draft-ietf-idr-bgp-prefix-sid-15.txt   draft-ietf-idr-bgp-prefix-sid-16.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 16, 2018 Cisco Systems Expires: August 17, 2018 Cisco Systems
A. Sreekantiah A. Sreekantiah
H. Gredler H. Gredler
RtBrick Inc. RtBrick Inc.
February 12, 2018 February 13, 2018
Segment Routing Prefix SID extensions for BGP Segment Routing Prefix SID extensions for BGP
draft-ietf-idr-bgp-prefix-sid-15 draft-ietf-idr-bgp-prefix-sid-16
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. 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 August 16, 2018. This Internet-Draft will expire on August 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
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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. 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 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
"conflicting" for a speaker M if the derived label value L lies "conflicting" 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.
If multiple different prefixes are received with the same label If multiple different prefixes are received with the same label
index, all these but one of these different prefixes MUST have their index, either all or all but one of the different prefixes MUST have
BGP Prefix-SID attribute considered as "conflicting" by the receiving their BGP Prefix-SID attribute considered as "conflicting". If one
speaker. Alternately, all the different prefixes with the same label of the different prefixes is considered "acceptable", it is
index MAY be considered "conflicting". RECOMMENDED that the first prefix using the label index is selected.
If multiple valid paths for the same prefix are received from If multiple valid paths for the same prefix are received from
multiple BGP speakers or, in the case of [RFC7911], from the same BGP multiple BGP speakers or, in the case of [RFC7911], from the same BGP
speaker, and the BGP Prefix-SID attributes do not contain the same speaker, and the BGP Prefix-SID attributes do not contain the same
label index, then the label index from the best path BGP Prefix-SID label index, then the label index from the best path BGP Prefix-SID
attribute SHOULD be chosen. attribute SHOULD be chosen with a notable exception being when
[RFC5005] is being used to dampen route changes.
When a BGP speaker receives a path from a neighbor with an When a BGP speaker receives a path from a neighbor with an
"acceptable" BGP Prefix-SID attribute and that path is selected as "acceptable" BGP Prefix-SID attribute and that path is selected as
the best path, it SHOULD program the derived label as the label for the best path, it SHOULD program the derived label as the label for
the prefix in its local MPLS dataplane. the prefix in its local MPLS dataplane.
When a BGP speaker receives a path from a neighbor with an "invalid" When a BGP speaker receives a path from a neighbor with an "invalid"
or "conflicting" BGP Prefix-SID attribute or when a BGP speaker or "conflicting" BGP Prefix-SID attribute or when a BGP speaker
receives a path from a neighbor with a BGP Prefix-SID attribute but receives 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 is unable to process it (e.g., local policy disables the
policy disables the capability), it MUST ignore the BGP Prefix-SID functionality), it MUST ignore the BGP Prefix-SID attribute. For the
attribute. For the purposes of label allocation, a BGP speaker MUST purposes of label allocation, a BGP speaker MUST assign a local (also
assign a local (also called dynamic) label (non-SRGB) for such a called dynamic) label (non-SRGB) for such a prefix as per classic
prefix as per classic Multiprotocol BGP labeled IPv4/IPv6 Unicast Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]) operation.
([RFC8277]) operation.
In the case of an "invalid" BGP Prefix-SID attribute, a BGP speaker In the case of an "invalid" BGP Prefix-SID attribute, a BGP speaker
MUST follow to the error handling rules specified in Section 6. A MUST follow to the error handling rules specified in Section 6. A
BGP speaker SHOULD log an error for further analysis. In the case of BGP speaker SHOULD log an error for further analysis. In the case of
a "conflicting" BGP Prefix-SID attribute, a BGP speaker SHOULD NOT a "conflicting" BGP Prefix-SID attribute, a BGP speaker SHOULD NOT
treat it as error and SHOULD propagate the attribute unchanged. A treat it as error and SHOULD propagate the attribute unchanged. A
BGP Speaker SHOULD log a warning for further analysis, i.e., in the BGP Speaker SHOULD log a warning for further analysis, i.e., in the
case the conflict is not due to a label index transition. case the conflict is not due to a label index transition.
When a BGP Prefix-SID attribute changes and transitions from When a BGP Prefix-SID attribute changes and transitions from
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when forwarding traffic to the prefix. The label NLRI defines the when forwarding traffic to the prefix. The label NLRI defines the
outbound label that MUST be used by the receiving node. outbound label that MUST be used by the receiving node.
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 and "acceptable". whether the IPv6 SID TLV is present and "acceptable".
If multiple different prefixes are received with the same IPv6 SID, If multiple different prefixes are received with the same IPv6 SID,
all these but one of these different prefixes MUST have their BGP either all or all but one of the different prefixes MUST have their
Prefix-SID attribute considered as "conflicting" by the receiving BGP Prefix-SID attribute considered as "conflicting". If one of the
speaker. Alternately, all the different prefixes with the same IPv6 different prefixes is considered "acceptable", it is RECOMMENDED that
SID MAY be considered "conflicting". the first prefix using the IPv6 SID is selected.
If multiple valid paths for the same prefix are received from If multiple valid paths for the same prefix are received from
multiple BGP speakers or, in the case of [RFC7911], from the same BGP multiple BGP speakers or, in the case of [RFC7911], from the same BGP
speaker, and the BGP Prefix-SID attributes do not contain the same speaker, and the BGP Prefix-SID attributes do not contain the same
IPv6 SID, then the IPv6 SID from the best path BGP Prefix-SID IPv6 SID, then the IPv6 SID from the best path BGP Prefix-SID
attributes SHOULD be chosen. attribute SHOULD be chosen with a notable exception being when
[RFC5005] is being used to dampen route changes.
If "acceptable" and chosen as the best path, the prefix is installed If "acceptable" and chosen as the best path, the prefix is installed
into the Segment Routing IPv6 dataplane as described in into the Segment Routing IPv6 dataplane as described in
[I-D.ietf-spring-segment-routing]. [I-D.ietf-spring-segment-routing].
When a BGP speaker receives a path from a neighbor with an "invalid" When a BGP speaker receives a path from a neighbor with an "invalid"
or "conflicting" BGP Prefix-SID attribute or when a BGP speaker or "conflicting" BGP Prefix-SID attribute or when a BGP speaker
receives a path from a neighbor with a BGP Prefix-SID attribute but receives 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 is unable to process it (e.g, local policy disables the
policy disables the capability), it MUST ignore the BGP Prefix-SID functionality), it MUST ignore the BGP Prefix-SID attribute and
attribute and revert to [RFC2545] and [RFC4271]. Consistent with the revert to [RFC2545] and [RFC4271]. Consistent with the MPLS
MPLS dataplane Section 4.1, a BGP speaker SHOULD log the condition dataplane Section 4.1, a BGP speaker SHOULD log the condition for
for further analysis. further analysis.
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 IPv6 SIDs corresponding to these newly "acceptable" BGP Prefix- the IPv6 SIDs corresponding to these newly "acceptable" BGP Prefix-
SID attributes. SID attributes.
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 extensibility, no TLVs are required for the reception. For future extensibility, no TLVs are required for the
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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
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.
[RFC5005] Nottingham, M., "Feed Paging and Archiving", RFC 5005,
DOI 10.17487/RFC5005, September 2007, <https://www.rfc-
editor.org/info/rfc5005>.
[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 (editor)
Cisco Systems Cisco Systems
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