draft-ietf-idr-bgp-prefix-sid-24.txt   draft-ietf-idr-bgp-prefix-sid-25.txt 
IDR S. Previdi, Ed. IDR S. Previdi
Internet-Draft C. Filsfils Internet-Draft C. Filsfils
Intended status: Standards Track A. Lindem, Ed. Intended status: Standards Track A. Lindem, Ed.
Expires: December 16, 2018 Cisco Systems Expires: December 17, 2018 Cisco Systems
A. Sreekantiah A. Sreekantiah
H. Gredler H. Gredler
RtBrick Inc. RtBrick Inc.
June 14, 2018 June 15, 2018
Segment Routing Prefix SID extensions for BGP Segment Routing Prefix SID extensions for BGP
draft-ietf-idr-bgp-prefix-sid-24 draft-ietf-idr-bgp-prefix-sid-25
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. An 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 the specification for SR-MPLS SIDs.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
Status of This Memo Status of This Memo
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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 December 16, 2018. This Internet-Draft will expire on December 17, 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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. BGP-Prefix-SID . . . . . . . . . . . . . . . . . . . . . . . 4 2. MPLS BGP Prefix SID . . . . . . . . . . . . . . . . . . . . . 4
2.1. MPLS BGP Prefix SID . . . . . . . . . . . . . . . . . . . 4
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. Originator SRGB TLV . . . . . . . . . . . . . . . . . . . 6 3.2. Originator SRGB TLV . . . . . . . . . . . . . . . . . . . 6
4. Receiving BGP Prefix-SID Attribute . . . . . . . . . . . . . 8 4. Receiving BGP Prefix-SID Attribute . . . . . . . . . . . . . 8
4.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 8 4.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 8
5. Advertising BGP Prefix-SID Attribute . . . . . . . . . . . . 9 5. Advertising BGP Prefix-SID Attribute . . . . . . . . . . . . 9
5.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 10 5.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 10
6. Error Handling of BGP Prefix-SID Attribute . . . . . . . . . 10 6. Error Handling of BGP Prefix-SID Attribute . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Manageability Considerations . . . . . . . . . . . . . . . . 12 8. Manageability Considerations . . . . . . . . . . . . . . . . 12
9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 13 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 13
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
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
The Segment Routing (SR) architecture leverages the source routing The Segment Routing (SR) architecture leverages the source routing
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ASes agree on the SID allocation scheme. Alternatively, when ASes agree on the SID allocation scheme. Alternatively, when
interconnecting ASes, the ASBRs of each domain will have to handle interconnecting ASes, the ASBRs of each domain will have to handle
the advertisement of unique SIDs. The mechanisms for such the advertisement of unique SIDs. The mechanisms for such
interconnection are outside the scope of the protocol extensions interconnection are outside the scope of the protocol extensions
defined in this document. defined in this document.
o A BGP Prefix-SID MAY be attached to a prefix. This implies that o A BGP Prefix-SID MAY be attached to a prefix. This implies that
each prefix is advertised individually, reducing the ability to each prefix is advertised individually, reducing the ability to
pack BGP advertisements (when sharing common attributes). pack BGP advertisements (when sharing common attributes).
2. BGP-Prefix-SID 2. MPLS 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 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 originated prefix of a BGP speaker N which is advertised locally originated prefix of a BGP speaker N which is advertised
to all other BGP speakers in the SR domain. to 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
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[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 a prefix segment is to be included in an MPLS label stack,
if traffic-engineering within the SR domain is required, each node e.g., for traffic engineering purposes, the knowledge of the SRGB
may be required to advertise its local SRGB in addition to the of the originator of the prefix is required in order to compute
topological information. the local label used by the originator.
This document assumes that BGP-LS is the preferred method for This document 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
[I-D.ietf-idr-bgp-ls-segment-routing-ext]. However, as an [I-D.ietf-idr-bgp-ls-segment-routing-ext]. However, as an
optional alternative for the advertisement of the local SRGB optional alternative for the advertisement of the local SRGB
without the topology nor the peer SIDs, hence without without the topology nor the peer SIDs, hence without
applicability for TE, the Originator SRGB TLV of the BGP Prefix- applicability for TE, the Originator SRGB TLV of the BGP Prefix-
SID attribute is specified in Section 3.2 of this document. SID attribute is specified in Section 3.2 of this document.
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registration policy for flag bits will Expert Review [RFC8126] registration policy for flag bits will Expert Review [RFC8126]
consistent with the BGP Prefix-SID TLV Types registry. consistent with the BGP Prefix-SID TLV Types registry.
Finally, this document requests creation of the "BGP Prefix-SID Finally, this document requests creation of the "BGP Prefix-SID
Originator SRGB TLV Flags" registry under the "Border Gateway Originator SRGB TLV Flags" registry under the "Border Gateway
Protocol (BGP) Parameters" registry, Reference: draft-ietf-idr-bgp- 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.
The registration policy for flag bits will Expert Review [RFC8126] The registration policy for flag bits will Expert Review [RFC8126]
consistent with the BGP Prefix-SID TLV Types registry. consistent with the BGP Prefix-SID TLV Types registry.
The designated experts must be good and faithful stewards of the
above registries, assuring that each request is legitimate and
corresponds to a viable use case. Given the limited number of bits
in the flags registries and the applicability to a single TLV,
additional scrutiny should be afforded to flag bit allocation
requests. In general, no single use case should require more than
one flag bit and, should the use case require more, alternate
encodings using new TLVs should be considered.
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
attached to a prefix and advertised. Hence, BGP Prefix-SID attached to a prefix and advertised. Hence, BGP Prefix-SID
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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-
editor.org/info/rfc7752>. editor.org/info/rfc7752>.
Authors' Addresses Authors' Addresses
Stefano Previdi (editor) Stefano Previdi
Cisco Systems Cisco Systems
IT IT
Email: stefano@previdi.net Email: stefano@previdi.net
Clarence Filsfils Clarence Filsfils
Cisco Systems Cisco Systems
Brussels Brussels
Belgium Belgium
Email: cfilsfils@cisco.com Email: cfilsfils@cisco.com
Acee Lindem (editor) Acee Lindem (editor)
Cisco Systems Cisco Systems
301 Midenhall Way 301 Midenhall Way
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