Bidirectional Forwarding Detection (BFD) for MPLS Label Switched Paths (LSPs)
draft-ietf-bfd-rfc5884-bis-01
| Document | Type | Active Internet-Draft (bfd WG) | |
|---|---|---|---|
| Authors | Rahul Aggarwal , Kireeti Kompella , Thomas Nadeau , George Swallow , Vengada Prasad Govindan , Kalyani Rajaraman , Greg Mirsky , Sam Aldrin | ||
| Last updated | 2026-08-15 | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
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draft-ietf-bfd-rfc5884-bis-01
Network Working Group R. Aggarwal
Internet-Draft K. Kompella
Obsoletes: 5884, 7726 (if approved) Juniper Networks
Intended status: Standards Track T. Nadeau
Expires: 16 February 2027 BT
G. Swallow
Retired
V. Govindan, Ed.
K. Rajaraman
Cisco Systems, Inc.
G. Mirsky
Ciena
S. Aldrin
NVIDIA
15 August 2026
Bidirectional Forwarding Detection (BFD) for MPLS Label Switched Paths
(LSPs)
draft-ietf-bfd-rfc5884-bis-01
Abstract
One desirable application of Bidirectional Forwarding Detection (BFD)
is to detect a Multiprotocol Label Switching (MPLS) Label Switched
Path (LSP) data plane failure. LSP Ping is an existing mechanism for
detecting MPLS data plane failures and for verifying the MPLS LSP
data plane against the control plane. BFD can be used for the
former, but not for the latter. However, the control plane
processing required for BFD Control packets is relatively smaller
than the processing required for LSP Ping messages. A combination of
LSP Ping and BFD can be used to provide faster data plane failure
detection and/or make it possible to provide such detection on a
greater number of LSPs. This document describes the applicability of
BFD in relation to LSP Ping for this application. It also describes
procedures for using BFD in this environment. This document
obsoletes RFC5884 and RFC7726.
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/.
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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 February 2027.
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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Specification of Requirements . . . . . . . . . . . . . . . . 3
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. BFD for MPLS LSPs: Motivation . . . . . . . . . . . . . . 3
3.2. Using BFD in Conjunction with LSP Ping . . . . . . . . . 5
4. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 6
5. Initialization and Demultiplexing . . . . . . . . . . . . . . 7
6. Session Establishment . . . . . . . . . . . . . . . . . . . . 7
6.1. BFD Discriminator TLV in LSP Ping . . . . . . . . . . . . 8
7. Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . 8
8. Procedures for multiple BFD over MPLS sessions . . . . . . . 10
8.1. Procedures for establishment of multiple BFD sessions . . 10
8.2. Procedures for maintenance of multiple BFD sessions . . . 11
8.3. Procedures for removing BFD sessions at the egress LSR . 11
8.4. Changing discriminators for a BFD session . . . . . . . . 12
8.5. Backwards Compatibility . . . . . . . . . . . . . . . . . 12
9. Security Considerations . . . . . . . . . . . . . . . . . . . 12
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
12.1. Normative References . . . . . . . . . . . . . . . . . . 13
12.2. Informative References . . . . . . . . . . . . . . . . . 13
Appendix A. Discussions about the loopback address to be used in
the BFD packet . . . . . . . . . . . . . . . . . . . . . 15
Appendix B. Implementation Status . . . . . . . . . . . . . . . 15
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B.1. TBF . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
One desirable application of Bidirectional Forwarding Detection (BFD)
is to track the liveness of a Multiprotocol Label Switching (MPLS)
Label Switched Path (LSP). In particular, BFD can be used to detect
a data plane failure in the forwarding path of an MPLS LSP. LSP Ping
[RFC4379] is an existing mechanism for detecting MPLS LSP data plane
failures and for verifying the MPLS LSP data plane against the
control plane. This document describes the applicability of BFD in
relation to LSP Ping for detecting MPLS LSP data plane failures. It
also describes procedures for using BFD for detecting MPLS LSP data
plane failures.
2. Specification of Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Applicability
In the event of an MPLS LSP failing to deliver data traffic, it may
not always be possible to detect the failure using the MPLS control
plane. For instance, the control plane of the MPLS LSP may be
functional while the data plane may be mis-forwarding or dropping
data. Hence, there is a need for a mechanism to detect a data plane
failure in the MPLS LSP path [RFC4377].
3.1. BFD for MPLS LSPs: Motivation
LSP Ping described in [RFC4379] is an existing mechanism for
detecting an MPLS LSP data plane failure. In addition, LSP Ping also
provides a mechanism for verifying the MPLS control plane against the
data plane. This is done by ensuring that the LSP is mapped to the
same Forwarding Equivalence Class (FEC), at the egress, as the
ingress.
BFD cannot be used for verifying the MPLS control plane against the
data plane. However, BFD can be used to detect a data plane failure
in the forwarding path of an MPLS LSP. The LSP may be associated
with any of the following FECs:
a) Resource Reservation Protocol (RSVP) LSP_Tunnel IPv4/IPv6
Session [RFC3209]
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b) Label Distribution Protocol (LDP) IPv4/IPv6 prefix [RFC5036]
c) Virtual Private Network (VPN) IPv4/IPv6 prefix [RFC4364] d)
Layer 2 VPN [L2-VPN]
e) Pseudowires based on PWid FEC and Generalized PWid FEC
[RFC4447]
f) Border Gateway Protocol (BGP) labeled prefixes [RFC3107]
LSP Ping includes extensive control plane verification. BFD, on the
other hand, was designed as a lightweight means of testing only the
data plane. As a result, LSP Ping is computationally more expensive
than BFD for detecting MPLS LSP data plane faults. BFD is also more
suitable for being implemented in hardware or firmware due to its
fixed packet format. Thus, the use of BFD for detecting MPLS LSP
data plane faults has the following advantages:
a) Support for fault detection for greater number of LSPs.
b) Fast detection. Detection with sub-second granularity is
considered as fast detection. LSP Ping is intended to be used
in an environment where fault detection messages are exchanged,
either for diagnostic purposes or for infrequent periodic fault
detection, in the order of tens of seconds or minutes. Hence,
it is not appropriate for fast detection. BFD, on the other
hand, is designed for sub-second fault detection intervals.
Following are some potential cases when fast detection may be
desirable for MPLS LSPs:
1. In the case of a bypass LSP used for a facility-based link
or node protection [RFC4090]. In this case, the bypass LSP
is essentially being used as an alternate link to protect
one or more LSPs. It represents an aggregate and is used
to carry data traffic belonging to one or more LSPs, when
the link or the node being protected fails. Hence, fast
failure detection of the bypass LSP may be desirable
particularly in the event of link or node failure when the
data traffic is moved to the bypass LSP.
2. MPLS Pseudowires (PWs). Fast detection may be desired for
MPLS PWs depending on i) the model used to layer the MPLS
network with the Layer 2 network, and ii) the service that
the PW is emulating. For a non-overlay model between the
Layer 2 network and the MPLS network, the provider may rely
on PW fault detection to provide service status to the end-
systems. Also, in that case, interworking scenarios such
as ATM/Frame Relay interworking may force periodic PW fault
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detection messages. Depending on the requirements of the
service that the MPLS PW is emulating, fast failure
detection may be desirable.
There may be other potential cases where fast failure detection is
desired for MPLS LSPs.
3.2. Using BFD in Conjunction with LSP Ping
BFD can be used for MPLS LSP data plane fault detection. However, it
does not have all the functionality of LSP Ping. In particular, it
cannot be used for verifying the control plane against the data
plane. LSP Ping performs the following functions that are outside
the scope of BFD:
a) Association of an LSP Ping Echo request message with a FEC.
In
the case of Penultimate Hop Popping (PHP) or when the egress
Label Switching Router (LSR) distributes an explicit null label
to the penultimate hop router, for a single label stack LSP,
the only way to associate a fault detection message with a FEC
is by carrying the FEC in the message. LSP Ping provides this
functionality. Next-hop label allocation also makes it
necessary to carry the FEC in the fault detection message as
the label alone is not sufficient to identify the LSP being
verified. In addition, presence of the FEC in the Echo request
message makes it possible to verify the control plane against
the data plane at the egress LSR.
b) Equal Cost Multi-Path (ECMP) considerations. LSP Ping
traceroute makes it possible to probe multiple alternate paths
for LDP IP FECs.
c) Traceroute. LSP Ping supports traceroute for a FEC and it
can
be used for fault isolation.
Hence, BFD is used in conjunction with LSP Ping for MPLS LSP fault
detection:
i) LSP Ping is used for bootstrapping the BFD session as
described later in this document.
ii) BFD is used to exchange fault detection (i.e., BFD
session) packets at the required detection interval.
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iii) LSP Ping is used to periodically verify the control
plane
against the data plane by ensuring that the LSP is
mapped to the same FEC, at the egress, as the ingress.
4. Theory of Operation
To use BFD for fault detection on an MPLS LSP, a BFD session MUST be
established for that particular MPLS LSP. BFD Control packets MUST
be sent along the same data path as the LSP being verified and are
processed by the BFD processing module of the egress LSR. If the LSP
is associated with multiple FECs, a BFD session SHOULD be established
for each FEC. For instance, this may happen in the case of next-hop
label allocation. Hence, the operation is conceptually similar to
the data plane fault detection procedures of LSP Ping.
If MPLS fast-reroute is being used for the MPLS LSP, the use of BFD
for fault detection can result in false fault detections if the BFD
fault detection interval is less than the MPLS fast-reroute
switchover time. When MPLS fast-reroute is triggered because of a
link or node failure, BFD Control packets will be dropped until
traffic is switched on to the backup LSP. If the time taken to
perform the switchover exceeds the BFD fault detection interval, a
fault will be declared even though the MPLS LSP is being locally
repaired. To avoid this, the BFD fault detection interval should be
greater than the fast-reroute switchover time. An implementation
SHOULD provide configuration options to control the BFD fault
detection interval.
If there are multiple alternate paths from an ingress LSR to an
egress LSR for an LDP IP FEC, LSP Ping traceroute MAY be used to
determine each of these alternate paths. A BFD session SHOULD be
established for each alternate path that is discovered.
Periodic LSP Ping Echo request messages SHOULD be sent by the ingress
LSR to the egress LSR along the same data path as the LSP. This is
to periodically verify the control plane against the data plane by
ensuring that the LSP is mapped to the same FEC, at the egress, as
the ingress. The rate of generation of these LSP Ping Echo request
messages SHOULD be significantly less than the rate of generation of
the BFD Control packets. An implementation MAY provide configuration
options to control the rate of generation of the periodic LSP Ping
Echo request messages.
To enable fault detection procedures specified in this document, for
a particular MPLS LSP, this document requires the ingress and egress
LSRs to be configured. This includes configuration for supporting
BFD and LSP Ping as specified in this document. It also includes
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configuration that enables the ingress LSR to determine the method
used by the egress LSR to identify Operations, Administration, and
Maintenance (OAM) packets, e.g., whether the Time to Live (TTL) of
the innermost MPLS label needs to be set to 1 to enable the egress
LSR to identify the OAM packet. For fault detection for MPLS PWs,
this document assumes that the PW control channel type [RFC5885] is
configured and the support of LSP Ping is also configured.
5. Initialization and Demultiplexing
A BFD session may be established for a FEC associated with an MPLS
LSP. As described above, in the case of PHP or when the egress LSR
distributes an explicit null label to the penultimate hop router, or
next-hop label allocation, the BFD Control packet received by the
egress LSR does not contain sufficient information to associate it
with a BFD session. Hence, the demultiplexing MUST be done using the
remote discriminator field in the received BFD Control packet. The
exchange of BFD discriminators for this purpose is described in the
next section.
6. Session Establishment
A BFD session is bootstrapped using LSP Ping. This specification
describes procedures only for BFD asynchronous mode. BFD demand mode
is outside the scope of this specification. Further, the use of the
BFD Echo function is outside the scope of this specification. The
initiation of fault detection for a particular <MPLS LSP, FEC>
combination results in the exchange of LSP Ping Echo request and Echo
reply packets, in the ping mode, between the ingress and egress LSRs
for that <MPLS LSP, FEC>. To establish a BFD session, an LSP Ping
Echo request message MUST carry the local discriminator assigned by
the ingress LSR for the BFD session. This MUST subsequently be used
as the My Discriminator field in the BFD session packets sent by the
ingress LSR.
On receipt of the LSP Ping Echo request message, the egress LSR MUST
send a BFD Control packet to the ingress LSR, if the validation of
the FEC in the LSP Ping Echo request message succeeds. This BFD
Control packet MUST set the Your Discriminator field to the
discriminator received from the ingress LSR in the LSP Ping Echo
request message. The local discriminator assigned by the egress LSR
MUST be used as the My Discriminator field in the BFD session packets
sent by the egress LSR.
The ingress LSR follows the procedures in [RFC5880] to send BFD
Control packets to the egress LSR in response to the BFD Control
packets received from the egress LSR. The BFD Control packets from
the ingress to the egress LSR MUST set the local discriminator of the
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egress LSR in the Your Discriminator field. The egress LSR
demultiplexes the BFD session based on the received Your
Discriminator field. As mentioned above, the egress LSR MUST send
Control packets to the ingress LSR with the Your Discriminator field
set to the local discriminator of the ingress LSR.The ingress LSR
uses this to demultiplex the BFD session.
The egress LSR processes the LSP Ping Echo request message in
accordance with the procedures defined in [RFC 8029]. The LSP Ping
Echo reply message generated by the egress LSR MAY carry the local
discriminator assigned by it for the BFD session, as specified in
section 6.1.
6.1. BFD Discriminator TLV in LSP Ping
LSP Ping Echo request and Echo reply messages carry a BFD
discriminator TLV for the purpose of session establishment as
described above. IANA has assigned a type value of 15 to this TLV.
This TLV has a length of 4. The value contains the 4-byte local
discriminator that the LSR, sending the LSP Ping message, associates
with the BFD session.
If the BFD session is not in UP state, the periodic LSP Ping Echo
request messages MUST include the BFD Discriminator TLV.
7. Encapsulation
BFD Control packets sent by the ingress LSR MUST be encapsulated in
the MPLS label stack that corresponds to the FEC for which fault
detection is being performed. If the label stack has a depth greater
than one, the TTL of the inner MPLS label MAY be set to 1. This may
be necessary for certain FECs to enable the egress LSR's control
plane to receive the packet [RFC4379]. For MPLS PWs, alternatively,
the presence of a fault detection message may be indicated by setting
a bit in the control word [RFC5885].
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The BFD Control packet sent by the ingress LSR MUST be a UDP packet
with a well-known destination port 3784 [RFC5881] and a source port
assigned by the sender as per the procedures in [RFC5881]. The
source IP address is a routable address of the sender. The
destination IP address MUST be randomly chosen from the 127/8 range
for IPv4 and from the 0:0:0:0:0:FFFF:7F00:0/104 range for IPv6 with
the following exception. If the FEC is an LDP IP FEC, the ingress
LSR may discover multiple alternate paths to the egress LSR for this
FEC using LSP Ping traceroute. In this case, the destination IP
address, used in a BFD session established for one such alternate
path, is the address in the 127/8 range for IPv4 or
0:0:0:0:0:FFFF:7F00:0/104 range for IPv6 discovered by LSP Ping
traceroute [RFC4379] to exercise that particular alternate path.
The motivation for using the address range 127/8 is the same as
specified in Section 2.1 of [RFC4379]. This is an exception to the
behavior defined in [RFC1122].
The IP TTL or hop limit MUST be set to 1 [RFC4379].
BFD Control packets sent by the egress LSR are UDP packets. The
source IP address is a routable address of the replier.
The BFD Control packet sent by the egress LSR to the ingress LSR MAY
be routed based on the destination IP address as per the procedures
in [RFC5883]. If this is the case, the destination IP address MUST
be set to the source IP address of the LSP Ping Echo request message,
received by the egress LSR from the ingress LSR.
Or the BFD Control packet sent by the egress LSR to the ingress LSR
MAY be encapsulated in an MPLS label stack. In this case, the
presence of the fault detection message is indicated as described
above. This may be the case if the FEC for which the fault detection
is being performed corresponds to a bidirectional LSP or an MPLS PW.
This may also be the case when there is a return LSP from the egress
LSR to the ingress LSR. In this case, the destination IP address
MUST be randomly chosen from the 127/8 range for IPv4 and from the
0:0:0:0:0:FFFF:7F00:0/104 range for IPv6.
The BFD Control packet sent by the egress LSR MUST have a well-known
destination port 4784, if it is routed [RFC5883], or it MUST have a
well-known destination port 3784 [RFC5881] if it is encapsulated in a
MPLS label stack. The source port MUST be assigned by the egress LSR
as per the procedures in [BFD-IP].
Note that once the BFD session for the MPLS LSP is UP, either end of
the BFD session MUST NOT change the source IP address and the local
discriminator values of the BFD Control packets it generates, unless
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it first brings down the session. This implies that an LSR MUST
ignore BFD packets for a given session, demultiplexed using the
received Your Discriminator field, if the session is in UP state and
if the My Discriminator or the Source IP address fields of the
received packet do not match the values associated with the session.
8. Procedures for multiple BFD over MPLS sessions
8.1. Procedures for establishment of multiple BFD sessions
To support the requirement that a BFD session SHOULD be established
for each alternate path that is discovered and to disallow either end
to change local discriminator values in BFD control packets after the
session reaches the UP state, the following procedures are to be
implemented:
At the ingress LSR:
* MPLS LSP ping can be used to bootstrap multiple BFD sessions for a
given <MPLS FEC, LSP>. Each LSP ping MUST carry a different
discriminator value in the BFD discriminator TLV [RFC4379].
The egress LSR needs to perform the following:
* If the validation of the FEC in the MPLS Echo request message
succeeds, check the discriminator specified in the BFD
discriminator TLV of the MPLS Echo request. If there is no local
session that corresponds to the (remote) discriminator received in
the MPLS Echo request, a new session is bootstrapped and a local
discriminator is allocated. The validation of a FEC is a
necessary condition to be satisfied to create a new BFD session at
the egress LSR. However, the policy or procedure if any, to be
applied by the egress LSR before allowing a new BFD session to be
created is outside the scope of this document. Such policies or
procedures could consider availability of system resources before
allowing a session to be created. When the egress LSR disallows
the creation of a BFD session due to policy, it MUST drop the MPLS
Echo request message.
* Ensure the uniqueness of the <MPLS FEC, LSP, Remote
Discriminiator> tuple.
* Except for the clarification mentioned above, the remaining
procedures of BFD session establishment are as specified in
Sections 4-6 of [RFC5884].
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8.2. Procedures for maintenance of multiple BFD sessions
Both the ingress LSR and egress LSR use the YourDiscriminator of the
received BFD packet to demultiplex BFD sessions.
8.3. Procedures for removing BFD sessions at the egress LSR
[RFC5884] does not specify an explicit procedure for deleting BFD
sessions. The procedure for removing a BFD session established by an
out-of-band discriminator exchange using the MPLS LSP ping can
improve resource management (like memory etc.) especially in
scenarios involving thousands or more of such sessions. A few
observations are made here:
* The BFD session MAY be removed in the egress LSR if the BFD
session transitions from UP to DOWN. This can either be done
immediately after the BFD session transitions from UP to DOWN or
after the expiry of a configurable timer started after the BFD
session state transitions from UP to DOWN at the egress LSR to
reduce flapping by adding hysteresis.
* The BFD session on the egress LSR MAY be removed by the ingress
LSR by using the BFD diagnostic code AdminDown(7) as specified in
[RFC5880]. When the ingress LSR wants to remove a session without
triggering any state change at the egress, it MAY transmit BFD
packets indicating the State as Down(1), diagnostic code
AdminDown(7) detectMultiplier number of times. Upon receiving
such a packet, the egress LSR MAY remove the BFD session, without
triggering a change of state.
* The procedures to be followed at the egress LSR when BFD
session(s) remain in the DOWN state for a significant amount of
time is a local matter. Such procedures are outside the scope of
this document.
* All BFD sessions established with the FEC MUST be removed
automatically if the FEC is removed.
* The egress MUST use the discriminators exchanged when the session
was brought UP, to indicate any session state change to the
ingress. The egress SHOULD reset this to zero after transmitting
bfd.detectMult number of packets if the BFD session transitions to
DOWN state.
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8.4. Changing discriminators for a BFD session
The discriminators of a BFD session established over an MPLS LSP
cannot be changed when it is in UP state. The BFD session could be
removed after a graceful transition to AdminDown state using the BFD
diagnostic code AdminDown. A new session could be established with a
different discriminator. The initiation of the transition from the
Up to Down state can be done either by the ingress LSR or the egress
LSR.
8.5. Backwards Compatibility
The procedures clarified by this document are fully backward
compatible with an existing implementation of [RFC5884]. While the
capability to bootstrap and maintain multiple BFD sessions may not be
present in current implementations, the procedures outlined by this
document can be implemented as a software upgrade without affecting
existing sessions. In particular, the egress LSR needs to support
multiple BFD sessions per <MPLS FEC, LSP> before the ingress LSR is
upgraded.
9. Security Considerations
Security considerations discussed in [RFC5880], [RFC5883], and
[RFC4379] apply to this document. For BFD Control packets sent by
the ingress LSR or when the BFD Control packet sent by the egress LSR
are encapsulated in an MPLS label stack, MPLS security considerations
apply. These are discussed in [RFC5920]. When BFD Control packets
sent by the egress LSR are routed, the authentication considerations
discussed in [RFC5883] should be followed.
It is highly important to ensure only minimum number of BFD sessions
are provisioned per FEC, and bootstrapped BFD sessions are properly
deleted when no longer required. Additionally security measures
described in [RFC4379] and [RFC5884] are to be followed.
10. IANA Considerations
This document introduces a BFD discriminator TLV in LSP Ping. The
BFD Discriminator has been assigned a value of 15 from the LSP Ping
TLVs and sub-TLVs registry maintained by IANA.
11. Acknowledgments
Thanks to Jeffrey Haas, Reshad Rehman, Mathew Bocci, John Scudder,
Eric Vyncke, Ketan Talaulikar for their comments and feedback.
12. References
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12.1. Normative References
[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122,
DOI 10.17487/RFC1122, October 1989,
<https://www.rfc-editor.org/info/rfc1122>.
[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>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
DOI 10.17487/RFC5881, June 2010,
<https://www.rfc-editor.org/info/rfc5881>.
[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
"Bidirectional Forwarding Detection (BFD) for MPLS Label
Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
June 2010, <https://www.rfc-editor.org/info/rfc5884>.
12.2. Informative References
[RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in
BGP-4", RFC 3107, DOI 10.17487/RFC3107, May 2001,
<https://www.rfc-editor.org/info/rfc3107>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
DOI 10.17487/RFC4090, May 2005,
<https://www.rfc-editor.org/info/rfc4090>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <https://www.rfc-editor.org/info/rfc4364>.
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[RFC4377] Nadeau, T., Morrow, M., Swallow, G., Allan, D., and S.
Matsushima, "Operations and Management (OAM) Requirements
for Multi-Protocol Label Switched (MPLS) Networks",
RFC 4377, DOI 10.17487/RFC4377, February 2006,
<https://www.rfc-editor.org/info/rfc4377>.
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
DOI 10.17487/RFC4379, February 2006,
<https://www.rfc-editor.org/info/rfc4379>.
[RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
G. Heron, "Pseudowire Setup and Maintenance Using the
Label Distribution Protocol (LDP)", RFC 4447,
DOI 10.17487/RFC4447, April 2006,
<https://www.rfc-editor.org/info/rfc4447>.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
October 2007, <https://www.rfc-editor.org/info/rfc5036>.
[RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
June 2010, <https://www.rfc-editor.org/info/rfc5883>.
[RFC5885] Nadeau, T., Ed. and C. Pignataro, Ed., "Bidirectional
Forwarding Detection (BFD) for the Pseudowire Virtual
Circuit Connectivity Verification (VCCV)", RFC 5885,
DOI 10.17487/RFC5885, June 2010,
<https://www.rfc-editor.org/info/rfc5885>.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<https://www.rfc-editor.org/info/rfc5920>.
[RFC9780] Mirsky, G., Mishra, G., and D. Eastlake 3rd,
"Bidirectional Forwarding Detection (BFD) for Multipoint
Networks over Point-to-Multipoint MPLS Label Switched
Paths (LSPs)", RFC 9780, DOI 10.17487/RFC9780, May 2025,
<https://www.rfc-editor.org/info/rfc9780>.
[L2-VPN] Kompella, K., Leelanivas, M., Vohra, Q., Achirica, J.,
Bonica, R., Cooper, D., Liljenstolpe, C., Metz, E., Ould-
Brahim, H., Sargor, C., Shah, H., Srinivasan, and Z.
Zhang, "Layer 2 VPNs Over Tunnels", Work in Progress,
February 2003.
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Appendix A. Discussions about the loopback address to be used in the
BFD packet
For IPv4, BFD over MPLS Control packets use destination addresses
from the 127.0.0.0/8 loopback prefix to prevent off-link forwarding,
which complies with standard IPv4 addressing architecture. In IPv6,
however, the use of IPv4-mapped IPv6 loopback addresses is not
natively supported by the IPv6 addressing architecture.
During the original development of [RFC5884], architectural
compliance aspects regarding IPv4-mapped loopback addresses were
discussed, but these considerations were not fully incorporated into
the published specification. Because commercial implementations
based on [RFC5884] have been widely deployed using IPv4-mapped
addresses, interoperability and backward compatibility remain crucial
requirements. Consequently, the addressing recommendations in this
document account for existing deployed behavior and may not strictly
align with the loopback prefix defined in [RFC9780].
Appendix B. Implementation Status
Note to the RFC Editor: This section may be removed upon publication
as an RFC.
This section documents the [RFC5880] [RFC5884] implementation status
of this document. [RFC5884] is built as an application of the BFD
protocol in [RFC5880], hence the coverage discusses applicable
sections of the BFD protocol to the MPLS transport. For e.g.
sections related to BFD Echo functionality and Demand mode are
skipped.
* The organization responsible for the implementation, if any.
* The implementation's name and/or a link to a web page where the
implementation or a description of it can be found.
* A brief general description.
* The implementation's level of maturity: research, prototype,
alpha, beta, production, widely used, etc.
* Coverage: which parts of the protocol specification are
implemented.
* Version compatibility: what version/versions of the Internet-Draft
are known to be implemented.
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* Licensing: the terms under which the implementation can be used.
For example: proprietary, royalty licensing, freely distributable
with acknowledgement (BSD style), freely distributable with
requirement to redistribute source (General Public License (GPL)
style), and other (specify).
* Implementation experience: any useful information the implementers
want to share with the community.
* Contact information: ideally a person's name and email address,
but possibly just a URL or mailing list.
* The date when information about this particular implementation was
last updated.
B.1. TBF
Organization:
TBF
Implementation Name:
TBF
Description:
BFD over MPLS feature
Maturity:
TBF
Coverage:
* Section x.
* RFC5884 - 3.2: Bootstrapping BFD over LSP using LSP ping
* RFC5884 - 3.2: Setting BFD fault detection parameters for the
LSP
* RFC5884 - 4.0: Periodic LSP Ping echo request messages
* RFC5884 - 4.0: Configuration knobs for enablement and operation
of BFD and LSP ping
* RFC5884 - 5.0: Demultiplexing logic for BFD sessions based on
remote Discriminator
* RFC5884 - 6.0: LSP Ping Echo request message with local
discriminator for session establishment using BFD Discriminator
TLV (Sec 6.1)
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* RFC5884 - 6.0: Egress LSR validates FEC and follows procedures
for discriminators
* RFC5883 - 6.0: How does the ingress LER handle the case when
the Mydiscriminator returned in the BFD packet differs from the
discriminator value returned in the LSP Ping Echo reply?
* RFC5884 - 7.0: Dataplane formats for BFD over MPLS using TTL=1.
* RFC5880 - 6.3: unique discriminator per session
* RFC5880 6.5: Poll Sequence
* RFC5880 6.7: Authentication
* RFC5880 6.7.2: Simple Password Authentication
* RFC5880 6.7.3: Keyed MD5 and Meticulous Keyed MD5
Authentication
* RFC5880 6.7.4: Keyed SHA1 and Meticulous Keyed SHA1
Authentication
* RFC5880 6.8.1: State Variables
* RFC5880 6.8.2: Timer Negotiation
* RFC5880 6.8.3: Timer Manipulation
* RFC5880 6.8.4: Detection Time Calculation
* RFC5880 6.8.6: Reception of BFD Control Packets
* RFC5880 6.8.7: Transmitting BFD Control Packets
* RFC5880 6.8.7: What source/destination IPv6 loopback addresses
are used for BFD control packets over IPv6 LSPs?
* RFC5880 6.8.10: Min Rx Interval Change
* RFC5880 6.8.11: Min Tx Interval Change
* RFC5880 6.8.12: Detect Multiplier Change
* RFC5880 6.8.15: Forwarding Plane Reset
* RFC5880 6.8.16: Administrative Control
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* RFC5880 6.8.17: Concatenated Paths
* RFC5880 6.8.18: Session Hold Down
* RFC5880 9: Generalized TTL Security Mechanism
Version Compatibility:
TBF
Licensing:
TBF
Implementation Experience:
Contact Information:
TBF
Last Updated:
TBF
Authors' Addresses
Rahul Aggarwal
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
USA
Email: rahul@juniper.net
Kireeti Kompella
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
USA
Email: kireeti@juniper.net
Thomas D. Nadeau
BT
BT Centre
81 Newgate Street
London EC1A 7AJ
UK
Email: tom.nadeau@bt.com
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George Swallow
Retired
Email: swallow@tbd.com
Vengada Prasad Govindan (editor)
Cisco Systems, Inc.
Email: venggovi@cisco.com
Kalyani Rajaraman
Cisco Systems, Inc.
Email: kalyanir@cisco.com
Gregory Mirsky
Ciena
Email: gregimirsky@gmail.com
Sam Aldrin
NVIDIA
Email: aldrin.ietf@gmail.com
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