Internet DRAFT - draft-xu-lsr-ospf-service-function-adv
draft-xu-lsr-ospf-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 OSPF
draft-xu-lsr-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
attributes (e.g., segment ID) using OSPF. Here the OSPF means both
OSPFv2 and OSPFv3.
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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 10 September 2023.
Copyright Notice
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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.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Advertising Service Functions and Corresponding SIDs . . . . 3
3.1. Service Function TLV . . . . . . . . . . . . . . . . . . 3
3.2. Service Function SID 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.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 OSPF. Here the OSPF means both OSPFv2 [RFC2328] and OSPFv3
[RFC5340].
2. Terminology
This memo makes use of the terms defined in [RFC7770] and
[I-D.xu-spring-sfc-use-case].
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.
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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 TLV within the body of the OSPF
Router Information (RI) Opaque LSA [RFC7770]. 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 within a given Router Information (RI) Opaque LSA 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 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
format of an MPLS label, an IPv6 address, 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 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 corresponding 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. 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.
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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[RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
February 2016, <https://www.rfc-editor.org/rfc/rfc7770>.
[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.xu-spring-sfc-use-case]
Xu, X., Li, Z., Shah, H. C., and L. M. Contreras, "Service
Function Chaining Use Case for SPRING", Work in Progress,
Internet-Draft, draft-xu-spring-sfc-use-case-02, 29 June
2014, <https://datatracker.ietf.org/doc/html/draft-xu-
spring-sfc-use-case-02>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/rfc/rfc2328>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/rfc/rfc5340>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/rfc/rfc8402>.
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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