Network Working Group X. Xu
Internet-Draft N. Wu
Intended status: Standards Track Huawei
Expires: December 29, 2014 H. Shah
Ciena
L. Contreras
Telefonica I+D
June 27, 2014
Advertising Service Functions Using IS-IS
draft-xu-isis-service-function-adv-02
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
attributes (e.g.,segment ID) using IS-IS.
Status of This Memo
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This Internet-Draft will expire on December 29, 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 . . . . 3
3.1. Service Function Sub-TLV . . . . . . . . . . . . . . . . 3
3.2. Service Function SID Sub-TLV . . . . . . . . . . . . . . 4
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 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 a service classifier to encode the segment list
representing 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 attributes (e.g.,SID) using
IS-IS.
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 [RFC4971] and
[I-D.xu-spring-sfc-use-case].
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3. Advertising Service Functions and Corresponding SIDs
Service nodes within the network need to advertise each service
function they are offering by using a new sub-TLV of the IS-IS Router
CAPABILITY TLV [RFC4971]. This new sub-TLV is called as Service
Function sub-TLV. The Service Function sub-TLV could appear multiple
times wihin a given IS-IS Router CAPABILITY TLV when 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
they are offering and advertise it by using a sub-TLV of the above
Service Function sub-TLV, called Service Function SID sub-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 format of an MPLS label, an IPv6 address, or
both.
3.1. Service Function 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 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 corresponding to the
particular attributes of a given service function. The Service
Function SID sub-TLV as defined in Section 3.2 is one such sub-TLV
which is used to indicate the corrresponding service function SID.
Other sub-TLVs are to be defined in the future.
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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 ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD.
Length: variable (3 or 16).
Value: if the Length is set to 3, the rightmost 20 bits represent
an 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 for allocating type codes for
the Service Function sub-TLV and 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., Li, Z., and H. Shah, "Service Function Chaining
Use Case for SPRING", draft-xu-spring-sfc-use-case-01
(work in progress), June 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4971] Vasseur, JP., Shen, N., and R. Aggarwal, "Intermediate
System to Intermediate System (IS-IS) Extensions for
Advertising Router Information", RFC 4971, July 2007.
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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-03 (work in progress), June 2014.
Authors' Addresses
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
Nan Wu
Huawei
Email: eric.wu@huawei.com
Himanshu Shah
Ciena
Email: hshah@ciena.com
Luis M. Contreras
Telefonica I+D
Ronda de la Comunicacion, s/n
Sur-3 building, 3rd floor
Madrid, 28050
Spain
Email: luismiguel.contrerasmurillo@telefonica.com
URI: http://people.tid.es/LuisM.Contreras/
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