Internet DRAFT - draft-xu-lsr-isis-service-function-adv
draft-xu-lsr-isis-service-function-adv
LSR Working Group X. Xu
Internet-Draft China Mobile
Intended status: Standards Track H. Huang
Expires: 10 September 2023 Huawei
H. Shah
Ciena
L. Contreras
Telefonica I+D
9 March 2023
Advertising Service Functions Using IS-IS
draft-xu-lsr-isis-service-function-adv-00
Abstract
The MPLS source routing mechanism developed by Source Packet Routing
in Networking (SPRING) WG can be leveraged to realize a unified
source routing instruction which works across both IPv4 and IPv6
underlays in addition to the MPLS underlay. The unified source
routing instruction can be used to realize a transport-independent
service function chaining by encoding the service function path
information or service function chain information as an MPLS label
stack. This document describes how to advertise service functions
and their corresponding attributes (e.g., service function label)
using IS-IS.
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-
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 10 September 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) 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 Revised BSD License text as
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Solution Description . . . . . . . . . . . . . . . . . . . . 3
3.1. Service Function Sub-TLV . . . . . . . . . . . . . . . . 3
3.2. SF Label Sub-TLV . . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . 4
8.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
[I-D.draft-ietf-spring-sr-service-programming] describes how to
leverage the unified source routing instruction [RFC8663] to realize
a transport-independent service function chaining by encoding the
Service Function Path (SFP) or Service Function Chain (SFC)
information as an MPLS label stack. To allow a service classifier to
attach the MPLS label stack which represents a particular SFP or SFC
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 service function label is used to indicate that
SF. This document describes how to advertise SFs and their
corresponding attributes (e.g., service function label) using IS-IS.
2. Terminology
This memo makes use of the terms defined in
[I-D.draft-ietf-spring-sr-service-programming] and [RFC7981].
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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
[RFC7981]. This new sub-TLV is called as Service Function sub-TLV.
The Service Function sub-TLV could appear multiple times within 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. To
support the approach of encoding SFP information in the form of an
MPLS label stack as described in
[I-D.draft-ietf-spring-sr-service-programming], SFFs SHOULD allocate
a locally significant MPLS label to each SF they are offering.
Therefore, SFFs need to advertise the corresponding service function
label to each SF they are offering by using a sub-TLV of the above
Service Function sub-TLV, called SF Label sub-TLV.
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 ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD1.
Length: variable.
Service Function Identifier: A unique identifier that represents
an SF within an SFC-enabled domain.
Sub-TLVs: contains zero or more sub-TLVs corresponding to the
particular attributes of a given SF. The SF Label sub-TLV as
defined in Section 3.2 is one such sub-TLV. Other sub-TLVs are to
be defined in the future.
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3.2. SF Label 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 Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD2.
Length: 3.
Value: The rightmost 20 bits represent an MPLS label which is the
SF Label of the corresponding SF.
4. IANA Considerations
This document includes a request to IANA for allocating type codes
for the Service Function sub-TLV and the SF Label sub-TLV.
5. Security Considerations
This document does not introduce any new security risk.
6. Acknowledgements
TBD.
7. Contributors
*Nan Wu*
Huawei
eric.wu@huawei.com
8. References
8.1. 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,
<https://www.rfc-editor.org/rfc/rfc2119>.
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[RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
for Advertising Router Information", RFC 7981,
DOI 10.17487/RFC7981, October 2016,
<https://www.rfc-editor.org/rfc/rfc7981>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
8.2. Informative References
[I-D.draft-ietf-spring-sr-service-programming]
Clad, F., Xu, X., Filsfils, C., Bernier, D., Li, C.,
Decraene, B., Ma, S., Yadlapalli, C., Henderickx, W., and
S. Salsano, "Service Programming with Segment Routing",
Work in Progress, Internet-Draft, draft-ietf-spring-sr-
service-programming-07, 15 February 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
sr-service-programming-07>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<https://www.rfc-editor.org/rfc/rfc7665>.
[RFC8663] Xu, X., Bryant, S., Farrel, A., Hassan, S., Henderickx,
W., and Z. Li, "MPLS Segment Routing over IP", RFC 8663,
DOI 10.17487/RFC8663, December 2019,
<https://www.rfc-editor.org/rfc/rfc8663>.
Authors' Addresses
Xiaohu Xu
China Mobile
Email: xuxiaohu@cmss.chinamobile.com
Hongyi Huang
Huawei
Email: hongyi.huang@huawei.com
Himanshu Shah
Ciena
Email: hshah@ciena.com
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Luis M. Contreras
Telefonica I+D
Email: luismiguel.contrerasmurillo@telefonica.com
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