draft-ietf-bfd-multipoint-12.txt   draft-ietf-bfd-multipoint-13.txt 
Internet Engineering Task Force D. Katz Internet Engineering Task Force D. Katz
Internet-Draft Juniper Networks Internet-Draft Juniper Networks
Intended status: Standards Track D. Ward Updates: 5880, 7880 (if approved) D. Ward
Expires: June 22, 2018 Cisco Systems Intended status: Standards Track Cisco Systems
S. Pallagatti, Ed. Expires: August 3, 2018 S. Pallagatti, Ed.
Individual contributor Individual contributor
G. Mirsky, Ed. G. Mirsky, Ed.
ZTE Corp. ZTE Corp.
December 19, 2017 January 30, 2018
BFD for Multipoint Networks BFD for Multipoint Networks
draft-ietf-bfd-multipoint-12 draft-ietf-bfd-multipoint-13
Abstract Abstract
This document describes extensions to the Bidirectional Forwarding This document describes extensions to the Bidirectional Forwarding
Detection (BFD) protocol for its use in multipoint and multicast Detection (BFD) protocol for its use in multipoint and multicast
networks. Comments on this draft should be directed to rtg- networks.
bfd@ietf.org.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
Status of This Memo Status of This Memo
skipping to change at page 1, line 46 skipping to change at page 1, line 45
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 22, 2018. This Internet-Draft will expire on August 3, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 4 4. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Multipoint BFD Control Packets . . . . . . . . . . . . . 4 4.1. Multipoint BFD Control Packets . . . . . . . . . . . . . 4
4.2. Session Model . . . . . . . . . . . . . . . . . . . . . . 5 4.2. Session Model . . . . . . . . . . . . . . . . . . . . . . 4
4.3. Session Failure Semantics . . . . . . . . . . . . . . . . 5 4.3. Session Failure Semantics . . . . . . . . . . . . . . . . 5
4.4. State Variables . . . . . . . . . . . . . . . . . . . . . 5 4.4. State Variables . . . . . . . . . . . . . . . . . . . . . 5
4.4.1. New State Variables . . . . . . . . . . . . . . . . . 5 4.4.1. New State Variable Values . . . . . . . . . . . . . . 5
4.4.2. State Variable Initialization and Maintenance . . . . 6 4.4.2. State Variable Initialization and Maintenance . . . . 6
4.5. State Machine . . . . . . . . . . . . . . . . . . . . . . 6 4.5. State Machine . . . . . . . . . . . . . . . . . . . . . . 6
4.6. Session Establishment . . . . . . . . . . . . . . . . . . 7 4.6. Session Establishment . . . . . . . . . . . . . . . . . . 6
4.7. Discriminators and Packet Demultiplexing . . . . . . . . 7 4.7. Discriminators and Packet Demultiplexing . . . . . . . . 7
4.8. Packet consumption on tails . . . . . . . . . . . . . . . 8 4.8. Packet consumption on tails . . . . . . . . . . . . . . . 7
4.9. Bringing Up and Shutting Down Multipoint BFD Service . . 8 4.9. Bringing Up and Shutting Down Multipoint BFD Service . . 8
4.10. Timer Manipulation . . . . . . . . . . . . . . . . . . . 9 4.10. Timer Manipulation . . . . . . . . . . . . . . . . . . . 8
4.11. Detection Times . . . . . . . . . . . . . . . . . . . . . 9 4.11. Detection Times . . . . . . . . . . . . . . . . . . . . . 9
4.12. State Maintenance for Down/AdminDown Sessions . . . . . . 9 4.12. State Maintenance for Down/AdminDown Sessions . . . . . . 9
4.12.1. MultipointHead Sessions . . . . . . . . . . . . . . 10 4.12.1. MultipointHead Sessions . . . . . . . . . . . . . . 9
4.12.2. MultipointTail Sessions . . . . . . . . . . . . . . 10 4.12.2. MultipointTail Sessions . . . . . . . . . . . . . . 9
4.13. Base Specification Text Replacement . . . . . . . . . . . 10 4.13. Base Specification Text Replacement . . . . . . . . . . . 10
4.13.1. Reception of BFD Control Packets . . . . . . . . . . 10 4.13.1. Reception of BFD Control Packets . . . . . . . . . . 10
4.13.2. Demultiplexing BFD Control Packets . . . . . . . . . 13 4.13.2. Demultiplexing BFD Control Packets . . . . . . . . . 12
4.13.3. Transmitting BFD Control Packets . . . . . . . . . . 14 4.13.3. Transmitting BFD Control Packets . . . . . . . . . . 13
5. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 16 5. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 16
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 17 7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
10. Normative References . . . . . . . . . . . . . . . . . . . . 17 10. Normative References . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
The Bidirectional Forwarding Detection protocol [RFC5880] specifies a The Bidirectional Forwarding Detection protocol [RFC5880] specifies a
method for verifying unicast connectivity between a pair of systems. method for verifying unicast connectivity between a pair of systems.
This document defines a method for using BFD to provide verification This document defines a method for using BFD to provide verification
of multipoint or multicast connectivity between a multipoint sender of multipoint or multicast connectivity between a multipoint sender
(the "head") and a set of one or more multipoint receivers (the (the "head") and a set of one or more multipoint receivers (the
"tails"). "tails").
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As an option, the tail may notify the head of the lack of multipoint As an option, the tail may notify the head of the lack of multipoint
connectivity. Details of tail notification to head are outside the connectivity. Details of tail notification to head are outside the
scope of this document. scope of this document.
Throughout this document, the term "multipoint" is defined as a Throughout this document, the term "multipoint" is defined as a
mechanism by which one or more systems receive packets sent by a mechanism by which one or more systems receive packets sent by a
single sender. This specifically includes such things as IP single sender. This specifically includes such things as IP
multicast and point-to-multipoint MPLS. multicast and point-to-multipoint MPLS.
Term "connectivity" in this document is not being used in context of Term "connectivity" in this document is not being used in the context
connectivity verification in transport network but as an alternative of connectivity verification in transport network but as an
to "continuity", i.e. existence of a path between the sender and the alternative to "continuity", i.e. existence of a path between the
receiver. sender and the receiver.
This document effectively modifies and adds to the base BFD This document effectively modifies and adds to the base BFD
specification. It is the intention of the authors to fold these specification [RFC5880].
extensions into the base specification at the appropriate time.
2. Goals 2. Goals
The primary goal of this mechanism is to allow tails to rapidly The primary goal of this mechanism is to allow tails to rapidly
detect the fact that multipoint connectivity from the head has detect the fact that multipoint connectivity from the head has
failed. failed.
Another goal is for the mechanism to work on any multicast or Another goal is for the mechanism to work on any multicast
multipoint medium. technology.
A further goal is to support multiple, overlapping multipoint paths,
as well as multipoint paths with multiple heads, and to allow point-
to-point BFD sessions to operate simultaneously among the systems
participating in Multipoint BFD.
A final goal is to integrate multipoint operation into the base A further goal is to support multiple, overlapping point-to-
specification in such a way as to make it relatively easy to support multipoint paths, as well as multipoint-to-multipoint paths, and to
both multipoint and point-to-point operation in a single allow point-to-point BFD sessions to operate simultaneously among the
implementation. systems participating in Multipoint BFD.
It is a non-goal for this protocol to verify point-to-point bi- It is not a goal for this protocol to verify point-to-point bi-
directional connectivity between the head and any tails. This can be directional connectivity between the head and any tail. This can be
done independently (and with no penalty in protocol overhead) by done independently (and with no penalty in protocol overhead) by
using point-to-point BFD. using point-to-point BFD.
3. Overview 3. Overview
The heart of this protocol is the periodic transmission of BFD The heart of this protocol is the periodic transmission of BFD
Control packets along a multipoint path, from the head to all tails Control packets along a multipoint path, from the head to all tails
on the tree. The contents of the BFD packets provide the means for on the tree. The contents of the BFD packets provide the means for
the tails to calculate the detection time for path failure. If no the tails to calculate the detection time for path failure. If no
BFD Control packets are received by a tail for a detection time, the BFD Control packets are received by a tail for a detection time, the
tail declares the path to have failed. For some applications this is tail declares the path to have failed. For some applications this is
the only mechanism necessary; the head can remain ignorant of the the only mechanism necessary; the head can remain ignorant of the
tails. tails.
Head may wish to be alerted to the tails' connectivity (or lack A head may wish to be alerted to the tails' connectivity (or lack
thereof). Details of how head keeps track of tails and how tails thereof). Details of how the head keeps track of tails and how tails
alert it's connectivity to head are outside scope of this document. alert their connectivity to the head are outside scope of this
document.
Although this document describes a single head and a set of tails Although this document describes a single head and a set of tails
spanned by a single multipoint path, the protocol is capable of spanned by a single multipoint path, the protocol is capable of
supporting (and discriminating between) more than one multipoint path supporting (and discriminating between) more than one multipoint path
at both heads and tails. Furthermore, the same head and tail may at both heads and tails. Furthermore, the same head and tail may
share multiple multipoint paths, and a multipoint path may have share multiple multipoint paths, and a multipoint path may have
multiple heads. multiple heads.
4. Protocol Details 4. Protocol Details
This section describes the operation of Multipoint BFD in detail. This section describes the operation of Multipoint BFD in detail.
4.1. Multipoint BFD Control Packets 4.1. Multipoint BFD Control Packets
Multipoint BFD Control packets (packets sent by the head over a Multipoint BFD Control packets (packets sent by the head over a
multipoint path) are explicitly marked as such, via the setting of multipoint path) are explicitly marked as such, via the setting of
the M bit. This means that Multipoint BFD does not depend on the the M bit [RFC5880]. This means that Multipoint BFD does not depend
recipient of a packet to know whether the packet was received over a on the recipient of a packet to know whether the packet was received
multipoint path. This can be useful in scenarios where this over a multipoint path. This can be useful in scenarios where this
information may not be available to the recipient. information may not be available to the recipient.
4.2. Session Model 4.2. Session Model
Multipoint BFD is modeled as a set of sessions of different types. Multipoint BFD is modeled as a set of sessions of different types.
The elements of procedure differ slightly for each type. The elements of procedure differ slightly for each type.
Point-to-point sessions, as described in [RFC5880], are of type Point-to-point sessions, as described in [RFC5880], are of type
PointToPoint. PointToPoint.
The head has a session of type MultipointHead that is bound to a The head has a session of type MultipointHead, as defined in
multipoint path. Multipoint BFD Control packets are sent by this Section 4.4.1, that is bound to a multipoint path. Multipoint BFD
session over the multipoint path, and no BFD Control packets are Control packets are sent by this session over the multipoint path,
received by it. and no BFD Control packets are received by it.
Each tail has a session of type MultipointTail associated with a Each tail has a session of type MultipointTail, as defined in
multipoint path. These sessions receive BFD Control packets from the Section 4.4.1, associated with a multipoint path. These sessions
head over multipoint path. receive BFD Control packets from the head over the multipoint path.
4.3. Session Failure Semantics 4.3. Session Failure Semantics
The semantics of session failure are subtle enough to warrant further The semantics of session failure are subtle enough to warrant further
explanation. explanation.
MultipointHead sessions cannot fail (since they are controlled MultipointHead sessions cannot fail (since they are controlled
administratively.) administratively).
If a MultipointTail session fails, it means that the tail definitely If a MultipointTail session fails, it means that the tail definitely
has lost contact with the head (or the head has been administratively has lost contact with the head (or the head has been administratively
disabled) and the tail should take appropriate action. disabled) and the tail should take appropriate action.
4.4. State Variables 4.4. State Variables
Multipoint BFD introduces some new state variables, and modifies the Multipoint BFD introduces some new state variables, and modifies the
usage of a few existing ones. usage of a few existing ones.
4.4.1. New State Variables 4.4.1. New State Variable Values
A number of state variables and their values are added to the base A number of new values of the state variable bfd.SessionType are
BFD [RFC5880] and base S-BFD [RFC7880] specifications in support of added to the base BFD [RFC5880] and base S-BFD [RFC7880]
Multipoint BFD. specifications in support of Multipoint BFD.
bfd.SessionType bfd.SessionType
The type of this session as defined in [RFC7880]. Newly added The type of this session as defined in [RFC7880]. Newly added
values are: values are:
PointToPoint: Classic point-to-point BFD. PointToPoint: Classic point-to-point BFD.
MultipointHead: A session on the head responsible for the MultipointHead: A session on the head responsible for the
periodic transmission of multipoint BFD Control packets periodic transmission of multipoint BFD Control packets
along the multipoint path. along the multipoint path.
MultipointTail: A multipoint session on a tail. MultipointTail: A multipoint session on a tail.
This variable MUST be initialized to the appropriate type when This variable MUST be initialized to the appropriate type when
the session is created, according to the rules in Section 4.13 the session is created, according to the rules in Section 4.13
bfd.SilentTail
Always set to 1, a tail will never transmit any BFD Control
packets to the head under any circumstances. Setting to 0 is
outside the scope of this document.
This variable is only pertinent when bfd.SessionType is
MultipointTail.
4.4.2. State Variable Initialization and Maintenance 4.4.2. State Variable Initialization and Maintenance
Some state variables defined in section 6.8.1 of the [RFC5880] needs Some state variables defined in section 6.8.1 of [RFC5880] need to be
to be initialized or manipulated differently depending on the session initialized or manipulated differently depending on the session type.
type.
bfd.RequiredMinRxInterval bfd.RequiredMinRxInterval
This variable MUST be set to 0 for session type MultipointHead. This variable MUST be set to 0 for session type MultipointHead.
bfd.DemandMode bfd.DemandMode
This variable MUST be initialized to 1 for session type This variable MUST be initialized to 1 for session type
MultipointHead and MUST be initialized to 0 for session type MultipointHead and MUST be initialized to 0 for session type
MultipointTail. MultipointTail.
4.5. State Machine 4.5. State Machine
The BFD state machine works slightly differently in the multipoint The BFD state machine works slightly differently in the multipoint
application. In particular, since there is a many-to-one mapping, application. In particular, since there is a many-to-one mapping,
three-way handshakes for session establishment and teardown are three-way handshakes for session establishment and teardown are
neither possible nor appropriate. As such there is no Init state. neither possible nor appropriate. As such there is no Init state.
Session of type MultipointHead MUST NOT send BFD control packets with Sessions of type MultipointHead MUST NOT send BFD control packets
the State field being set to INIT, and must be ignored on receipt. with the State field being set to INIT, and MUST be ignored on
receipt.
The following diagram provides an overview of the state machine for The following diagram provides an overview of the state machine for
session type MultipointTail. The notation on each arc represents the session type MultipointTail. The notation on each arc represents the
state of the remote system (as received in the State field in the BFD state of the remote system (as received in the State field in the BFD
Control packet) or indicates the expiration of the Detection Timer. Control packet) or indicates the expiration of the Detection Timer.
DOWN, ADMIN DOWN, DOWN, ADMIN DOWN,
+------+ TIMER +------+ +------+ TIMER +------+
+----| |<---------------------| |----+ +----| |<---------------------| |----+
DOWN,| | DOWN | | UP | |UP DOWN,| | DOWN | | UP | |UP
ADMIN DOWN,+--->| |--------------------->| |<---+ ADMIN DOWN,+--->| |--------------------->| |<---+
TIMER +------+ UP +------+ TIMER +------+ UP +------+
Sessions of type MultipointHead never receive packets and have no Sessions of type MultipointHead never receive packets and have no
Detection Timer, and as such all state transitions are Detection Timer, and as such all state transitions are
administratively driven. administratively driven.
4.6. Session Establishment 4.6. Session Establishment
Unlike Point-to-point BFD, Multipoint BFD provides a form of Unlike point-to-point BFD, Multipoint BFD provides a form of
discovery mechanism for tails to discover the head. The minimum discovery mechanism for tails to discover the head. The minimum
amount of a priori information required both on the head and tails is amount of a priori information required both on the head and tails is
the binding to the multipoint path over which BFD is running. The the binding to the multipoint path over which BFD is running. The
head transmits Multipoint BFD packets on that tree, and the tails head transmits Multipoint BFD packets on that tree, and the tails
listen for BFD packets on that tree. All other information MAY be listen for BFD packets on that tree. All other information MAY be
determined dynamically. determined dynamically.
A session of type MultipointHead is created for each multipoint path A session of type MultipointHead is created for each multipoint path
over which the head wishes to run BFD. This session runs in the over which the head wishes to run BFD. This session runs in the
Active role. Except when terminating BFD service, this session is Active role , per section 6.1 [RFC5880]. Except when
always in state Up and always operates in Demand mode. No received administratively terminating BFD service, this session is always in
packets are ever demultiplexed to the MultipointHead session. In state Up and always operates in Demand mode. No received packets are
this sense it is a degenerate form of a session. ever demultiplexed to the MultipointHead session. In this sense it
is a degenerate form of a session.
Sessions on the tail MAY be established dynamically, based on the Sessions on the tail MAY be established dynamically, based on the
receipt of a Multipoint BFD Control packet from the head, and are of receipt of a Multipoint BFD Control packet from the head, and are of
type MultipointTail. Tail sessions always take the Passive role. type MultipointTail. Tail sessions always take the Passive role, per
section 6.1 [RFC5880].
4.7. Discriminators and Packet Demultiplexing 4.7. Discriminators and Packet Demultiplexing
The use of Discriminators is somewhat different in Multipoint BFD The use of Discriminators is somewhat different in Multipoint BFD
than in Point-to-point BFD. than in Point-to-point BFD.
The head sends Multipoint BFD Control packets over the MultipointHead The head sends Multipoint BFD Control packets over the multipoint
session with My Discr set to a value bound to the multipoint path, path via the MultipointHead session with My Discr set to a value
and with Your Discr set to zero. bound to the multipoint path, and with Your Discr set to zero.
IP and MPLS multipoint tails MUST demultiplex BFD packets based on a IP and MPLS multipoint tails MUST demultiplex BFD packets based on a
combination of the source address, My Discriminator and the identity combination of the source address, My Discriminator and the identity
of the multipoint tree which the Multipoint BFD Control packet was of the multipoint tree which the Multipoint BFD Control packet was
received from. Together they uniquely identify the head of the received from. Together they uniquely identify the head of the
multipoint path. Bootstrapping BFD session to a multipoint LSP in multipoint path. Bootstrapping BFD session to multipoint MPLS LSP in
case of penultimate hop popping is outside the scope of this case of penultimate hop popping is outside the scope of this
document. document.
Note that, unlike PointToPoint sessions, the My Discriminator value Note that, unlike point-to-point sessions, the My Discriminator value
on MultipointHead session MUST NOT be changed during the life of a on MultipointHead session MUST NOT be changed during the life of a
session. This is a side effect of the more complex demultiplexing session. This is a side effect of the more complex demultiplexing
scheme. scheme.
4.8. Packet consumption on tails 4.8. Packet consumption on tails
BFD packets received on tails for a multicast group MUST be consumed BFD packets received on tails for an IP multicast group MUST be
by tails and MUST NOT be forwarded to receivers. Session of type consumed by tails and MUST NOT be forwarded to receivers. Session of
MultipointTail MUST identify the packet as BFD with the help of type MultipointTail MUST identify the packet as BFD with the help of
destination UDP port number "3784" on IP multipoint path. destination UDP port number "3784" on IP multipoint path.
For multipoint LSP, when IP/UDP encapsulation of BFD control packet For multipoint LSPs, when IP/UDP encapsulation of BFD control packets
used, MultipointTail MUST use destination UDP port "3784" and is used, MultipointTail MUST use destination UDP port "3784" and
"127.0.0.0/8" range for IPv4 or "0:0:0:0:0:FFFF:7F00:0/104" range for "127.0.0.0/8" range for IPv4 or "0:0:0:0:0:FFFF:7F00:0/104" range for
IPv6. Packet identified as BFD packet MUST be consumed by IPv6 ([RFC8029]). Packets identified as BFD packets MUST be consumed
MultipointTail and demultiplex as described in Section 4.13.2. Use by MultipointTail and demultiplex as described in Section 4.13.2.
of other types of encapsulation for multipoint LSP is outside the Use of other types of encapsulation for multipoint LSP is outside the
scope of this document. scope of this document.
4.9. Bringing Up and Shutting Down Multipoint BFD Service 4.9. Bringing Up and Shutting Down Multipoint BFD Service
Because there is no three-way handshake in Multipoint BFD, a newly Because there is no three-way handshake in Multipoint BFD, a newly
started head (that does not have any previous state information started head (that does not have any previous state information
available) SHOULD start with bfd.SessionState set to Down and with available) SHOULD start with bfd.SessionState set to Down and with
bfd.RequiredMinRxInterval set to zero in the MultipointHead session. bfd.RequiredMinRxInterval set to zero in the MultipointHead session.
The session SHOULD remain in this state for a time equal to The session SHOULD remain in this state for a time equal to
(bfd.DesiredMinTxInterval * bfd.DetectMult). This will ensure that (bfd.DesiredMinTxInterval * bfd.DetectMult). This will ensure that
all MultipointTail sessions are reset (so long as the restarted head all MultipointTail sessions are reset (so long as the restarted head
is using the same or larger value of bfd.DesiredMinTxInterval than it is using the same or larger value of bfd.DesiredMinTxInterval than it
did previously.) did previously).
Multipoint BFD service is brought up by administratively setting Multipoint BFD service is brought up by administratively setting
bfd.SessionState to Up in the MultipointHead session. bfd.SessionState to Up in the MultipointHead session.
A head may wish to shut down its BFD service in a controlled fashion. A head may wish to shut down its BFD service in a controlled fashion.
This is desirable because the tails need not wait a detection time This is desirable because the tails need not wait a detection time
prior to declaring the multipoint session to be down (and taking prior to declaring the multipoint session to be down (and taking
whatever action is necessary in that case.) whatever action is necessary in that case).
To shut down a multipoint session a head MUST administratively set To shut down a multipoint session a head MUST administratively set
bfd.SessionState in the MultipointHead session to either Down or bfd.SessionState in the MultipointHead session to either Down or
AdminDown and SHOULD set bfd.RequiredMinRxInterval to zero. The AdminDown and SHOULD set bfd.RequiredMinRxInterval to zero. The
session SHOULD send BFD Control packets in this state for a period session SHOULD send BFD Control packets in this state for a period
equal to (bfd.DesiredMinTxInterval * bfd.DetectMult). equal to (bfd.DesiredMinTxInterval * bfd.DetectMult).
The semantic difference between Down and AdminDown state is for The semantic difference between Down and AdminDown state is for
further discussion. further discussion.
4.10. Timer Manipulation 4.10. Timer Manipulation
Because of the one-to-many mapping, a session of type MultipointHead Because of the one-to-many mapping, a session of type MultipointHead
SHOULD NOT initiate a Poll Sequence in conjunction with timer value SHOULD NOT initiate a Poll Sequence in conjunction with timer value
changes. However to indicate change in packet MultipointHead session changes. However, to indicate a change in the packets,
MUST send packet with P bit set. MultipointTail session MUST NOT MultipointHead session MUST send packets with the P bit set.
reply if packet has M, P bit set and bfd.RequiredMinRxInterval set to MultipointTail session MUST NOT reply if packet has M, P bit set and
0. bfd.RequiredMinRxInterval set to 0.
The MultipointHead, when changing the transmit interval to higher The MultipointHead, when changing the transmit interval to higher
value, MUST send BFD control packets with P bit set at the old value, MUST send BFD control packets with P bit set at the old
transmit interval before using the higher value in order to avoid transmit interval before using the higher value in order to avoid
false detection timeouts at the tails. MultipointHead MAY also wait false detection timeouts at the tails. MultipointHead session MAY
some amount of time before making the changes to the transmit also wait some amount of time before making the changes to the
interval (through configuration). transmit interval (through configuration).
Change in the value of bfd.RequiredMinRxInterval is outside the scope Change in the value of bfd.RequiredMinRxInterval is outside the scope
of this document. of this document.
4.11. Detection Times 4.11. Detection Times
Multipoint BFD is inherently asymmetric. As such, each session type Multipoint BFD is inherently asymmetric. As such, each session type
has a different approach to detection times. has a different approach to detection times.
Since the MultipointHead session never receives packets, it does not Since MultipointHead sessions never receive packets, they do not
calculate a detection time. calculate a detection time.
MultipointTail sessions cannot influence the transmission rate of the MultipointTail sessions cannot influence the transmission rate of the
MultipointHead session using the Required Min Rx Interval field MultipointHead session using the Required Min Rx Interval field
because of its one-to-many nature. As such, the Detection Time because of its one-to-many nature. As such, the detection time
calculation for a MultipointTail session does not use calculation for a MultipointTail session does not use
bfd.RequiredMinRxInterval in the calculation. The detection time is bfd.RequiredMinRxInterval in the calculation. The detection time is
calculated as the product of the last received values of Desired Min calculated as the product of the last received values of Desired Min
TX Interval and Detect Mult. TX Interval and Detect Mult.
The value of bfd.DetectMult may be changed at any time on any session The value of bfd.DetectMult may be changed at any time on any session
type. type.
4.12. State Maintenance for Down/AdminDown Sessions 4.12. State Maintenance for Down/AdminDown Sessions
The length of time session state is kept after the session goes down The length of time session state is kept after the session goes down
determines how long the session will continue to send BFD Control determines how long the session will continue to send BFD Control
packets (since no packets can be sent after the session is packets (since no packets can be sent after the session is
destroyed.) destroyed).
4.12.1. MultipointHead Sessions 4.12.1. MultipointHead Sessions
When a MultipointHead session transitions to states Down or When a MultipointHead session transitions to states Down or
AdminDown, the state SHOULD be maintained for a period equal to AdminDown, the state SHOULD be maintained for a period equal to
(bfd.DesiredMinTxInterval * bfd.DetectMult) to ensure that the tails (bfd.DesiredMinTxInterval * bfd.DetectMult) to ensure that the tails
more quickly detect the session going down (by continuing to transmit more quickly detect the session going down (by continuing to transmit
BFD Control packets with the new state.) BFD Control packets with the new state).
4.12.2. MultipointTail Sessions 4.12.2. MultipointTail Sessions
MultipointTail sessions MAY be destroyed immediately upon leaving Up MultipointTail sessions MAY be destroyed immediately upon leaving Up
state, since tail will transmit no packets. state, since tail will transmit no packets.
Otherwise, MultipointTail sessions SHOULD be maintained as long as Otherwise, MultipointTail sessions SHOULD be maintained as long as
BFD Control packets are being received by it (which by definition BFD Control packets are being received by it (which by definition
will indicate that the head is not Up.) will indicate that the head is not Up).
4.13. Base Specification Text Replacement 4.13. Base Specification Text Replacement
The following sections are meant to replace the corresponding The following sections are meant to replace the corresponding
sections in the base specification. sections in the base specification [RFC5880] in support of BFD for
multipoint networks while not changing processing for point-to-point
BFD.
4.13.1. Reception of BFD Control Packets 4.13.1. Reception of BFD Control Packets
The following procedure replaces section 6.8.6 of [RFC5880]. The following procedure replaces section 6.8.6 of [RFC5880].
When a BFD Control packet is received, the following procedure MUST When a BFD Control packet is received, the following procedure MUST
be followed, in the order specified. If the packet is discarded be followed, in the order specified. If the packet is discarded
according to these rules, processing of the packet MUST cease at that according to these rules, processing of the packet MUST cease at that
point. point.
skipping to change at page 11, line 7 skipping to change at page 10, line 38
If the Length field is greater than the payload of the If the Length field is greater than the payload of the
encapsulating protocol, the packet MUST be discarded. encapsulating protocol, the packet MUST be discarded.
If the Detect Mult field is zero, the packet MUST be discarded. If the Detect Mult field is zero, the packet MUST be discarded.
If the My Discriminator field is zero, the packet MUST be If the My Discriminator field is zero, the packet MUST be
discarded. discarded.
Demultiplex the packet to a session according to Section 4.13.2 Demultiplex the packet to a session according to Section 4.13.2
below. The result is either a session of the proper type, or the below. The result is either a session of the proper type, or the
packet is discarded (and packet processing MUST cease.) packet is discarded (and packet processing MUST cease).
If the A bit is set and no authentication is in use (bfd.AuthType If the A bit is set and no authentication is in use (bfd.AuthType
is zero), the packet MUST be discarded. is zero), the packet MUST be discarded.
If the A bit is clear and authentication is in use (bfd.AuthType If the A bit is clear and authentication is in use (bfd.AuthType
is nonzero), the packet MUST be discarded. is nonzero), the packet MUST be discarded.
If the A bit is set, the packet MUST be authenticated under the If the A bit is set, the packet MUST be authenticated under the
rules of section 6.7, based on the authentication type in use rules of [RFC5880] section 6.7, based on the authentication type
(bfd.AuthType.) This may cause the packet to be discarded. in use (bfd.AuthType). This may cause the packet to be discarded.
Set bfd.RemoteDiscr to the value of My Discriminator. Set bfd.RemoteDiscr to the value of My Discriminator.
Set bfd.RemoteState to the value of the State (Sta) field. Set bfd.RemoteState to the value of the State (Sta) field.
Set bfd.RemoteDemandMode to the value of the Demand (D) bit. Set bfd.RemoteDemandMode to the value of the Demand (D) bit.
Set bfd.RemoteMinRxInterval to the value of Required Min RX Set bfd.RemoteMinRxInterval to the value of Required Min RX
Interval. Interval.
skipping to change at page 12, line 45 skipping to change at page 12, line 26
Set bfd.LocalDiag to 3 (Neighbor signaled session down) Set bfd.LocalDiag to 3 (Neighbor signaled session down)
Set bfd.SessionState to Down Set bfd.SessionState to Down
Check to see if Demand mode should become active or not (see Check to see if Demand mode should become active or not (see
[RFC5880] section 6.6). [RFC5880] section 6.6).
If bfd.RemoteDemandMode is 1, bfd.SessionState is Up, and If bfd.RemoteDemandMode is 1, bfd.SessionState is Up, and
bfd.RemoteSessionState is Up, Demand mode is active on the remote bfd.RemoteSessionState is Up, Demand mode is active on the remote
system and the local system MUST cease the periodic transmission system and the local system MUST cease the periodic transmission
of BFD Control packets (see Section 4.13.3.) of BFD Control packets (see Section 4.13.3).
If bfd.RemoteDemandMode is 0, or bfd.SessionState is not Up, or If bfd.RemoteDemandMode is 0, or bfd.SessionState is not Up, or
bfd.RemoteSessionState is not Up, Demand mode is not active on the bfd.RemoteSessionState is not Up, Demand mode is not active on the
remote system and the local system MUST send periodic BFD Control remote system and the local system MUST send periodic BFD Control
packets (see see Section 4.13.3.) packets (see see Section 4.13.3).
If the packet was not discarded, it has been received for purposes If the packet was not discarded, it has been received for purposes
of the Detection Time expiration rules in [RFC5880] section 6.8.4. of the Detection Time expiration rules in [RFC5880] section 6.8.4.
4.13.2. Demultiplexing BFD Control Packets 4.13.2. Demultiplexing BFD Control Packets
This section is part of the replacement for [RFC5880] section 6.8.6, This section is part of the replacement for [RFC5880] section 6.8.6,
separated for clarity. separated for clarity.
If the Multipoint (M) bit is set If the Multipoint (M) bit is set
skipping to change at page 14, line 19 skipping to change at page 13, line 47
The following procedure replaces section 6.8.7 of [RFC5880]. The following procedure replaces section 6.8.7 of [RFC5880].
BFD Control packets MUST be transmitted periodically at the rate BFD Control packets MUST be transmitted periodically at the rate
determined according to [RFC5880] section 6.8.2, except as specified determined according to [RFC5880] section 6.8.2, except as specified
in this section. in this section.
A system MUST NOT transmit any BFD Control packets if bfd.RemoteDiscr A system MUST NOT transmit any BFD Control packets if bfd.RemoteDiscr
is zero and the system is taking the Passive role. is zero and the system is taking the Passive role.
A system MUST NOT transmit any BFD Control packets if bfd.SilentTail A system MUST NOT transmit any BFD Control packets if bfd.SessionType
is 1. is MultipointTail.
A system MUST NOT periodically transmit BFD Control packets if Demand A system MUST NOT periodically transmit BFD Control packets if Demand
mode is active on the remote system (bfd.RemoteDemandMode is 1, mode is active on the remote system (bfd.RemoteDemandMode is 1,
bfd.SessionState is Up, and bfd.RemoteSessionState is Up) and a Poll bfd.SessionState is Up, and bfd.RemoteSessionState is Up) and a Poll
Sequence is not being transmitted. Sequence is not being transmitted.
A system MUST NOT periodically transmit BFD Control packets if A system MUST NOT periodically transmit BFD Control packets if
bfd.RemoteMinRxInterval is zero. bfd.RemoteMinRxInterval is zero.
If bfd.SessionType is MultipointHead, the transmit interval MUST be If bfd.SessionType is MultipointHead, the transmit interval MUST be
set to bfd.DesiredMinTxInterval (this should happen automatically, as set to bfd.DesiredMinTxInterval (this should happen automatically, as
bfd.RemoteMinRxInterval will be zero.) bfd.RemoteMinRxInterval will be zero).
If bfd.SessionType is not MultipointHead, the transmit interval MUST If bfd.SessionType is not MultipointHead, the transmit interval MUST
be recalculated whenever bfd.DesiredMinTxInterval changes, or be recalculated whenever bfd.DesiredMinTxInterval changes, or
whenever bfd.RemoteMinRxInterval changes, and is equal to the greater whenever bfd.RemoteMinRxInterval changes, and is equal to the greater
of those two values. See [RFC5880] sections 6.8.2 and 6.8.3 for of those two values. See [RFC5880] sections 6.8.2 and 6.8.3 for
details on transmit timers. details on transmit timers.
A system MUST NOT set the Demand (D) bit if bfd.SessionType is A system MUST NOT set the Demand (D) bit if bfd.SessionType is
MultipointTail. MultipointTail.
skipping to change at page 15, line 35 skipping to change at page 15, line 17
Final (F) Final (F)
Set to 1 if the local system is responding to a Control packet Set to 1 if the local system is responding to a Control packet
received with the Poll (P) bit set, or 0 if not. received with the Poll (P) bit set, or 0 if not.
Control Plane Independent (C) Control Plane Independent (C)
Set to 1 if the local system's BFD implementation is Set to 1 if the local system's BFD implementation is
independent of the control plane (it can continue to function independent of the control plane (it can continue to function
through a disruption of the control plane.) through a disruption of the control plane).
Authentication Present (A) Authentication Present (A)
Set to 1 if authentication is in use on this session Set to 1 if authentication is in use on this session
(bfd.AuthType is nonzero), or 0 if not. (bfd.AuthType is nonzero), or 0 if not.
Demand (D) Demand (D)
Set to bfd.DemandMode if bfd.SessionState is Up and Set to bfd.DemandMode if bfd.SessionState is Up and
bfd.RemoteSessionState is Up. Set to 1 if bfd.SessionType is bfd.RemoteSessionState is Up. Set to 1 if bfd.SessionType is
skipping to change at page 16, line 37 skipping to change at page 16, line 20
Set to bfd.RequiredMinRxInterval. Set to bfd.RequiredMinRxInterval.
Required Min Echo RX Interval Required Min Echo RX Interval
Set to 0 if bfd.SessionType is MultipointHead or Set to 0 if bfd.SessionType is MultipointHead or
MultipointTail. MultipointTail.
Authentication Section Authentication Section
Included and set according to the rules in section 6.7 if Included and set according to the rules in [RFC5880] section
authentication is in use (bfd.AuthType is nonzero.) Otherwise 6.7 if authentication is in use (bfd.AuthType is nonzero).
this section is not present. Otherwise this section is not present.
5. Assumptions 5. Assumptions
If authentication is in use, all tails must be configured to have a If authentication is in use, all tails must be configured to have a
common authentication key in order to receive the multipoint BFD common authentication key in order to receive the multipoint BFD
Control packets. Control packets.
6. IANA Considerations 6. IANA Considerations
This document has no actions for IANA. This document has no actions for IANA.
7. Security Considerations 7. Security Considerations
Implementations that create MultpointTail sessions dynamically upon The same security considerations as those described in [RFC5880]
receipt of Multipoint BFD Control packets MUST implement protective apply to this document. Additionally, implementations that create
measures to prevent infinite number of MultipointTail sessions being MultpointTail sessions dynamically upon receipt of Multipoint BFD
created. Below are listed some points to be considered in such Control packets MUST implement protective measures to prevent
implementations. infinite number of MultipointTail sessions being created. Below are
listed some points to be considered in such implementations.
If a Multipoint BFD Control packet did not arrive on a multicast If a Multipoint BFD Control packet did not arrive on a multicast
tree (ex: on expected interface, with expected MPLS label, etc), tree (e.g. on expected interface, with expected MPLS label, etc),
then a MultipointTail session should not be created. then a MultipointTail session should not be created.
If redundant streams are expected for a given multicast stream, If redundant streams are expected for a given multicast stream,
then the implementations should not create more MultipointTail then the implementations should not create more MultipointTail
sessions than the number of streams. Additionally, when the sessions than the number of streams. Additionally, when the
number of MultipointTail sessions exceeds the number of expected number of MultipointTail sessions exceeds the number of expected
streams, then the implementation should generate an alarm to users streams, then the implementation should generate an alarm to users
to indicate the anomaly. to indicate the anomaly.
The implementation should have a reasonable upper bound on the The implementation should have a reasonable upper bound on the
skipping to change at page 18, line 10 skipping to change at page 17, line 38
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>. <https://www.rfc-editor.org/info/rfc5880>.
[RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S. [RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
Pallagatti, "Seamless Bidirectional Forwarding Detection Pallagatti, "Seamless Bidirectional Forwarding Detection
(S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016, (S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016,
<https://www.rfc-editor.org/info/rfc7880>. <https://www.rfc-editor.org/info/rfc7880>.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017,
<https://www.rfc-editor.org/info/rfc8029>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Authors' Addresses Authors' Addresses
Dave Katz Dave Katz
Juniper Networks Juniper Networks
1194 N. Mathilda Ave. 1194 N. Mathilda Ave.
Sunnyvale, California 94089-1206 Sunnyvale, California 94089-1206
USA USA
Email: dkatz@juniper.net Email: dkatz@juniper.net
Dave Ward Dave Ward
Cisco Systems Cisco Systems
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