Internet DRAFT - draft-xu-idr-bgp-ls-sfc-extension
draft-xu-idr-bgp-ls-sfc-extension
Network Working Group X. Xu
Internet-Draft Huawei
Intended status: Standards Track April 28, 2014
Expires: October 30, 2014
BGP Link-State Extensions for SR-based SFC
draft-xu-idr-bgp-ls-sfc-extension-00
Abstract
The Segment Routing mechanism can be leveraged to realize the service
path layer functionality of the Service Function Chaining (i.e,
steering traffic through the service function path). The link-state
IGPs (i.e., IS-IS and OSPF) have been extended to advertise service
information including services and the corrresponding service segment
identifiers. For the purpose of building service function paths
which span across IGP areas, or even across ASes, this draft defines
extensions to the BGP Link-state address-family to carry service
information including services and the corrresponding service segment
identifiers.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on October 30, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. BGP-LS Extensions for SR-based SFC . . . . . . . . . . . . . 3
3.1. Node Attribute TLVs . . . . . . . . . . . . . . . . . . . 3
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
[I-D.xu-spring-sfc-use-case] describes a particular use case for
SPRING where the Segment Routing (SR) mechanism is leveraged to
realize the service path layer functionality of the SFC (i.e,
steering traffic through the service function path). To allow the
service classifier to encode the segment list represeting a
particular service path, the classifier needs to know on which
service node(s) a given service is located and what segment ID (SID)
is used to indicate that service on a given service node.The link-
state IGPs (i.e., IS-IS [I-D.xu-isis-service-sid-adv] and OSPF
[I-D.xu-ospf-service-sid-adv]) have been extended to advertise
service information including services and the corresponding service
SIDs. However, the flooding-based propagation using IGPs is limited
by the perimeter of the IGP domain.
To address the need for applications that require visibility into
LSDB across IGP areas, or even across ASes, the BGP-LS address-
family/sub-address-family have been defined that allows BGP to carry
LSDB information. The BGP Network Layer Reachability Information
(NLRI) encoding format for BGP-LS and a new BGP Path Attribute called
BGP-LS attribute are defined in [I-D.ietf-idr-ls-distribution]. The
identifying key of each LSDB object, namely a node, a link or a
prefix, is encoded in the NLRI and the properties of the object are
encoded in the BGP-LS attribute.
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This document describes extensions to BGP-LS to carry service
informaiton inlcuding services and their corresponding service SIDs.
With such extensions, a service path can be computed across IGP
areas, or even across ASes.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. Terminology
This memo makes use of the terms defined in
[I-D.ietf-idr-ls-distribution]
3. BGP-LS Extensions for SR-based SFC
The BGP-LS NLRI can be a node NLRI, a link NLRI or a prefix NLRI.
The corresponding BGP-LS attribute is a node attribute, a link
attribute or a prefix attribute. BGP-LS defines the TLVs that map
link-state information to BGP-LS NLRI and BGP-LS attribute. This
document adds additional BGP-LS attribute TLVs to encode service
information currently including services and the corresponding
service SIDs. [I-D.xu-isis-service-sid-adv] defines the following
two type of TLVs to encode service information:
a. Service TLVs
b. Service SID Sub-TLVs
Therefore, the document defined the corresponding Node Attribute TLVs
in the following subsection.
3.1. Node Attribute TLVs
The following 'Node Attribute' TLVs are defined:
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+---------------+--------------------+----------+--------------------+
| TLV Code Point| Description | Length | IS-IS Service |
| | | | TLV/sub-TLV |
+---------------+--------------------+----------+--------------------+
| TBD1 | Service 1 (S1) | variable | Service TLV for S1 |
| | | | |
| ... | ... | ... | ... |
| | | | |
| TBDn | Service n (Sn) | variable | Service TLV for Sn |
| | | | |
| TBDn+1 | Service SID in | variable | MPLS SID Sub-TLV |
| | MPLS label format | | |
| | | | |
| TBDn+2 | Service SID in | variable | IPv6 SID Sub-TLV |
| | IPv6 address format| | |
+---------------+--------------------+----------+--------------------+
The sections refer to [I-D.xu-isis-service-sid-adv]. These TLVs can
ONLY be added to the Node Attribute associated with the Node NLRI
that originates the corresponding Service TLV.
4. Acknowledgements
TBD.
5. IANA Considerations
TBD.
6. Security Considerations
This document does not introduce any new security risk.
7. References
7.1. Normative References
[I-D.ietf-idr-ls-distribution]
Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
Ray, "North-Bound Distribution of Link-State and TE
Information using BGP", draft-ietf-idr-ls-distribution-04
(work in progress), November 2013.
[I-D.xu-isis-service-sid-adv]
Xu, X., "Signaling Services and Service SIDs Using IS-IS",
draft-xu-isis-service-sid-adv-00 (work in progress), April
2014.
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[I-D.xu-ospf-service-sid-adv]
Xu, X., "Signaling Services and Service SIDs Using OSPF",
draft-xu-ospf-service-sid-adv-00 (work in progress), April
2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. Informative References
[I-D.xu-spring-sfc-use-case]
Xu, X., "Service Function Chaining Use Case", draft-xu-
spring-sfc-use-case-00 (work in progress), April 2014.
Author's Address
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
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