ISIS Working Group X. Xu
Internet-Draft N. Wu
Intended status: Standards Track Huawei
Expires: May 4, 2017 H. Shah
L. Contreras
Telefonica I+D
October 31, 2016

Advertising Service Functions Using IS-IS


Source Packet Routing in Networking (SPRING) WG is developing an MPLS source routing mechanism. This MPLS source routing mechanism can be leveraged to realize the service path layer functionality of the service function chaining (i.e., steering the selected traffic through a particular service function path) by encoding the service function path information as an MPLS label stack. This document describes how to advertise service functions and their corresponding attributes (e.g.,segment ID) using IS-IS.

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].

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at

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This Internet-Draft will expire on May 4, 2017.

Copyright Notice

Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents ( in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

Table of Contents

1. Introduction

[I-D.xu-mpls-service-chaining] describes how to leverage MPLS-SPRING [I-D.ietf-spring-segment-routing-mpls] (a.k.a., an MPLS-based source routing mechanism) to realize the service path layer functionality of the Service Function Chaining (SFC), i.e, steering traffic through the Service Function Path (SFP). To allow a service classifier to attach the segment list (i.e., an MPLS label stack) which represents a particular SFP to the selected traffic, the service classifier needs to know on which Service Function Forwarder (SFF) a given Service Function (SF) is located and what segment ID (SID) is used to indicate that SF. This document describes how to advertise Service Functions (SFs) and their corresponding attributes (e.g.,SID) using IS-IS.

2. Terminology

This memo makes use of the terms defined in [I-D.xu-mpls-service-chaining] and [RFC4971].

3. Solution Description

SFFs within the SFC domain need to advertise each SF 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 SF needs to be advertised. The scope of the advertisement depends on the application but it is recommended that it SHOULD be domain-wide. Furthermore, SFFs need to allocate a corresponding SID to each SF they are offering and advertise it by using a sub-TLV of the above Service Function sub-TLV, called SF SID sub-TLV. To support the approach of encoding SFP information in the form of an MPLS label stack as described in [I-D.xu-mpls-service-chaining], SFFs SHOULD allocate a locally significant MPLS label to each SF they are offering.

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=TBD1   |    Length     |
     |                  Service Function Identifier                  |
     ~                          Sub-TLVs                             ~

3.2. SF 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=TBD2   |    Length     |
     |  Resv |                  SF SID               |

4. Acknowledgements


5. IANA Considerations

This document includes a request to IANA for allocating type codes for the Service Function sub-TLV and the SF SID sub-TLV.

6. Security Considerations

This document does not introduce any new security risk.

7. References

7.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC4971] Vasseur, JP., Shen, N. and R. Aggarwal, "Intermediate System to Intermediate System (IS-IS) Extensions for Advertising Router Information", RFC 4971, DOI 10.17487/RFC4971, July 2007.

7.2. Informative References

[I-D.ietf-sfc-architecture] Halpern, J. and C. Pignataro, "Service Function Chaining (SFC) Architecture", Internet-Draft draft-ietf-sfc-architecture-11, July 2015.
[I-D.ietf-spring-segment-routing-mpls] Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Litkowski, S., Horneffer, M., Shakir, R.,, j. and E. Crabbe, "Segment Routing with MPLS data plane", Internet-Draft draft-ietf-spring-segment-routing-mpls-05, July 2016.
[I-D.xu-mpls-service-chaining] Xu, X., Bryant, S., Assarpour, H., Shah, H., Contreras, L. and d., "Service Chaining using MPLS Source Routing", Internet-Draft draft-xu-mpls-service-chaining-00, October 2016.

Authors' Addresses

Xiaohu Xu Huawei EMail:
Nan Wu Huawei EMail:
Himanshu Shah Ciena EMail:
Luis M. Contreras Telefonica I+D Ronda de la Comunicacion, s/n Sur-3 building, 3rd floor Madrid,, 28050 Spain EMail: URI: