BGP-LS Extension for Inter-AS Topology Retrieval
draft-ietf-idr-bgpls-inter-as-topology-ext-30
| Document | Type | Active Internet-Draft (idr WG) | |
|---|---|---|---|
| Authors | Aijun Wang , Huaimo Chen , Ketan Talaulikar , Shunwan Zhuang , Changwang Lin | ||
| Last updated | 2026-05-11 | ||
| Replaces | draft-wang-idr-bgpls-inter-as-topology-ext | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Gunter Van de Velde | ||
| Send notices to | (None) |
draft-ietf-idr-bgpls-inter-as-topology-ext-30
IDR Working Group A. Wang
Internet-Draft China Telecom
Intended status: Standards Track H. Chen
Expires: 13 November 2026 Individual
K. Talaulikar
Cisco Systems
S. Zhuang
Huawei Technologies
C. Lin
New H3C Technologies
12 May 2026
BGP-LS Extension for Inter-AS Topology Retrieval
draft-ietf-idr-bgpls-inter-as-topology-ext-30
Abstract
This document specifies the procedure for distributing Border Gateway
Protocol-Link State (BGP-LS) key parameters for inter-domain links
between two Autonomous Systems (ASes). It defines a new type within
the BGP-LS Network Layer Reachability Information (NLRI) for an
inter-AS Link, as well as three new type-length-values (TLVs) for the
BGP-LS inter-AS Link descriptor. These BGP-LS extensions enable
Software-Defined Networking (SDN) controllers to retrieve network
topology across inter-AS environments.
These extensions and procedures allow network operators to collect
inter-domain interconnect information and automatically compute the
end-to-end network topology using information provided by the BGP-LS
protocol.
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 https://datatracker.ietf.org/drafts/current/.
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 13 November 2026.
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Copyright Notice
Copyright (c) 2026 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 (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. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Inter-AS Domain Scenarios . . . . . . . . . . . . . . . . . . 3
5. Inter-AS Link NLRI . . . . . . . . . . . . . . . . . . . . . 4
6. Inter-AS Link Descriptor TLVs . . . . . . . . . . . . . . . . 6
6.1. Remote AS Number TLV . . . . . . . . . . . . . . . . . . 7
6.2. IPv4 Remote ASBR ID . . . . . . . . . . . . . . . . . . . 7
6.3. IPv6 Remote ASBR ID . . . . . . . . . . . . . . . . . . . 8
7. Advertisement of IGP Information for Inter-AS Links . . . . . 8
8. Solutions for other Alternative Scenarios . . . . . . . . . . 9
9. End-to-End Inter-AS Topology Use Case . . . . . . . . . . . . 11
10. Security Considerations . . . . . . . . . . . . . . . . . . . 11
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
11.1. New BGP-LS NLRI type . . . . . . . . . . . . . . . . . . 12
11.2. New Inter-AS Link Descriptors . . . . . . . . . . . . . 12
12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 13
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
13.1. Normative References . . . . . . . . . . . . . . . . . . 13
13.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction
BGP-LS [RFC9552] describes the use of the BGP protocol for
advertising Link-State topology information. It enables applications
such as an SDN controllers to collect the underlay network topology.
[RFC9552] covers the advertisement of topology information from
within an Interior Gateway Protocol (IGP) domain. If the network has
more than one IGP domain, and these domains interconnect with each
other via inter-AS links, there is no mechanism within [RFC9552] to
advertise the interconnect topology information.
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[RFC9086] defines extensions for exporting BGP peering node topology
information (including peers, interfaces, and peering ASes) in a way
that is used to compute efficient BGP peering engineering policies
and strategies. This information can also be used to compute
interconnection topology among different IGP domains, but it requires
every border router to run the BGP-LS protocol and report such
information to SDN controllers. Considering there will be several
border routers on the network boundary, such a solution restricts its
deployment flexibility.
This document defines the inter-AS Link NLRI and some new TLVs for
BGP-LS to cover scenarios where an SDN controller needs to get the
interconnection topology information between different AS domains
when sourced from IGPs.
2. Requirements Language
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. Terminology
The following terms are defined in this document:
* DCs: Data Centers
* SDN: Software-Defined Network
4. Inter-AS Domain Scenarios
Figure 1 illustrates the multi-domain scenarios discussed in this
document. Typically, the SDN controller can retrieve the topology of
IGP A and IGP B individually via the BGP-LS protocol, but it cannot
obtain topology connection information between these two IGP domains,
as IGP protocols are generally not run on the inter-AS links.
In Figure 1, S2 (in IGP domain A) and T1 (in IGP domain B) are
connected to the IP SDN controller via BGP-LS, but they can only
report the topology information among the IGP A and IGP B themselves,
and can't report the inter-AS topology information among them because
there is no IGP protocol running on the inter-AS links. The border
routers, SB1/SB3 in IGP A and TB2/TB4 in IGP B know the inter-AS
links among them, and can advertise such information via underlying
OSPF [RFC5392] or IS-IS [RFC9346], but there is no place in [RFC9552]
to transfer such information.
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+-----------------+
+------+IP SDN Controller+-----+
| +-----------------+ |
| |
|BGP-LS |BGP-LS
| |
+---------------+-------+ +------+--------------+
| +--+ +|-+ +-+-+ +-+-+ +|-+ +--+|
| |S1+---------+S2+---+SB1+-----------+TB2+---+T1+--------+T2||
| +-++ +--+ +-+-+ +-+-+ +--+ +-++|
| | | | | |
| | | | | |
| +-++ +--+ +-+-+ +-+-+ +--+ +-++|
| |S4+--------+S3+----+SB3+-----------+TB4+---+T3+--------+T4||
| +--+ +--+ +-+-+ +-+-+ +--+ +--+|
| | | |
| | | |
| IGP A | | IGP B |
+-----------------------+ +---------------------+
Figure 1: Inter-AS Domain Scenario
5. Inter-AS Link NLRI
[RFC9552] defines four NLRI types (Node, Link, IPv4 Topology Prefix,
and IPv6 Topology Prefix) to transfer the topology and prefix
information. For an inter-AS link, as the two ends of the link
belong in different IGP domains and the link does not run an IGP
protocol, it is not appropriate to advertise their information within
the existing NLRI types listed above.
This document defines a new NLRI type 7, seeSection 11) within the
BGP-LS NLRI, referred to as the inter-AS Link NLRI. The inter-AS
Link NLRI is encoded in the format shown in Figure 2 as explained
below:
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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
+-+-+-+-+-+-+-+-+
| Protocol-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
| (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Local Node Descriptors (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// inter-AS Link Descriptors (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: inter-AS Link NLRI Format
This document specifies the advertisement of inter-AS Links using the
inter-AS Link NLRI when originating the information from the
underlying OSPF [RFC5392] and IS-IS [RFC9346] advertisements.
This section describes the encoding of the inter-AS Link NLRI while
the more detailed procedures for sourcing of this information from
the underlying IGP are described in Section 7.
The "Protocol-ID" is set to the value indicating the source protocol
of the inter-AS Link information, as specified in Section 5.2
of[RFC9552].
The semantics of the "Identifier" field are the same as defined in
[RFC9552] and will be set to the BGP-LS Instance Identifier to
identify the IGP domain into which the information associated with
the inter-AS link is advertised. Therefore, the "Identifier" values
for the two half-links (see Section 5.2 of [RFC9552]) of the inter-AS
link could be different depending on the configuration of Identifiers
for the two IGP domains.
The "Local Node Descriptors" field is encoded using the TLV 256
defined in section 5.2.1.2 of [RFC9552] to identify the ASBR
associated with the specific half-link of the inter-AS link. The
following Sub-TLVs MUST be included as the Local Node Descriptors:
- Autonomous System (TLV 512) [RFC9552].
- OSPF Area-ID (TLV 514) [RFC9552] to be included only in the case of
OSPF, when the inter-AS TE LSA from which information is sourced is
being flooded with an area-scope. It is not included when the LSA is
flooded with AS-scope.
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- IGP Router ID (TLV 515) encoded for either OSPF or IS-IS, depending
on the source protocol as specified in section 5.2.1.4 of [RFC9552].
- One or both of IPv4 and IPv6 Router-ID of the ASBR using TLV 1028
and/or 1029 [RFC9552], depending on whether the ASBR is configured
with one or both of the IPv4 and IPv6 TE Router-IDs. (Note: while
[RFC9552] introduced these TLVs for use in the BGP-LS attribute, this
document also leverages the same TLVs for use in the NLRI.)
Inter-AS Link Descriptors are encoded as TLVs that identify the
specific half-link of the inter-AS link. Section 6 of this document
introduces the TLVs that MUST be included as the inter-AS Link
Descriptors:
- Remote AS Number (TLV 270), and
- One or both of IPv4 and IPv6 Remote ASBR ID using TLV 271 and/or
TLV 272, depending on whether the Remote ASBR is configured with one
or both of the IPv4 and IPv6 TE Router-IDs.
Additionally, the following TLVs MUST be included as inter-AS Link
Descriptors if they are being advertised in the underlying IGP
advertisement of the inter-AS link as they help identify individual
links when there is more than one inter-AS link between two ASBRs.
- Link Local/Remote Identifiers (TLV 258) [RFC9552]
- IPv4 Interface Address (TLV 259) [RFC9552]
- IPv4 Neighbor Address (TLV 260) [RFC9552]
- IPv6 Interface Address (TLV 261) [RFC9552]
- IPv6 Neighbor Address (TLV 262) [RFC9552]
Use of any other TLVs as Local Node Descriptors or inter-AS Link
Descriptors may cause challenges in the correlation of the two inter-
AS Link NLRI half-links when the BGP-LS Producer implementations
vary.
6. Inter-AS Link Descriptor TLVs
This document introduces three TLVs for inclusion as inter-AS Link
Descriptors within the inter-AS Link NLRI for the advertisement of
inter-AS link information via BGP-LS.
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+-----------+---------------------+--------------+----------------+
| TLV Code | Description |IS-IS/OSPF TLV| Reference |
| Point | | /Sub-TLV | (RFC/Section) |
+-----------+---------------------+--------------+----------------+
| 270 |Remote AS Number | 24/21 | [RFC9346]/3.4.1|
| | | | [RFC5392]/3.3.1|
| 271 |IPv4 Remote ASBR ID | 25/22 | [RFC9346]/3.4.2|
| | | | [RFC5392]/3.3.2|
| 272 |IPv6 Remote ASBR ID | 26/24 | [RFC9346]/3.4.3|
| | | | [RFC5392]/3.3.3|
+-----------+---------------------+--------------+----------------+
Figure 3: inter-AS Link Descriptor TLVs
The encoding of these TLVs is aligned with the corresponding
advertisements in [RFC9346] and [RFC5392], which keeps the BGP-LS
protocol agnostic to the underlying protocol.
6.1. Remote AS Number TLV
The Remote AS Number TLV specifies the AS number of the neighboring
AS to which the advertised link connects.
The Remote AS Number TLV is TLV Type 270 and is 4 octets in length.
Its format is as follows:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Remote AS Number TLV Format
The Remote AS Number field has 4 octets. When only 2 octets are used
for the AS number (for example, when such information is advertised
from OSPF), the left (high-order) 2 octets MUST be set to 0.
6.2. IPv4 Remote ASBR ID
The IPv4 Remote ASBR ID TLV specifies the IPv4 identifier of the
remote ASBR to which the advertised inter-AS link connects. This can
be any stable, routable IPv4 address of the remote ASBR. The use of
the TE Router ID, as specified in the Traffic Engineering Router ID
TLV [RFC9346] is RECOMMENDED.
The IPv4 Remote ASBR ID TLV is TLV Type 271 and is 4 octets in
length. Its format is as follows:
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: IPv4 Remote ASBR ID TLV Format
6.3. IPv6 Remote ASBR ID
The IPv6 Remote ASBR ID TLV specifies the IPv6 identifier of the
remote ASBR to which the advertised inter-AS link connects. This can
be any stable, routable IPv6 address of the remote ASBR. The use of
the TE Router ID, as specified in the IPv6 Traffic Engineering Router
ID TLV [RFC9346] is RECOMMENDED.
The IPv6 Remote ASBR ID TLV is TLV Type 272 and is 16 octets in
length. Its format is as follows:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: IPv6 Remote ASBR ID TLV Format
The IPv6 Remote ASBR ID TLV MUST be included if the neighboring ASBR
has an IPv6 address. If the neighboring ASBR does not have an IPv6
address, the IPv4 Remote ASBR ID TLV MUST be included instead. Both
an IPv4 Remote ASBR ID TLV and an IPv6 Remote ASBR ID TLV MAY be
present in an inter-AS Link NLRI.
7. Advertisement of IGP Information for Inter-AS Links
Advertisement of inter-AS Links along with their TE information is
done is done in IGPs as follows:
- In OSPFv2 via the inter-AS-TE-v2 LSA [RFC5392]
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- In OSPFv3 via the inter-AS-TE-v3 LSA[RFC5392]
- In IS-IS via the inter-AS Reachability Information TLV (TLV 141)
[RFC9346]
The routers that connect to the SDN controller via the BGP-LS
protocol within each domain will advertise the information from the
above IGPs for the inter-AS link. To retrieve the inter-AS topology,
the Autonomous System TLV(TLV 512), Remote AS number, IPv6 Remote
ASBR ID and/or IPv4 Remote ASBR ID MUST be presented within the
inter-AS Link NLRI of each inter-AS link.
When advertising these inter-AS Links from the IGPs into BGP-LS as
inter-AS Links, the sourcing of information for the inter-AS Link
NLRI except for the inter-AS Link Descriptors follows the same
procedures as specified in [RFC9552]. The information about the
Remote AS Number and the IPv4/IPv6 Remote ASBR IDs specified in
Section 6 are derived from the Remote AS Number and IPv4/IPv6 Remote
ASBR ID TLVs specified for OSPF and IS-IS in [RFC5392] and [RFC9346]
respectively. The rest of the inter-AS Link Descriptor TLVs of the
inter-AS Link NLRI are sourced from the base OSPF/ISIS TE TLVs that
were originally introduced for normal IGP links and which are also
encoded for the inter-AS TE links as specified in [RFC5392] and
[RFC9346]; their procedures are therefore the same as in [RFC9552].
The OSPF/ISIS inter-AS Link advertisements also include various link
properties (e.g., TE metric, Admin Groups, SRLGs, etc.) which are
encoded using the same TLVs as for normal IGP links. These link
properties are advertised using their corresponding BGP-LS TLVs as
specified in [RFC9552] and other BGP-LS extensions in the BGP-LS
Attribute associated with the inter-AS Link NLRI of that specific
link.
8. Solutions for other Alternative Scenarios
In some scenario, it is possible that the router running BGP-LS acts
as also the role of the ASBR. Take the topology in following figure
as the example:
In this alternative topology, it is SB1, which is also the ASBR of
IGP A, runs BGP-LS protocol with the IP SDN controller. All other
information are kept the same as that in Figure 1.
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+-----------------+
+------+IP SDN Controller+-----+
| +-----------------+ |
| |
+-------+BGP-LS |BGP-LS
| |
+-----------------------+ +------+--------------+
| +--+ +--+ +-+-+ +-+-+ ++-+ +--+|
| |S1+---------+S2+---+SB1+-----------+TB2+---+T1+--------+T2||
| +-++ +--+ +-+-+ +-+-+ +--+ +-++|
| | | | | |
| | | | | |
| +-++ +--+ +-+-+ +-+-+ +--+ +-++|
| |S4+--------+S3+----+SB3+-----------+TB4+---+T3+--------+T4||
| +--+ +--+ +-+-+ +-+-+ +--+ +--+|
| | | |
| | | |
| IGP A | | IGP B |
+-----------------------+ +---------------------+
Figure 7: Alternative Inter-AS Domain Scenario
To retrieval the inter-AS topology among IGP A and IGP B in above
alternative scenario, one possible solution is to utilize the BGP EPE
[RFC9086] solution on SB1(reports the local information via the Link
NLRI with 'protocol-id' set to 'BGP'), together with solution
proposed in this document(reports the Inter-as link information on
another ASBR via the inter-AS Link NLRI, with 'protocol-id' set to
'OSPF' or 'IS-IS').
Considering the inter-AS link information on SB1 is configured
locally, and they are either from direct connect interfaces, or from
static configuration routes, using also the inter-AS NLRI, with the
'protocol-id' set to either 'direct' or 'static' is aligned well with
the definition of [RFC9552], and can also keep the implementation and
deployment of the solution universal, regardless of whether the
routers runs BGP-LS with the controller is within the AS or at the
border of the AS.
All the inter-AS topology information will be coming from the inter-
AS Link NLRI, and is easy to be distinguished with other information
from Link NLRI of IGP.
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9. End-to-End Inter-AS Topology Use Case
[RFC8735] section 3.3 "Traffic Engineering for Multi-domain"
describes the scenario that the service provider needs to do traffic
engineering from end to end that spans multiple domains. To program
the end to end path, and let the traffic pass the non-congested
links, especially the links that interconnect to the different
domains, the SDN controller that covers all these domains which
belong to the service provider needs to know the inter-AS topology
information from the inter-AS Link NLRI via the BGP-LS. It binds the
half link information from each domain together, calculates the end-
to-end path for the assured service traffic and uses the final path
information to control the transmission of the assured traffic.
The use case can also be explained via the scenario described in
Figure 1.
If S1 wants to send traffic to T2 with assured performance, it should
know the end-to-end path from the IP SDN controller, especially the
connection topology among the four border routers(SB1, SB3, TB2 and
TB4).
Such connection topology information is sent by S2 and T1
respectively via the BGP-LS protocol, to the IP SDN controller. The
IP SDN controller can then stick the two IGP domain topologies
together, calculate the end-to-end path that spans two IGP domains
and their inter-connection links, guide the traffic from S1 (in IGP
A) to T2 (IGP B) traverse the desired nodes and links.
If there are no inter-connection links from the inter-AS NLRI that is
defined in this document, the IP SDN controller can't stick the two
IGP domains together and can't then calculate the end-to-end path for
the communication nodes located in different domains.
10. Security Considerations
BGP-LS security is specified in [RFC9552]. This extension to BGP-LS
focuses on scenarios where a single entity-operated network includes
multiple IGP domains composed of its backbone network, several
Metropolitan-Area Networks (MANs), and Data Centers (DCs). The
configuration of these networks, operated by a single administrative
entity, creates a "walled garden". Within this single administrative
domain, the network operator needs to monitor and engineer traffic
flows traversing a network that spans multiple Autonomous Systems
(ASes). The network operator can obtain this inter-AS topology
information via the procedure described in this document.
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A single administrative domain consisting of two ASes that passes
information about inter-AS Link characteristics does not cause issues
within a "walled garden". However, the inter-AS Link NLRI and its
characteristics (Link/Local Identifier, IPv4 Interface Address, IPv4
Neighbor Address, IPv6 Interface Address, IPv6 Neighbor Address,
Multi-Topology Identifier, Remote-AS Number, IPv4 Remote ASBR ID, and
IPv6 Remote ASBR ID) constitute critical network information. As
such, operators SHOULD handle this critical information in a manner
that restricts it to the walled garden.
11. IANA Considerations
This document requests IANA to update the allocated codepoints from
under the "Border Gateway Protocol - Link State (BGP-LS) Parameters"
registry group as follows:
11.1. New BGP-LS NLRI type
IANA has allocated a codepoint for the inter-AS Link NLRI type from
the "BGP-LS NLRI Types" registry in the "Border Gateway Protocol –
Link State (BGP-LS) Parameter" Group:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | NLRI Type | Reference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 7 | inter-AS Link NLRI| This document |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Inter-AS Link NLRI Codepoint
11.2. New Inter-AS Link Descriptors
IANA has allocated codepoints for the following TLVs from "BGP-LS
NLRI and Attribute TLVs" registry in the "Border Gateway Protocol –
Link State (BGP-LS) Parameter" Group:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Code Point | Description | Reference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 270 | Remote AS Number | This document |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 271 | IPv4 Remote ASBR ID | This document |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 272 | IPv6 Remote ASBR ID | This document |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: BGP-LS Link Descriptors TLV
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12. Acknowledgement
The author would like to thank Susan Hares, Acee Lindem, Jie Dong,
Shaowen Ma, Jeff Tantsura and Dhruv Dhody for their valuable comments
and suggestions.
13. References
13.1. 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>.
[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>.
[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/info/rfc8174>.
[RFC8735] Wang, A., Huang, X., Kou, C., Li, Z., and P. Mi,
"Scenarios and Simulation Results of PCE in a Native IP
Network", RFC 8735, DOI 10.17487/RFC8735, February 2020,
<https://www.rfc-editor.org/info/rfc8735>.
[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>.
[RFC9552] Talaulikar, K., Ed., "Distribution of Link-State and
Traffic Engineering Information Using BGP", RFC 9552,
DOI 10.17487/RFC9552, December 2023,
<https://www.rfc-editor.org/info/rfc9552>.
13.2. Informative References
[RFC9086] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Patel, K.,
Ray, S., and J. Dong, "Border Gateway Protocol - Link
State (BGP-LS) Extensions for Segment Routing BGP Egress
Peer Engineering", RFC 9086, DOI 10.17487/RFC9086, August
2021, <https://www.rfc-editor.org/info/rfc9086>.
Wang, et al. Expires 13 November 2026 [Page 13]
Internet-Draft BGP-LS-Inter-AS-Ext May 2026
Authors' Addresses
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing
Beijing, 102209
China
Email: wangaj3@chinatelecom.cn
Huaimo Chen
Individual
Boston, MA
United States of America
Email: hchen.ietf@gmail.com
Ketan Talaulikar
Cisco Systems
India
Email: ketant.ietf@gmail.com
Shunwan Zhuang
Huawei Technologies
Huawei Building, No.156 Beiqing Rd.
Beijing
100095
China
Email: zhuangshunwan@huawei.com
Changwang Lin
New H3C Technologies
Huawei Building, No.156 Beiqing Rd.
Beijing
China
Email: linchangwang.04414@h3c.com
Wang, et al. Expires 13 November 2026 [Page 14]