . . . 9 | |||
| 4.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 9 | 4.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 9 | |||
| 4.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 10 | 4.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 10 | |||
| 5. Advertising BGP Prefix-SID Attribute . . . . . . . . . . . . 10 | 5. Advertising BGP Prefix-SID Attribute . . . . . . . . . . . . 11 | |||
| 5.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 11 | 5.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 11 | |||
| 5.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 11 | 5.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 12 | |||
| 6. Error Handling of BGP Prefix-SID Attribute . . . . . . . . . 11 | 6. Error Handling of BGP Prefix-SID Attribute . . . . . . . . . 12 | |||
| 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 | 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 | |||
| 8. Manageability Considerations . . . . . . . . . . . . . . . . 13 | 8. Manageability Considerations . . . . . . . . . . . . . . . . 13 | |||
| 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 | 9. Security Considerations . . . . . . . . . . . . . . . . . . . 14 | |||
| 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 13 | 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 14 | |||
| 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 | 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 | |||
| 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 | 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 | |||
| 12.1. Normative References . . . . . . . . . . . . . . . . . . 14 | 12.1. Normative References . . . . . . . . . . . . . . . . . . 15 | |||
| 12.2. Informative References . . . . . . . . . . . . . . . . . 15 | 12.2. Informative References . . . . . . . . . . . . . . . . . 16 | |||
| Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 | Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 | |||
| 1. Introduction | 1. Introduction | |||
| Segment Routing (SR) architecture leverages the source routing | Segment Routing (SR) architecture leverages the source routing | |||
| paradigm. A group of inter-connected nodes that use SR forms an SR | paradigm. A group of inter-connected nodes that use SR forms an SR | |||
| domain. A segment represents either a topological instruction such | domain. A segment represents either a topological instruction such | |||
| as "go to prefix P following shortest path" or a service instruction | 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. | segments may be defined in the future. | |||
| A segment is identified through a Segment Identifier (SID). | A segment is identified through a Segment Identifier (SID). | |||
| Typically, the ingress node of the SR domain prepends an SR header | Typically, the ingress node of the SR domain prepends an SR header | |||
| containing segments identifiers (SIDs) to an incoming packet. | containing segments identifiers (SIDs) to an incoming packet. | |||
| As described in [I-D.ietf-spring-segment-routing], when SR is applied | 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 | SID consists of a label while when SR is applied to the IPv6 | |||
| dataplane the SID consists of an IPv6 address. | dataplane the SID consists of an IPv6 address. | |||
| A BGP-Prefix Segment (and its BGP Prefix-SID), is a BGP segment | 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 | 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., | ([I-D.ietf-spring-segment-routing]) within the SR/BGP domain (i.e., | |||
| the set of Autonomous Systems under a common administration and | the set of Autonomous Systems under a common administration and | |||
| control and where SR is used) and identifies an instruction to | control and where SR is used) and identifies an instruction to | |||
| forward the packet over the ECMP-aware best-path computed by BGP 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 | 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. | by the BGP Prefix-SID. | |||
| This document describes the BGP extension to signal the BGP Prefix- | This document describes the BGP extension to signal the BGP Prefix- | |||
| skipping to change at page 3, line 45 ¶ | skipping to change at page 3, line 45 ¶ | |||
| the BGP Prefix-SID attribute and specifies the rules to originate, | the BGP Prefix-SID attribute and specifies the rules to originate, | |||
| receive, and handle error conditions for the attribute. | receive, and handle error conditions for the attribute. | |||
| The BGP Prefix-SID attribute defined in this document can be attached | The BGP Prefix-SID attribute defined in this document can be attached | |||
| to prefixes from AFI/SAFI combinations: | to prefixes from AFI/SAFI combinations: | |||
| Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]). | Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]). | |||
| Multiprotocol BGP ([RFC4760]) unlabeled IPv6 Unicast. | Multiprotocol BGP ([RFC4760]) unlabeled IPv6 Unicast. | |||
| Usage of the BGP Prefix-SID attribute for other AFI/SAFI combinations | ||||
| is not defined herein but may be specified in future specifications. | ||||
| [I-D.ietf-spring-segment-routing-msdc] describes example use cases | [I-D.ietf-spring-segment-routing-msdc] describes example use cases | |||
| where the BGP Prefix-SID is used for the above AFI/SAFI combinations. | where the BGP Prefix-SID is used for the above AFI/SAFI combinations. | |||
| It should be noted that: | It should be noted that: | |||
| o A BGP Prefix-SID MAY be global between domains when the | o A BGP Prefix-SID MAY be global between domains when the | |||
| interconnected domains agree on the SID allocation scheme. | interconnected domains agree on the SID allocation scheme. | |||
| Alternatively, when interconnecting domains, the ASBRs of each | Alternatively, when interconnecting domains, the ASBRs of each | |||
| domain will have to handle the advertisement of unique SIDs. The | domain will have to handle the advertisement of unique SIDs. The | |||
| mechanisms for such interconnection are outside the scope of the | mechanisms for such interconnection are outside the scope of the | |||
| protocol extensions defined in this document. | protocol extensions defined in this document. | |||
| o A BGP Prefix-SID MAY be attached to a prefix. In addition, each | o A BGP Prefix-SID MAY be attached to a prefix. In addition, each | |||
| prefix will likely have a different AS_PATH attribute. This | prefix will likely have a different AS_PATH attribute. This | |||
| implies that each prefix is advertised individually, reducing the | implies that each prefix is advertised individually, reducing the | |||
| ability to pack BGP advertisements (when sharing common | ability to pack BGP advertisements (when sharing common | |||
| attributes). | attributes). | |||
| 2. BGP-Prefix-SID | 2. BGP-Prefix-SID | |||
| The BGP Prefix-SID attached to a BGP prefix P represents the | The BGP Prefix-SID advertised for BGP prefix P indicates that the | |||
| instruction "go to Prefix P" along its BGP best path (potentially | segment routed path should be used (as described below) if the BGP | |||
| ECMP-enabled). | best path selects the corresponding NLRI. | |||
| 2.1. MPLS BGP Prefix SID | 2.1. MPLS BGP Prefix SID | |||
| The BGP Prefix-SID is realized on the MPLS dataplane | The BGP Prefix-SID is realized on the MPLS dataplane | |||
| ([I-D.ietf-spring-segment-routing-mpls]) in the following way: | ([I-D.ietf-spring-segment-routing-mpls]) in the following way: | |||
| The operator assigns a globally unique label index, L_I, to a | The operator assigns a globally unique label index, L_I, to a | |||
| locally sourced prefix of a BGP speaker N which is advertised to | locally sourced prefix of a BGP speaker N which is advertised to | |||
| all other BGP speakers in the SR domain. | all other BGP speakers in the SR domain. | |||
| skipping to change at page 5, line 24 ¶ | skipping to change at page 5, line 26 ¶ | |||
| As defined in [I-D.ietf-spring-segment-routing], the label index | 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 | 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 | 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 | SRGB, and programs L in its MPLS dataplane as its incoming/local | |||
| label for the prefix. It should be noted that while SRGBs and | label for the prefix. It should be noted that while SRGBs and | |||
| SIDs are advertised using 32-bit values, the derived label is | SIDs are advertised using 32-bit values, the derived label is | |||
| advertised in the 20 right-most bits. See Section 4.1 for more | advertised in the 20 right-most bits. See Section 4.1 for more | |||
| details. | details. | |||
| The outgoing label for the prefix is found in the NLRI of the | The outgoing label for the prefix is found in the NLRI of the | |||
| Multiprotocol BGP labeled IPv4/IPv6 Unicast prefix advertisement. | Multiprotocol BGP labeled IPv4/IPv6 Unicast prefix advertisement | |||
| The label index L_I is only used as a hint to derive the local/ | as defined in [RFC8277]. The label index L_I is only used as a | |||
| incoming label. | hint to derive the local/incoming label. | |||
| Section 3.1 of this document specifies the Label-Index TLV of the | 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 | BGP Prefix-SID attribute; this TLV can be used to advertise the | |||
| label index for a given prefix. | label index for a given prefix. | |||
| In order to advertise the label index of a given prefix P and, | 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- | optionally, the SRGB, an extension to BGP is needed: the BGP Prefix- | |||
| SID attribute. This extension is described in subsequent sections. | SID attribute. This extension is described in subsequent sections. | |||
| 2.2. IPv6 Prefix Segment | 2.2. IPv6 Prefix Segment | |||
| skipping to change at page 8, line 38 ¶ | skipping to change at page 8, line 38 ¶ | |||
| o Length is the total length in octets of the value portion of the | 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. | o Flags: 16 bits of flags. None are defined in this document. | |||
| Flags MUST be clear on transmission and MUST be ignored on | Flags MUST be clear on transmission and MUST be ignored on | |||
| reception. | reception. | |||
| o SRGB: 3 octets of base followed by 3 octets of range. Note that | 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 | the SRGB field MAY appear multiple times. If the SRGB field | |||
| appears multiple times, the SRGB consists of multiple ranges. | appears multiple times, the SRGB consists of multiple ranges that | |||
| are concatenated. | ||||
| The Originator SRGB TLV contains the SRGB of the node originating the | The Originator SRGB TLV contains the SRGB of the node originating the | |||
| prefix to which the BGP Prefix-SID is attached. The Originator SRGB | prefix to which the BGP Prefix-SID is attached. The Originator SRGB | |||
| TLV MUST NOT be changed during the propagation of the BGP update. | TLV MUST NOT be changed during the propagation of the BGP update. | |||
| The originator SRGB describes the SRGB of the node where the BGP | The originator SRGB describes the SRGB of the node where the BGP | |||
| Prefix SID is attached. It is used to build segment routing policies | Prefix SID is attached. It is used to build segment routing policies | |||
| when different SRGBs are used in the fabric, for example | when different SRGBs are used in the fabric, for example | |||
| ([I-D.ietf-spring-segment-routing-msdc]). | ([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 | ||||
| ... | ||||
| The originator SRGB may only appear in a BGP Prefix-SID attribute | The originator SRGB may only appear in a BGP Prefix-SID attribute | |||
| attached to Labeled IPv4/IPv6 unicast prefixes ([RFC8277]). It MUST | attached to Labeled IPv4/IPv6 unicast prefixes ([RFC8277]). It MUST | |||
| be ignored when received for other BGP AFI/SAFI combinations. | 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 | 4. Receiving BGP Prefix-SID Attribute | |||
| A BGP speaker receiving a BGP Prefix-SID attribute from an EBGP | 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 | discard the attribute unless it is configured to accept the attribute | |||
| from the EBGP neighbor. A BGP speaker MAY log an error for further | from the EBGP neighbor. A BGP speaker MAY log an error for further | |||
| analysis when discarding an attribute. | analysis when discarding an attribute. | |||
| 4.1. MPLS Dataplane: Labeled Unicast | 4.1. MPLS Dataplane: Labeled Unicast | |||
| skipping to change at page 9, line 29 ¶ | skipping to change at page 9, line 51 ¶ | |||
| SRGB_End]. The preferred method for deriving the SRGB is a matter of | SRGB_End]. The preferred method for deriving the SRGB is a matter of | |||
| local node configuration. | local node configuration. | |||
| Given a label index L_I, we refer to (L = L_I + SRGB_Start) as the | 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 | derived label. A BGP Prefix-SID attribute is designated | |||
| "unacceptable" for a speaker M if the derived label value L lies | "unacceptable" for a speaker M if the derived label value L lies | |||
| outside the SRGB configured on M. Otherwise the Label-Index TLV is | outside the SRGB configured on M. Otherwise the Label-Index TLV is | |||
| designated "acceptable" to speaker M. | designated "acceptable" to speaker M. | |||
| The mechanisms through which a given label index value is assigned to | The mechanisms through which a given label index value is assigned to | |||
| a given prefix are outside the scope of this document. The label- | a given prefix are outside the scope of this document. | |||
| 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 | The BGP Prefix-SID attribute MUST contain the Label-Index TLV and MAY | |||
| contain the Originator SRGB TLV. A BGP Prefix-SID attribute received | contain the Originator SRGB TLV. A BGP Prefix-SID attribute received | |||
| without a Label-Index TLV MUST be considered as "unacceptable" by the | without a Label-Index TLV MUST be considered as "unacceptable" by the | |||
| receiving speaker. | receiving speaker. | |||
| If multiple prefixes are received with the same label index value, | If multiple prefixes are received with the same label index value, | |||
| all these prefixes MUST have their BGP Prefix-SID attribute | all these prefixes MUST have their BGP Prefix-SID attribute | |||
| considered as "unacceptable" by the receiving speaker. | considered as "unacceptable" by the receiving speaker. | |||
| skipping to change at page 10, line 12 ¶ | skipping to change at page 10, line 33 ¶ | |||
| a path from a neighbor with a BGP Prefix-SID attribute but is unable | a path from a neighbor with a BGP Prefix-SID attribute but is unable | |||
| to process it (it does not have the capability or local policy | to process it (it does not have the capability or local policy | |||
| disables the capability), it MUST treat the path as if it came | disables the capability), it MUST treat the path as if it came | |||
| without a BGP Prefix-SID attribute. For the purposes of local label | without a BGP Prefix-SID attribute. For the purposes of local label | |||
| allocation, a BGP speaker MUST assign a local (also called dynamic) | allocation, a BGP speaker MUST assign a local (also called dynamic) | |||
| label (non-SRGB) for such a prefix as per classic Multiprotocol BGP | label (non-SRGB) for such a prefix as per classic Multiprotocol BGP | |||
| labeled IPv4/IPv6 Unicast ([RFC8277]) operation. A BGP speaker MAY | labeled IPv4/IPv6 Unicast ([RFC8277]) operation. A BGP speaker MAY | |||
| log an error for further analysis. | log an error for further analysis. | |||
| The outgoing label is always programmed as per classic Multiprotocol | The outgoing label is always programmed as per classic Multiprotocol | |||
| BGP labeled IPv4/IPv6 Unicast ([RFC8277]) operation. | BGP labeled IPv4/IPv6 Unicast ([RFC8277]) operation. Specifically, a | |||
| BGP speaker receiving a prefix with a BGP Prefix-SID attribute and a | ||||
| label NLRI field of Implicit NULL 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. | ||||
| Specifically, a BGP speaker receiving a prefix with a BGP Prefix-SID | The label index provides the receiving BGP speaker with guidance as | |||
| attribute and a label NLRI field of Implicit NULL from a neighbor | to the incoming label that SHOULD be assigned by that BGP speaker. | |||
| 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 | 4.2. IPv6 Dataplane | |||
| When an SR IPv6 BGP speaker receives an IPv6 Unicast BGP Update with | When an SR IPv6 BGP speaker receives an IPv6 Unicast BGP Update with | |||
| a prefix having the BGP Prefix-SID attribute attached, it checks | a prefix having the BGP Prefix-SID attribute attached, it checks | |||
| whether the IPv6 SID TLV is present. If present and chosen as the | whether the IPv6 SID TLV is present. If present and chosen as the | |||
| best path, the prefix is installed into the Segment Routing IPv6 | best path, the prefix is installed into the Segment Routing IPv6 | |||
| dataplane as described in [I-D.ietf-spring-segment-routing]. | dataplane as described in [I-D.ietf-spring-segment-routing]. | |||
| The Label-Index and Originator SRGB TLVs MUST be ignored on | The Label-Index and Originator SRGB TLVs MUST be ignored on | |||
| skipping to change at page 14, line 21 ¶ | skipping to change at page 14, line 48 ¶ | |||
| The authors would like to thank Satya Mohanty for his contribution to | The authors would like to thank Satya Mohanty for his contribution to | |||
| this document. | this document. | |||
| The authors would like to thank Alvaro Retana for substantive | The authors would like to thank Alvaro Retana for substantive | |||
| comments as part of the Routing AD review. | comments as part of the Routing AD review. | |||
| The authors would like to thank Shyam Sethuram for comments and | The authors would like to thank Shyam Sethuram for comments and | |||
| discussion of TLV processing and validation. | discussion of TLV processing and validation. | |||
| The authors would like to thank Peter Lee for IETF last call review. | The authors would like to thank Peter Yee and Tony Przygienda for | |||
| IETF last call directorate reviews. | ||||
| 12. References | 12. References | |||
| 12.1. Normative References | 12.1. Normative References | |||
| [I-D.ietf-spring-segment-routing] | [I-D.ietf-spring-segment-routing] | |||
| Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., | Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., | |||
| Litkowski, S., and R. Shakir, "Segment Routing | Litkowski, S., and R. Shakir, "Segment Routing | |||
| Architecture", draft-ietf-spring-segment-routing-15 (work | Architecture", draft-ietf-spring-segment-routing-15 (work | |||
| in progress), January 2018. | in progress), January 2018. | |||
| End of changes. 19 change blocks. | ||||
| 33 lines changed or deleted | 57 lines changed or added | |||
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