Network Working Group X. Xu
Internet-Draft Huawei
Intended status: Standards Track May 29, 2014
Expires: November 30, 2014
Advertising Service Functions Using OSPF
draft-xu-ospf-service-function-adv-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). This document
describes how to advertise service functions and their corresponding
segment IDs using OSPF. Here the OSPF means both OSPFv2 and OSPFv3.
Status of This Memo
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This Internet-Draft will expire on November 30, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Advertising Service Functions and Corresponding SIDs . . . . 2
3.1. Service Function TLV . . . . . . . . . . . . . . . . . . 3
3.2. Service Function SID Sub-TLV . . . . . . . . . . . . . . 3
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 4
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 Service Function
Chaining (SFC), i.e, steering traffic through the service function
path. To allow the service classifier to encode the segment list
represeting a particular service function path, the classifier needs
to know on which service node(s) a given service function is located
and what segment ID (SID) is used to indicate that service function
on a given service node. This document describes how to advertise
service functions and their corresponding SIDs using OSPF. Here the
OSPF means both OSPFv2 [RFC2328] and OSPFv3 [RFC2740].
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 [RFC4970].
3. Advertising Service Functions and Corresponding SIDs
Service nodes within the network need to advertise each service
function they are offering by using a TLV within the body of the OSPF
Router Information (RI) Opaque LSA [RFC4970]. This new TLV is called
as Service Function TLV. The Service Function TLV is applicable to
both OSPFv2 and OSPFv3. The Service Function TLV could appear
multiple times wihin a given Router Information (RI) Opaque LSA when
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more than one service function needs to be advertised by a given
service node. The scope of the advertisement depends on the
application but it is recommended that it SHOULD be domain-wide.
Furthermore, service nodes need to allocate a corresponding SID to
each service function and meanwhile advertise it by using a sub-TLV
of the above Service Function TLV. In the MPLS-SR case, service
nodes within the network would allocate a locally significant MPLS
label to each service function they are offering. In the IPv6-SR
case, service nodes within the network would allocate a locally
unique link-local IPv6 address to each service function they are
offering. For a given service function, the service node offering
that service function could advertise the corresponding SID in the
MPLS label format or in the IPv6 address format, or both.
3.1. Service Function TLV
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Function Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Sub-TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD.
Length: variable.
Service Function Identifier: A unique identifier that represents a
service function within an SFC-enabled domain.
Sub-TLVs: contains zero or more sub-TLVs related to service
functions. Besides the Service Function SID sub-TLVs, other sub-
TLVs (to be defined in future) which are used to describe some
characters of a given service function could also be added.
3.2. Service Function SID Sub-TLV
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Service Function SID ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Type: TBD
Length: variable (3 or 16).
Value: if the Length is set to 3, the 20 rightmost bits represent
a MPLS label. If the length is set to 16, the value represents an
IPv6 address.
4. Acknowledgements
TBD.
5. IANA Considerations
This memo includes a request to IANA to allocate one TLV type codes
for the Service Function TLV within the body of the OSPF Router
Information (RI) Opaque LSA , and one sub-TLV type code within the
Service Function TLV for the Service Function SID sub-TLV.
6. Security Considerations
This document does not introduce any new security risk.
7. References
7.1. Normative 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.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4970] Lindem, A., Shen, N., Vasseur, JP., Aggarwal, R., and S.
Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 4970, July 2007.
7.2. Informative References
[I-D.filsfils-spring-segment-routing]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R.,
Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe,
"Segment Routing Architecture", draft-filsfils-spring-
segment-routing-02 (work in progress), May 2014.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
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[RFC2740] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", RFC
2740, December 1999.
Author's Address
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
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