BMP Extension for Path Status TLV
draft-ietf-grow-bmp-path-marking-tlv-05
| Document | Type | Active Internet-Draft (grow WG) | |
|---|---|---|---|
| Authors | Camilo Cardona , Paolo Lucente , Pierre Francois , Yunan Gu , Thomas Graf | ||
| Last updated | 2026-05-15 | ||
| Replaces | draft-cppy-grow-bmp-path-marking-tlv | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
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draft-ietf-grow-bmp-path-marking-tlv-05
Network Working Group C. Cardona
Internet-Draft P. Lucente
Intended status: Standards Track NTT
Expires: 16 November 2026 P. Francois
INSA-Lyon
Y. Gu
Huawei
T. Graf
Swisscom
15 May 2026
BMP Extension for Path Status TLV
draft-ietf-grow-bmp-path-marking-tlv-05
Abstract
The BGP Monitoring Protocol (BMP) provides an interface for obtaining
BGP path information, which is conveyed through BMP Route Monitoring
(RM) messages. This document specifies a BMP extension to convey the
status of a path after being processed by the BGP process.
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 [RFC2119] and RFC8174 [RFC8174] when, and only when, they
appear in all capitals, as shown here.
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 16 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
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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Path Status TLV encoding . . . . . . . . . . . . . . . . . . 3
3. IANA encoding of Path Status TLV . . . . . . . . . . . . . . 4
3.1. IANA path status codes . . . . . . . . . . . . . . . . . 4
3.2. IANA reason codes . . . . . . . . . . . . . . . . . . . . 6
4. Path Marking Statistics . . . . . . . . . . . . . . . . . . . 7
4.1. Per-Status Counters . . . . . . . . . . . . . . . . . . . 7
4.2. Generic Path Status Counters . . . . . . . . . . . . . . 8
5. Implementation notes . . . . . . . . . . . . . . . . . . . . 8
5.1. Configuration of BMP Path Marking . . . . . . . . . . . . 9
5.2. Scalability and churn . . . . . . . . . . . . . . . . . . 9
5.3. Paths with no markings . . . . . . . . . . . . . . . . . 9
5.4. Path markings applicability and consistency . . . . . . . 10
5.4.1. Significance of status and origin RIBs . . . . . . . 10
5.5. Multiple TLVs assigned to the same route. . . . . . . . . 10
5.6. Enterprise-specific status . . . . . . . . . . . . . . . 10
5.7. Multiple reason codes . . . . . . . . . . . . . . . . . . 11
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. Normative References . . . . . . . . . . . . . . . . . . 13
9.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Implementation Status . . . . . . . . . . . . . . . 15
A.1. Huawei VRP NE8000 . . . . . . . . . . . . . . . . . . . . 15
A.2. pmacct BMP Collector . . . . . . . . . . . . . . . . . . 15
A.3. NetGauze and Wireshark Decoders . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
Multiple paths with different path statuses (e.g., the "best path",
"backup path", "invalid", and so on) may co-exist for a given prefix
in the BGP RIBs after being processed by the BGP decision process.
The path status information is not carried in the BGP UPDATE Message
[RFC4271] or in the BMP Route Monitoring Message [RFC7854].
External systems can use the path status for various applications.
For example, operators commonly use path status during
troubleshooting. Having such status stored and tracked enables the
development of tools that facilitate this process. Optimization
systems can consider path status in their process, e.g., as a
validation source (since it can compare the calculated state to the
actual outcome of the network, such as primary and backup path).
Moreover, path status information can complement other centralized
sources of data. For example, flow collectors can leverage it to
identify the exact forwarding paths, yielding more accurate traffic
matrices than existing methods.
This document defines a Path Status TLV to convey the BGP path status
to a BMP server. The BMP Path Status TLV is carried in the BMP Route
Monitoring (RM) Message [RFC7854].
2. Path Status TLV encoding
The path status TLV follows the common header defined in
[I-D.ietf-grow-bmp-tlv] and [I-D.ietf-grow-bmp-tlv-ebit].
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
+-------------------------------+-------------------------------+
| Common TLV Header (Variable bits) |
+---------------------------------------------------------------+
| Path Status (4 octets) |
+---------------------------------------------------------------+
| Reason Code (2 oct., opt.) |
+-------------------------------+
Figure 2: Encoding of Path Status TLV
* The common TLV header that can encode IANA-registered TLV or
Enterprise-specific markings using [I-D.ietf-grow-bmp-tlv-ebit].
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* Path Status (4 Octets): indicates the path status of the BGP
Update PDU encapsulated in the RM Message. The path status is
encoded using a bitmap where each bit position encodes a specific
role of the path. Multiple bits may be set when multiple path
statuses apply to a path. All zeros are reserved for paths with
no marking.
* Reason Code (2 Octets, optional): indicates the reason of the path
status indicated in the Path Status field. The reason code field
is optional. If no reason code is carried, this field is not
included. If a reason code is carried, the reason code is
indicated by a two-byte value.
3. IANA encoding of Path Status TLV
3.1. IANA path status codes
+============+=============================+
| Value | Path Status |
+============+=============================+
| 0x00000001 | Invalid |
+------------+-----------------------------+
| 0x00000002 | Best |
+------------+-----------------------------+
| 0x00000004 | Nonselected |
+------------+-----------------------------+
| 0x00000008 | Primary |
+------------+-----------------------------+
| 0x00000010 | Backup |
+------------+-----------------------------+
| 0x00000020 | Non-installed |
+------------+-----------------------------+
| 0x00000040 | Best-external |
+------------+-----------------------------+
| 0x00000080 | Add-Path |
+------------+-----------------------------+
| 0x00000100 | Filtered in inbound policy |
+------------+-----------------------------+
| 0x00000200 | Filtered in outbound policy |
+------------+-----------------------------+
| 0x00000400 | Stale |
+------------+-----------------------------+
| 0x00000800 | Suppressed |
+------------+-----------------------------+
Table 1: IANA-Registered Path Status
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Table 1 includes a list of IANA status codes. This list might be
extended. An explanation of each of the types is included next:
* An invalid route is a route that does not enter the BGP decision
process as indicated in Section 9.1.2 of RFC4271 [RFC4271].
* The best route is defined in Section 9.1 of RFC4271 [RFC4271].
* Nonselected routes are those that are not selected in the BGP
decision process. Backup routes are considered nonselected, while
the best and primary routes are not considered as nonselected.
* A primary route is a path used for traffic forwarding. See
draft-ietf-rtgwg-bgp-pic [I-D.ietf-rtgwg-bgp-pic]. A prefix can
have more than one primary path when multipath is configured
draft-lapukhov-bgp-ecmp-considerations
[I-D.lapukhov-bgp-ecmp-considerations]. The best path is also a
primary path.
* A backup path is installed in the RIB, but it is not used until
some or all primary paths become unreachable. Backup paths are
used for fast convergence in the event of primary path failures.
* A non-installed path refers to the route that is not installed
into the IP routing table.
* The best external path is defined in draft-ietf-idr-best-external
[I-D.ietf-idr-best-external].
* The add-path status is applied when the advertisement includes
multiple paths for the same address prefix without the new paths
implicitly replacing any previous ones [RFC7911].
* Filtered in inbound policy routes are those that are filtered in
the Adj-RIB-In policy.
* Filtered in outbound policy routes are those that are filtered in
the Adj-RIB-Out policy.
* Stale routes refer to paths which have been declared stale by the
BGP Graceful Restart mechanism, as described in Section 4.1 of
[RFC4724].
* Suppressed routes refer to a path which has been declared
suppressed by the BGP Route Flap Damping mechanism as described in
Section 2.2 of [RFC2439].
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3.2. IANA reason codes
Table 2 includes a list of IANA reason codes. This list can be
extended in future documents. This document includes a brief
explanation of each code and the path status they are intended to
explain. Please see Section 5.4 for notes on potentially
inconsistencies in the path marking data.
* Invalid routes due to AS loop and unresolvable nexthop are defined
in Section 9.1.2 of [RFC4271]. These codes target routes of type
"Invalid".
* The reason codes starting with 'not preferred' are aimed at paths
not selected as best, and describe the reason they were ranked
lower in the decision process. AIGP is explained in RFC7311
[RFC7311]. The rest of the codes are described in Section 9.1.2.2
of [RFC4271].
+========+=====================================+
| Value | Reason Code |
+========+=====================================+
| 0x0001 | Invalid due to AS loop |
+--------+-------------------------------------+
| 0x0002 | Invalid due to unresolvable nexthop |
+--------+-------------------------------------+
| 0x0003 | Not preferred for local preference |
+--------+-------------------------------------+
| 0x0004 | Not preferred for AS Path Length |
+--------+-------------------------------------+
| 0x0005 | Not preferred for origin |
+--------+-------------------------------------+
| 0x0006 | Not preferred for MED |
+--------+-------------------------------------+
| 0x0007 | Not preferred for peer type |
+--------+-------------------------------------+
| 0x0008 | Not preferred for IGP cost |
+--------+-------------------------------------+
| 0x0009 | Not preferred for router ID |
+--------+-------------------------------------+
| 0x000A | Not preferred for peer address |
+--------+-------------------------------------+
| 0x000B | Not preferred for AIGP |
+--------+-------------------------------------+
Table 2: IANA-Registered Reason Codes
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4. Path Marking Statistics
This section defines statistics to account and summarize Path Status
TLV in the BGP Local-RIB. The statistics specified in this section
are exported by BMP speakers using the Stats Reports message type
defined in Section 4.8 of [RFC7854].
Unless otherwise stated, all counters defined in this section are
unsigned 64-bit integers. Counters are maintained per BMP session
and per monitored peer. The reset behavior of these counters (for
example, upon BMP session restart or operator-triggered reset)
follows the general semantics of BMP Stats Reports as defined in
RFC7854 [RFC7854].
4.1. Per-Status Counters
For each IANA-registered Path Status bit defined in Table 1, an
implementation SHOULD maintain a counter that reflects the number of
paths currently marked with that status. These counters are
conceptually similar to the per-status gauges defined for primary,
backup, stale, and suppressed routes in the BMP RIB statistics
document [I-D.ietf-grow-bmp-bgp-rib-stats].
The following counters are defined:
* Type = TBD1: Current number of paths for which the Path Status TLV
has the Invalid status bit set.
* Type = TBD2: Current number of paths for which the Path Status TLV
has the Best status bit set.
* Type = TBD3: Current number of paths for which the Path Status TLV
has the Nonselected status bit set.
* Type = TBD4: Current number of paths for which the Path Status TLV
has the Primary status bit set.
* Type = TBD5: Current number of paths for which the Path Status TLV
has the Backup status bit set.
* Type = TBD6: Current number of paths for which the Path Status TLV
has the Non-installed status bit set.
* Type = TBD7: Current number of paths for which the Path Status TLV
has the Best-external status bit set.
* Type = TBD8: Current number of paths for which the Path Status TLV
has the Add-Path status bit set.
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* Type = TBD9: Current number of paths for which the Path Status TLV
has the Filtered in inbound policy status bit set.
* Type = TBD10: Current number of paths for which the Path Status
TLV has the Filtered in outbound policy status bit set.
* Type = TBD11: Current number of paths for which the Path Status
TLV has the Stale status bit set.
* Type = TBD12: Current number of paths for which the Path Status
TLV has the Suppressed status bit set.
Since the Path Status field is encoded as a bitmap, multiple status
bits can be set for a single path. The corresponding per-status
counters are incremented independently; that is, a single path may
contribute to more than one per-status counter.
4.2. Generic Path Status Counters
In addition to the per-status counters defined above, the following
generic counters MAY be maintained by a BMP implementation:
* Type = TBD13: Current number of paths that carry a Path Status TLV
with at least one status bit set (that is, paths that are
explicitly marked).
* Type = TBD14: Current number of paths that either do not carry a
Path Status TLV or carry a Path Status TLV with all bits set to
zero.
5. Implementation notes
The BMP path marking TLV remains optional within BMP implementations.
An implementation of the BMP path marking TLV may not fully support
marking of all statuses defined in Table 1 or any future extensions.
Similarly, an implementation may choose to support the inclusion of
the reason code (for which support is also optional), without
necessarily incorporating any of the reason codes defined in Table 2
or future extensions.
This document refrains from defining mechanisms for signaling the
status or reason codes an implementation supports. This could be
established through external means (e.g. documentation) or
potentially addressed in a subsequent document.
The remainder of this section covers additional points related to the
implementation of the BMP Path Marking TLV.
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5.1. Configuration of BMP Path Marking
Implementations supporting the BMP Path Marking TLV should provide an
option for enabling/disabling the Path Marking TLV over BMP
monitoring sessions. Furthermore, the configuration options for this
TLV should provide the means to enable/disable the transmission of
reason codes, if the reason codes are supported by the
implementation.
5.2. Scalability and churn
The Path Marking TLV introduces metadata on the routes, which could
increase the churn (Section 8.1.6 of RFC4098 [RFC4098]) of paths
within the BMP session. For instance, if BMP Path Marking is
configured, and a non-installed path changes status to a backup
route, the device should send an update about this path with the new
markings, even if its BGP attributes remain unchanged. Enabling
reason codes could additionally increase the churn. Churn could be
more pronounced during the start of a BGP session, where the device
is processing all available routes.
If churn is undesired, an implementation could make use of "state
compression" to hide state until paths converge (Section 5 of
[RFC7854]). It could also initially send BMP routes without the path
marking TLV, even if it were configured, and then add them once the
implementation considers the path to be stable enough. This document
does not provide a definitive solution for churn since it depends on
the capabilities of an implementation and the requirements of an
operator.
5.3. Paths with no markings
Some BGP routes might not require any type of status or reasons. For
example, a path in Adj-RIB-In where the BGP best path decision has
not been applied yet, falls under this category, since there is
really nothing to mark for that path. This document suggests
applying an explicit marking of this route, by attaching a BMP path
marking TLV with no bits set. This will help BMP monitor stations to
differentiate this case from those in which markings are not
configured, or not yet attached by the device.
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5.4. Path markings applicability and consistency
The status and reason codes from Table 1 and Table 2 are included
based on use cases from network operators and defined following the
most relevant protocol references available. While implementations
are strongly encouraged to align with these code definitions, this
document does not enforce strict validity rules for code combinations
to accommodate the diversity of BGP implementations.
The experience during testing of this TLV revealed scenarios where
implementations might combine codes differently than originally
anticipated. For example, one test implementation marked routes with
both 'Invalid' and 'Best' status bits set, which is contradictory
from the point of view of [RFC4271], but made sense for their
specific implementation.
Operators should apply their own validation checks on the data from
TLVs and discuss potential inconsistencies with their vendors, and
raise bugs if applicable.
5.4.1. Significance of status and origin RIBs
This document refrains from imposing on any implementation the
requirement to mark specific status from specific RIBs. Some
implementations might be able to mark some status over one RIB while
others do it on others. For instance, some might be able to mark
Adj-RIB-In filtered routes when obtained from the Adj-RIB-In pre-
policy, while others could do it only from the Adj-RIB-In post-
policy. To remove ambiguities in implementations, it is recommended
that the meaning of status (and reason codes) does not depend on the
origin RIB of a route.
5.5. Multiple TLVs assigned to the same route.
We advocate for the use of TLV grouping wherever feasible
(Section 5.2.1 of [I-D.ietf-grow-bmp-tlv]). The inclusion of all
marking information within a single message is recommended. In
situations where multiple TLVs are associated with a single route,
all markings and reasons will be applicable to that route.
5.6. Enterprise-specific status
Implementations introducing their own status and reason codes are
advised to adhere to [I-D.ietf-grow-bmp-tlv-ebit] and use the
enterprise-bit (ebit) for vendor-specific status and reasons.
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For scenarios where a path state combines a standard status with an
enterprise-specific reason code (or vice versa), the following
alternatives are presented:
* Replication of the standard definitions within the enterprise-
specific space, thus permitting direct marking within the same
packet using the ebit.
* Assigning two TLVs to the same path(s): one containing the
standard part and another housing the vendor-specific part.
5.7. Multiple reason codes
The path marking TLV was not designed to optimally hold more than one
reason code per path. However, if needed by a specific use case, the
implementation can use two or more path markings TLVs for the same
path listing the multiple reasons that apply to it.
6. Acknowledgments
We would like to thank Jeff Haas and Maxence Younsi for their
valuable comments.
7. IANA Considerations
This document requests that IANA assign the following new TLV type to
the BMP Route Monitoring TLVs.
Type = 5: indicates that this is the IANA-registered Path marking
TLV. The value field is defined in Section 2.
RFC Editor and IANA registry note: The registry is created with
Section 10 of [I-D.ietf-grow-bmp-tlv] and populated with initial
values 1-4. This document adds value 5 to the registry. Please
remove this sentence before publishing the document as RFC.
In addition, this document requests IANA to assign new statistic
types in the BMP Statistics Types (https://www.iana.org/assignments/
bmp-parameters/bmp-parameters.xhtml#statistics-types) registry, part
of the BMP parameters (https://www.iana.org/assignments/bmp-
parameters/bmp-parameters.xhtml) registry group, for the Path Marking
Statistics defined in Section 4.
Unless otherwise stated, all statistics defined below are 64-bit
unsigned integer gauges whose Stat Data value field and Stat Length
follow the rules defined in Section 4.8 of [RFC7854].
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This document requests IANA to assign the following new BMP
Statistics Types and to update the registry to reference the RFC
number of this document:
* Type TBD1: Current number of paths for which the Path Status TLV
has the Invalid status bit set.
* Type TBD2: Current number of paths for which the Path Status TLV
has the Best status bit set.
* Type TBD3: Current number of paths for which the Path Status TLV
has the Nonselected status bit set.
* Type TBD4: Current number of paths for which the Path Status TLV
has the Primary status bit set.
* Type TBD5: Current number of paths for which the Path Status TLV
has the Backup status bit set.
* Type TBD6: Current number of paths for which the Path Status TLV
has the Non-installed status bit set.
* Type TBD7: Current number of paths for which the Path Status TLV
has the Best-external status bit set.
* Type TBD8: Current number of paths for which the Path Status TLV
has the Add-Path status bit set.
* Type TBD9: Current number of paths for which the Path Status TLV
has the Filtered in inbound policy status bit set.
* Type TBD10: Current number of paths for which the Path Status TLV
has the Filtered in outbound policy status bit set.
* Type TBD11: Current number of paths for which the Path Status TLV
has the Stale status bit set.
* Type TBD12: Current number of paths for which the Path Status TLV
has the Suppressed status bit set.
* Type TBD13: Current number of paths that carry a Path Status TLV
with at least one status bit set (paths that are explicitly
marked).
* Type TBD14: Current number of paths that either do not carry a
Path Status TLV or carry a Path Status TLV with all bits set to
zero.
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8. Security Considerations
Using the path status information may affect other applications which
rely on this information for operational decisions. Operators should
secure BMP sessions and control access to TLV data to mitigate these
risks.
9. References
9.1. Normative References
[I-D.ietf-grow-bmp-bgp-rib-stats]
Srivastava, M., Liu, Y., Lin, C., and J. Li, "Advanced BGP
Monitoring Protocol (BMP) Statistics Types", Work in
Progress, Internet-Draft, draft-ietf-grow-bmp-bgp-rib-
stats-17, 3 December 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-grow-
bmp-bgp-rib-stats-17>.
[I-D.ietf-grow-bmp-tlv]
Lucente, P., Gu, Y., Younsi, M., and P. Francois, "BMP v4:
Extended TLV Support for BGP Monitoring Protocol (BMP)",
Work in Progress, Internet-Draft, draft-ietf-grow-bmp-tlv-
20, 2 March 2026, <https://datatracker.ietf.org/doc/html/
draft-ietf-grow-bmp-tlv-20>.
[I-D.ietf-grow-bmp-tlv-ebit]
Lucente, P. and Y. Gu, "Support for Enterprise-specific
TLVs in the BGP Monitoring Protocol", Work in Progress,
Internet-Draft, draft-ietf-grow-bmp-tlv-ebit-06, 17
January 2025, <https://datatracker.ietf.org/doc/html/
draft-ietf-grow-bmp-tlv-ebit-06>.
[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>.
[RFC2439] Villamizar, C., Chandra, R., and R. Govindan, "BGP Route
Flap Damping", RFC 2439, DOI 10.17487/RFC2439, November
1998, <https://www.rfc-editor.org/info/rfc2439>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
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[RFC4724] Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y.
Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724,
DOI 10.17487/RFC4724, January 2007,
<https://www.rfc-editor.org/info/rfc4724>.
[RFC7311] Mohapatra, P., Fernando, R., Rosen, E., and J. Uttaro,
"The Accumulated IGP Metric Attribute for BGP", RFC 7311,
DOI 10.17487/RFC7311, August 2014,
<https://www.rfc-editor.org/info/rfc7311>.
[RFC7854] Scudder, J., Ed., Fernando, R., and S. Stuart, "BGP
Monitoring Protocol (BMP)", RFC 7854,
DOI 10.17487/RFC7854, June 2016,
<https://www.rfc-editor.org/info/rfc7854>.
[RFC7911] Walton, D., Retana, A., Chen, E., and J. Scudder,
"Advertisement of Multiple Paths in BGP", RFC 7911,
DOI 10.17487/RFC7911, July 2016,
<https://www.rfc-editor.org/info/rfc7911>.
[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>.
9.2. Informative References
[I-D.ietf-idr-best-external]
Marques, P., Fernando, R., Chen, E., Mohapatra, P., and H.
Gredler, "Advertisement of the best external route in
BGP", Work in Progress, Internet-Draft, draft-ietf-idr-
best-external-05, 3 January 2012,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
best-external-05>.
[I-D.ietf-rtgwg-bgp-pic]
Bashandy, A., Filsfils, C., Mohapatra, P., and Y. Qu, "BGP
Prefix Independent Convergence", Work in Progress,
Internet-Draft, draft-ietf-rtgwg-bgp-pic-23, 15 February
2026, <https://datatracker.ietf.org/doc/html/draft-ietf-
rtgwg-bgp-pic-23>.
[I-D.lapukhov-bgp-ecmp-considerations]
Lapukhov, P. and J. Tantsura, "Equal-Cost Multipath
Considerations for BGP", Work in Progress, Internet-Draft,
draft-lapukhov-bgp-ecmp-considerations-13, 6 January 2025,
<https://datatracker.ietf.org/doc/html/draft-lapukhov-bgp-
ecmp-considerations-13>.
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[RFC4098] Berkowitz, H., Davies, E., Ed., Hares, S., Krishnaswamy,
P., and M. Lepp, "Terminology for Benchmarking BGP Device
Convergence in the Control Plane", RFC 4098,
DOI 10.17487/RFC4098, June 2005,
<https://www.rfc-editor.org/info/rfc4098>.
Appendix A. Implementation Status
Note to the Editor: Please remove this section before publication.
This section records the status of known implementations of the BMP
Path Marking TLV specified in this document. The information is
based on interoperability and testbed activities, including the
Swisscom IETF Daisy testbed, and is intended to help reviewers and
operators understand current implementation and deployment status.
This section is non-normative.
A.1. Huawei VRP NE8000
Huawei implemented the BMP Path Marking TLV, including Path Status
and Path Reason, on NE8000 platforms running VRP R025C00SPC305T and
subsequent R025C10 test images.
The implementation exports Path Marking information in BMP Route
Monitoring messages for IPv4 and IPv6 unicast, as well as VPNv4 and
VPNv6 Local-RIB. Support includes ADD-PATH and VPN peer
distinguishers.
In the test environment, BMP sessions were established from NE8000
PEs to a collector and configured to monitor Adj-RIB-In and Adj-RIB-
Out, both pre-policy and post-policy, as well as VPNv4 and VPNv6
Local-RIB across multiple VRF instances.
The implementation was exercised against a set of path selection
scenarios, including best path, backup path, non-installed paths, and
policy-filtered paths. The exported Path Status bits, such as Best,
Nonselected, Primary, Backup, and Non-installed, and the
corresponding Path Reason codes, for example not preferred due to
local preference or router ID, were verified against the
corresponding VRF RIB and BGP routing state.
A.2. pmacct BMP Collector
The BMP collector used in the implementation is pmacct with support
for the Path Marking TLVs as defined in this document.
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The implementation includes updates to align TLV type and value
handling with the current draft, as well as changes to the TLV
parsing logic to correctly process Path Status and Path Reason
information in BMP Route Monitoring messages.
In the implementation tests, the collector is configured to receive
BMP sessions and export decoded data as JSON logs, including Path
Marking TLVs where available. This allows comparison between the BGP
path state observed on the NE8000, for example best, backup, non-
installed, or policy-filtered, and the corresponding BMP-exported
Path Status and Reason values.
A.3. NetGauze and Wireshark Decoders
NetGauze is used as an independent BMP decoder to validate the
encoding of Path Marking TLVs. Updates were made to improve BMPv4
support, including handling of ADD-PATH for IPv4/IPv6 MPLS unicast,
Loc-RIB Peer Up messages, and general BMP message parsing. These
changes help decode and inspect Route Monitoring messages carrying
Path Status and Path Reason TLVs.
Wireshark nightly builds are used to inspect BMP Route Monitoring
messages and verify the presence and decoding of Path Marking TLVs,
including VPN peer distinguishers and SAFI-specific updates.
Improvements in BMP TLV and Group TLV decoding help inspect VRF
context and associated path-marking information.
Authors' Addresses
Camilo Cardona
NTT
164-168, Carrer de Numancia
08029 Barcelona
Spain
Email: camilo@ntt.net
Paolo Lucente
NTT
Siriusdreef 70-72
2132 Hoofddorp
Netherlands
Email: paolo@ntt.net
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Pierre Francois
INSA-Lyon
Lyon
France
Email: Pierre.Francois@insa-lyon.fr
Yunan Gu
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing
100095
China
Email: guyunan@huawei.com
Thomas Graf
Swisscom
Binzring 17
CH-8045 Zurich
Switzerland
Email: thomas.graf@swisscom.com
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