Advertisement of Remote Interface Identifiers for Layer 2 Bundle Members
draft-ietf-lsr-l2-bundle-member-remote-id-07
| Document | Type | Active Internet-Draft (lsr WG) | |
|---|---|---|---|
| Authors | Liyan Gong , Changwang Lin , huxiaolong , Les Ginsberg , Peter Psenak | ||
| Last updated | 2026-09-29 | ||
| Replaces | draft-glctgp-lsr-l2-bundle-member-remote-id | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Acee Lindem | ||
| Shepherd write-up | Show Last changed 2026-09-04 | ||
| IESG | IESG state | In Last Call (ends 2026-10-13) | |
| Action Holder | |||
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Gunter Van de Velde | ||
| Send notices to | acee.ietf@gmail.com | ||
| IANA | IANA review state | IANA - Review Needed |
draft-ietf-lsr-l2-bundle-member-remote-id-07
LSR Working Group L. Gong
Internet-Draft China Mobile
Intended status: Standards Track C. Lin
Expires: 2 April 2027 X. Hu
New H3C Technologies
L. Ginsberg
P. Psenak
Cisco Systems
29 September 2026
Advertisement of Remote Interface Identifiers for Layer 2 Bundle Members
draft-ietf-lsr-l2-bundle-member-remote-id-07
Abstract
In networks where Layer 2 (L2) interface bundles (such as a Link
Aggregation Group (LAG) as defined in IEEE 802.1AX) are deployed, a
controller may need to collect the connectivity relationships between
bundle members for traffic engineering (TE) purposes. For example,
when performing topology management and bidirectional path
computation for TE, it is essential to know the connectivity
relationships among bundle members.
This document describes how Open Shortest Path First (OSPF) and
Intermediate System to Intermediate System (IS-IS) would advertise
the remote interface identifiers for L2 bundle members. The
corresponding extension of BGP Link State (BGP-LS) is also specified.
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 2 April 2027.
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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
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Advertising L2 Bundle Member Remote Interface Identifier . . 4
3.1. OSPF Advertisement . . . . . . . . . . . . . . . . . . . 5
3.2. IS-IS Advertisement . . . . . . . . . . . . . . . . . . . 5
3.3. BGP-LS Advertisement . . . . . . . . . . . . . . . . . . 6
4. OSPF Extension . . . . . . . . . . . . . . . . . . . . . . . 6
5. IS-IS Extension . . . . . . . . . . . . . . . . . . . . . . . 7
6. BGP-LS Extension . . . . . . . . . . . . . . . . . . . . . . 9
7. Acquisition of the Remote Interface Identifier . . . . . . . 10
8. Operational Considerations . . . . . . . . . . . . . . . . . 11
9. Security Considerations . . . . . . . . . . . . . . . . . . . 11
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
12.1. Normative References . . . . . . . . . . . . . . . . . . 14
12.2. Informative References . . . . . . . . . . . . . . . . . 15
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
BGP Link State (BGP-LS) [RFC9552] is widely used for collecting
topology information from Interior Gateway Protocols (IGPs). In
networks where Layer 2 (L2) interface bundles (such as a Link
Aggregation Group (LAG) [IEEE802.1AX]) are deployed, a controller may
need to collect the connectivity relationships between bundle members
for traffic engineering (TE) purposes. For example, when performing
topology management and bidirectional path computation for TE (e.g.,
for a co-routed associated bidirectional path as defined in
Section 2.2.2 of [RFC8537] or Section 3.3 of [RFC9059]), knowledge of
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the connectivity relationships among bundle members is required.
When advertising L2 bundles in Open Shortest Path First (OSPF)
[RFC9356] and Intermediate System to Intermediate System (IS-IS)
[RFC8668], a member link is described by its local interface
identifier, also referred to as a link local identifier. If the
remote interface identifier could be advertised for each member link,
the pairing relationships between the local and remote interfaces
would be clear.
This document describes the mechanism for advertising the remote
interface identifier for L2 bundle members in OSPF and IS-IS. The
BGP-LS extension for advertising L2 bundle member interface remote
identifier is also specified in this document.
1.1. 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.
2. Use Case
Figure 1 shows a network, in which an L2 bundle is deployed between
R1 and R2. The controller collects the topology information from R3
via BGP-LS.
+----------+ BGP-LS
|Controller|<-------------------+
+----------+ |
|
|
|
+----+ L2-Bundle +----+ +-+--+
| | /-------member 1-------\ | | | |
| | / \ | | | |
| R1 +----------member 2----------+ R2 +---+ R3 |
| | \ / | | | |
| | \-------member 3-------/ | | | |
+----+ +----+ +----+
Figure 1: Network Topology with L2 Bundle
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The network operator may want to control bidirectional traffic flows
on the individual member links of the underlying L2 bundle for TE
purposes. The real-time bandwidth, delay, and link loss might be
measured for each bundle member at both ends. Labels or Segment
Identifiers (SIDs) might be allocated for each bundle member at both
ends. So, there would be requirements for the controller to figure
out the connectivity relationships between bundle members.
This document defines a mechanism for IGP routers to advertise the
remote interface identifiers for each L2 bundle member, along with
the corresponding mechanism for the controller to collect such
information via BGP-LS. The controller can then correlate the member
links at the two ends of the L2 bundle: as specified in Section 7,
the remote identifier advertised by one router for a bundle member
equals the local identifier advertised by its neighbor for that same
member, so a remote identifier advertised at one end matches the
local identifier advertised at the other end.
An absent remote identifier means that the value is not learned or
not advertised for that member; it does not indicate that the peer
has no corresponding member. In particular, when one endpoint of the
L2 bundle implements the extension described in this document and the
other endpoint does not, the members advertised by the endpoint that
supports the extension will not carry remote identifiers.
3. Advertising L2 Bundle Member Remote Interface Identifier
The routers at both ends of the LAG (e.g., R1 and R2 in Figure 1)
independently advertise their local member interface information
along with the corresponding remote interface identifiers.
The following subsections describe how the remote interface
identifiers of L2 bundle members are advertised in OSPF, IS-IS, and
BGP-LS, respectively. The L2 bundle member information is advertised
in association with the parent Layer 3 (L3) link (i.e., the logical
link directly operated on by the L3 protocol, as distinguished from
the individual L2 bundle member links which are not directly visible
to L3).
The descriptions in this section are intended to be illustrative and
are not meant to be normative. The normative definitions of the L2
bundle member attribute objects (the L2 Bundle Member Attributes
Type-Length-Value (TLV) for IS-IS and BGP-LS, and the L2 Bundle
Member Attributes sub-TLV for OSPF) and of their sub-TLVs are
provided in [RFC9356] for OSPF, [RFC8668] for IS-IS, and [RFC9085]
for BGP-LS. Note that the term "sub-TLV" is used throughout this
document (consistent with the referenced RFCs) to refer to TLVs that
are nested within a parent TLV.
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3.1. OSPF Advertisement
In OSPF, the remote interface identifiers of L2 bundle members are
advertised as follows.
OSPFv2 Extended Link TLV [RFC7684], or OSPFv3 Router-Link TLV
[RFC8362], for the parent L3 link:
L2 Bundle Member Attributes sub-TLV:
L2 Bundle Member Descriptor of Member #1
L2 Bundle Member Interface Remote Identifier sub-TLV (Optional -
as defined in Section 4)
L2 Bundle Member Attributes sub-TLV:
L2 Bundle Member Descriptor of Member #2
L2 Bundle Member Interface Remote Identifier sub-TLV (Optional -
as defined in Section 4)
...
L2 Bundle Member Attributes sub-TLV:
L2 Bundle Member Descriptor of Member #n
L2 Bundle Member Interface Remote Identifier sub-TLV (Optional -
as defined in Section 4)
3.2. IS-IS Advertisement
In IS-IS, the remote interface identifiers of L2 bundle members are
advertised as follows. Note that IS-IS can advertise a set of
members in a single L2 Bundle Attribute Descriptor, so the L2 Bundle
Member Interface Remote Identifier sub-TLV MUST carry multiple remote
interface identifiers, one for each bundle member advertised in the
associated L2 Bundle Member Descriptor.
L2 Bundle Member Attributes TLV:
Parent L3 Neighbor Descriptor
L2 Bundle Attribute Descriptor (one or more may be present):
Length of L2 Bundle Attribute Descriptor
Number of L2 Bundle Member Descriptors
L2 Bundle Member Link Local Identifiers of Member #1,#2,...,#n
sub-TLV(s)
L2 Bundle Member Interface Remote Identifier sub-TLV (Optional -
as defined in Section 5) for Member #1,#2,...,#n
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3.3. BGP-LS Advertisement
In BGP-LS, the remote interface identifiers of L2 bundle members are
advertised in the BGP-LS Link Network Layer Reachability Information
(NLRI) as follows. As specified in Section 2.2.3 of [RFC9085], the
L2 Bundle Member Attributes TLV is associated with the Link NLRI that
describes the parent L3 link.
BGP-LS Link NLRI: The parent L3 link for R1->R2 (as described in
Section 2.2.3 of [RFC9085])
Link Attributes:
L2 Bundle Member Attributes TLV:
L2 Bundle Member Descriptor of Member #1
L2 Bundle Member Interface Remote Identifier sub-TLV (Optional -
as defined in Section 6)
L2 Bundle Member Attributes TLV:
L2 Bundle Member Descriptor of Member #2
L2 Bundle Member Interface Remote Identifier sub-TLV (Optional -
as defined in Section 6)
...
L2 Bundle Member Attributes TLV:
L2 Bundle Member Descriptor of Member #n
L2 Bundle Member Interface Remote Identifier sub-TLV (Optional -
as defined in Section 6)
4. OSPF Extension
This document defines a new L2 Bundle Member Interface Remote
Identifier sub-TLV in both OSPFv2 and OSPFv3. This sub-TLV is used
to advertise the remote interface identifier for an L2 bundle member.
It can be carried as a sub-TLV of the OSPF L2 Bundle Member
Attributes sub-TLV [RFC9356]. It 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 (TBA) | Length (4) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBA (to be assigned from the "OSPFv2 Extended Link TLV Sub-
TLVs" registry and the "OSPFv3 Extended-LSA Sub-TLVs" registry).
Length: 4.
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Remote Interface ID: Remote identifier of interface, 4 octets. See
Section 7 for the definition of the remote interface identifier.
A remote interface ID with value of zero is not valid and MUST be
ignored and handled as if the sub-TLV was not present. An originator
MUST NOT advertise a value of zero for the Remote Interface ID, since
a value of zero is reserved to indicate that the remote interface
identifier is unknown, consistent with the Link Local Identifier
defined in [RFC4202] (see Section 7).
If the Length of this sub-TLV is not 4, the sub-TLV MUST be ignored
and handled as if it was not present.
The L2 Bundle Member Interface Remote Identifier sub-TLV MUST NOT
appear more than once within the same L2 Bundle Member Attributes
sub-TLV. If multiple instances of this sub-TLV are received within
the same L2 Bundle Member Attributes sub-TLV, implementations MUST
use the first occurrence and ignore subsequent occurrences.
5. IS-IS Extension
This document defines a new L2 Bundle Member Interface Remote
Identifier sub-TLV in IS-IS. This sub-TLV is used to advertise the
remote interface identifiers for L2 bundle members.
It can be carried as a sub-TLV of the IS-IS L2 Bundle Member
Attributes TLV [RFC8668]. It 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 (TBA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBA (to be assigned from the "IS-IS Sub-TLVs for TLVs
Advertising Neighbor Information" registry).
Length: A non-zero multiple of 4: 4 * Number of L2 Bundle Member
Descriptors in the enclosing L2 Bundle Attribute Descriptor.
Remote Interface ID: Remote identifier of interface, 4 octets. See
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Section 7 for the definition of the remote interface identifier.
The number of Remote Interface IDs carried in this sub-TLV MUST equal
the Number of L2 Bundle Member Descriptors advertised in the
enclosing L2 Bundle Attribute Descriptor. The Remote Interface IDs
are ordered such that the first Remote Interface ID corresponds to
the first L2 Bundle Member Descriptor listed in the L2 Bundle
Attribute Descriptor, the second Remote Interface ID corresponds to
the second L2 Bundle Member Descriptor, and so on. A remote
interface ID with value of zero MUST be ignored and handled as if the
value was unknown.
If the Length of this sub-TLV is zero or is not a multiple of 4, or
if the number of Remote Interface IDs it carries does not equal the
Number of L2 Bundle Member Descriptors in the enclosing L2 Bundle
Attribute Descriptor, the sub-TLV MUST be ignored and handled as if
it was not present (i.e., the remote identifiers of all the bundle
members in that descriptor are treated as unknown).
The L2 Bundle Member Interface Remote Identifier sub-TLV MUST NOT
appear more than once within the sub-TLV set of a single L2 Bundle
Attribute Descriptor. If multiple instances of this sub-TLV are
received within the same L2 Bundle Attribute Descriptor (e.g., during
transient conditions), implementations MUST use the first occurrence
in the lowest numbered Link State Protocol Data Unit (LSP) fragment
and ignore subsequent occurrences.
A value of zero in a Remote Interface ID is permitted only as a
positional placeholder indicating that the remote identifier for the
corresponding bundle member is unknown; it MUST NOT be used with any
other meaning. As described in Section 7, when the remote identifier
of every bundle member in an L2 Bundle Attribute Descriptor is
unknown, the originator SHOULD omit the sub-TLV entirely rather than
advertise zero for each member.
The L2 Bundle Attribute Descriptor has a one-octet Length field, and
the Number of L2 Bundle Member Descriptors field is also one octet;
the sub-TLV space available for this sub-TLV within an L2 Bundle
Attribute Descriptor is therefore bounded. When the remote
identifiers for a set of bundle members do not fit within these one-
octet limits (including the sub-TLV header), the originator SHOULD
split the members across multiple L2 Bundle Attribute Descriptors
within the same L2 Bundle Member Attributes TLV, with each instance
of this sub-TLV covering the members of its associated descriptor.
The Multi-Part TLV (MP-TLV) applicability [RFC9885] for the new IS-IS
sub-TLV is N (MP-TLV procedures are not applicable to this sub-TLV).
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6. BGP-LS Extension
This document defines a new L2 Bundle Member Interface Remote
Identifier sub-TLV in BGP-LS. This sub-TLV is derived from the
Remote Interface Identifier sub-TLV of OSPF (Section 4) and IS-IS
(Section 5).
It can be carried as a sub-TLV of the BGP-LS L2 Bundle Member
Attributes TLV [RFC9085]. It 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 (TBA) | Length (4) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBA (to be assigned from the "BGP-LS NLRI and Attribute TLVs"
registry).
Length: 4.
Remote Interface ID: Remote identifier of interface, 4 octets. See
Section 7 for the definition of the remote interface identifier.
A remote interface ID with value of zero is not valid and MUST be
ignored and handled as if the sub-TLV was not present.
The L2 Bundle Member Interface Remote Identifier sub-TLV MUST NOT
appear more than once within the same L2 Bundle Member Attributes
TLV. If multiple instances of this sub-TLV are received within the
same L2 Bundle Member Attributes TLV, implementations MUST use the
first occurrence and ignore subsequent occurrences.
The L2 Bundle Member Attributes TLV (type 1172) carrying this sub-TLV
is associated with the Link NLRI that describes the parent L3 link.
An L2 Bundle Member Descriptor and its L2 Bundle Member Interface
Remote Identifier sub-TLV advertised in OSPF (Section 4) map one-to-
one to an L2 Bundle Member Attributes TLV instance in BGP-LS. For
IS-IS (Section 5), the ordered list of Remote Interface IDs carried
in a single sub-TLV instance maps positionally to the ordered list of
L2 Bundle Member Link Local Identifiers advertised under the
associated L2 Bundle Attribute Descriptor, and each member and its
remote identifier are exported in the corresponding L2 Bundle Member
Attributes TLV instance in BGP-LS.
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A member whose remote identifier is unknown, or which is advertised
with a value of zero in IS-IS as described in Section 7, is exported
without the L2 Bundle Member Interface Remote Identifier sub-TLV in
the corresponding L2 Bundle Member Attributes TLV instance; a value
of zero is never exported in BGP-LS.
With respect to the roles defined in Section 3 of [RFC9552], a BGP-LS
Producer originates this sub-TLV as part of the BGP-LS Attribute of
the Link NLRI describing the parent L3 link, following the mapping
described above. A BGP-LS Propagator does not perform semantic
validation of this sub-TLV and does not remove it due to semantic or
syntactic length mismatches beyond the 'Attribute Discard' fault
handling defined in Section 8.2.2 of [RFC9552]. Semantic validation
of the sub-TLV (e.g., consistency checking as described in Section 7)
is performed by the BGP-LS Consumer, and the handling of any
resulting errors is specific to the application and outside the scope
of this document.
7. Acquisition of the Remote Interface Identifier
The routers at both ends of the L2 bundle independently assign a non-
zero 32-bit identifier to each of their bundle members and advertise
it as the L2 Bundle Member Link Local Identifier in the L2 Bundle
Member Descriptor ([RFC9356], [RFC8668]), consistent with the Link
Local Identifier defined in [RFC4202].
The remote interface identifier advertised by a router for a bundle
member MUST be the exact non-zero 32-bit value that the neighboring
router advertises as the L2 Bundle Member Link Local Identifier for
that same bundle member. In other words, if R1 advertises remote
identifier X for its local member with identifier A, then R2 (the
neighbor) advertises local identifier X for that member, and
symmetrically R2 advertises remote identifier A for its local member
with identifier X. This relationship ensures that a controller can
correlate the advertisements from the two ends of each member link.
IGPs provide no direct way for a router to learn the identifiers
assigned by its neighbor to the individual bundle members, since the
L3 protocol does not operate on the bundle members. The acquisition
of the exact remote identifier value is therefore outside the scope
of this document. Implementations MAY obtain the value through
configuration or through implementation-specific discovery
procedures. L2 protocols such as the Link Layer Discovery Protocol
(LLDP) ([IEEE802.1AB]) and the Link Aggregation Control Protocol
(LACP) ([IEEE802.1AX]) allow a router to discover the identity of the
neighboring port on each member link, and implementations MAY use
them as part of such procedures. Note, however, that the identifiers
carried by these protocols are not required to match the L2 Bundle
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Member Link Local Identifiers advertised by the neighbor: the LLDP
Port ID is subtype-dependent and is not necessarily a 32-bit numeric
value, and the LACP Actor and Partner Port Numbers are 16-bit values
assigned independently by each end. Any mapping between the
identifiers discovered via these protocols and the neighbor's
advertised L2 Bundle Member Link Local Identifiers is implementation-
specific.
To verify the correctness of the acquired remote identifiers,
implementations SHOULD provide mechanisms to validate that received
advertisements are consistent with the relationship defined above,
i.e., that the value advertised as the remote identifier for a member
equals the value advertised as the L2 Bundle Member Link Local
Identifier for the corresponding member by the neighboring router.
Mismatched pairs may indicate misconfiguration or incorrect
discovery.
8. Operational Considerations
Implementations MUST NOT enable the advertisement of the L2 Bundle
Member Interface Remote Identifier sub-TLV by default and MUST
provide a configuration option to enable its advertisement on
specific links.
9. Security Considerations
This document describes how OSPF, IS-IS and BGP-LS would advertise
the remote interface identifiers for L2 bundle members. The security
considerations of [RFC8668], [RFC9356], [RFC9552], [RFC9085] and
[RFC9086] are applicable to this document. In addition, the
acquisition of the remote interface identifiers specified in
Section 7 introduces the trust considerations described below.
The advertisement of the remote interface identifier introduces a new
trust boundary. IGP authentication protects the advertisement once
the originating router has created it, but it does not authenticate
the local L2 information from which the router obtained the remote
member mapping. As described in Section 7, the value of the remote
identifier may be acquired through configuration or through
implementation-specific discovery procedures that may rely on L2
protocols such as LLDP and LACP. The trust placed in these
acquisition mechanisms therefore directly affects the trustworthiness
of the information advertised by this document.
A spoofed, stale, or inconsistent mapping produced by the acquisition
mechanism could cause a router to advertise a false remote interface
identifier and thus create a false association between the member
links at the two ends of the L2 bundle. A controller that consumes
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this information for TE or failure correlation might then steer
traffic onto member links that are not actually connected or
misdiagnose the scope of a failure. To limit the impact of stale
information, an originator MUST NOT continue to advertise a remote
identifier that it knows to be no longer valid and SHOULD withdraw or
replace the value when its source changes or ages out, as specified
in Section 7.
The relationship between the local and remote identifiers is
reciprocal as defined in Section 7: the remote identifier advertised
by one router for a bundle member MUST equal the local identifier
advertised by its neighbor for that same member. Recipients such as
a BGP-LS Consumer can use this reciprocity to validate the mapping.
As noted in Section 7, implementations SHOULD provide mechanisms to
validate received advertisements against this relationship;
mismatched pairs may indicate misconfiguration, incorrect discovery,
or tampering with the acquisition mechanism.
Advertising the remote interface identifier exposes additional
topology detail beyond that provided by the advertisements specified
in [RFC8668], [RFC9356], and [RFC9085]: it reveals the pairing of the
individual member links between the two ends of the L2 bundle. An
operator who considers this detail sensitive should take it into
account when deciding whether to enable the advertisement (see
Section 8). The isolation of BGP-LS peering sessions is recommended
to ensure that BGP-LS topology information (including the newly added
remote interface identifier information) is not advertised to an
external BGP peering session outside the trusted domain, as described
in Section 10 of [RFC9552].
If the IS-IS protocol is used in an environment where unauthorized
access to the physical links on which IS-IS Protocol Data Units
(PDUs) are sent occurs, then attacks are possible. The use of
authentication as defined in [RFC5304] and [RFC5310] is recommended
to prevent such attacks.
If the OSPF protocol is used in an environment where unauthorized
access to the physical links on which OSPF packets are sent occurs,
then attacks are possible. The use of authentication as defined in
[RFC5709], [RFC7474], [RFC4552], and [RFC7166] is recommended for
preventing such attacks.
10. IANA Considerations
This document adds the following new sub-TLV to the "OSPFv2 Extended
Link TLV Sub-TLVs" registry. The L2 Bundle Member (L2BM) column
indicates whether the sub-TLV MAY appear ("Y") or MUST NOT appear
("N") within the L2 Bundle Member Attributes sub-TLV [RFC9356].
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+------+----------------------------------------------+----+
| Type | Designation |L2BM|
+======+==============================================+====+
| TBA | L2 Bundle Member Interface Remote Identifier | Y |
+------+----------------------------------------------+----+
This document adds the following new sub-TLV to the "OSPFv3 Extended-
LSA Sub-TLVs" registry. In this registry, the "L2BM" column has an
additional value "X", which indicates that a sub-TLV is not a sub-TLV
of the Router-Link TLV and MUST NOT appear within the L2 Bundle
Member Attributes sub-TLV.
+------+----------------------------------------------+----+
| Type | Description |L2BM|
+======+==============================================+====+
| TBA | L2 Bundle Member Interface Remote Identifier | Y |
+------+----------------------------------------------+----+
This document adds the following new sub-TLV to the "IS-IS Sub-TLVs
for TLVs Advertising Neighbor Information" registry.
+------+-----------------------------+---+---+---+---+---+---+---+
| Type | Description | 22| 23| 25|141|222|223| MP|
+======+=============================+===+===+===+===+===+===+===+
| TBA | L2 Bundle Member | n | n | y | n | n | n | n |
| | Interface Remote Identifier | | | | | | | |
+------+-----------------------------+---+---+---+---+---+---+---+
This document adds the following new sub-TLV to the "BGP-LS NLRI and
Attribute TLVs" registry.
+------+----------------------------------------------+
| Type | Description |
+======+==============================================+
| TBA | L2 Bundle Member Interface Remote Identifier |
+------+----------------------------------------------+
11. Acknowledgements
The authors would like to thank Acee Lindem for his shepherd review
and helpful comments to improve this document.
The authors would like to thank Michael Richardson for RTGDIR early
review.
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The authors would also like to thank Shraddha Hegde, and Tom Petch
for their review of this document and their comments.
12. References
12.1. Normative References
[IEEE802.1AX]
IEEE, "IEEE Standard for Local and Metropolitan Area
Networks--Link Aggregation", IEEE Std 802.1AX,
DOI 10.1109/IEEESTD.2020.9105034, May 2020,
<https://doi.org/10.1109/IEEESTD.2020.9105034>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4202] Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, DOI 10.17487/RFC4202, October 2005,
<https://www.rfc-editor.org/info/rfc4202>.
[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>.
[RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
Authentication", RFC 5709, DOI 10.17487/RFC5709, October
2009, <https://www.rfc-editor.org/info/rfc5709>.
[RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting
Authentication Trailer for OSPFv3", RFC 7166,
DOI 10.17487/RFC7166, March 2014,
<https://www.rfc-editor.org/info/rfc7166>.
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[RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
"Security Extension for OSPFv2 When Using Manual Key
Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
<https://www.rfc-editor.org/info/rfc7474>.
[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <https://www.rfc-editor.org/info/rfc7684>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, May 2017,
<https://www.rfc-editor.org/info/rfc8174>.
[RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and
F. Baker, "OSPFv3 Link State Advertisement (LSA)
Extensibility", RFC 8362, DOI 10.17487/RFC8362, April
2018, <https://www.rfc-editor.org/info/rfc8362>.
[RFC8668] Ginsberg, L., Ed., Bashandy, A., Filsfils, C., Nanduri,
M., and E. Aries, "Advertising Layer 2 Bundle Member Link
Attributes in IS-IS", RFC 8668, DOI 10.17487/RFC8668,
December 2019, <https://www.rfc-editor.org/info/rfc8668>.
[RFC9085] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Gredler,
H., and M. Chen, "Border Gateway Protocol - Link State
(BGP-LS) Extensions for Segment Routing", RFC 9085,
DOI 10.17487/RFC9085, August 2021,
<https://www.rfc-editor.org/info/rfc9085>.
[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>.
[RFC9356] Talaulikar, K. and P. Psenak, "Advertising L2 Bundle
Member Link Attributes in OSPF", RFC 9356, January 2023,
<https://www.rfc-editor.org/info/rfc9356>.
[RFC9885] Kaneriya, P., Li, T., Przygienda, A., Hegde, S., and L.
Ginsberg, "Multi-Part TLVs in IS-IS", RFC 9885, October
2025, <https://www.rfc-editor.org/info/rfc9885>.
12.2. Informative References
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[IEEE802.1AB]
"IEEE Standard for Local and Metropolitan Area Networks -
Station and Media Access Control Connectivity Discovery",
IEEE Std 802.1AB-2016, 29 January 2016.
[RFC8537] Gandhi, R., Ed., Shah, H., and J. Whittaker, "Updates to
the Fast Reroute Procedures for Co-routed Associated
Bidirectional Label Switched Paths (LSPs)", RFC 8537,
DOI 10.17487/RFC8537, February 2019,
<https://www.rfc-editor.org/info/rfc8537>.
[RFC9059] Gandhi, R., Ed., Barth, C., and B. Wen, "Path Computation
Element Communication Protocol (PCEP) Extensions for
Associated Bidirectional Label Switched Paths (LSPs)",
RFC 9059, DOI 10.17487/RFC9059, June 2021,
<https://www.rfc-editor.org/info/rfc9059>.
[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>.
Contributors
Ketan Talaulikar
Cisco Systems
India
Email: ketant.ietf@gmail.com
Authors' Addresses
Liyan Gong
China Mobile
China
Email: gongliyan@chinamobile.com
Changwang Lin
New H3C Technologies
China
Email: linchangwang.04414@h3c.com
Xiaolong Hu
New H3C Technologies
China
Email: huxiaolong.1260@outlook.com
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Les Ginsberg
Cisco Systems
United States of America
Email: ginsberg@cisco.com
Peter Psenak
Cisco Systems
Apollo Business Center
Mlynske nivy 43
Bratislava 821 09
Slovakia
Email: ppsenak@cisco.com
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