LSR Working Group A. Wang
Internet-Draft China Telecom
Intended status: Standards Track Z. Hu
Expires: March 26, 2022 Huawei Technologies
G. Mishra
Verizon Inc.
A. Lindem
Cisco Systems
J. Sun
ZTE Corporation
September 22, 2021
Advertisement of Stub Link Attributes
draft-wang-lsr-stub-link-attributes-01
Abstract
This document describes the mechanism that can be used to
differentiate the stub links from the normal interfaces within ISIS
or OSPF domain.
Status of This Memo
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This Internet-Draft will expire on March 26, 2022.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Consideration for Identifying Stub Link . . . . . . . . . . . 3
4. Protocol Extension for Stub Link Attributes . . . . . . . . . 3
4.1. OSPF Stub-Link TLV . . . . . . . . . . . . . . . . . . . 4
4.2. ISIS Stub-link Sub-TLV . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Stub links are used commonly within an operators enterprise or
service provider networks. One of the most common use cases for stub
links is in a data center Layer 2 and Layer 3 Top of Rack(TOR) switch
where the inter connected links between the TOR switches and uplinks
to the core switch are only a few links and a majority of the links
are Layer 3 VLAN switched virtual interface trunked between the TOR
switches serving Layer 2 broadcast domains. In this scenario all the
VLANs are made as stub links as it is recommended to limit the number
of network LSAs between routers and switches to avoid unnecessary
hello processing overhead.
Another common use case is an inter-AS routing scenario where the
same routing protocol but different IGP instance is running between
the adjacent BGP domains. Using stub link on the inter-AS
connections can ensure that prefixes contained within a domain are
only reachable within the domain itself and not allow the link state
database to be merged between domain which could result in
undesirable consequences.
For operator which runs different IGP domains that interconnect with
each other via the stub links, there is desire to obtain the inter-AS
topology information as described in
[I-D.ietf-idr-bgpls-inter-as-topology-ext]. If the router that runs
BGP-LS within one IGP domain can distinguish stub links from other
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normal interfaces, it is then easy for the router to report these
stub links using BGP-LS to a centralized PCE controller.
Draft [I-D.dunbar-lsr-5g-edge-compute] describes the case that edge
compute server attach the network and needs to flood some performance
index information to the network to facilitate the network select the
optimized application resource. The edge compute server will also
not run IGP protocol.
And, stub links are normally the boundary of one IGP domain, knowing
them can facilitate the operators to apply various policies on such
interfaces, for example, to secure their networks, or filtering the
incoming traffic with scrutiny.
But OSPF and ISIS have no position to identify such stub links and
their associated attributes now.
This document defines the protocol extension for OSPFv2/v3 and ISIS
to indicate the stub links and their associated attributes.
2. Conventions used in this document
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 [RFC2119] .
3. Consideration for Identifying Stub Link
OSPF[RFC5392] defines the Inter-AS-TE-v2 LSA and Inter-AS-TE-v3 LSA
to carry the TE information about inter-AS links. These LSAs can be
used to transfer the information about the stub link which is located
at the boundary of one AS. This document defines the Stub-Link TLV
within these LSAs to identify the stub link and transfer the
associated attributes then.
ISIS[RFC5316] defines the Inter-AS Reachability TLV to carry the TE
information about inter-AS links. This TLV can be used to transfer
the information about the stub link which is located at the boundary
of one AS. This document defines the Stub-Link sub-TLV within this
TLV to identify the stub link and transfer the associated attributes.
4. Protocol Extension for Stub Link Attributes
The following sections define the protocol extension to indicate the
stub link and its associated attributes in OSPFv2/v3 and ISIS.
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4.1. OSPF Stub-Link TLV
This document defines the OSPF Stub-Link TLV to describe stub link of
a single router. This Stub-Link TLV is only applicable to the Inter-
AS-TE-v2 LSA and Inter-AS-TE-v3 LSA. Inclusion in other LSA MUST be
ignored.
The OSPF Stub-Link TLV which is under the IANA codepoint "Top Level
Types in TE LSAs" has the following format:
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(Stub-Link) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Type | Prefix Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Prefix(variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: OSPF Stub-Link TLV
Type: The TLV type. The value is 7(TBD) for OSPF Stub-Link
Length: Variable, dependent on sub-TLVs
Link Type: Define the type of the stub-link. This document defines
the followings type:
o 0: Reserved
o 1: AS boundary link
o 2: Loopback link
o 3: Vlan interface link
o 4-255: For future extension
Prefix Length: The length of the interface address, in octet.
Link Prefix: The prefix of the stub-link. It's length is determined
by the field "Prefix Length".
Sub-TLVs: Existing sub-TLV that defined within "Open Shortest Path
First (OSPF) Traffic Engineering TLVs" for TE Link TLV(Value 2) can
be included if necessary.
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If this TLV is advertised multiple times in the same Inter-AS-TE-v2/
v3 LSA, only the first instance of the TLV is used by receiving
OSPFv2/v3 routers. This situation SHOULD be logged as an error.
If this TLV is advertised multiple times for the same link in
different Inter-AS-TE-v2/v3 LSA originated by the same OSPFrouter,
the OSPFStub-Link TLV in these LSAs with the smallest Opaque ID is
used by receiving OSPFrouters. This situation may be logged as a
warning.
It is RECOMMENDED that OSPF routers advertising OSPF Stub-Link TLVs
in different OSPF Inter-AS-TE v2/v3 LSAs re-originate these LSAs in
ascending order of Opaque ID to minimize the disruption.
This document creates a registry for Stub-Link attributes in
Section 6.
4.2. ISIS Stub-link Sub-TLV
This document defines the ISIS Stub-Link sub-TLV to describes stub
link of a single router. This Stub-Link sub-TLV is only applicable
to the Inter-AS Reachability TLV. Inclusion in other TLV MUST be
ignored.
The ISIS Stub-Link sub-TLV which is under the IANA codepoint "Sub-
TLVs for TLVs 22, 23, 25, 141, 222, and 223" has the following
format:
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(Stub-Link) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Type | Prefix Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Prefix(variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs(Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: ISIS Stub-Link Sub-TLV
Type: ISIS sub-TLV codepoint. Value is 45(TBD) for stub-link TLV.
Length: Variable, dependent on sub-TLVs
Link Type: Define the type of the stub-link. This document defines
the followings type:
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o 0: Reserved
o 1: AS boundary link
o 2: Loopback link
o 3: Vlan interface link
o 4-255: For future extension
Prefix Length: The length of the interface address, in octet.
Link Prefix: The prefix of the stub-link. It's length is determined
by the field "Prefix Length".
Sub-TLVs: Existing sub-TLVs that defined within "Sub-TLVs for TLVs
22, 23, 25, 141, 222, and 223" can be included if necessary.
5. Security Considerations
Security concerns for ISIS are addressed in [RFC5304] and[RFC5310]
Security concern for OSPFv3 is addressed in [RFC4552]
Advertisement of the additional information defined in this document
introduces no new security concerns.
6. IANA Considerations
IANA is requested to the allocation in following registries:
+===========================+======+===========================+
| Registry | Type | Meaning |
+===========================+======+===========================+
|Top Level Types in TE LSAs | 7 |OSPF Stub-Link TLV |
+---------------------------+------+---------------------------+
|Sub-TLVs for TLVs 22, 23, | | |
| 25, 141, 222, and 223 | 45 |IS-IS Stub-Link sub-TLV |
+---------------------------+------+---------------------------+
Figure 3: IANA Allocation for newly defined TLVs
7. Acknowledgement
Thanks Shunwan Zhang, Tony Li, Les Ginsberg, Acee Lindem, Dhruv
Dhody, Jeff Tantsura and Robert Raszuk for their suggestions and
comments on this idea.
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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/info/rfc2119>.
[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
<https://www.rfc-editor.org/info/rfc4552>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <https://www.rfc-editor.org/info/rfc5304>.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, DOI 10.17487/RFC5310, February
2009, <https://www.rfc-editor.org/info/rfc5310>.
[RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in
Support of Inter-Autonomous System (AS) MPLS and GMPLS
Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316,
December 2008, <https://www.rfc-editor.org/info/rfc5316>.
[RFC5392] Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in
Support of Inter-Autonomous System (AS) MPLS and GMPLS
Traffic Engineering", RFC 5392, DOI 10.17487/RFC5392,
January 2009, <https://www.rfc-editor.org/info/rfc5392>.
8.2. Informative References
[I-D.dunbar-lsr-5g-edge-compute]
Dunbar, L., Chen, H., and C. Telecom, "IS-IS & OSPF
extension for 5G Edge Computing Service", draft-dunbar-
lsr-5g-edge-compute-00 (work in progress), July 2021.
[I-D.ietf-idr-bgpls-inter-as-topology-ext]
Wang, A., Chen, H., Talaulikar, K., and S. Zhuang, "BGP-LS
Extension for Inter-AS Topology Retrieval", draft-ietf-
idr-bgpls-inter-as-topology-ext-09 (work in progress),
September 2020.
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Authors' Addresses
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing 102209
China
Email: wangaj3@chinatelecom.cn
Zhibo Hu
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: huzhibo@huawei.com
Gyan S. Mishra
Verizon Inc.
13101 Columbia Pike
Silver Spring MD 20904
United States of America
Email: gyan.s.mishra@verizon.com
Acee Lindem
Cisco Systems
No. 301 Midenhall Way
Cary NC 27513
United States of America
Email: acee@cisco.com
Jinsong Sun
ZTE Corporation
No. 68, Ziijnhua Road
Nan Jing 210012
China
Email: sun.jinsong@zte.com.cn
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