draft-ietf-idr-bgp-prefix-sid-10.txt   draft-ietf-idr-bgp-prefix-sid-11.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: July 20, 2018 Cisco Systems Expires: August 4, 2018 Cisco Systems
A. Sreekantiah A. Sreekantiah
H. Gredler H. Gredler
RtBrick Inc. RtBrick Inc.
January 16, 2018 January 31, 2018
Segment Routing Prefix SID extensions for BGP Segment Routing Prefix SID extensions for BGP
draft-ietf-idr-bgp-prefix-sid-10 draft-ietf-idr-bgp-prefix-sid-11
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.
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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 July 20, 2018. This Internet-Draft will expire on August 4, 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 3, line 11 skipping to change at page 3, line 11
12.1. Normative References . . . . . . . . . . . . . . . . . . 14 12.1. Normative References . . . . . . . . . . . . . . . . . . 14
12.2. Informative References . . . . . . . . . . . . . . . . . 15 12.2. Informative References . . . . . . . . . . . . . . . . . 15
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-
SID. Specifically, this document defines a BGP attribute known as SID. Specifically, this document defines a BGP attribute known as
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:
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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.
According to [I-D.ietf-spring-segment-routing], each BGP speaker According to [I-D.ietf-spring-segment-routing], each BGP speaker
is configured with a label block called the Segment Routing Global is configured with a label block called the Segment Routing Global
Block (SRGB). While [I-D.ietf-spring-segment-routing] recommends Block (SRGB). While [I-D.ietf-spring-segment-routing] recommends
to use the same SRGB across all the nodes within the SR domain, using the same SRGB across all the nodes within the SR domain, the
the SRGB of a node is a local property and could be different on SRGB of a node is a local property and could be different on
different speakers. The drawbacks of the use case where BGP different speakers. The drawbacks of the use case where BGP
speakers have different SRGBs are documented in speakers have different SRGBs are documented in
[I-D.ietf-spring-segment-routing] and [I-D.ietf-spring-segment-routing] and
[I-D.ietf-spring-segment-routing-msdc]. [I-D.ietf-spring-segment-routing-msdc].
If traffic-engineering within the SR domain is required, each node If traffic-engineering within the SR domain is required, each node
may also be required to advertise topological information and may also be required to advertise topological information and
Peering SIDs for each of its links and peers. This information is Peering SIDs for each of its links and peers. This information is
required to perform the explicit path computation and to express required to perform the explicit path computation and to express
an explicit path as a list of SIDs. The advertisement of 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]. through [I-D.ietf-idr-bgpls-segment-routing-epe].
If the BGP speakers are not all configured with the same SRGB, and If the BGP speakers are not all configured with the same SRGB, and
if traffic-engineering within the SR domain is required, each node if traffic-engineering within the SR domain is required, each node
may be required to advertise its local SRGB in addition to the may be required to advertise its local SRGB in addition to the
topological information. topological information.
This documents assumes that BGP-LS is the preferred method for This documents assumes that BGP-LS is the preferred method for
collecting both peer segments (Peer SIDs) and SRGB information collecting both peer segments (Peer SIDs) and SRGB information
through [RFC7752], [I-D.ietf-idr-bgpls-segment-routing-epe], and through [RFC7752], [I-D.ietf-idr-bgpls-segment-routing-epe], and
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o IPv6 SID TLV o IPv6 SID TLV
o Originator SRGB TLV o Originator SRGB TLV
The Label-Index and Originator SRGB TLVs are used only when SR is The Label-Index and Originator SRGB TLVs are used only when SR is
applied to the MPLS dataplane. applied to the MPLS dataplane.
The IPv6 SID TLV is used only when SR is applied to the IPv6 The IPv6 SID TLV is used only when SR is applied to the IPv6
dataplane. dataplane.
For future extendibility, unknown TLVs are ignored and propagated For future extendibility, unknown TLVs MUST be ignored and propagated
unmodified. unmodified.
3.1. Label-Index TLV 3.1. Label-Index TLV
The Label-Index TLV MUST be present in the BGP Prefix-SID attribute 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 be ignored when received for other BGP AFI/SAFI combinations. The
Label-Index TLV has the following format: Label-Index TLV has the following format:
0 1 2 3 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 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 | | Type | Length | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Label Index | | Flags | Label Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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flag field MUST be clear on transmission and MUST be ignored on flag field MUST be clear on transmission and MUST be ignored on
reception. reception.
o Label Index: 32-bit value representing the index value in the SRGB o Label Index: 32-bit value representing the index value in the SRGB
space. space.
3.2. IPv6 SID 3.2. IPv6 SID
The IPv6 SID TLV MAY be present in the BGP Prefix-SID attribute The IPv6 SID TLV MAY be present in the BGP Prefix-SID attribute
attached to MP-BGP unlabeled IPv6 unicast prefixes ([RFC4760]). It 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: TLV has the following format:
0 1 2 3 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 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 | | Type | Length | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | | | RESERVED | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| | | |
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| SRGB n (6 octets) | | SRGB n (6 octets) |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
o Type is 3. o Type is 3.
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.
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 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 will 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.
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
A Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]) session A Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]) session
type is required. type is required.
A BGP speaker may be locally configured with an SRGB=[SRGB_Start, 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 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 call L = L_I + SRGB_Start as the derived Given a label index L_I, we refer to (L = L_I + SRGB_Start) as the
label. A BGP Prefix-SID attribute is designated "unacceptable" for a derived label. A BGP Prefix-SID attribute is designated
speaker M if the derived label value L lies outside the SRGB "unacceptable" for a speaker M if the derived label value L lies
configured on M. Otherwise the Label-Index TLV is designated outside the SRGB configured on M. Otherwise the Label-Index TLV is
"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. The label-
index value associated with a prefix is locally configured at the BGP index value associated with a prefix is locally configured at the BGP
node originating the prefix. 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.
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MUST adhere to standard behavior and program its MPLS dataplane to MUST adhere to standard behavior and program its MPLS dataplane to
pop the top label when forwarding traffic to the prefix. The label pop the top label when forwarding traffic to the prefix. The label
NLRI defines the outbound label that MUST be used by the receiving NLRI defines the outbound label that MUST be used by the receiving
node. The label index gives the information to the receiving node on node. The label index gives the information to the receiving node on
which local/incoming label the BGP speaker SHOULD assign. 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 the chosen as whether the IPv6 SID TLV is present. If present and chosen as the
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
reception. For future extendibility, no TLVs are required for the reception. For future extendibility, no TLVs are required for the
BGP IPv6 unicast address family. However, a BGP Prefix-SID attribute BGP IPv6 unicast address family. However, a BGP Prefix-SID attribute
corresponding to the BGP IPv6 address family without an IPv6 SID TLV corresponding to the BGP IPv6 address family without an IPv6 SID TLV
will be ignored. MUST be ignored.
5. Advertising BGP Prefix-SID Attribute 5. Advertising BGP Prefix-SID Attribute
The BGP Prefix-SID attribute MAY be attached to labeled BGP prefixes The BGP Prefix-SID attribute MAY be attached to labeled BGP prefixes
(IPv4/IPv6) [RFC8277] or to IPv6 unicast prefixes [RFC4760]. In (IPv4/IPv6) [RFC8277] or to IPv6 unicast prefixes [RFC4760]. In
order to prevent distribution of the BGP Prefix-SID attribute beyond order to prevent distribution of the BGP Prefix-SID attribute beyond
its intended scope of applicability, attribute filtering SHOULD be its intended scope of applicability, attribute filtering SHOULD be
deployed. deployed.
A BGP speaker that advertises a path received from one of its A BGP speaker that advertises a path received from one of its
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unlabeled IPv6 unicast prefix [RFC4760], it MUST treat the unlabeled IPv6 unicast prefix [RFC4760], it MUST treat the
advertisement as a withdrawal. This is equivalent to the "Treat-as- advertisement as a withdrawal. This is equivalent to the "Treat-as-
withdraw" action specified in [RFC7606]. This action is required withdraw" action specified in [RFC7606]. This action is required
since simply ignoring the BGP Prefix-SID attribute would modify the since simply ignoring the BGP Prefix-SID attribute would modify the
installed path and the "Attribute discard" option is not applicable installed path and the "Attribute discard" option is not applicable
in this case [RFC7606]. When withdrawing the prefix, a BGP speaker in this case [RFC7606]. When withdrawing the prefix, a BGP speaker
SHOULD log an error for further analysis. SHOULD log an error for further analysis.
Consistent with [RFC7606], only the first occurrence of the BGP Consistent with [RFC7606], only the first occurrence of the BGP
Prefix-SID attribute will be considered and subsequent occurrences 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 Prefix-SID attribute TLV of a given TLV type will be considered
unless the specification of that TLV type allows for multiple unless the specification of that TLV type allows for multiple
occurrences. occurrences.
For future extendibility, unknown TLVs should be ignored and For future extendibility, unknown TLVs MUST be ignored and propagated
propagated unmodified. unmodified.
7. IANA Considerations 7. IANA Considerations
This document defines a BGP path attribute known as the BGP Prefix- This document defines a BGP path attribute known as the BGP Prefix-
SID attribute. This document requests IANA to assign an attribute SID attribute. This document requests IANA to assign an attribute
code type (suggested value: 40) the BGP Prefix-SID attribute from the code type (suggested value: 40) to the BGP Prefix-SID attribute from
BGP Path Attributes registry. the BGP Path Attributes registry.
Currently, IANA temporarily assigned the following: Currently, IANA temporarily assigned the following:
40 BGP Prefix-SID (TEMPORARY - registered 2015-09-30, expires 40 BGP Prefix-SID (TEMPORARY - registered 2015-09-30, expires
2016-09-30) [draft-ietf-idr-bgp-prefix-sid] 2016-09-30) [draft-ietf-idr-bgp-prefix-sid]
This document defines 3 TLVs for the BGP Prefix-SID attribute. These 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 TLVs need to be registered with IANA. We request IANA to create a
registry for BGP Prefix-SID Attribute TLVs as follows: registry for BGP Prefix-SID Attribute TLVs as follows:
Under "Border Gateway Protocol (BGP) Parameters" registry, "BGP Under "Border Gateway Protocol (BGP) Parameters" registry, "BGP
Prefix-SID TLV Types" Reference: draft-ietf-idr-bgp-prefix-sid Prefix-SID TLV Types" Reference: draft-ietf-idr-bgp-prefix-sid
Registration Procedure(s): Values 1-254 First Come, First Served, Registration Procedure(s): Values 1-254 First Come First Served
Value 0 and 255 reserved (FCFS), Value 0 and 255 reserved
Value Type Reference Value Type Reference
0 Reserved this document 0 Reserved this document
1 Label-Index this document 1 Label-Index this document
2 IPv6 SID this document 2 IPv6 SID this document
3 Originator SRGB this document 3 Originator SRGB this document
4-254 Unassigned 4-254 Unassigned
255 Reserved this document 255 Reserved this document
This document also creates a registry for the 16 bits of flags in the 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 Label-Index TLV. Initially, the registry will be empty. Flag bits
will be allocated First-Come, First Served consistent with the BGP- will be allocated First Come First Served (FCFS) consistent with the
SID TLV Types registry. BGP-SID TLV Types registry.
Finally, this document creates a registry for the 16 bits of flags in Finally, this document creates a registry for the 16 bits of flags in
the SRGB Originator TLV. Initially, the registry will be empty. the SRGB Originator TLV. Initially, the registry will be empty.
Flag bits will be allocated First-Come, First Served consistent with Flag bits will be allocated First Come First Served (FCFS) consistent
the BGP-SID TLV Types registry. with the BGP-SID TLV Types registry.
8. Manageability Considerations 8. Manageability Considerations
This document defines a BGP attribute to address use cases such as 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 the one described in [I-D.ietf-spring-segment-routing-msdc]. It is
assumed that advertisement of the BGP Prefix-SID attribute is assumed that advertisement of the BGP Prefix-SID attribute is
controlled by the operator in order to: controlled by the operator in order to:
o Prevent undesired origination/advertisement of the BGP Prefix-SID o Prevent undesired origination/advertisement of the BGP Prefix-SID
attribute. By default, a BGP Prefix-SID attribute SHOULD NOT be attribute. By default, a BGP Prefix-SID attribute SHOULD NOT be
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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.
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-14 (work Architecture", draft-ietf-spring-segment-routing-15 (work
in progress), December 2017. in progress), January 2018.
[I-D.ietf-spring-segment-routing-mpls] [I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-11 data plane", draft-ietf-spring-segment-routing-mpls-11
(work in progress), October 2017. (work in progress), October 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, <https://www.rfc- DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
skipping to change at page 15, line 26 skipping to change at page 15, line 26
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8277] Rosen, E., "Using BGP to Bind MPLS Labels to Address [RFC8277] Rosen, E., "Using BGP to Bind MPLS Labels to Address
Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017, Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017,
<https://www.rfc-editor.org/info/rfc8277>. <https://www.rfc-editor.org/info/rfc8277>.
12.2. Informative References 12.2. Informative References
[I-D.ietf-idr-bgp-ls-segment-routing-ext] [I-D.ietf-idr-bgp-ls-segment-routing-ext]
Previdi, S., Psenak, P., Filsfils, C., Gredler, H., and M. Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,
Chen, "BGP Link-State extensions for Segment Routing", and M. Chen, "BGP Link-State extensions for Segment
draft-ietf-idr-bgp-ls-segment-routing-ext-03 (work in Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-04
progress), July 2017. (work in progress), January 2018.
[I-D.ietf-idr-bgpls-segment-routing-epe] [I-D.ietf-idr-bgpls-segment-routing-epe]
Previdi, S., Filsfils, C., Patel, K., Ray, S., and J. Previdi, S., Filsfils, C., Patel, K., Ray, S., and J.
Dong, "BGP-LS extensions for Segment Routing BGP Egress Dong, "BGP-LS extensions for Segment Routing BGP Egress
Peer Engineering", draft-ietf-idr-bgpls-segment-routing- Peer Engineering", draft-ietf-idr-bgpls-segment-routing-
epe-14 (work in progress), December 2017. epe-14 (work in progress), December 2017.
[I-D.ietf-spring-segment-routing-msdc] [I-D.ietf-spring-segment-routing-msdc]
Filsfils, C., Previdi, S., Mitchell, J., Aries, E., and P. Filsfils, C., Previdi, S., Mitchell, J., Aries, E., and P.
Lapukhov, "BGP-Prefix Segment in large-scale data Lapukhov, "BGP-Prefix Segment in large-scale data
 End of changes. 27 change blocks. 
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