RFC 9127 PROPOSED STANDARD YANG · BFD · MANAGEMENT
YANG for BFD: YANG Data Model for Bidirectional Forwarding Detection (BFD)
A set of YANG modules for configuring and monitoring BFD sessions on IP, MPLS and LAG paths.
RFC EDITOR
Rahman, R., Ed., Zheng, L., Ed., Jethanandani, M., Ed., Pallagatti, S., and G. Mirsky, "YANG Data Model for Bidirectional Forwarding Detection (BFD)", RFC 9127, DOI 10.17487/RFC9127, October 2021, <https://www.rfc-editor.org/info/rfc9127>.
BIBTEX
@misc{rfc9127,
series = {Request for Comments},
number = 9127,
howpublished = {RFC 9127},
publisher = {RFC Editor},
doi = {10.17487/RFC9127},
url = {https://www.rfc-editor.org/info/rfc9127},
author = {R. Rahman and L. Zheng and M. Jethanandani and S. Pallagatti and G. Mirsky},
title = {{YANG Data Model for Bidirectional Forwarding Detection (BFD)}},
pagetotal = 64,
year = 2021,
month = oct,
} RFC text
Contents
Internet Engineering Task Force (IETF) R. Rahman, Ed.
Request for Comments: 9127
Category: Standards Track L. Zheng, Ed.
ISSN: 2070-1721 Huawei Technologies
M. Jethanandani, Ed.
Xoriant Corporation
S. Pallagatti
VMware
G. Mirsky
Ericsson
October 2021
YANG Data Model for Bidirectional Forwarding Detection (BFD)
Abstract
This document defines a YANG data model that can be used to configure
and manage Bidirectional Forwarding Detection (BFD).
The YANG modules in this document conform to the Network Management
Datastore Architecture (NMDA) (RFC 8342).
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9127.
Copyright Notice
Copyright (c) 2021 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 Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction
1.1. Tree Diagrams
2. Design of the Data Model
2.1. Design of the Configuration Model
2.1.1. Common BFD Configuration Parameters
2.1.2. Single-Hop IP
2.1.3. Multihop IP
2.1.4. MPLS Label Switched Paths
2.1.5. Link Aggregation Groups
2.2. Design of the Operational State Model
2.3. Notifications
2.4. RPC Operations
2.5. BFD Top-Level Hierarchy
2.6. BFD IP Single-Hop Hierarchy
2.7. BFD IP Multihop Hierarchy
2.8. BFD-over-LAG Hierarchy
2.9. BFD-over-MPLS-LSPs Hierarchy
2.10. Interaction with Other YANG Modules
2.10.1. "ietf-interfaces" Module
2.10.2. "ietf-ip" Module
2.10.3. "ietf-mpls" Module
2.11. IANA BFD YANG Module
2.12. BFD Types YANG Module
2.13. BFD Top-Level YANG Module
2.14. BFD IP Single-Hop YANG Module
2.15. BFD IP Multihop YANG Module
2.16. BFD-over-LAG YANG Module
2.17. BFD-over-MPLS YANG Module
3. Data Model Examples
3.1. IP Single-Hop
3.2. IP Multihop
3.3. LAG
3.4. MPLS
4. Security Considerations
5. IANA Considerations
5.1. IANA-Maintained "iana-bfd-types" Module
6. References
6.1. Normative References
6.2. Informative References
Appendix A. Echo Function Configuration Example
A.1. Example YANG Module for BFD Echo Function Configuration
Acknowledgments
Authors' Addresses
1. Introduction
This document defines a YANG data model that can be used to configure
and manage Bidirectional Forwarding Detection (BFD) [RFC5880]. BFD
is a network protocol that is used for liveness detection of
arbitrary paths between systems. Some examples of different types of
paths over which we have BFD are as follows:
1. Two systems directly connected via IP. This is known as BFD over
single-hop IP, a.k.a. BFD for IPv4 and IPv6 [RFC5881].
2. Two systems connected via multiple hops as described in
"Bidirectional Forwarding Detection (BFD) for Multihop Paths"
[RFC5883].
3. Two systems connected via MPLS Label Switched Paths (LSPs) as
described in "Bidirectional Forwarding Detection (BFD) for MPLS
Label Switched Paths (LSPs)" [RFC5884].
4. Two systems connected via a Link Aggregation Group (LAG)
interface as described in "Bidirectional Forwarding Detection
(BFD) on Link Aggregation Group (LAG) Interfaces" [RFC7130].
5. Two systems connected via pseudowires (PWs). This is known as
Virtual Circuit Connectivity Verification (VCCV), as described in
"Bidirectional Forwarding Detection (BFD) for the Pseudowire
Virtual Circuit Connectivity Verification (VCCV)" [RFC5885].
This scenario is not addressed in this document.
BFD typically does not operate on its own. Various control
protocols, also known as BFD clients, use the services provided by
BFD for their own operation, as described in "Generic Application of
Bidirectional Forwarding Detection (BFD)" [RFC5882]. The obvious
candidates that use BFD are those that do not have "hellos" to detect
failures, e.g., static routes, and routing protocols whose "hellos"
do not support sub-second failure detection, e.g., OSPF and IS-IS.
The YANG modules in this document conform to the Network Management
Datastore Architecture (NMDA) [RFC8342]. This means that the data
models do not have separate top-level or sibling containers for
configuration data and operational state data.
1.1. Tree Diagrams
This document uses the graphical representation of data models, as
defined in [RFC8340].
2. Design of the Data Model
Since BFD is used for liveness detection of various forwarding paths,
there is no uniform key to identify a BFD session, and so the BFD
data model is split into multiple YANG modules where each module
corresponds to one type of forwarding path. For example, BFD for IP
single-hop is in one YANG module, and BFD for MPLS is in another YANG
module. The main difference between these modules is how a BFD
session is uniquely identified, i.e., the key for the list containing
the BFD sessions for that forwarding path. To avoid duplication of
BFD definitions, we have common types and groupings that are used by
all the modules.
A new control-plane protocol, "bfdv1", is defined, and a "bfd"
container is created under "control-plane-protocol" as specified in
"A YANG Data Model for Routing Management (NMDA Version)" [RFC8349].
This new "bfd" container is augmented by the following YANG modules
for their respective specific information:
1. The "ietf-bfd-ip-sh" module (Section 2.14) augments "/routing/
control-plane-protocols/control-plane-protocol/bfd/" with the
"ip-sh" container for BFD sessions over IP single-hop.
2. The "ietf-bfd-ip-mh" module (Section 2.15) augments "/routing/
control-plane-protocols/control-plane-protocol/bfd/" with the
"ip-mh" container for BFD sessions over IP multihop.
3. The "ietf-bfd-lag" module (Section 2.16) augments "/routing/
control-plane-protocols/control-plane-protocol/bfd/" with the
"lag" container for BFD sessions over a LAG.
4. The "ietf-bfd-mpls" module (Section 2.17) augments "/routing/
control-plane-protocols/control-plane-protocol/bfd/" with the
"mpls" container for BFD-over-MPLS LSPs.
BFD can operate in the following contexts:
1. At the network device level.
2. In logical network elements (LNEs) as described in "YANG Model
for Logical Network Elements" [RFC8530].
3. In network instances as described in "YANG Data Model for Network
Instances" [RFC8529].
When used at the network device level, the BFD YANG data model is
used "as is". When the BFD YANG data model is used in an LNE or
network instance, the BFD YANG data model augments the mounted
routing model for the LNE or network instance.
2.1. Design of the Configuration Model
The configuration model consists mainly of the parameters specified
in BFD [RFC5880] -- for example, desired minimum transmit interval,
required minimum receive interval, and detection multiplier.
BFD clients are applications that use BFD for fast detection of
failures. Some implementations have BFD session configuration under
the BFD clients -- for example, BFD session configuration under
routing applications such as OSPF, IS-IS, or BGP. Other
implementations have BFD session configuration centralized under BFD,
i.e., outside the multiple BFD clients.
The main BFD parameters of interest to a BFD client are those related
to the multiplier and interval(s), since those parameters impact the
convergence time of the BFD clients when a failure occurs. Other
parameters, such as BFD authentication, are not specific to the
requirements of the BFD client. Configuration of BFD for all clients
should be centralized. However, this is a problem for BFD clients
that auto-discover their peers. For example, IGPs do not have the
peer address configured; instead, the IGP is enabled on an interface,
and the IGP peers are auto-discovered. So, for an operator to
configure BFD to an IGP peer, the operator would first have to
determine the peer addresses. And when a new peer is discovered, BFD
configuration would need to be added. To avoid this issue, we define
the grouping "client-cfg-parms" in Section 2.12 for BFD clients to
configure BFD: this allows BFD clients, such as the IGPs, to have
configuration (multiplier and intervals) for the BFD sessions they
need. For example, when a new IGP peer is discovered, the IGP would
create a BFD session to the newly discovered peer; similarly, when an
IGP peer goes away, the IGP would remove the BFD session to that
peer. The mechanism for how the BFD sessions are created and removed
by the BFD clients is outside the scope of this document, but this
would typically be done by using an API implemented by the BFD module
on the system. In the case of BFD clients that create BFD sessions
via their own configuration, authentication parameters (if required)
are still specified in BFD.
2.1.1. Common BFD Configuration Parameters
The basic BFD configuration parameters are as follows:
local-multiplier
This is the detection time multiplier as defined in BFD [RFC5880].
desired-min-tx-interval
This is the Desired Min TX Interval as defined in BFD [RFC5880].
required-min-rx-interval
This is the Required Min RX Interval as defined in BFD [RFC5880].
Although BFD [RFC5880] allows for different values for transmit and
receive intervals, some implementations allow users to specify just
one interval that is used for both transmit and receive intervals, or
separate values for transmit and receive intervals. The BFD YANG
data model supports this: there is a choice between "min-interval",
used for both transmit and receive intervals, and "desired-min-tx-
interval" and "required-min-rx-interval". This is supported via the
"base-cfg-parms" grouping (Section 2.12), which is used by the YANG
modules for the various forwarding paths.
For BFD authentication, we have the following:
key-chain
This is a reference to "key-chain" as defined in "YANG Data Model
for Key Chains" [RFC8177]. The keys, cryptographic algorithms,
key lifetime, etc. are all defined in the "key-chain" model.
meticulous
This enables a meticulous mode as per BFD [RFC5880].
2.1.2. Single-Hop IP
For single-hop IP, there is an augment of the "bfd" data node, as
described in Section 2. The "ip-sh" node contains a list of IP
single-hop sessions where each session is uniquely identified by the
interface and destination address pair. We use the configuration
parameters defined in Section 2.1.1. The "ip-sh" node also contains
a list of interfaces and is used to specify authentication parameters
for BFD sessions that are created by BFD clients. See Section 2.1.
[RFC5880] and [RFC5881] do not specify whether the Echo function
operates continuously or on demand. Therefore, the mechanism used to
start and stop the Echo function is implementation specific and
should be done by augmentation:
1. Configuration. This is suitable for an Echo function that
operates continuously. An example is provided in Appendix A.
2. RPC. This is suitable for an Echo function that operates on
demand.
2.1.3. Multihop IP
For multihop IP, there is an augment of the "bfd" data node, as
described in Section 2.
Because of multiple paths, there could be multiple multihop IP
sessions between a source and a destination address. We identify
this set of sessions as a "session-group". The key for each
"session-group" consists of the following:
Source address
Address belonging to the local system as per "Bidirectional
Forwarding Detection (BFD) for Multihop Paths" [RFC5883].
Destination address
Address belonging to the remote system as per [RFC5883].
We use the configuration parameters defined in Section 2.1.1.
This document also provides the following parameters:
tx-ttl
TTL of outgoing BFD control packets.
rx-ttl
Minimum TTL of incoming BFD control packets.
2.1.4. MPLS Label Switched Paths
Here, we address MPLS LSPs whose Forwarding Equivalence Class (FEC)
[RFC3031] is an IP address. The "bfd" node (Section 2) is augmented
with "mpls", which contains a list of sessions uniquely identified by
an IP prefix. Because of multiple paths, there could be multiple
MPLS sessions to an MPLS FEC. We identify this set of sessions as a
"session-group".
Since these LSPs are unidirectional, there is no LSP configuration on
the egress node.
The BFD parameters for the egress node are added under "mpls".
2.1.5. Link Aggregation Groups
Per "Bidirectional Forwarding Detection (BFD) on Link Aggregation
Group (LAG) Interfaces" [RFC7130], configuring BFD on a LAG consists
of having micro-BFD sessions on each LAG member link. Since the BFD
parameters are an attribute of the LAG, they should be under the LAG.
However, there is no LAG YANG data model that we can augment. So, a
"lag" data node is added to the "bfd" node; see Section 2. The
configuration is per LAG: we have a list of LAGs. The destination IP
address of the micro-BFD sessions is configured per LAG and per
address family (IPv4 and IPv6).
2.2. Design of the Operational State Model
The operational state model contains both the overall statistics for
the BFD sessions running on the device and the per-session
operational information.
The overall statistics for the BFD sessions consist of the number of
BFD sessions, the number of BFD sessions that are up, etc. This
information is available globally (i.e., for all BFD sessions) under
the "bfd" node (Section 2) and also per type of forwarding path.
For each BFD session, three main categories of operational state data
are shown.
1. The first category includes fundamental information regarding a
BFD session, such as the local discriminator, the remote
discriminator, and the ability to support Demand mode.
2. The second category includes BFD "session-running" information,
e.g., the remote BFD state and the diagnostic code received.
Another example is the actual transmit interval between the
control packets, which may be different from the configured
desired minimum transmit interval. Similar examples include the
actual receive interval between the control packets and the
actual transmit interval between the Echo packets.
3. The third category contains the detailed statistics for the
session, e.g., when the session transitioned up/down and how long
it has been in that state.
For some path types, there may be more than one session on the
virtual path to the destination. For example, with IP multihop and
MPLS LSPs, there could be multiple BFD sessions from the source to
the same destination to test the various paths (ECMP) to the
destination. This is represented by having multiple "sessions" under
each "session-group".
2.3. Notifications
This YANG data model defines notifications to inform end users of
important events detected during the protocol operation. The local
discriminator identifies the corresponding BFD session on the local
system, and the remote discriminator identifies the BFD session on
the remote system. Notifications also give more important details
about BFD sessions, e.g., new state, time in previous state, network
instance, and the reason that the BFD session state changed. The
notifications are defined for each type of forwarding path but use
groupings for common information.
2.4. RPC Operations
None.
2.5. BFD Top-Level Hierarchy
At the "bfd" node under "control-plane-protocol", there is no
configuration data -- only operational state data. The operational
state data consists of overall BFD session statistics, i.e., for BFD
on all types of forwarding paths.
module: ietf-bfd
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol:
+--rw bfd
+--ro summary
+--ro number-of-sessions? yang:gauge32
+--ro number-of-sessions-up? yang:gauge32
+--ro number-of-sessions-down? yang:gauge32
+--ro number-of-sessions-admin-down? yang:gauge32
2.6. BFD IP Single-Hop Hierarchy
An "ip-sh" node is added under the "bfd" node in "control-plane-
protocol". The configuration data and operational state data for
each BFD IP single-hop session are under this "ip-sh" node.
module: ietf-bfd-ip-sh
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd:
+--rw ip-sh
+--ro summary
| +--ro number-of-sessions? yang:gauge32
| +--ro number-of-sessions-up? yang:gauge32
| +--ro number-of-sessions-down? yang:gauge32
| +--ro number-of-sessions-admin-down? yang:gauge32
+--rw sessions
| +--rw session* [interface dest-addr]
| +--rw interface if:interface-ref
| +--rw dest-addr inet:ip-address
| +--rw source-addr? inet:ip-address
| +--rw local-multiplier? multiplier
| +--rw (interval-config-type)?
| | +--:(tx-rx-intervals)
| | | +--rw desired-min-tx-interval? uint32
| | | +--rw required-min-rx-interval? uint32
| | +--:(single-interval) {single-minimum-interval}?
| | +--rw min-interval? uint32
| +--rw demand-enabled? boolean
| | {demand-mode}?
| +--rw admin-down? boolean
| +--rw authentication! {authentication}?
| | +--rw key-chain? key-chain:key-chain-ref
| | +--rw meticulous? boolean
| +--ro path-type? identityref
| +--ro ip-encapsulation? boolean
| +--ro local-discriminator? discriminator
| +--ro remote-discriminator? discriminator
| +--ro remote-multiplier? multiplier
| +--ro demand-capability? boolean
| | {demand-mode}?
| +--ro source-port? inet:port-number
| +--ro dest-port? inet:port-number
| +--ro session-running
| | +--ro session-index? uint32
| | +--ro local-state? state
| | +--ro remote-state? state
| | +--ro local-diagnostic?
| | | iana-bfd-types:diagnostic
| | +--ro remote-diagnostic?
| | | iana-bfd-types:diagnostic
| | +--ro remote-authenticated? boolean
| | +--ro remote-authentication-type?
| | | iana-bfd-types:auth-type {authentication}?
| | +--ro detection-mode? enumeration
| | +--ro negotiated-tx-interval? uint32
| | +--ro negotiated-rx-interval? uint32
| | +--ro detection-time? uint32
| | +--ro echo-tx-interval-in-use? uint32
| | {echo-mode}?
| +--ro session-statistics
| +--ro create-time?
| | yang:date-and-time
| +--ro last-down-time?
| | yang:date-and-time
| +--ro last-up-time?
| | yang:date-and-time
| +--ro down-count? yang:counter32
| +--ro admin-down-count? yang:counter32
| +--ro receive-packet-count? yang:counter64
| +--ro send-packet-count? yang:counter64
| +--ro receive-invalid-packet-count? yang:counter64
| +--ro send-failed-packet-count? yang:counter64
+--rw interfaces* [interface]
+--rw interface if:interface-ref
+--rw authentication! {authentication}?
+--rw key-chain? key-chain:key-chain-ref
+--rw meticulous? boolean
notifications:
+---n singlehop-notification
+--ro local-discr? discriminator
+--ro remote-discr? discriminator
+--ro new-state? state
+--ro state-change-reason? iana-bfd-types:diagnostic
+--ro time-of-last-state-change? yang:date-and-time
+--ro dest-addr? inet:ip-address
+--ro source-addr? inet:ip-address
+--ro session-index? uint32
+--ro path-type? identityref
+--ro interface? if:interface-ref
+--ro echo-enabled? boolean
2.7. BFD IP Multihop Hierarchy
An "ip-mh" node is added under the "bfd" node in "control-plane-
protocol". The configuration data and operational state data for
each BFD IP multihop session are under this "ip-mh" node. In the
operational state model, we support multiple BFD multihop sessions
per remote address (ECMP); the local discriminator is used as the
key.
module: ietf-bfd-ip-mh
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd:
+--rw ip-mh
+--ro summary
| +--ro number-of-sessions? yang:gauge32
| +--ro number-of-sessions-up? yang:gauge32
| +--ro number-of-sessions-down? yang:gauge32
| +--ro number-of-sessions-admin-down? yang:gauge32
+--rw session-groups
+--rw session-group* [source-addr dest-addr]
+--rw source-addr inet:ip-address
+--rw dest-addr inet:ip-address
+--rw local-multiplier? multiplier
+--rw (interval-config-type)?
| +--:(tx-rx-intervals)
| | +--rw desired-min-tx-interval? uint32
| | +--rw required-min-rx-interval? uint32
| +--:(single-interval) {single-minimum-interval}?
| +--rw min-interval? uint32
+--rw demand-enabled? boolean
| {demand-mode}?
+--rw admin-down? boolean
+--rw authentication! {authentication}?
| +--rw key-chain? key-chain:key-chain-ref
| +--rw meticulous? boolean
+--rw tx-ttl? bfd-types:hops
+--rw rx-ttl bfd-types:hops
+--ro sessions* []
+--ro path-type? identityref
+--ro ip-encapsulation? boolean
+--ro local-discriminator? discriminator
+--ro remote-discriminator? discriminator
+--ro remote-multiplier? multiplier
+--ro demand-capability? boolean {demand-mode}?
+--ro source-port? inet:port-number
+--ro dest-port? inet:port-number
+--ro session-running
| +--ro session-index? uint32
| +--ro local-state? state
| +--ro remote-state? state
| +--ro local-diagnostic?
| | iana-bfd-types:diagnostic
| +--ro remote-diagnostic?
| | iana-bfd-types:diagnostic
| +--ro remote-authenticated? boolean
| +--ro remote-authentication-type?
| | iana-bfd-types:auth-type {authentication}?
| +--ro detection-mode? enumeration
| +--ro negotiated-tx-interval? uint32
| +--ro negotiated-rx-interval? uint32
| +--ro detection-time? uint32
| +--ro echo-tx-interval-in-use? uint32
| {echo-mode}?
+--ro session-statistics
+--ro create-time?
| yang:date-and-time
+--ro last-down-time?
| yang:date-and-time
+--ro last-up-time?
| yang:date-and-time
+--ro down-count?
| yang:counter32
+--ro admin-down-count?
| yang:counter32
+--ro receive-packet-count?
| yang:counter64
+--ro send-packet-count?
| yang:counter64
+--ro receive-invalid-packet-count?
| yang:counter64
+--ro send-failed-packet-count?
yang:counter64
notifications:
+---n multihop-notification
+--ro local-discr? discriminator
+--ro remote-discr? discriminator
+--ro new-state? state
+--ro state-change-reason? iana-bfd-types:diagnostic
+--ro time-of-last-state-change? yang:date-and-time
+--ro dest-addr? inet:ip-address
+--ro source-addr? inet:ip-address
+--ro session-index? uint32
+--ro path-type? identityref
2.8. BFD-over-LAG Hierarchy
A "lag" node is added under the "bfd" node in "control-plane-
protocol". The configuration data and operational state data for
each BFD LAG session are under this "lag" node.
module: ietf-bfd-lag
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd:
+--rw lag
+--rw micro-bfd-ipv4-session-statistics
| +--ro summary
| +--ro number-of-sessions? yang:gauge32
| +--ro number-of-sessions-up? yang:gauge32
| +--ro number-of-sessions-down? yang:gauge32
| +--ro number-of-sessions-admin-down? yang:gauge32
+--rw micro-bfd-ipv6-session-statistics
| +--ro summary
| +--ro number-of-sessions? yang:gauge32
| +--ro number-of-sessions-up? yang:gauge32
| +--ro number-of-sessions-down? yang:gauge32
| +--ro number-of-sessions-admin-down? yang:gauge32
+--rw sessions
+--rw session* [lag-name]
+--rw lag-name if:interface-ref
+--rw ipv4-dest-addr?
| inet:ipv4-address
+--rw ipv6-dest-addr?
| inet:ipv6-address
+--rw local-multiplier? multiplier
+--rw (interval-config-type)?
| +--:(tx-rx-intervals)
| | +--rw desired-min-tx-interval? uint32
| | +--rw required-min-rx-interval? uint32
| +--:(single-interval) {single-minimum-interval}?
| +--rw min-interval? uint32
+--rw demand-enabled? boolean
| {demand-mode}?
+--rw admin-down? boolean
+--rw authentication! {authentication}?
| +--rw key-chain? key-chain:key-chain-ref
| +--rw meticulous? boolean
+--rw use-ipv4? boolean
+--rw use-ipv6? boolean
+--ro member-links* [member-link]
+--ro member-link if:interface-ref
+--ro micro-bfd-ipv4
| +--ro path-type? identityref
| +--ro ip-encapsulation? boolean
| +--ro local-discriminator? discriminator
| +--ro remote-discriminator? discriminator
| +--ro remote-multiplier? multiplier
| +--ro demand-capability? boolean
| | {demand-mode}?
| +--ro source-port? inet:port-number
| +--ro dest-port? inet:port-number
| +--ro session-running
| | +--ro session-index? uint32
| | +--ro local-state? state
| | +--ro remote-state? state
| | +--ro local-diagnostic?
| | | iana-bfd-types:diagnostic
| | +--ro remote-diagnostic?
| | | iana-bfd-types:diagnostic
| | +--ro remote-authenticated? boolean
| | +--ro remote-authentication-type?
| | | iana-bfd-types:auth-type
| | | {authentication}?
| | +--ro detection-mode? enumeration
| | +--ro negotiated-tx-interval? uint32
| | +--ro negotiated-rx-interval? uint32
| | +--ro detection-time? uint32
| | +--ro echo-tx-interval-in-use? uint32
| | {echo-mode}?
| +--ro session-statistics
| +--ro create-time?
| | yang:date-and-time
| +--ro last-down-time?
| | yang:date-and-time
| +--ro last-up-time?
| | yang:date-and-time
| +--ro down-count?
| | yang:counter32
| +--ro admin-down-count?
| | yang:counter32
| +--ro receive-packet-count?
| | yang:counter64
| +--ro send-packet-count?
| | yang:counter64
| +--ro receive-invalid-packet-count?
| | yang:counter64
| +--ro send-failed-packet-count?
| yang:counter64
+--ro micro-bfd-ipv6
+--ro path-type? identityref
+--ro ip-encapsulation? boolean
+--ro local-discriminator? discriminator
+--ro remote-discriminator? discriminator
+--ro remote-multiplier? multiplier
+--ro demand-capability? boolean
| {demand-mode}?
+--ro source-port? inet:port-number
+--ro dest-port? inet:port-number
+--ro session-running
| +--ro session-index? uint32
| +--ro local-state? state
| +--ro remote-state? state
| +--ro local-diagnostic?
| | iana-bfd-types:diagnostic
| +--ro remote-diagnostic?
| | iana-bfd-types:diagnostic
| +--ro remote-authenticated? boolean
| +--ro remote-authentication-type?
| | iana-bfd-types:auth-type
| | {authentication}?
| +--ro detection-mode? enumeration
| +--ro negotiated-tx-interval? uint32
| +--ro negotiated-rx-interval? uint32
| +--ro detection-time? uint32
| +--ro echo-tx-interval-in-use? uint32
| {echo-mode}?
+--ro session-statistics
+--ro create-time?
| yang:date-and-time
+--ro last-down-time?
| yang:date-and-time
+--ro last-up-time?
| yang:date-and-time
+--ro down-count?
| yang:counter32
+--ro admin-down-count?
| yang:counter32
+--ro receive-packet-count?
| yang:counter64
+--ro send-packet-count?
| yang:counter64
+--ro receive-invalid-packet-count?
| yang:counter64
+--ro send-failed-packet-count?
yang:counter64
notifications:
+---n lag-notification
+--ro local-discr? discriminator
+--ro remote-discr? discriminator
+--ro new-state? state
+--ro state-change-reason? iana-bfd-types:diagnostic
+--ro time-of-last-state-change? yang:date-and-time
+--ro dest-addr? inet:ip-address
+--ro source-addr? inet:ip-address
+--ro session-index? uint32
+--ro path-type? identityref
+--ro lag-name? if:interface-ref
+--ro member-link? if:interface-ref
2.9. BFD-over-MPLS-LSPs Hierarchy
An "mpls" node is added under the "bfd" node in "control-plane-
protocol". The configuration is per MPLS FEC under this "mpls" node.
In the operational state model, we support multiple BFD sessions per
MPLS FEC (ECMP); the local discriminator is used as the key. The
"mpls" node can be used in a network device (top level) or can be
mounted in an LNE or network instance.
module: ietf-bfd-mpls
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd:
+--rw mpls
+--ro summary
| +--ro number-of-sessions? yang:gauge32
| +--ro number-of-sessions-up? yang:gauge32
| +--ro number-of-sessions-down? yang:gauge32
| +--ro number-of-sessions-admin-down? yang:gauge32
+--rw egress
| +--rw enabled? boolean
| +--rw local-multiplier? multiplier
| +--rw (interval-config-type)?
| | +--:(tx-rx-intervals)
| | | +--rw desired-min-tx-interval? uint32
| | | +--rw required-min-rx-interval? uint32
| | +--:(single-interval) {single-minimum-interval}?
| | +--rw min-interval? uint32
| +--rw authentication! {authentication}?
| +--rw key-chain? key-chain:key-chain-ref
| +--rw meticulous? boolean
+--rw session-groups
+--rw session-group* [mpls-fec]
+--rw mpls-fec inet:ip-prefix
+--rw local-multiplier? multiplier
+--rw (interval-config-type)?
| +--:(tx-rx-intervals)
| | +--rw desired-min-tx-interval? uint32
| | +--rw required-min-rx-interval? uint32
| +--:(single-interval) {single-minimum-interval}?
| +--rw min-interval? uint32
+--rw demand-enabled? boolean
| {demand-mode}?
+--rw admin-down? boolean
+--rw authentication! {authentication}?
| +--rw key-chain? key-chain:key-chain-ref
| +--rw meticulous? boolean
+--ro sessions* []
+--ro path-type? identityref
+--ro ip-encapsulation? boolean
+--ro local-discriminator? discriminator
+--ro remote-discriminator? discriminator
+--ro remote-multiplier? multiplier
+--ro demand-capability? boolean {demand-mode}?
+--ro source-port? inet:port-number
+--ro dest-port? inet:port-number
+--ro session-running
| +--ro session-index? uint32
| +--ro local-state? state
| +--ro remote-state? state
| +--ro local-diagnostic?
| | iana-bfd-types:diagnostic
| +--ro remote-diagnostic?
| | iana-bfd-types:diagnostic
| +--ro remote-authenticated? boolean
| +--ro remote-authentication-type?
| | iana-bfd-types:auth-type {authentication}?
| +--ro detection-mode? enumeration
| +--ro negotiated-tx-interval? uint32
| +--ro negotiated-rx-interval? uint32
| +--ro detection-time? uint32
| +--ro echo-tx-interval-in-use? uint32
| {echo-mode}?
+--ro session-statistics
| +--ro create-time?
| | yang:date-and-time
| +--ro last-down-time?
| | yang:date-and-time
| +--ro last-up-time?
| | yang:date-and-time
| +--ro down-count?
| | yang:counter32
| +--ro admin-down-count?
| | yang:counter32
| +--ro receive-packet-count?
| | yang:counter64
| +--ro send-packet-count?
| | yang:counter64
| +--ro receive-invalid-packet-count?
| | yang:counter64
| +--ro send-failed-packet-count?
| yang:counter64
+--ro mpls-dest-address? inet:ip-address
notifications:
+---n mpls-notification
+--ro local-discr? discriminator
+--ro remote-discr? discriminator
+--ro new-state? state
+--ro state-change-reason? iana-bfd-types:diagnostic
+--ro time-of-last-state-change? yang:date-and-time
+--ro dest-addr? inet:ip-address
+--ro source-addr? inet:ip-address
+--ro session-index? uint32
+--ro path-type? identityref
+--ro mpls-dest-address? inet:ip-address
2.10. Interaction with Other YANG Modules
"Generic YANG Data Model for the Management of Operations,
Administration, and Maintenance (OAM) Protocols That Use
Connectionless Communications" [RFC8532] describes how the Layer-
Independent OAM Management in the Multi-Layer Environment (LIME)
connectionless OAM model could be extended to support BFD.
Also, the operation of the BFD data model depends on configuration
parameters that are defined in other YANG modules.
2.10.1. "ietf-interfaces" Module
The following boolean configuration is defined in "A YANG Data Model
for Interface Management" [RFC8343]:
/if:interfaces/if:interface/if:enabled
If this configuration is set to "false", no BFD packets can be
transmitted or received on that interface.
2.10.2. "ietf-ip" Module
The following boolean configuration is defined in "A YANG Data Model
for IP Management" [RFC8344]:
/if:interfaces/if:interface/ip:ipv4/ip:enabled
If this configuration is set to "false", no BFD IPv4 packets can
be transmitted or received on that interface.
/if:interfaces/if:interface/ip:ipv4/ip:forwarding
If this configuration is set to "false", no BFD IPv4 packets can
be transmitted or received on that interface.
/if:interfaces/if:interface/ip:ipv6/ip:enabled
If this configuration is set to "false", no BFD IPv6 packets can
be transmitted or received on that interface.
/if:interfaces/if:interface/ip:ipv6/ip:forwarding
If this configuration is set to "false", no BFD IPv6 packets can
be transmitted or received on that interface.
2.10.3. "ietf-mpls" Module
The following boolean configuration is defined in "A YANG Data Model
for MPLS Base" [RFC8960]:
/rt:routing/mpls:mpls/mpls:interfaces/mpls:interface/
mpls:mpls-enabled
If this configuration is set to "false", no BFD MPLS packets can
be transmitted or received on that interface.
2.11. IANA BFD YANG Module
This YANG module imports definitions from [RFC5880]. It references
[RFC5880] and [RFC6428].
<CODE BEGINS> file "iana-bfd-types@2021-10-21.yang"
module iana-bfd-types {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:iana-bfd-types";
prefix iana-bfd-types;
organization
"IANA";
contact
"Internet Assigned Numbers Authority
Postal: ICANN
12025 Waterfront Drive, Suite 300
Los Angeles, CA 90094-2536
United States of America
Tel: +1 310 301 5800
<mailto:iana@iana.org>";
description
"This module defines YANG data types for IANA-registered
BFD parameters.
This YANG module is maintained by IANA and reflects the
'BFD Diagnostic Codes' and 'BFD Authentication Types'
registries.
Copyright (c) 2021 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 9127; see the
RFC itself for full legal notices.";
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
revision 2021-10-21 {
description
"Initial revision.";
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
/*
* Type definitions
*/
typedef diagnostic {
type enumeration {
enum none {
value 0;
description
"No Diagnostic.";
}
enum control-expiry {
value 1;
description
"Control Detection Time Expired.";
}
enum echo-failed {
value 2;
description
"Echo Function Failed.";
}
enum neighbor-down {
value 3;
description
"Neighbor Signaled Session Down.";
}
enum forwarding-reset {
value 4;
description
"Forwarding Plane Reset.";
}
enum path-down {
value 5;
description
"Path Down.";
}
enum concatenated-path-down {
value 6;
description
"Concatenated Path Down.";
}
enum admin-down {
value 7;
description
"Administratively Down.";
}
enum reverse-concatenated-path-down {
value 8;
description
"Reverse Concatenated Path Down.";
}
enum mis-connectivity-defect {
value 9;
description
"Mis-connectivity defect.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD)
RFC 6428: Proactive Connectivity Verification, Continuity
Check, and Remote Defect Indication for the MPLS Transport
Profile";
}
}
description
"BFD diagnostic codes as defined in RFC 5880. Values are
maintained in the 'BFD Diagnostic Codes' IANA registry.
Range is 0 to 31.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD)";
}
typedef auth-type {
type enumeration {
enum reserved {
value 0;
description
"Reserved.";
}
enum simple-password {
value 1;
description
"Simple Password.";
}
enum keyed-md5 {
value 2;
description
"Keyed MD5.";
}
enum meticulous-keyed-md5 {
value 3;
description
"Meticulous Keyed MD5.";
}
enum keyed-sha1 {
value 4;
description
"Keyed SHA1.";
}
enum meticulous-keyed-sha1 {
value 5;
description
"Meticulous Keyed SHA1.";
}
}
description
"BFD authentication type as defined in RFC 5880. Values are
maintained in the 'BFD Authentication Types' IANA registry.
Range is 0 to 255.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD)";
}
}
<CODE ENDS>
2.12. BFD Types YANG Module
This YANG module imports typedefs from [RFC6991] and [RFC8177]. It
also imports definitions from [RFC5880], [RFC5881], [RFC5883],
[RFC5884], and [RFC7130], as well as the "control-plane-protocol"
identity from [RFC8349].
<CODE BEGINS> file "ietf-bfd-types@2021-10-21.yang"
module ietf-bfd-types {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-types";
prefix bfd-types;
import iana-bfd-types {
prefix iana-bfd-types;
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-yang-types {
prefix yang;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-routing {
prefix rt;
reference
"RFC 8349: A YANG Data Model for Routing Management
(NMDA Version)";
}
import ietf-key-chain {
prefix key-chain;
reference
"RFC 8177: YANG Data Model for Key Chains";
}
organization
"IETF BFD Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/bfd/>
WG List: <mailto:rtg-bfd@ietf.org>
Editor: Reshad Rahman
<mailto:reshad@yahoo.com>
Editor: Lianshu Zheng
<mailto:veronique_cheng@hotmail.com>
Editor: Mahesh Jethanandani
<mailto:mjethanandani@gmail.com>";
description
"This module contains a collection of BFD-specific YANG data type
definitions, as per RFC 5880, and also groupings that are common
to other BFD YANG modules.
Copyright (c) 2021 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 9127; see the
RFC itself for full legal notices.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD)
RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
revision 2021-10-21 {
description
"Initial revision.";
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
/*
* Feature definitions
*/
feature single-minimum-interval {
description
"This feature indicates that the server supports configuration
of one minimum interval value that is used for both transmit
and receive minimum intervals.";
}
feature authentication {
description
"This feature indicates that the server supports BFD
authentication.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD),
Section 6.7";
}
feature demand-mode {
description
"This feature indicates that the server supports BFD Demand
mode.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD),
Section 6.6";
}
feature echo-mode {
description
"This feature indicates that the server supports BFD Echo
mode.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD),
Section 6.4";
}
/*
* Identity definitions
*/
identity bfdv1 {
base rt:control-plane-protocol;
description
"BFD protocol version 1.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD)";
}
identity path-type {
description
"Base identity for the BFD path type. The path type indicates
the type of path on which BFD is running.";
}
identity path-ip-sh {
base path-type;
description
"BFD on IP single-hop.";
reference
"RFC 5881: Bidirectional Forwarding Detection (BFD)
for IPv4 and IPv6 (Single Hop)";
}
identity path-ip-mh {
base path-type;
description
"BFD on IP multihop paths.";
reference
"RFC 5883: Bidirectional Forwarding Detection (BFD) for
Multihop Paths";
}
identity path-mpls-te {
base path-type;
description
"BFD on MPLS Traffic Engineering.";
reference
"RFC 5884: Bidirectional Forwarding Detection (BFD)
for MPLS Label Switched Paths (LSPs)";
}
identity path-mpls-lsp {
base path-type;
description
"BFD on an MPLS Label Switched Path.";
reference
"RFC 5884: Bidirectional Forwarding Detection (BFD)
for MPLS Label Switched Paths (LSPs)";
}
identity path-lag {
base path-type;
description
"Micro-BFD on LAG member links.";
reference
"RFC 7130: Bidirectional Forwarding Detection (BFD) on
Link Aggregation Group (LAG) Interfaces";
}
identity encap-type {
description
"Base identity for BFD encapsulation type.";
}
identity encap-ip {
base encap-type;
description
"BFD with IP encapsulation.";
}
/*
* Type definitions
*/
typedef discriminator {
type uint32;
description
"BFD Discriminator as described in RFC 5880.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD)";
}
typedef state {
type enumeration {
enum adminDown {
value 0;
description
"'adminDown' state.";
}
enum down {
value 1;
description
"'Down' state.";
}
enum init {
value 2;
description
"'Init' state.";
}
enum up {
value 3;
description
"'Up' state.";
}
}
description
"BFD states as defined in RFC 5880.";
}
typedef multiplier {
type uint8 {
range "1..255";
}
description
"BFD multiplier as described in RFC 5880.";
}
typedef hops {
type uint8 {
range "1..255";
}
description
"This corresponds to Time To Live for IPv4 and corresponds to
the hop limit for IPv6.";
}
/*
* Groupings
*/
grouping auth-parms {
description
"Grouping for BFD authentication parameters
(see Section 6.7 of RFC 5880).";
container authentication {
if-feature "authentication";
presence "Enables BFD authentication (see Section 6.7
of RFC 5880).";
description
"Parameters for BFD authentication.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD),
Section 6.7";
leaf key-chain {
type key-chain:key-chain-ref;
description
"Name of the 'key-chain' as per RFC 8177.";
}
leaf meticulous {
type boolean;
description
"Enables a meticulous mode as per Section 6.7 of
RFC 5880.";
}
}
}
grouping base-cfg-parms {
description
"BFD grouping for base configuration parameters.";
leaf local-multiplier {
type multiplier;
default "3";
description
"Multiplier transmitted by the local system.";
}
choice interval-config-type {
default "tx-rx-intervals";
description
"Two interval values or one value used for both transmit and
receive.";
case tx-rx-intervals {
leaf desired-min-tx-interval {
type uint32;
units "microseconds";
default "1000000";
description
"Desired minimum transmit interval of control packets.";
}
leaf required-min-rx-interval {
type uint32;
units "microseconds";
default "1000000";
description
"Required minimum receive interval of control packets.";
}
}
case single-interval {
if-feature "single-minimum-interval";
leaf min-interval {
type uint32;
units "microseconds";
default "1000000";
description
"Desired minimum transmit interval and required
minimum receive interval of control packets.";
}
}
}
}
grouping client-cfg-parms {
description
"BFD grouping for configuration parameters
used by BFD clients, e.g., IGP or MPLS.";
leaf enabled {
type boolean;
default "false";
description
"Indicates whether BFD is enabled.";
}
uses base-cfg-parms;
}
grouping common-cfg-parms {
description
"BFD grouping for common configuration parameters.";
uses base-cfg-parms;
leaf demand-enabled {
if-feature "demand-mode";
type boolean;
default "false";
description
"To enable Demand mode.";
}
leaf admin-down {
type boolean;
default "false";
description
"Indicates whether the BFD session is administratively
down.";
}
uses auth-parms;
}
grouping all-session {
description
"BFD session operational information.";
leaf path-type {
type identityref {
base path-type;
}
config false;
description
"BFD path type. This indicates the path type that BFD is
running on.";
}
leaf ip-encapsulation {
type boolean;
config false;
description
"Indicates whether BFD encapsulation uses IP.";
}
leaf local-discriminator {
type discriminator;
config false;
description
"Local discriminator.";
}
leaf remote-discriminator {
type discriminator;
config false;
description
"Remote discriminator.";
}
leaf remote-multiplier {
type multiplier;
config false;
description
"Remote multiplier.";
}
leaf demand-capability {
if-feature "demand-mode";
type boolean;
config false;
description
"Local Demand mode capability.";
}
leaf source-port {
when "../ip-encapsulation = 'true'" {
description
"Source port valid only when IP encapsulation is used.";
}
type inet:port-number;
config false;
description
"Source UDP port.";
}
leaf dest-port {
when "../ip-encapsulation = 'true'" {
description
"Destination port valid only when IP encapsulation
is used.";
}
type inet:port-number;
config false;
description
"Destination UDP port.";
}
container session-running {
config false;
description
"BFD 'session-running' information.";
leaf session-index {
type uint32;
description
"An index used to uniquely identify BFD sessions.";
}
leaf local-state {
type state;
description
"Local state.";
}
leaf remote-state {
type state;
description
"Remote state.";
}
leaf local-diagnostic {
type iana-bfd-types:diagnostic;
description
"Local diagnostic.";
}
leaf remote-diagnostic {
type iana-bfd-types:diagnostic;
description
"Remote diagnostic.";
}
leaf remote-authenticated {
type boolean;
description
"Indicates whether incoming BFD control packets are
authenticated.";
}
leaf remote-authentication-type {
when "../remote-authenticated = 'true'" {
description
"Only valid when incoming BFD control packets are
authenticated.";
}
if-feature "authentication";
type iana-bfd-types:auth-type;
description
"Authentication type of incoming BFD control packets.";
}
leaf detection-mode {
type enumeration {
enum async-with-echo {
value 1;
description
"Async with echo.";
}
enum async-without-echo {
value 2;
description
"Async without echo.";
}
enum demand-with-echo {
value 3;
description
"Demand with echo.";
}
enum demand-without-echo {
value 4;
description
"Demand without echo.";
}
}
description
"Detection mode.";
}
leaf negotiated-tx-interval {
type uint32;
units "microseconds";
description
"Negotiated transmit interval.";
}
leaf negotiated-rx-interval {
type uint32;
units "microseconds";
description
"Negotiated receive interval.";
}
leaf detection-time {
type uint32;
units "microseconds";
description
"Detection time.";
}
leaf echo-tx-interval-in-use {
when "../../path-type = 'bfd-types:path-ip-sh'" {
description
"Echo is supported for IP single-hop only.";
}
if-feature "echo-mode";
type uint32;
units "microseconds";
description
"Echo transmit interval in use.";
}
}
container session-statistics {
config false;
description
"BFD per-session statistics.";
leaf create-time {
type yang:date-and-time;
description
"Time and date when this session was created.";
}
leaf last-down-time {
type yang:date-and-time;
description
"Time and date of the last time this session went down.";
}
leaf last-up-time {
type yang:date-and-time;
description
"Time and date of the last time this session went up.";
}
leaf down-count {
type yang:counter32;
description
"The number of times this session has transitioned to the
'down' state.";
}
leaf admin-down-count {
type yang:counter32;
description
"The number of times this session has transitioned to the
'admin-down' state.";
}
leaf receive-packet-count {
type yang:counter64;
description
"Count of received packets in this session. This includes
valid and invalid received packets.";
}
leaf send-packet-count {
type yang:counter64;
description
"Count of sent packets in this session.";
}
leaf receive-invalid-packet-count {
type yang:counter64;
description
"Count of invalid received packets in this session.";
}
leaf send-failed-packet-count {
type yang:counter64;
description
"Count of packets that failed to be sent in this session.";
}
}
}
grouping session-statistics-summary {
description
"Grouping for session statistics summary.";
container summary {
config false;
description
"BFD session statistics summary.";
leaf number-of-sessions {
type yang:gauge32;
description
"Number of BFD sessions.";
}
leaf number-of-sessions-up {
type yang:gauge32;
description
"Number of BFD sessions currently in the 'Up' state
(as defined in RFC 5880).";
}
leaf number-of-sessions-down {
type yang:gauge32;
description
"Number of BFD sessions currently in the 'Down' or 'Init'
state but not 'adminDown' (as defined in RFC 5880).";
}
leaf number-of-sessions-admin-down {
type yang:gauge32;
description
"Number of BFD sessions currently in the 'adminDown' state
(as defined in RFC 5880).";
}
}
}
grouping notification-parms {
description
"This group describes common parameters that will be sent
as part of BFD notifications.";
leaf local-discr {
type discriminator;
description
"BFD local discriminator.";
}
leaf remote-discr {
type discriminator;
description
"BFD remote discriminator.";
}
leaf new-state {
type state;
description
"Current BFD state.";
}
leaf state-change-reason {
type iana-bfd-types:diagnostic;
description
"Reason for the BFD state change.";
}
leaf time-of-last-state-change {
type yang:date-and-time;
description
"Calendar time of the most recent previous state change.";
}
leaf dest-addr {
type inet:ip-address;
description
"BFD peer address.";
}
leaf source-addr {
type inet:ip-address;
description
"BFD local address.";
}
leaf session-index {
type uint32;
description
"An index used to uniquely identify BFD sessions.";
}
leaf path-type {
type identityref {
base path-type;
}
description
"BFD path type.";
}
}
}
<CODE ENDS>
2.13. BFD Top-Level YANG Module
This YANG module imports and augments "/routing/control-plane-
protocols/control-plane-protocol" from [RFC8349]. It also references
[RFC5880].
<CODE BEGINS> file "ietf-bfd@2021-10-21.yang"
module ietf-bfd {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-bfd";
prefix bfd;
import ietf-bfd-types {
prefix bfd-types;
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
import ietf-routing {
prefix rt;
reference
"RFC 8349: A YANG Data Model for Routing Management
(NMDA Version)";
}
organization
"IETF BFD Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/bfd/>
WG List: <mailto:rtg-bfd@ietf.org>
Editor: Reshad Rahman
<mailto:reshad@yahoo.com>
Editor: Lianshu Zheng
<mailto:veronique_cheng@hotmail.com>
Editor: Mahesh Jethanandani
<mailto:mjethanandani@gmail.com>";
description
"This module contains the YANG definition for BFD parameters as
per RFC 5880.
Copyright (c) 2021 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 9127; see the
RFC itself for full legal notices.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD)
RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
revision 2021-10-21 {
description
"Initial revision.";
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol" {
when "derived-from-or-self(rt:type, 'bfd-types:bfdv1')" {
description
"This augmentation is only valid for a control-plane protocol
instance of BFD (type 'bfdv1').";
}
description
"BFD augmentation.";
container bfd {
description
"BFD top-level container.";
uses bfd-types:session-statistics-summary;
}
}
}
<CODE ENDS>
2.14. BFD IP Single-Hop YANG Module
This YANG module imports "interface-ref" from [RFC8343] and typedefs
from [RFC6991]. It also imports and augments "/routing/control-
plane-protocols/control-plane-protocol" from [RFC8349], and it
references [RFC5881].
<CODE BEGINS> file "ietf-bfd-ip-sh@2021-10-21.yang"
module ietf-bfd-ip-sh {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh";
prefix bfd-ip-sh;
import ietf-bfd-types {
prefix bfd-types;
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
import ietf-bfd {
prefix bfd;
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
import ietf-interfaces {
prefix if;
reference
"RFC 8343: A YANG Data Model for Interface Management";
}
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-routing {
prefix rt;
reference
"RFC 8349: A YANG Data Model for Routing Management
(NMDA Version)";
}
organization
"IETF BFD Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/bfd/>
WG List: <mailto:rtg-bfd@ietf.org>
Editor: Reshad Rahman
<mailto:reshad@yahoo.com>
Editor: Lianshu Zheng
<mailto:veronique_cheng@hotmail.com>
Editor: Mahesh Jethanandani
<mailto:mjethanandani@gmail.com>";
description
"This module contains the YANG definition for BFD IP single-hop
as per RFC 5881.
Copyright (c) 2021 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 9127; see the
RFC itself for full legal notices.";
reference
"RFC 5881: Bidirectional Forwarding Detection (BFD)
for IPv4 and IPv6 (Single Hop)
RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
revision 2021-10-21 {
description
"Initial revision.";
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
/*
* Augments
*/
augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/bfd:bfd" {
description
"BFD augmentation for IP single-hop.";
container ip-sh {
description
"BFD IP single-hop top-level container.";
uses bfd-types:session-statistics-summary;
container sessions {
description
"BFD IP single-hop sessions.";
list session {
key "interface dest-addr";
description
"List of IP single-hop sessions.";
leaf interface {
type if:interface-ref;
description
"Interface on which the BFD session is running.";
}
leaf dest-addr {
type inet:ip-address;
description
"IP address of the peer.";
}
leaf source-addr {
type inet:ip-address;
description
"Local IP address.";
}
uses bfd-types:common-cfg-parms;
uses bfd-types:all-session;
}
}
list interfaces {
key "interface";
description
"List of interfaces.";
leaf interface {
type if:interface-ref;
description
"BFD information for this interface.";
}
uses bfd-types:auth-parms;
}
}
}
/*
* Notifications
*/
notification singlehop-notification {
description
"Notification for BFD single-hop session state change. An
implementation may rate-limit notifications, e.g., when a
session is continuously changing state.";
uses bfd-types:notification-parms;
leaf interface {
type if:interface-ref;
description
"Interface to which this BFD session belongs.";
}
leaf echo-enabled {
type boolean;
description
"Indicates whether Echo was enabled for BFD.";
}
}
}
<CODE ENDS>
2.15. BFD IP Multihop YANG Module
This YANG module imports typedefs from [RFC6991]. It also imports
and augments "/routing/control-plane-protocols/control-plane-
protocol" from [RFC8349], and it references [RFC5883].
<CODE BEGINS> file "ietf-bfd-ip-mh@2021-10-21.yang"
module ietf-bfd-ip-mh {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-ip-mh";
prefix bfd-ip-mh;
import ietf-bfd-types {
prefix bfd-types;
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
import ietf-bfd {
prefix bfd;
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-routing {
prefix rt;
reference
"RFC 8349: A YANG Data Model for Routing Management
(NMDA Version)";
}
organization
"IETF BFD Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/bfd/>
WG List: <mailto:rtg-bfd@ietf.org>
Editor: Reshad Rahman
<mailto:reshad@yahoo.com>
Editor: Lianshu Zheng
<mailto:veronique_cheng@hotmail.com>
Editor: Mahesh Jethanandani
<mailto:mjethanandani@gmail.com>";
description
"This module contains the YANG definition for BFD IP multihop
as per RFC 5883.
Copyright (c) 2021 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 9127; see the
RFC itself for full legal notices.";
reference
"RFC 5883: Bidirectional Forwarding Detection (BFD) for
Multihop Paths
RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
revision 2021-10-21 {
description
"Initial revision.";
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
/*
* Augments
*/
augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/bfd:bfd" {
description
"BFD augmentation for IP multihop.";
container ip-mh {
description
"BFD IP multihop top-level container.";
uses bfd-types:session-statistics-summary;
container session-groups {
description
"BFD IP multihop session groups.";
list session-group {
key "source-addr dest-addr";
description
"Group of BFD IP multihop sessions (for ECMP). A
group of sessions is between one source and one
destination. Each session has a different field
in the UDP/IP header for ECMP.";
leaf source-addr {
type inet:ip-address;
description
"Local IP address.";
}
leaf dest-addr {
type inet:ip-address;
description
"IP address of the peer.";
}
uses bfd-types:common-cfg-parms;
leaf tx-ttl {
type bfd-types:hops;
default "255";
description
"Hop count of outgoing BFD control packets.";
}
leaf rx-ttl {
type bfd-types:hops;
mandatory true;
description
"Minimum allowed hop count value for incoming BFD
control packets. Control packets whose hop count is
lower than this value are dropped.";
}
list sessions {
config false;
description
"The multiple BFD sessions between a source and a
destination.";
uses bfd-types:all-session;
}
}
}
}
}
/*
* Notifications
*/
notification multihop-notification {
description
"Notification for BFD multihop session state change. An
implementation may rate-limit notifications, e.g., when a
session is continuously changing state.";
uses bfd-types:notification-parms;
}
}
<CODE ENDS>
2.16. BFD-over-LAG YANG Module
This YANG module imports "interface-ref" from [RFC8343] and typedefs
from [RFC6991]. It also imports and augments "/routing/control-
plane-protocols/control-plane-protocol" from [RFC8349].
Additionally, it references [RFC7130].
<CODE BEGINS> file "ietf-bfd-lag@2021-10-21.yang"
module ietf-bfd-lag {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-lag";
prefix bfd-lag;
import ietf-bfd-types {
prefix bfd-types;
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
import ietf-bfd {
prefix bfd;
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
import ietf-interfaces {
prefix if;
reference
"RFC 8343: A YANG Data Model for Interface Management";
}
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-routing {
prefix rt;
reference
"RFC 8349: A YANG Data Model for Routing Management
(NMDA Version)";
}
organization
"IETF BFD Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/bfd/>
WG List: <mailto:rtg-bfd@ietf.org>
Editor: Reshad Rahman
<mailto:reshad@yahoo.com>
Editor: Lianshu Zheng
<mailto:veronique_cheng@hotmail.com>
Editor: Mahesh Jethanandani
<mailto:mjethanandani@gmail.com>";
description
"This module contains the YANG definition for BFD-over-LAG
interfaces as per RFC 7130.
Copyright (c) 2021 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 9127; see the
RFC itself for full legal notices.";
reference
"RFC 7130: Bidirectional Forwarding Detection (BFD) on
Link Aggregation Group (LAG) Interfaces
RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
revision 2021-10-21 {
description
"Initial revision.";
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
/*
* Augments
*/
augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/bfd:bfd" {
description
"BFD augmentation for a LAG.";
container lag {
description
"BFD-over-LAG top-level container.";
container micro-bfd-ipv4-session-statistics {
description
"Micro-BFD IPv4 session counters.";
uses bfd-types:session-statistics-summary;
}
container micro-bfd-ipv6-session-statistics {
description
"Micro-BFD IPv6 session counters.";
uses bfd-types:session-statistics-summary;
}
container sessions {
description
"BFD-over-LAG sessions.";
list session {
key "lag-name";
description
"List of BFD-over-LAG sessions.";
leaf lag-name {
type if:interface-ref;
description
"Name of the LAG.";
}
leaf ipv4-dest-addr {
type inet:ipv4-address;
description
"IPv4 address of the peer, for IPv4 micro-BFD.";
}
leaf ipv6-dest-addr {
type inet:ipv6-address;
description
"IPv6 address of the peer, for IPv6 micro-BFD.";
}
uses bfd-types:common-cfg-parms;
leaf use-ipv4 {
type boolean;
description
"Using IPv4 micro-BFD.";
}
leaf use-ipv6 {
type boolean;
description
"Using IPv6 micro-BFD.";
}
list member-links {
key "member-link";
config false;
description
"Micro-BFD over a LAG. This represents one
member link.";
leaf member-link {
type if:interface-ref;
description
"Member link on which micro-BFD is running.";
}
container micro-bfd-ipv4 {
when "../../use-ipv4 = 'true'" {
description
"Needed only if IPv4 is used.";
}
description
"Micro-BFD IPv4 session state on a member link.";
uses bfd-types:all-session;
}
container micro-bfd-ipv6 {
when "../../use-ipv6 = 'true'" {
description
"Needed only if IPv6 is used.";
}
description
"Micro-BFD IPv6 session state on a member link.";
uses bfd-types:all-session;
}
}
}
}
}
}
/*
* Notifications
*/
notification lag-notification {
description
"Notification for BFD-over-LAG session state change.
An implementation may rate-limit notifications, e.g., when a
session is continuously changing state.";
uses bfd-types:notification-parms;
leaf lag-name {
type if:interface-ref;
description
"LAG interface name.";
}
leaf member-link {
type if:interface-ref;
description
"Member link on which BFD is running.";
}
}
}
<CODE ENDS>
2.17. BFD-over-MPLS YANG Module
This YANG module imports typedefs from [RFC6991]. It also imports
and augments "/routing/control-plane-protocols/control-plane-
protocol" from [RFC8349]. Additionally, it references [RFC5586] and
[RFC5884].
<CODE BEGINS> file "ietf-bfd-mpls@2021-10-21.yang"
module ietf-bfd-mpls {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-mpls";
prefix bfd-mpls;
import ietf-bfd-types {
prefix bfd-types;
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
import ietf-bfd {
prefix bfd;
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-routing {
prefix rt;
reference
"RFC 8349: A YANG Data Model for Routing Management
(NMDA Version)";
}
organization
"IETF BFD Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/bfd/>
WG List: <mailto:rtg-bfd@ietf.org>
Editor: Reshad Rahman
<mailto:reshad@yahoo.com>
Editor: Lianshu Zheng
<mailto:veronique_cheng@hotmail.com>
Editor: Mahesh Jethanandani
<mailto:mjethanandani@gmail.com>";
description
"This module contains the YANG definition for BFD parameters for
MPLS LSPs as per RFC 5884.
Copyright (c) 2021 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 9127; see the
RFC itself for full legal notices.";
reference
"RFC 5884: Bidirectional Forwarding Detection (BFD)
for MPLS Label Switched Paths (LSPs)
RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
revision 2021-10-21 {
description
"Initial revision.";
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
/*
* Identity definitions
*/
identity encap-gach {
base bfd-types:encap-type;
description
"BFD with G-ACh encapsulation as per RFC 5586.";
reference
"RFC 5586: MPLS Generic Associated Channel";
}
identity encap-ip-gach {
base bfd-types:encap-type;
description
"BFD with IP and G-ACh encapsulation as per RFC 5586.";
}
/*
* Groupings
*/
grouping encap-cfg {
description
"Configuration for BFD encapsulation.";
leaf encap {
type identityref {
base bfd-types:encap-type;
}
default "bfd-types:encap-ip";
description
"BFD encapsulation.";
}
}
grouping mpls-dest-address {
description
"Destination address as per RFC 5884.";
reference
"RFC 5884: Bidirectional Forwarding Detection (BFD)
for MPLS Label Switched Paths (LSPs)";
leaf mpls-dest-address {
type inet:ip-address;
config false;
description
"Destination address as per RFC 5884.
Needed if IP encapsulation is used.";
}
}
/*
* Augments
*/
augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/bfd:bfd" {
description
"BFD augmentation for MPLS.";
container mpls {
description
"BFD MPLS top-level container.";
uses bfd-types:session-statistics-summary;
container egress {
description
"Egress configuration.";
uses bfd-types:client-cfg-parms;
uses bfd-types:auth-parms;
}
container session-groups {
description
"BFD-over-MPLS session groups.";
list session-group {
key "mpls-fec";
description
"Group of BFD MPLS sessions (for ECMP). A group of
sessions is for one FEC. Each session has a different
field in the UDP/IP header for ECMP.";
leaf mpls-fec {
type inet:ip-prefix;
description
"MPLS FEC.";
}
uses bfd-types:common-cfg-parms;
list sessions {
config false;
description
"The BFD sessions for an MPLS FEC. The local
discriminator is unique for each session in the
group.";
uses bfd-types:all-session;
uses bfd-mpls:mpls-dest-address;
}
}
}
}
}
/*
* Notifications
*/
notification mpls-notification {
description
"Notification for BFD-over-MPLS FEC session state change.
An implementation may rate-limit notifications, e.g., when a
session is continuously changing state.";
uses bfd-types:notification-parms;
leaf mpls-dest-address {
type inet:ip-address;
description
"Destination address as per RFC 5884.
Needed if IP encapsulation is used.";
}
}
}
<CODE ENDS>
3. Data Model Examples
This section presents some simple and illustrative examples of how to
configure BFD.
The examples are represented in XML [W3C.REC-xml-20081126].
3.1. IP Single-Hop
The following is an example configuration for a BFD IP single-hop
session. The desired transmit interval and the required receive
interval are both set to 10 ms.
<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
<interface>
<name>eth0</name>
<type xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">
ianaift:ethernetCsmacd
</type>
</interface>
</interfaces>
<routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
<control-plane-protocols>
<control-plane-protocol>
<type xmlns:bfd-types=
"urn:ietf:params:xml:ns:yang:ietf-bfd-types">
bfd-types:bfdv1
</type>
<name>name:BFD</name>
<bfd xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd">
<ip-sh xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh">
<sessions>
<session>
<interface>eth0</interface>
<dest-addr>2001:db8:0:113::101</dest-addr>
<desired-min-tx-interval>
10000
</desired-min-tx-interval>
<required-min-rx-interval>
10000
</required-min-rx-interval>
</session>
</sessions>
</ip-sh>
</bfd>
</control-plane-protocol>
</control-plane-protocols>
</routing>
</config>
3.2. IP Multihop
The following is an example configuration for a BFD IP multihop
session group. The desired transmit interval and the required
receive interval are both set to 150 ms.
<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
<control-plane-protocols>
<control-plane-protocol>
<type xmlns:bfd-types=
"urn:ietf:params:xml:ns:yang:ietf-bfd-types">
bfd-types:bfdv1
</type>
<name>name:BFD</name>
<bfd xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd">
<ip-mh xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd-ip-mh">
<session-groups>
<session-group>
<source-addr>2001:db8:0:113::103</source-addr>
<dest-addr>2001:db8:0:114::100</dest-addr>
<desired-min-tx-interval>
150000
</desired-min-tx-interval>
<required-min-rx-interval>
150000
</required-min-rx-interval>
<rx-ttl>240</rx-ttl>
</session-group>
</session-groups>
</ip-mh>
</bfd>
</control-plane-protocol>
</control-plane-protocols>
</routing>
</config>
3.3. LAG
The following is an example of BFD configuration for a LAG session.
In this case, an interface named "Bundle-Ether1" of interface type
"ieee8023adLag" has a desired transmit interval and required receive
interval set to 10 ms.
<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
<interface>
<name>Bundle-Ether1</name>
<type xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">
ianaift:ieee8023adLag
</type>
</interface>
</interfaces>
<routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
<control-plane-protocols>
<control-plane-protocol>
<type xmlns:bfd-types=
"urn:ietf:params:xml:ns:yang:ietf-bfd-types">
bfd-types:bfdv1
</type>
<name>name:BFD</name>
<bfd xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd">
<lag xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd-lag">
<sessions>
<session>
<lag-name>Bundle-Ether1</lag-name>
<ipv6-dest-addr>2001:db8:112::16</ipv6-dest-addr>
<desired-min-tx-interval>
100000
</desired-min-tx-interval>
<required-min-rx-interval>
100000
</required-min-rx-interval>
<use-ipv6>true</use-ipv6>
</session>
</sessions>
</lag>
</bfd>
</control-plane-protocol>
</control-plane-protocols>
</routing>
</config>
3.4. MPLS
The following is an example of BFD configured for an MPLS LSP. In
this case, the desired transmit interval and required receive
interval are both set to 250 ms.
<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
<control-plane-protocols>
<control-plane-protocol>
<type xmlns:bfd-types=
"urn:ietf:params:xml:ns:yang:ietf-bfd-types">
bfd-types:bfdv1
</type>
<name>name:BFD</name>
<bfd xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd">
<mpls xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd-mpls">
<session-groups>
<session-group>
<mpls-fec>2001:db8:114::/116</mpls-fec>
<desired-min-tx-interval>
250000
</desired-min-tx-interval>
<required-min-rx-interval>
250000
</required-min-rx-interval>
</session-group>
</session-groups>
</mpls>
</bfd>
</control-plane-protocol>
</control-plane-protocols>
</routing>
</config>
4. Security Considerations
The YANG modules specified in this document define a schema for data
that is designed to be accessed via network management protocols such
as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer
is the secure transport layer, and the mandatory-to-implement secure
transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer
is HTTPS, and the mandatory-to-implement secure transport is TLS
[RFC8446].
The Network Configuration Access Control Model (NACM) [RFC8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content.
There are a number of data nodes defined in these YANG modules that
are writable/creatable/deletable (i.e., config true, which is the
default). These data nodes may be considered sensitive or vulnerable
in some network environments. Write operations (e.g., edit-config)
to these data nodes without proper protection can have a negative
effect on network operations. These are the subtrees and data nodes
and their sensitivity/vulnerability from a write access perspective:
/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh/
sessions:
This list specifies the IP single-hop BFD sessions.
Data nodes "local-multiplier", "desired-min-tx-interval",
"required-min-rx-interval", and "min-interval" all impact the BFD
IP single-hop session. The "source-addr" and "dest-addr" data
nodes can be used to send BFD packets to unwitting recipients.
[RFC5880] describes how BFD mitigates such threats.
Authentication data nodes "key-chain" and "meticulous" impact the
security of the BFD IP single-hop session.
/routing/control-plane-protocols/control-plane-protocol/bfd/ip-mh/
session-group:
This list specifies the IP multihop BFD session groups.
Data nodes "local-multiplier", "desired-min-tx-interval",
"required-min-rx-interval", and "min-interval" all impact the BFD
IP multihop session. The "source-addr" and "dest-addr" data nodes
can be used to send BFD packets to unwitting recipients.
[RFC5880] describes how BFD mitigates such threats.
Authentication data nodes "key-chain" and "meticulous" impact the
security of the BFD IP multihop session.
/routing/control-plane-protocols/control-plane-protocol/bfd/lag/
sessions:
This list specifies the BFD sessions over a LAG.
Data nodes "local-multiplier", "desired-min-tx-interval",
"required-min-rx-interval", and "min-interval" all impact the BFD-
over-LAG session. The "ipv4-dest-addr" and "ipv6-dest-addr" data
nodes can be used to send BFD packets to unwitting recipients.
[RFC5880] describes how BFD mitigates such threats.
Authentication data nodes "key-chain" and "meticulous" impact the
security of the BFD-over-LAG session.
/routing/control-plane-protocols/control-plane-protocol/bfd/mpls/
session-group:
This list specifies the session groups for BFD over MPLS.
Data nodes "local-multiplier", "desired-min-tx-interval",
"required-min-rx-interval", and "min-interval" all impact the BFD-
over-MPLS-LSPs session. Authentication data nodes "key-chain" and
"meticulous" impact the security of the BFD-over-MPLS-LSPs
session.
/routing/control-plane-protocols/control-plane-protocol/bfd/mpls/
egress:
Data nodes "local-multiplier", "desired-min-tx-interval",
"required-min-rx-interval", and "min-interval" all impact the BFD-
over-MPLS-LSPs sessions for which this device is an MPLS LSP
egress node. Authentication data nodes "key-chain" and
"meticulous" impact the security of the BFD-over-MPLS-LSPs
sessions for which this device is an MPLS LSP egress node.
The YANG modules have writable data nodes that can be used for the
creation of BFD sessions and the modification of BFD session
parameters. The system should "police" the creation of BFD sessions
to prevent new sessions from causing existing BFD sessions to fail.
In the case of BFD session modification, the BFD protocol has
mechanisms in place that allow for in-service modification.
When BFD clients are used to modify BFD configuration (as described
in Section 2.1), the BFD clients need to be included in an analysis
of the security properties of the system that uses BFD (e.g., when
considering the authentication and authorization of control actions).
In many cases, BFD is not the most vulnerable portion of such a
composite system, since BFD is limited to generating well-defined
traffic at a fixed rate on a given path; in the case of an IGP acting
as a BFD client, attacking the IGP could cause more broad-scale
disruption than would (de)configuring a BFD session.
Some of the readable data nodes in these YANG modules may be
considered sensitive or vulnerable in some network environments. It
is thus important to control read access (e.g., via get, get-config,
or notification) to these data nodes. These are the subtrees and
data nodes and their sensitivity/vulnerability from a read access
perspective:
/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh/
summary:
Access to this information discloses the number of BFD IP single-
hop sessions that are in the "up", "down", or "admin-down" state.
The counters include BFD sessions for which the user does not have
read access.
/routing/control-plane-protocols/control-plane-protocol/bfd/ip-
sh/sessions/session/:
Access to data nodes "local-discriminator" and "remote-
discriminator" (combined with the data nodes in the authentication
container) provides the ability to spoof BFD IP single-hop
packets.
/routing/control-plane-protocols/control-plane-protocol/bfd/ip-mh/
summary:
Access to this information discloses the number of BFD IP multihop
sessions that are in the "up", "down", or "admin-down" state. The
counters include BFD sessions for which the user does not have
read access.
/routing/control-plane-protocols/control-plane-protocol/bfd/ip-mh/
session-groups/session-group/sessions:
Access to data nodes "local-discriminator" and "remote-
discriminator" (combined with the data nodes in the session
group's authentication container) provides the ability to spoof
BFD IP multihop packets.
/routing/control-plane-protocols/control-plane-protocol/bfd/lag/
micro-bfd-ipv4-session-statistics/summary:
Access to this information discloses the number of micro-BFD IPv4
LAG sessions that are in the "up", "down", or "admin-down" state.
The counters include BFD sessions for which the user does not have
read access.
/routing/control-plane-protocols/control-plane-
protocol/bfd/lag/sessions/session/member-links/member-link/micro-
bfd-ipv4:
Access to data nodes "local-discriminator" and "remote-
discriminator" (combined with the data nodes in the session's
authentication container) provides the ability to spoof BFD IPv4
LAG packets.
/routing/control-plane-protocols/control-plane-protocol/bfd/lag/
micro-bfd-ipv6-session-statistics/summary:
Access to this information discloses the number of micro-BFD IPv6
LAG sessions that are in the "up", "down", or "admin-down" state.
The counters include BFD sessions for which the user does not have
read access.
/routing/control-plane-protocols/control-plane-
protocol/bfd/lag/sessions/session/member-links/member-link/micro-
bfd-ipv6:
Access to data nodes "local-discriminator" and "remote-
discriminator" (combined with the data nodes in the session's
authentication container) provides the ability to spoof BFD IPv6
LAG packets.
/routing/control-plane-protocols/control-plane-protocol/bfd/mpls/
summary:
Access to this information discloses the number of BFD sessions
over MPLS LSPs that are in the "up", "down", or "admin-down"
state. The counters include BFD sessions for which the user does
not have read access.
/routing/control-plane-protocols/control-plane-protocol/bfd/mpls/
session-groups/session-group/sessions:
Access to data nodes "local-discriminator" and "remote-
discriminator" (combined with the data nodes in the session
group's authentication container) provides the ability to spoof
BFD-over-MPLS-LSPs packets.
This document does not define any RPC operations.
5. IANA Considerations
IANA has registered the following namespace URIs in the "IETF XML
Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:iana-bfd-types
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-bfd-types
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-bfd
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-bfd-ip-mh
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-bfd-lag
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-bfd-mpls
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
IANA has registered the following YANG modules in the "YANG Module
Names" registry [RFC6020]:
Name: iana-bfd-types
Namespace: urn:ietf:params:xml:ns:yang:iana-bfd-types
Prefix: iana-bfd-types
Reference: RFC 9127
Name: ietf-bfd-types
Namespace: urn:ietf:params:xml:ns:yang:ietf-bfd-types
Prefix: bfd-types
Reference: RFC 9127
Name: ietf-bfd
Namespace: urn:ietf:params:xml:ns:yang:ietf-bfd
Prefix: bfd
Reference: RFC 9127
Name: ietf-bfd-ip-sh
Namespace: urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh
Prefix: bfd-ip-sh
Reference: RFC 9127
Name: ietf-bfd-ip-mh
Namespace: urn:ietf:params:xml:ns:yang:ietf-bfd-ip-mh
Prefix: bfd-ip-mh
Reference: RFC 9127
Name: ietf-bfd-lag
Namespace: urn:ietf:params:xml:ns:yang:ietf-bfd-lag
Prefix: bfd-lag
Reference: RFC 9127
Name: ietf-bfd-mpls
Namespace: urn:ietf:params:xml:ns:yang:ietf-bfd-mpls
Prefix: bfd-mpls
Reference: RFC 9127
5.1. IANA-Maintained "iana-bfd-types" Module
This document defines the initial version of the IANA-maintained
"iana-bfd-types" YANG module.
The "iana-bfd-types" YANG module mirrors the "BFD Diagnostic Codes"
and "BFD Authentication Types" registries at
<https://www.iana.org/assignments/bfd-parameters/>. Whenever these
registries change, IANA must update the "iana-bfd-types" YANG module.
6. References
6.1. Normative References
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009,
<https://www.rfc-editor.org/info/rfc5586>.
[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>.
[RFC5882] Katz, D. and D. Ward, "Generic Application of
Bidirectional Forwarding Detection (BFD)", RFC 5882,
DOI 10.17487/RFC5882, June 2010,
<https://www.rfc-editor.org/info/rfc5882>.
[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>.
[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>.
[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>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[RFC7130] Bhatia, M., Ed., Chen, M., Ed., Boutros, S., Ed.,
Binderberger, M., Ed., and J. Haas, Ed., "Bidirectional
Forwarding Detection (BFD) on Link Aggregation Group (LAG)
Interfaces", RFC 7130, DOI 10.17487/RFC7130, February
2014, <https://www.rfc-editor.org/info/rfc7130>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8177] Lindem, A., Ed., Qu, Y., Yeung, D., Chen, I., and J.
Zhang, "YANG Data Model for Key Chains", RFC 8177,
DOI 10.17487/RFC8177, June 2017,
<https://www.rfc-editor.org/info/rfc8177>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.
[RFC8343] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
<https://www.rfc-editor.org/info/rfc8343>.
[RFC8344] Bjorklund, M., "A YANG Data Model for IP Management",
RFC 8344, DOI 10.17487/RFC8344, March 2018,
<https://www.rfc-editor.org/info/rfc8344>.
[RFC8349] Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
Routing Management (NMDA Version)", RFC 8349,
DOI 10.17487/RFC8349, March 2018,
<https://www.rfc-editor.org/info/rfc8349>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC8960] Saad, T., Raza, K., Gandhi, R., Liu, X., and V. Beeram, "A
YANG Data Model for MPLS Base", RFC 8960,
DOI 10.17487/RFC8960, December 2020,
<https://www.rfc-editor.org/info/rfc8960>.
6.2. Informative References
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>.
[RFC6428] Allan, D., Ed., Swallow, G., Ed., and J. Drake, Ed.,
"Proactive Connectivity Verification, Continuity Check,
and Remote Defect Indication for the MPLS Transport
Profile", RFC 6428, DOI 10.17487/RFC6428, November 2011,
<https://www.rfc-editor.org/info/rfc6428>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
[RFC8529] Berger, L., Hopps, C., Lindem, A., Bogdanovic, D., and X.
Liu, "YANG Data Model for Network Instances", RFC 8529,
DOI 10.17487/RFC8529, March 2019,
<https://www.rfc-editor.org/info/rfc8529>.
[RFC8530] Berger, L., Hopps, C., Lindem, A., Bogdanovic, D., and X.
Liu, "YANG Model for Logical Network Elements", RFC 8530,
DOI 10.17487/RFC8530, March 2019,
<https://www.rfc-editor.org/info/rfc8530>.
[RFC8532] Kumar, D., Wang, Z., Wu, Q., Ed., Rahman, R., and S.
Raghavan, "Generic YANG Data Model for the Management of
Operations, Administration, and Maintenance (OAM)
Protocols That Use Connectionless Communications",
RFC 8532, DOI 10.17487/RFC8532, April 2019,
<https://www.rfc-editor.org/info/rfc8532>.
[W3C.REC-xml-20081126]
Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and
F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth
Edition)", World Wide Web Consortium Recommendation REC-
xml-20081126, November 2008,
<https://www.w3.org/TR/2008/REC-xml-20081126>.
Appendix A. Echo Function Configuration Example
As mentioned in Section 2.1.2, the mechanism to start and stop the
Echo function, as defined in [RFC5880] and discussed in [RFC5881], is
implementation specific. In this appendix, we provide an example of
how the Echo function can be implemented via configuration.
module: example-bfd-echo
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh
/bfd-ip-sh:sessions:
+--rw echo {bfd-types:echo-mode}?
+--rw desired-min-echo-tx-interval? uint32
+--rw required-min-echo-rx-interval? uint32
A.1. Example YANG Module for BFD Echo Function Configuration
This appendix provides an example YANG module for configuration of
the BFD Echo function. It imports and augments "/routing/control-
plane-protocols/control-plane-protocol" from [RFC8349], and it
references [RFC5880].
module example-bfd-echo {
namespace "tag:example.com,2021:example-bfd-echo";
prefix example-bfd-echo;
import ietf-bfd-types {
prefix bfd-types;
}
import ietf-bfd {
prefix bfd;
}
import ietf-bfd-ip-sh {
prefix bfd-ip-sh;
}
import ietf-routing {
prefix rt;
}
organization
"IETF BFD Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/bfd/>
WG List: <mailto:rtg-bfd@ietf.org>
Editor: Reshad Rahman
<mailto:reshad@yahoo.com>
Editor: Lianshu Zheng
<mailto:veronique_cheng@hotmail.com>
Editor: Mahesh Jethanandani
<mailto:mjethanandani@gmail.com>";
description
"This module contains an example YANG augmentation for
configuration of the BFD Echo function.
Copyright (c) 2021 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 9127; see the
RFC itself for full legal notices.";
revision 2021-09-03 {
description
"Initial revision.";
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
/*
* Groupings
*/
grouping echo-cfg-parms {
description
"BFD grouping for Echo configuration parameters.";
leaf desired-min-echo-tx-interval {
type uint32;
units "microseconds";
default "0";
description
"This is the minimum interval that the local system would
like to use when transmitting BFD Echo packets. If 0,
the Echo function as defined in BFD (RFC 5880) is
disabled.";
}
leaf required-min-echo-rx-interval {
type uint32;
units "microseconds";
default "0";
description
"This is the Required Min Echo RX Interval as defined in BFD
(RFC 5880).";
}
}
augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh/"
+ "bfd-ip-sh:sessions" {
description
"Augmentation for the BFD Echo function.";
container echo {
if-feature "bfd-types:echo-mode";
description
"BFD Echo function container.";
uses echo-cfg-parms;
}
}
}
Acknowledgments
We would like to thank Nobo Akiya and Jeff Haas for their
encouragement on this work. We would also like to thank Tom Petch
for his comments on the document. We would also like to thank Acee
Lindem for his guidance. Thanks also to Jürgen Schönwälder, who was
instrumental in improving the YANG modules.
Authors' Addresses
Reshad Rahman (editor)
Canada
Email: reshad@yahoo.com
Lianshu Zheng (editor)
Huawei Technologies
China
Email: veronique_cheng@hotmail.com
Mahesh Jethanandani (editor)
Xoriant Corporation
1248 Reamwood Ave
Sunnyvale, California 94089
United States of America
Email: mjethanandani@gmail.com
Santosh Pallagatti
VMware
India
Email: santosh.pallagatti@gmail.com
Greg Mirsky
Ericsson
Email: gregimirsky@gmail.com
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PROBLEMBFD detects liveness of many kinds of forwarding paths, but there was no standard data model to configure BFD or read its state, and no single key identifies a BFD session across path types.
MECHANISMThe RFC defines a family of NMDA-conformant YANG modules: shared types, a common bfd container, and one module each for IP single-hop, IP multihop, LAG and MPLS LSPs.
WHY IT MATTERSOperators and tools get a common way to configure sessions, read per-session state and statistics, and receive notifications. The RFC is a Proposed Standard and is updated by RFC 9314.
§1Introduction
This document defines a YANG data model that can be used to configure and manage Bidirectional Forwarding Detection (BFD) of RFC 5880. BFD is a network protocol used for liveness detection of arbitrary paths between systems. The RFC lists the types of path over which BFD runs: two systems directly connected over IP, which is BFD over single-hop IP for IPv4 and IPv6 as in RFC 5881; two systems connected over multiple hops, as in RFC 5883; two systems connected over MPLS label switched paths, as in RFC 5884; and two systems connected over a Link Aggregation Group interface, as in RFC 7130. Two systems connected over pseudowires, which is Virtual Circuit Connectivity Verification of RFC 5885, is not addressed by this document.
BFD typically does not operate on its own. Various control protocols, also known as BFD clients, use the services BFD provides for their own operation, as described in RFC 5882. The obvious candidates are the protocols that have no hellos of their own to detect failures, such as static routes, and the routing protocols whose hellos do not support sub-second failure detection, such as OSPF and IS-IS.
The YANG modules in this document conform to the Network Management Datastore Architecture of RFC 8342, so the data models do not have separate top-level or sibling containers for configuration data and operational state data.
BFD is a protocol that two ends of a path use to check that the path is still working, and to notice a failure quickly. It is used on its own and also by other protocols that need to know about failures. This RFC defines the data model a management system uses to configure it and to read its state, in the same way other YANG models are written.
§2How the Model Is Split
Because BFD is used for liveness detection of various forwarding paths, there is no uniform key that identifies a BFD session, so the BFD data model is split into multiple YANG modules, each corresponding to one type of forwarding path. BFD for IP single-hop is in one module and BFD for MPLS in another. The main difference between the modules is how a BFD session is uniquely identified, that is, the key for the list that holds the sessions for that forwarding path. To avoid duplicating BFD definitions, the document defines common types and groupings that all the modules use.
A new control-plane protocol, bfdv1, is defined, and a bfd container is created under control-plane-protocol as specified in the YANG data model for routing management of RFC 8349. Four modules augment that container with their own information: ietf-bfd-ip-sh adds the ip-sh container for sessions over IP single-hop, ietf-bfd-ip-mh adds ip-mh for sessions over IP multihop, ietf-bfd-lag adds lag for sessions over a LAG, and ietf-bfd-mpls adds mpls for BFD over MPLS LSPs.
BFD can operate at the network device level, in logical network elements as described in RFC 8530, and in network instances as described in RFC 8529. At the device level the model is used as it is; in a logical network element or a network instance, the model augments the mounted routing model of that instance.
There is no single way to name a BFD session, because the session is identified by different things depending on the kind of path it runs over. So the model is split into four modules, one per kind of path, and they all add their part to the same BFD container in the routing configuration. The definitions they share, such as the timers, live in a common module so they are written once.
- control-plane-protocol (bfdv1)
- bfd The container augmented by the four path-type modules.
- ip-sh
- ip-mh
- lag
- mpls
- bfd The container augmented by the four path-type modules.
§2.1The Configuration Model
The configuration model consists mainly of the parameters specified in BFD itself, for example the desired minimum transmit interval, the required minimum receive interval and the detection multiplier.
Some implementations keep the configuration of a BFD session under the client that uses it, for example under a routing application such as OSPF, IS-IS or BGP. Others centralise the configuration of BFD sessions under BFD itself, outside the several clients. The parameters of most interest to a client are those related to the multiplier and the intervals, because they affect how quickly the client converges after a failure. Other parameters, such as BFD authentication, are not specific to the client's requirements.
Configuration of BFD for all clients should be centralised, but that is a problem for clients that discover their peers automatically. An IGP does not have the peer address configured; the IGP is enabled on an interface and its peers are discovered, so an operator would first have to find the peer addresses, and configuration would have to be added every time a new peer appeared. To avoid this, the document defines a grouping called client-cfg-parms, which lets BFD clients configure BFD. An IGP can then hold the configuration for the sessions it needs: when a new peer is discovered the IGP creates a session to it, and when a peer goes away it removes the session. How the sessions are created and removed is outside the scope of the document, but it would typically use an API implemented by the BFD module. For clients that create sessions through their own configuration, the authentication parameters are still specified in BFD.
The basic configuration parameters are the detection time multiplier, the desired minimum transmit interval and the required minimum receive interval. Although BFD allows different values for the transmit and receive intervals, some implementations let the user specify one interval for both. The model supports that with a choice between min-interval, used for both, and desired-min-tx-interval with required-min-rx-interval, through the grouping base-cfg-parms that the modules for the various forwarding paths use.
For BFD authentication there is a key-chain reference, which points at the key chain model of RFC 8177, where the keys, the cryptographic algorithms and the key lifetime are all defined, and a meticulous flag that enables the meticulous mode of BFD.
The configuration holds the three numbers that decide how fast a failure is noticed: the multiplier, the interval at which packets are sent, and the interval at which packets are expected. A single interval can be set for both directions, or the two can be set separately. Authentication is configured by pointing at a key chain, which holds the keys themselves elsewhere, and by a flag that asks for the stricter mode of BFD.
- local-multiplierThe detection time multiplier from the BFD specification.
- desired-min-tx-intervalThe shortest interval at which the system wants to send control packets.
- required-min-rx-intervalThe shortest interval at which the system is willing to receive control packets.
- min-intervalA single interval used for both sending and receiving.
- key-chainA reference to a key chain, where the keys and their lifetime are defined.
- meticulousEnables the meticulous mode of BFD.
§2.1.2One Module for Each Kind of Path
For single-hop IP, the ip-sh node holds a list of sessions, each uniquely identified by the interface and the destination address pair, and uses the common configuration parameters. The node also holds a list of interfaces, used to specify the authentication parameters for sessions that BFD clients create. Since RFC 5880 and RFC 5881 do not say whether the Echo function operates continuously or on demand, the mechanism for starting and stopping it is implementation specific and is done by augmentation: either by configuration, which suits a continuous Echo function, or by an RPC, which suits an on-demand one.
For multihop IP, the ip-mh node holds session groups, because there can be several multihop sessions between a source and a destination when there are multiple paths. The key of a session group is the source address, belonging to the local system, and the destination address, belonging to the remote system. Two more parameters are provided: tx-ttl, the TTL of outgoing BFD control packets, and rx-ttl, the minimum TTL of incoming ones.
For MPLS label switched paths, the document addresses LSPs whose forwarding equivalence class is an IP address. The mpls node holds sessions uniquely identified by an IP prefix, and, again because there can be several paths, sets of them are grouped into session groups. These LSPs are unidirectional, so the egress node has no LSP configuration, and the BFD parameters for the egress node are added under mpls.
For link aggregation groups, configuring BFD on a LAG means having micro-BFD sessions on each member link. The BFD parameters are an attribute of the LAG, so they should sit under the LAG, but there is no LAG YANG data model to augment, so a lag node is added to the bfd node. The configuration is per LAG, with the destination IP address of the micro-BFD sessions given per LAG and per address family, for IPv4 and for IPv6.
Each kind of path is named differently. A single-hop session is identified by the interface and the address at the far end. A multihop session group is identified by the two addresses, and it may contain several sessions when there is more than one path between them. An MPLS session is identified by the prefix of its forwarding equivalence class. A LAG session is identified by the name of the group and the address family, because BFD runs separately on each member link.
| Path type | Module | What identifies a session |
|---|---|---|
| IP single-hop THIS RFC | ietf-bfd-ip-sh | The interface and the destination address |
| IP multihop THIS RFC | ietf-bfd-ip-mh | The source and destination addresses of the session group |
| MPLS LSP THIS RFC | ietf-bfd-mpls | The IP prefix of the forwarding equivalence class |
| LAG THIS RFC | ietf-bfd-lag | The name of the LAG and the address family |
§2.2The Operational State Model
The operational state model holds both the overall statistics for the BFD sessions running on the device and the per-session operational information. The overall statistics, such as the number of sessions and the number that are up, are available globally under the bfd node and also per type of forwarding path.
For each session, three categories of operational state data are shown. The first holds fundamental information about the session, such as the local discriminator, the remote discriminator and the ability to support Demand mode. The second holds the session-running information, for example the remote BFD state and the diagnostic code received, and the actual transmit interval between the control packets, which may differ from the configured desired minimum transmit interval, along with the actual receive interval and the actual transmit interval of the Echo packets. The third holds the detailed statistics for the session, for example when the session last moved up or down and how long it has been in that state.
For some path types there may be more than one session on the virtual path to the destination. With IP multihop and MPLS LSPs there can be several BFD sessions from the source to the same destination, to test the various equal-cost paths to it. This is represented by having multiple sessions under each session group.
The state model gives the totals first, then the detail of each session. For each session it reports what it is, how it is running now, and how it has been running: when the session last came up or went down and how long it has stayed that way. The intervals reported are the ones in use, which can differ from the ones that were configured.
§2.3Notifications
The model defines notifications to tell end users about important events detected while the protocol runs. The local discriminator identifies the corresponding BFD session on the local system and the remote discriminator identifies the session on the remote system. The notifications also carry more important details about the sessions, for example the new state, the time in the previous state, the network instance, and the reason that the state changed. The notifications are defined for each type of forwarding path, and they use groupings for the common information.
The document defines no RPC operations.
When a session changes state, the model defines a notification to report it, with the reason for the change and how long the session was in its previous state. There are no remote procedure calls in this model, so nothing in it asks the device to do a one-off action.
§3Example Configurations
The document gives four examples, written in XML. The first is a BFD IP single-hop session whose desired transmit interval and required receive interval are both 10 ms, keyed by the interface eth0 and the destination address 2001:db8:0:113::101, with both intervals set to 10000.
<bfd xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd">
<ip-sh xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh">
<sessions>
<session>
<interface>eth0</interface>
<dest-addr>2001:db8:0:113::101</dest-addr>
<desired-min-tx-interval>10000</desired-min-tx-interval>
<required-min-rx-interval>10000</required-min-rx-interval>
</session>
</sessions>
</ip-sh>
</bfd>The second is a multihop session group with both intervals set to 150 ms and an rx-ttl of 240, between the source address 2001:db8:0:113::103 and the destination address 2001:db8:0:114::100.
The third is a LAG session on the interface Bundle-Ether1 of type ieee8023adLag, with the desired transmit and required receive intervals both set to 100000 and the IPv6 destination address 2001:db8:112::16.
The fourth is an MPLS session group for the forwarding equivalence class 2001:db8:114::/116, with both intervals set to 250 ms.
The examples show how a session is written in the XML form that a management system sends. A single-hop session names the interface and the address at the far end, a multihop session names the two addresses and a minimum TTL, a LAG session names the group and the address family, and an MPLS session names the prefix.
BFD over IP single-hop
<bfd xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd">
<ip-sh xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh">
<sessions>
<session>
<interface>eth0</interface>
<dest-addr>2001:db8:0:113::101</dest-addr>
<desired-min-tx-interval>10000</desired-min-tx-interval>
<required-min-rx-interval>10000</required-min-rx-interval>
</session>
</sessions>
</ip-sh>
</bfd>§4Security Considerations
The YANG modules define a schema for data that is designed to be accessed through network management protocols such as NETCONF or RESTCONF. The lowest NETCONF layer is the secure transport layer, where the mandatory secure transport is Secure Shell, and the lowest RESTCONF layer is HTTPS, where the mandatory secure transport is TLS.
The Network Configuration Access Control Model of RFC 8341 provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of the available operations and content.
A number of the data nodes are writable, and may be considered sensitive or vulnerable in some environments. Write operations to them without proper protection can have a negative effect on network operations. The RFC lists the sensitive nodes: in the single-hop session list, the multiplier and the intervals affect the session, the source and destination addresses can be used to send BFD packets to unwitting recipients, and the key chain and meticulous nodes affect the security of the session; the same applies to the multihop session groups, the LAG sessions and the MPLS session groups. RFC 5880 describes how BFD mitigates the threat of sending packets to unwitting recipients.
The data is read and written over the management protocols, so the session must be protected in transit and access to it must be controlled by the usual access control model. Some of the writable values are worth guarding: the timers change how the sessions behave, and the addresses could be used to aim BFD packets at hosts that are not expecting them.
§9References
[RFC5880]RFC 5880Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, June 2010.June 2010[RFC5881]RFC 5881Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881.June 2010[RFC5883]RFC 5883Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for Multihop Paths", RFC 5883, June 2010.June 2010[RFC5884]RFC 5884Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, "Bidirectional Forwarding Detection (BFD) for MPLS Label Switched Paths (LSPs)", RFC 5884, June 2010.June 2010[RFC7130]RFC 7130Bhatia, M., Ed., Chen, M., Ed., Boutros, S., Ed., Binderberger, M., Ed., and J. Haas, Ed., "Bidirectional Forwarding Detection (BFD) on Link Aggregation Group (LAG) Interfaces", RFC 7130, February 2014.February 2014[RFC8342]RFC 8342Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., and R. Wilton, "Network Management Datastore Architecture (NMDA)", RFC 8342, March 2018.March 2018