draft-ietf-idr-bgp-prefix-sid-20.txt   draft-ietf-idr-bgp-prefix-sid-21.txt 
IDR S. Previdi, Ed. IDR S. Previdi, Ed.
Internet-Draft C. Filsfils Internet-Draft C. Filsfils
Intended status: Standards Track A. Lindem, Ed. Intended status: Standards Track A. Lindem, Ed.
Expires: November 9, 2018 Cisco Systems Expires: November 30, 2018 Cisco Systems
A. Sreekantiah A. Sreekantiah
H. Gredler H. Gredler
RtBrick Inc. RtBrick Inc.
May 8, 2018 May 29, 2018
Segment Routing Prefix SID extensions for BGP Segment Routing Prefix SID extensions for BGP
draft-ietf-idr-bgp-prefix-sid-20 draft-ietf-idr-bgp-prefix-sid-21
Abstract Abstract
The Segment Routing (SR) architecture allows a node to steer a packet The 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. Ah SR domain maintained only on the ingress node of the SR domain. An SR domain
is defined as a single administrative domain for global SID is defined as a single administrative domain for global SID
assignment. assignment.
This document defines an optional, transitive BGP attribute for This document defines an optional, transitive BGP attribute for
announcing BGP Prefix Segment Identifiers (BGP Prefix-SID) announcing BGP Prefix Segment Identifiers (BGP Prefix-SID)
information. information.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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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 November 9, 2018. This Internet-Draft will expire on November 30, 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
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assignment. It may be comprised of a single AS or multiple ASes assignment. It may be comprised of a single AS or multiple ASes
under consolidated global SID administration. Typically, the ingress under consolidated global SID administration. Typically, the ingress
node of the SR domain prepends an SR header containing segments node of the SR domain prepends an SR header containing segments
identifiers (SIDs) to an incoming packet. 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. SID consists of a label.
[I-D.ietf-spring-segment-routing] also describes how segment routing [I-D.ietf-spring-segment-routing] also describes how segment routing
can be applied to an IPv6 dataplane can be applied to an IPv6 dataplane (SRv6) using an IPv6 routing
[I-D.ietf-6man-segment-routing-header] (SRv6) using a new IPv6 header containing a stack of SR SIDs encoded as IPv6 addresses
routing header containing a stack of SR SIDs encoded as IPv6 [I-D.ietf-6man-segment-routing-header]. The applicability and
addresses. The applicability and support for Segment Routing over support for Segment Routing over IPv6 is beyond the scope of this
IPv6 is beyond the scope of this document. document.
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.
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When a BGP Prefix-SID attribute changes and transitions from When a BGP Prefix-SID attribute changes and transitions from
"conflicting" to "acceptable", the BGP Prefix-SID attributes for "conflicting" to "acceptable", the BGP Prefix-SID attributes for
other prefixes may also transition to "acceptable" as well. other prefixes may also transition to "acceptable" as well.
Implementations SHOULD assure all impacted prefixes revert to using Implementations SHOULD assure all impacted prefixes revert to using
the label indices corresponding to these newly "acceptable" BGP the label indices corresponding to these newly "acceptable" BGP
Prefix-SID attributes. Prefix-SID attributes.
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. Specifically, a BGP labeled IPv4/IPv6 Unicast ([RFC8277]) operation. Specifically, a
BGP speaker receiving a prefix with a BGP Prefix-SID attribute and a BGP speaker receiving a prefix with a BGP Prefix-SID attribute and a
label NLRI field of Implicit NULL [IANA-MPLS-SPECIAL-LABEL] from a label NLRI field of Implicit NULL [RFC3032] from a neighbor MUST
neighbor MUST adhere to standard behavior and program its MPLS adhere to standard behavior and program its MPLS dataplane to pop the
dataplane to pop the top label when forwarding traffic to the prefix. top label when forwarding traffic to the prefix. The label NLRI
The label NLRI defines the outbound label that MUST be used by the defines the outbound label that MUST be used by the receiving node.
receiving node.
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]. In order to prevent distribution of the BGP (IPv4/IPv6) [RFC8277]. In order to prevent distribution of the BGP
Prefix-SID attribute beyond its intended scope of applicability, Prefix-SID attribute beyond its intended scope of applicability,
attribute filtering SHOULD be deployed to remove the BGP Prefix-SID attribute filtering SHOULD be deployed to remove the BGP Prefix-SID
attribute at the administrative boundary of the segment routing attribute at the administrative boundary of the segment routing
domain. domain.
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Since the label index value must be unique within an SR domain, by Since the label index value must be unique within an SR domain, by
default an implementation SHOULD NOT advertise the BGP Prefix-SID default an implementation SHOULD NOT advertise the BGP Prefix-SID
attribute outside an Autonomous System unless it is explicitly attribute outside an Autonomous System unless it is explicitly
configured to do so. configured to do so.
In all cases, the label field of the advertised NLRI ([RFC8277], In all cases, the label field of the advertised NLRI ([RFC8277],
[RFC4364]) MUST be set to the local/incoming label programmed in the [RFC4364]) MUST be set to the local/incoming label programmed in the
MPLS dataplane for the given advertised prefix. If the prefix is MPLS dataplane for the given advertised prefix. If the prefix is
associated with one of the BGP speaker's interfaces, this is the associated with one of the BGP speaker's interfaces, this is the
usual MPLS label (such as the Implicit or Explicit NULL label usual MPLS label (such as the Implicit or Explicit NULL label
[IANA-MPLS-SPECIAL-LABEL]). [RFC3032]).
6. Error Handling of BGP Prefix-SID Attribute 6. Error Handling of BGP Prefix-SID Attribute
When a BGP Speaker receives a BGP Update message containing a When a BGP Speaker receives a BGP Update message containing a
malformed or invalid BGP Prefix-SID attribute attached to a Labeled malformed or invalid BGP Prefix-SID attribute attached to a Labeled
IPv4/IPv6 unicast prefix [RFC8277], it MUST ignore the received BGP IPv4/IPv6 unicast prefix [RFC8277], it MUST ignore the received BGP
Prefix-SID attributes and not advertise it to other BGP peers. In Prefix-SID attributes and not advertise it to other BGP peers. In
this context, a malformed BGP Prefix-SID attribute is one that cannot this context, a malformed BGP Prefix-SID attribute is one that cannot
be parsed due to not meeting the minimum attribute length be parsed due to not meeting the minimum attribute length
requirement, contains a TLV length that doesn't conform to the length requirement, contains a TLV length that doesn't conform to the length
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[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-6man-segment-routing-header] [I-D.ietf-6man-segment-routing-header]
Previdi, S., Filsfils, C., Leddy, J., Matsushima, S., and Previdi, S., Filsfils, C., Leddy, J., Matsushima, S., and
d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
(SRH)", draft-ietf-6man-segment-routing-header-12 (work in (SRH)", draft-ietf-6man-segment-routing-header-13 (work in
progress), April 2018. progress), May 2018.
[I-D.ietf-idr-bgp-ls-segment-routing-ext] [I-D.ietf-idr-bgp-ls-segment-routing-ext]
Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,
and M. Chen, "BGP Link-State extensions for Segment and M. Chen, "BGP Link-State extensions for Segment
Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-06 Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-08
(work in progress), April 2018. (work in progress), May 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-15 (work in progress), March 2018. epe-15 (work in progress), March 2018.
[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
centers", draft-ietf-spring-segment-routing-msdc-08 (work centers", draft-ietf-spring-segment-routing-msdc-08 (work
in progress), December 2017. in progress), December 2017.
[IANA-MPLS-SPECIAL-LABEL] [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
"IANA Special-Purpose Multiprotocol Label Switching (MPLS) Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Label Values Registry", <https://www.iana.org/assignments/ Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
mpls-label-values/>. <https://www.rfc-editor.org/info/rfc3032>.
[RFC5004] Chen, E. and S. Sangli, "Avoid BGP Best Path Transitions [RFC5004] Chen, E. and S. Sangli, "Avoid BGP Best Path Transitions
from One External to Another", RFC 5004, from One External to Another", RFC 5004,
DOI 10.17487/RFC5004, September 2007, <https://www.rfc- DOI 10.17487/RFC5004, September 2007, <https://www.rfc-
editor.org/info/rfc5004>. editor.org/info/rfc5004>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752, Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016, <https://www.rfc- DOI 10.17487/RFC7752, March 2016, <https://www.rfc-
 End of changes. 11 change blocks. 
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