draft-ietf-pim-bfd-p2mp-use-case-07.txt   draft-ietf-pim-bfd-p2mp-use-case-08.txt 
PIM Working Group G. Mirsky PIM Working Group G. Mirsky
Internet-Draft Ericsson Internet-Draft Ericsson
Intended status: Standards Track J. Xiaoli Intended status: Standards Track J. Xiaoli
Expires: 14 March 2022 ZTE Corporation Expires: 28 March 2022 ZTE Corporation
10 September 2021 24 September 2021
Fast Failover in Protocol Independent Multicast - Sparse Mode (PIM-SM) Fast Failover in Protocol Independent Multicast - Sparse Mode (PIM-SM)
Using Bidirectional Forwarding Detection (BFD) for Multipoint Networks Using Bidirectional Forwarding Detection (BFD) for Multipoint Networks
draft-ietf-pim-bfd-p2mp-use-case-07 draft-ietf-pim-bfd-p2mp-use-case-08
Abstract Abstract
This document specifies how Bidirectional Forwarding Detection for This document specifies how Bidirectional Forwarding Detection for
multipoint networks can provide sub-second failover for routers that multipoint networks can provide sub-second failover for routers that
participate in Protocol Independent Multicast - Sparse Mode (PIM-SM). participate in Protocol Independent Multicast - Sparse Mode (PIM-SM).
An extension to the PIM Hello message used to bootstrap a point-to- An extension to the PIM Hello message used to bootstrap a point-to-
multipoint BFD session is also defined in this document. multipoint BFD session is also defined in this document.
Status of This Memo Status of This Memo
skipping to change at page 1, line 36 skipping to change at page 1, line 36
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 14 March 2022. This Internet-Draft will expire on 28 March 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 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 (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
skipping to change at page 2, line 34 skipping to change at page 2, line 34
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . 6 6.1. Normative References . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . 7 6.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
Faster convergence in the control plane, in general, is beneficial Faster convergence in the control plane minimizes the periods of
and allows minimizing periods of traffic blackholing, transient traffic blackholing, transient routing loops, and other situations
routing loops, and other scenarios that may negatively affect service that may negatively affect service data flow. Faster convergence in
data flow. That equally applies to unicast and multicast routing the control plane is beneficial to unicast and multicast routing
protocols. protocols.
[RFC7761] is the current specification of the Protocol Independent [RFC7761] is the current specification of the Protocol Independent
Multicast - Sparse Mode (PIM-SM) for IPv4 and IPv6 networks. A Multicast - Sparse Mode (PIM-SM) for IPv4 and IPv6 networks. A
conforming implementation of PIM-SM elects a Designated Router (DR) conforming implementation of PIM-SM elects a Designated Router (DR)
on each PIM-SM interface. When a group of PIM-SM nodes is connected on each PIM-SM interface. When a group of PIM-SM nodes is connected
to a shared media segment, e.g., Ethernet, the node elected as DR is to a shared media segment, e.g., Ethernet, the node elected as DR
to act on behalf of directly connected hosts in the context of the acts on behalf of directly connected hosts in the context of the PIM-
PIM-SM protocol. Failure of the DR impacts the quality of the SM protocol. Failure of the DR impacts the quality of the multicast
multicast services it provides to directly connected hosts because services it provides to directly connected hosts because the default
the default failure detection interval for PIM-SM routers is 105 failure detection interval for PIM-SM routers is 105 seconds.
seconds.
Bidirectional Forwarding Detection (BFD) [RFC5880] had been Bidirectional Forwarding Detection (BFD) [RFC5880] had been
originally defined to detect a failure of point-to-point (p2p) paths originally defined to detect a failure of a point-to-point (p2p)
- single-hop [RFC5881], multihop [RFC5883]. In some PIM-SM path, single-hop [RFC5881] or multihop [RFC5883]. In some PIM-SM
deployments, a p2p BFD can detect a failure and enable faster deployments, a p2p BFD can be used to detect a failure and enable
failover. [RFC8562] extends the BFD base specification [RFC5880] for faster failover. [RFC8562] extends the BFD base specification
multipoint and multicast networks precisely characterizes deployment [RFC5880] for multipoint and multicast networks, and it precisely
scenarios for PIM-SM over a LAN segment. Among specific characterizes deployment scenarios for PIM-SM over a LAN segment.
characteristics of p2mp BFD that particularly benefit PIM-SM over a Among specific characteristics of p2mp BFD that particularly benefit
LAN segment is a faster transition to the Up state of the p2mp BFD PIM-SM over a LAN segment is a faster transition to the Up state of
session due to avoidance of the three-way handshake required in p2p the p2mp BFD session due to avoidance of the three-way handshake
BFD [RFC5880]. Also, because the router that transmits BFD Control required in p2p BFD [RFC5880]. Also, because the router that
messages uses the BFD Demand mode [RFC5880], it maintains less BFD transmits BFD Control messages uses the BFD Demand mode [RFC5880], it
state than the Asynchronous mode. Point-to-multipoint (p2mp) BFD can maintains less BFD state than the Asynchronous mode. Point-to-
enable faster detection of PIM-SM router failure and thus minimize multipoint (p2mp) BFD can enable faster detection of PIM-SM router
multicast service disruption. The monitored PIM-SM router acts as failure and thus minimize multicast service disruption. The
the head and other routers as tails of a p2mp BFD session. This monitored PIM-SM router acts as the head and other routers as tails
document defines the monitoring of a PIM-SM router using p2mp BFD. of a p2mp BFD session. This document defines the monitoring of a
The document also defines the extension to PIM-SM [RFC7761] to PIM-SM router using p2mp BFD. The document also defines the
bootstrap a PIM-SM router to join in p2mp BFD session over shared extension to PIM-SM [RFC7761] to bootstrap a PIM-SM router to join in
media segment. p2mp BFD session over shared media segment.
1.1. Conventions used in this document 1.1. Conventions used in this document
1.1.1. Terminology 1.1.1. Terminology
This document uses terminology defined in [RFC5880], [RFC8562], and This document uses terminology defined in [RFC5880], [RFC8562], and
[RFC7761]. familiarity with these specifications and the terminology [RFC7761]. Familiarity with these specifications and the terminology
used is expected. used is expected.
1.1.2. Requirements Language 1.1.2. 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.
2. BFD Discriminator PIM Hello Option 2. BFD Discriminator PIM Hello Option
Figure 1 displays the new optional BFD Discriminator PIM Hello option Figure 1 displays the new optional BFD Discriminator PIM Hello option
to bootstrap a tail of the p2mp BFD session. to bootstrap a tail of the p2mp BFD session.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OptionType | OptionLength | | OptionType | OptionLength |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| My Discriminator | | HeadDiscriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: BFD Discriminator PIM Hello Option Figure 1: BFD Discriminator PIM Hello Option
where new fields are interpreted as: where new fields are interpreted as:
OptionType: TBA. OptionType: TBA.
OptionLength: MUST be set to 4. OptionLength: MUST be set to 4.
My Discriminator: My Discriminator ([RFC5880]) value allocated by HeadDiscriminator: equals the value of My Discriminator
the head. ([RFC5880]) allocated by the head.
If the value of the OptionLength field is not equal to 4, the BFD If the value of the OptionLength field is not equal to 4, the BFD
Discriminator PIM Hello option is considered malformed, and the Discriminator PIM Hello option is considered malformed, and the
receiver MUST stop processing PIM Hello options. If the value of the receiver MUST stop processing PIM Hello options. If the value of the
My Discriminator field equals zero, then the BFD Discriminator PIM HeadDiscriminator field equals zero, then the BFD Discriminator PIM
Hello option MUST be considered invalid, and the receiver MUST ignore Hello option MUST be considered invalid, and the receiver MUST ignore
it. The receiver SHOULD log a notification regarding the malformed it. The receiver SHOULD log a notification regarding the malformed
or invalid BFD Discriminator Hello option under the control of a or invalid BFD Discriminator Hello option under the control of a
throttling logging mechanism. throttling logging mechanism.
2.1. Using P2MP BFD in PIM Router Monitoring 2.1. Using P2MP BFD in PIM Router Monitoring
The head MUST create a BFD session of type MultipointHead [RFC8562]. The head MUST create a BFD session of type MultipointHead [RFC8562].
Note that any PIM-SM router, regardless of its role, MAY become a Note that any PIM-SM router, regardless of its role, MAY become a
head of a p2mp BFD session. To control the volume of BFD control head of a p2mp BFD session. To control the volume of BFD control
traffic on a shared media segment, an operator should carefully traffic on a shared media segment, an operator should carefully
select PIM-SM routers configured as a head of a p2mp BFD session. select PIM-SM routers configured as a head of a p2mp BFD session.
The head MUST include the BFD Discriminator option in its Hello The head MUST include the BFD Discriminator option in its Hello
messages. messages, and it MUST include a 4-byte HeadDiscriminator with a value
other than zero.
If a PIM-SM router is configured to monitor the head by using p2mp If a PIM-SM router is configured to monitor the head by using p2mp
BFD, referred to through this document as 'tail', receives a PIM- BFD, referred to through this document as 'tail', receives a PIM-
Hello packet with the BFD Discriminator PIM Hello option, the tail Hello packet with the BFD Discriminator PIM Hello option, the tail
MAY create a p2mp BFD session of type MultipointTail, as defined in MAY create a p2mp BFD session of type MultipointTail, as defined in
[RFC8562]. [RFC8562].
The node that includes the BFD Discriminator PIM Hello option The node that includes the BFD Discriminator PIM Hello option
transmits BFD Control packets periodically. For the tail to transmits BFD Control packets periodically. For the tail to
correctly demultiplex BFD [RFC8562], the source address, and My correctly demultiplex BFD [RFC8562], the source address, and My
Discriminator values of the BFD packets MUST be the same as those Discriminator values of the BFD packets MUST be the same as those of
used in the PIM Hello message. If that is not the case, the tail BFD the HeadDiscriminator in the PIM Hello message. If that is not the
node would not be able to monitor the state of the PIM-SM node, that case, the tail BFD node would not be able to monitor the state of the
is, the head of the p2mp BFD session, though the regular PIM-SM PIM-SM node, that is, the head of the p2mp BFD session, though the
mechanisms remain fully operational. regular PIM-SM mechanisms remain fully operational.
If the tail detects a MultipointHead failure [RFC8562], it MUST If the tail detects a MultipointHead failure [RFC8562], it MUST
delete the corresponding neighbor state and follow procedures defined delete the corresponding neighbor state and follow procedures defined
in [RFC7761]. in [RFC7761].
If the head ceases to include the BFD Discriminator PIM Hello option If the head ceases to include the BFD Discriminator PIM Hello option
in its PIM-Hello message, tails MUST close the corresponding in its PIM-Hello message, tails MUST close the corresponding
MultipointTail BFD session without affecting the PIM state in any MultipointTail BFD session without affecting the PIM state in any
way. Thus the tail stops using BFD to monitor the head and reverts way. Thus the tail stops using BFD to monitor the head and reverts
to the procedures defined in [RFC7761]. to the procedures defined in [RFC7761].
skipping to change at page 5, line 42 skipping to change at page 5, line 38
based on the value of the My Discriminator field and the source IP based on the value of the My Discriminator field and the source IP
address. If PIM DR detects a failure of one of the sessions, it MUST address. If PIM DR detects a failure of one of the sessions, it MUST
remove that router from the GDR Candidate list and immediately remove that router from the GDR Candidate list and immediately
transmit a new DRLB-List option. transmit a new DRLB-List option.
2.3. Multipoint BFD Encapsulation 2.3. Multipoint BFD Encapsulation
The MultipointHead of a p2mp BFD session when transmitting BFD The MultipointHead of a p2mp BFD session when transmitting BFD
Control packets: Control packets:
must set TTL or Hop Limit value to 255 (Section 5 [RFC5881]); MUST set TTL or Hop Limit value to 255 (Section 5 [RFC5881]);
MUST use the group address ALL-PIM-ROUTERS ('224.0.0.13' for IPv4 MUST use the group address ALL-PIM-ROUTERS ('224.0.0.13' for IPv4
and 'ff02::d' for IPv6) as destination IP address and 'ff02::d' for IPv6) as destination IP address
3. IANA Considerations 3. IANA Considerations
IANA is requested to allocate a new OptionType value from PIM-Hello IANA is requested to allocate a new OptionType value from PIM-Hello
Options registry according to: Options registry according to:
+=======+========+==========================+===============+ +=======+========+==========================+===============+
 End of changes. 14 change blocks. 
46 lines changed or deleted 45 lines changed or added

This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/