Internet DRAFT - draft-wang-lsr-stub-link-attributes
draft-wang-lsr-stub-link-attributes
LSR Working Group A. Wang
Internet-Draft China Telecom
Intended status: Standards Track Z. Hu
Expires: 27 May 2024 Huawei Technologies
G. Mishra
Verizon Inc.
J. Sun
ZTE Corporation
24 November 2023
Advertisement of Stub Link Attributes
draft-wang-lsr-stub-link-attributes-08
Abstract
This document describes the mechanism that can be used to advertise
the stub link attributes within the IS-IS or OSPF domain.
Status of This Memo
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This Internet-Draft will expire on 27 May 2024.
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
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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. OSPF Protocol Extension for Stub Link Attributes . . . . . . 3
4.1. OSPF Stub-Link TLV . . . . . . . . . . . . . . . . . . . 4
4.2. OSPF Stub Link IPv4 Prefix Sub-TLV . . . . . . . . . . . 5
4.3. OSPF Stub Link IPv6 Prefix Sub-TLV . . . . . . . . . . . 5
5. IS-IS Protocol Extension for Stub Link Attributes . . . . . . 6
5.1. IS-IS Stub-link TLV . . . . . . . . . . . . . . . . . . . 6
5.2. IS-IS Stub Link IPv4 Prefix Sub-TLV . . . . . . . . . . . 7
5.3. IS-IS Stub Link IPv6 Prefix Sub-TLV . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Applied Scenarios . . . . . . . . . . . . . . . . . 9
A.1. Inter-AS topology recovery . . . . . . . . . . . . . . . 10
A.2. Egress Engineering for Anycast Servers . . . . . . . . . 11
A.3. Egress Engineering for the path to BGP Next-hop . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
Stub links are used commonly within enterprise or service provider
networks. One common use case is the inter-AS routing scenario where
there are no IGP adjacencies between the adjacent BGP domains,
another use case is at the network boundary that the interfaces are
used to connect to the application servers.
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For operators that have multiple ASes interconnecting with each other
via the stub links, there is a requirement to obtain the inter-AS
topology information as described in
[I-D.ietf-idr-bgpls-inter-as-topology-ext]. To achieve such goal, it
is required that the BGP-LS to be enabled on every router that has
the stub links, which is challenging for the network operation. It
is desirable to advertise the stub link info into the IGP to ease the
deployment of BGP-LS on any router in the IGP domain.
For stub links that are used to connect the servers, knowing the
status of these stub links can facilitate the routers within the IGP
to accomplish TE tasks in some scenarios.
But OSPF and IS-IS have no capability to identify such stub links and
their associated attributes now.
This document defines the protocol extension for OSPFv2/v3 and IS-IS
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. IS-IS[RFC9346]
defines the Inter-AS Reachability TLV to carry the TE information
about inter-AS links. But they are normally being used under RSVP-
TE, especially inter-domain RSVP-TE scenarios. As illustrated in the
potential scenarios that described in Appendix A, there is still the
need for a generic solution which also covers non inter-AS stub
links.
Then, to solve the problems that described in the applied scenarios,
this document defines the Stub-Link TLV and some additional sub-TLVs
to identify the stub link and transmit the associated attributes for
OSPF and IS-IS respectively.
4. OSPF 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.
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4.1. OSPF Stub-Link TLV
This document defines the 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 [RFC5392]. Inclusion in other
LSAs 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stub Link Prefix Sub-TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Existing 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
Flags: Define the type of the stub-link:
* U bit(bit 0): Identify the unnumbered stub link if this bit is
set.
* bit 1-15: Reserved
Stub Link Prefix Sub-TLV: The prefix of the stub-link. It's format
is defined in Section 4.2 and Section 4.3.
Existing Sub-TLVs: Sub-TLV that defined within "Open Shortest Path
First (OSPF) Traffic Engineering TLVs" for TE Link TLV(Value 2) can
be included if necessary.
If the stub-link is identified as unnumbered stub link (U bit is
set), then the "Remote IPv4 Address Sub-TLV" or "Remote Interface
IPv6 Address Sub-TLV", which should be set to the identifier value of
remote router, SHOULD be included to facilitate the pairing of inter-
AS link.
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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 7.
4.2. OSPF Stub Link IPv4 Prefix Sub-TLV
The OSPF Stub Link IPv4 Prefix Sub-TLV 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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | IPv4 Prefix(variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: OSPF Stub Link IPv4 Prefix Sub-TLV
Type: IPv4 Prefix Sub-TLV codepoint. Value is 37(TBD) for OSPF(under
"Types for sub-TLVs of TE Link TLV (Value 2)")
Length: The length of the value portion in octets.
Prefix Length: the length of the IPv4 Prefix in bits.
IPv4 Prefix: The IPv4 Prefix value of stub link.
4.3. OSPF Stub Link IPv6 Prefix Sub-TLV
The OSPF Stub Link IPv6 Prefix Sub-TLV has the following format:
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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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | IPv6 Prefix(variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: OSPF Stub Link IPv6 Prefix Sub-TLV
Type: IPv6 Prefix Sub-TLV codepoint. Value is Value is 38(TBD) for
OSPF(under "Types for sub-TLVs of TE Link TLV (Value 2)")
Length: The length of the value portion in octets.
IPv6 Prefix: The IPv6 Prefix value of stub link.
5. IS-IS Protocol Extension for Stub Link Attributes
The following sections define the protocol extension to indicate the
stub link and its associated attributes in IS-IS.
5.1. IS-IS Stub-link TLV
This document defines the IS-IS Stub-Link TLV to describes stub link
of a single router.
The IS-IS Stub-Link TLV 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 |U| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stub Link Prefix Sub-TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Existing Sub-TLVs(Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: IS-IS Stub-Link TLV
Type: IS-IS TLV codepoint. Value is 151 (TBD) for stub-link TLV.
Length: Variable, dependent on sub-TLVs
Flags: Define the type of the stub-link:
* 0: U bit(bit 0): Identify the unnumbered stub link if this bit is
set.
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* bit 1-15: Reserved
Stub Link Prefix Sub-TLV: The prefix of the stub-link. It's format
is defined in Section 5.2 and Section 5.3.
Existing Sub-TLVs: Sub-TLVs that defined within "IS-IS Sub-TLVs for
TLVs Advertising Neighbor Information" can be included if necessary.
If the stub-link is identified as unnumbered stub link type (U bit is
set), then the "IPv4 Remote ASBR ID" or "IPv6 Remote ASBR ID" Sub-TLV
SHOULD be included to facilitate the pairing of inter-AS link.
5.2. IS-IS Stub Link IPv4 Prefix Sub-TLV
The IS-IS Stub Link IPv4 Prefix Sub-TLV 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 | Length | Reserved |Prefix Length|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Prefix(Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: IS-IS Stub Link IPv4 Prefix Sub-TLV
Type: IPv4 Prefix Sub-TLV codepoint. Value is 46(TBD) for IS-
IS(under "IS-IS Sub-TLVs for TLVs Advertising Neighbor Information")
Length: Length: The length of the value portion in octets.
Prefix Length: the length of the IPv4 Prefix in bits.
IPv4 Prefix: The IPv4 Prefix value of stub link.
5.3. IS-IS Stub Link IPv6 Prefix Sub-TLV
The IS-IS Stub Link IPv6 Prefix Sub-TLV 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 | Length | Reserved |Prefix Length|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix(Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: IS-IS Stub Link IPv6 Prefix Sub-TLV
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Type: IPv6 Prefix Sub-TLV codepoint. Value is 47(TBD) for IS-
IS(under "IS-IS Sub-TLVs for TLVs Advertising Neighbor Information")
Length: Length: The length of the value portion in octets.
Prefix Length: the length of the IPv6 Prefix in bits.
IPv6 Prefix: The IPv6 Prefix value of stub link.
6. Security Considerations
Security concerns for IS-IS 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.
7. IANA Considerations
IANA is requested to the allocation in following registries:
+===========================================+============+===============================+
| Registry | Type | Meaning |
| |(suggested) | |
+===========================================+============+===============================+
|Top Level Types in TE LSAs | 7 |OSPF Stub-Link |
+-------------------------------------------+------------+-------------------------------+
|IS-IS Top-Level TLV | 151 |IS-IS Stub-Link |
+-------------------------------------------+------------+-------------------------------+
|Types for sub-TLVs of TE Link TLV (Value 2)| 37 |OSPF Stub Link IPv4 Prefix |
+-------------------------------------------+------------+-------------------------------+
|Types for sub-TLVs of TE Link TLV (Value 2)| 38 |OSPF Stub Link IPv6 Prefix |
+-------------------------------------------+------------+-------------------------------+
|IS-IS Sub-TLVs for TLVs | | |
|Advertising Neighbor Information | 46 |IS-IS Stub Link IPv4 Prefix |
+-------------------------------------------+------------+-------------------------------+
|IS-IS Sub-TLVs for TLVs | | |
|Advertising Neighbor Information | 47 |IS-IS Stub Link IPv6 Prefix |
+-------------------------------------------+------------+-------------------------------+
Figure 7: IANA Allocation for newly defined TLVs and Sub-TLVs
8. Acknowledgement
Thanks Ketan Talaulikar, Acee Lindem, Shunwan Zhang, Peter Psenak,
Tony Li, Les Ginsberg, Dhruv Dhody, Jeff Tantsura and Robert Raszuk
for their suggestions and comments on this idea.
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9. References
9.1. 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>.
[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>.
[RFC9346] Chen, M., Ginsberg, L., Previdi, S., and D. Xiaodong, "IS-
IS Extensions in Support of Inter-Autonomous System (AS)
MPLS and GMPLS Traffic Engineering", RFC 9346,
DOI 10.17487/RFC9346, February 2023,
<https://www.rfc-editor.org/info/rfc9346>.
9.2. Informative References
[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", Work in
Progress, Internet-Draft, draft-ietf-idr-bgpls-inter-as-
topology-ext-13, 3 April 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
bgpls-inter-as-topology-ext-13>.
Appendix A. Applied Scenarios
The following sections describe the scenarios that knowing the stub
link related attributes information can help solve the corresponding
necessity in questions.
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A.1. Inter-AS topology recovery
Figure 1 describes the scenario that the necessity of inter-AS
topology recovery for Native IP point-to-point stub link scenario.
R10, R11 and R12 are located in AS1. R20, R21,R22 are located in
AS2. The controller runs BGP-LS with R10 in AS1 and R20 in AS2
respectively.
There is one BGP session among the border router R11 and R21, which
are connected by several stub links(passive interfaces) between them.
The situation within the R21 and R22 are the same.
Since the links between the border routers are passive, there will be
no IGP neighbors between them. The BGP-LS information carried in
each AS will not report these stub links,and the controller can't
recovery the inter-AS topology automatically.
+----------+
+--------------+Controller+--------------+
^ +----------+ ^
| |
BGP-LS| |BGP-LS
| +---+BGP+----+ |
+-----------------+ +-------------------+
| | | | | |
| | +---+-+ +-+---+ | |
| | | +--------+ | | |
| +--------+R11 |--------| R21+----------+ |
| | | +--------+ | | |
| | +---+-+ +-+---+ | |
| +--+--+ | | +--+--+ |
| | | | | | | |
| |R10 | | | |R20 | |
| | | | | | | |
| +--+--+ +---+-+ +-+---+ +--+--+ |
| | | +--------+ | | |
| +--------+R12 |--------| R22+----------+ |
| | +--------+ | |
| +---+-+ +-+---+ |
| | | |
+--------AS1------+ +----------AS2------+
+---+BGP+----+
Figure 1: Inter-AS Topology Recovery(P2P Scenario)
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Figure 2 describes the similar situation but in LAN environment. The
border routers of AS1, AS2 and AS3 are connected via one LAN
interfaces(that is to say, the corresponding interfaces on R1, R2 and
R3 are on the same subnet). There are three different BGP sessions
from the loopback address of the border routers among them
respectively. It is necessary to recovery the underlying inter-AS
topology automatically.
+---------+ +---------+
| | | |
| +--+--+ +--+--+ |
| | | | | |
| |R1 +-------+ +------+R2 | |
| | | | | | | |
| +--+--+ | | +--+--+ |
| | | | | |
+---AS1---+ | | +----AS2--+
+-+-+-+
| |
| SW |
| |
+--+--+
|
+--+--+
+--+ +--+
| | R3 | |
| +-----+ |
| |
| |
+-----AS3---+
Figure 2: Inter-AS Topology Recovery(LAN Scenario)
A.2. Egress Engineering for Anycast Servers
Figure 3 describes the scenario that the stub link information can be
used for egress engineering for Anycast servers that connected to the
network. In the example, the R1, R2 and R3 are border routers which
are connected directly the server S1, S2 and S3 that have the same IP
address IPa. The characteristics of the stub links that connected to
these Anycast servers are different. It will be help for the router
R0, to know the attributes of the stub links and select the optimal
Anycast server to serve the customer's application.
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+----------------+
| |
| +---+-+ +-----+
| | | | S1 |
| +-------+R1 +------+ |
| | | +---+ |(IPa)|
| | +---+-+ | +-----+
| | | |
| +--+--+ +---+-+ | +-----+
| | | | | +--| S2 |
| |R0 +----+R2 +------+ |
| | | | | +--|(IPa)|
| +--+--+ +---+-+ | +-----+
| | | |
| | +---+-+ | +-----+
| | | |---+ | S3 |
| +-------+R3 +------+ |
| | | |(IPa)|
| +---+-+ +-----+
| |
+----------------+
Figure 3: Egress Engineering for Anycast Server
A.3. Egress Engineering for the path to BGP Next-hop
Figure 4 describes the scenario that the stub link information can
facilitate the selection of path to BGP next hop. The router R10 and
R20 which are located in different AS establish the BGP session
directly.The attributes of the stub links among the border routers
are vary. It is certainly will be helpful for the router R10 and R20
to select the optimized forwarding path to BGP next hop, that is via
the stub links among them, to reach each other.
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|<---------------+BGP+------------------>|
| |
| |
+-----------------+ +-------------------+
| | | | | |
| | +---+-+ +-+---+ | |
| | | +--------+ | | |
| +--------+R11 |--------| R21+----------+ |
| | | +--------+ | | |
| | +---+-+ +-+---+ | |
| +--+--+ | | +--+--+ |
| | | | | | | |
| |R10 | | | |R20 | |
| | | | | | | |
| +--+--+ +---+-+ +-+---+ +--+--+ |
| | | +--------+ | | |
| +--------+R12 |--------| R22+----------+ |
| | +--------+ | |
| +---+-+ +-+---+ |
| | | |
+-------+AS1+-----+ +---------+AS2+-----+
Figure 4: Optimized BGP next hop selection
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
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Gyan S. Mishra
Verizon Inc.
13101 Columbia Pike
Silver Spring, MD 20904
United States of America
Email: gyan.s.mishra@verizon.com
Jinsong Sun
ZTE Corporation
No. 68, Ziijnhua Road
Nan Jing
210012
China
Email: sun.jinsong@zte.com.cn
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