draft-ietf-pim-bfd-p2mp-use-case-06.txt   draft-ietf-pim-bfd-p2mp-use-case-07.txt 
PIM Working Group G. Mirsky PIM Working Group G. Mirsky
Internet-Draft ZTE Corp. Internet-Draft Ericsson
Intended status: Standards Track J. Xiaoli Intended status: Standards Track J. Xiaoli
Expires: 5 February 2022 ZTE Corporation Expires: 14 March 2022 ZTE Corporation
4 August 2021 10 September 2021
The Use of Bidirectional Forwarding Detection (BFD) for Multipoint Fast Failover in Protocol Independent Multicast - Sparse Mode (PIM-SM)
Networks in Protocol Independent Multicast - Sparse Mode (PIM-SM) Using Bidirectional Forwarding Detection (BFD) for Multipoint Networks
draft-ietf-pim-bfd-p2mp-use-case-06 draft-ietf-pim-bfd-p2mp-use-case-07
Abstract Abstract
This document specifies the use of Bidirectional Forwarding Detection This document specifies how Bidirectional Forwarding Detection for
(BFD) for multipoint networks to provide nodes that participate in multipoint networks can provide sub-second failover for routers that
Protocol Independent Multicast - Sparse Mode (PIM-SM) with sub-second participate in Protocol Independent Multicast - Sparse Mode (PIM-SM).
convergence. An extension to the PIM Hello message used to bootstrap An extension to the PIM Hello message used to bootstrap a point-to-
point-to-multipoint BFD sessions is also defined in this document. multipoint BFD session is also defined in this document.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on 5 February 2022. This Internet-Draft will expire on 14 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
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as described in Section 4.e of the Trust Legal Provisions and are as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License. provided without warranty as described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3 1.1. Conventions used in this document . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
2. BFD Discriminator PIM Hello Option . . . . . . . . . . . . . 3 2. BFD Discriminator PIM Hello Option . . . . . . . . . . . . . 3
2.1. Using P2MP BFD in PIM DR/BDR Monitoring . . . . . . . . . 4 2.1. Using P2MP BFD in PIM Router Monitoring . . . . . . . . . 4
2.2. P2MP BFD in PIM DR Load Balancing . . . . . . . . . . . . 5 2.2. P2MP BFD in PIM DR Load Balancing . . . . . . . . . . . . 5
2.3. Multipoint BFD Encapsulation . . . . . . . . . . . . . . 5 2.3. Multipoint BFD Encapsulation . . . . . . . . . . . . . . 5
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
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Faster convergence in the control plane, in general, is beneficial Faster convergence in the control plane, in general, is beneficial
and allows minimizing periods of traffic blackholing, transient and allows minimizing periods of traffic blackholing, transient
routing loops, and other scenarios that may negatively affect service routing loops, and other scenarios that may negatively affect service
data flow. That equally applies to unicast and multicast routing data flow. That equally applies 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 is
to act on behalf of directly connected hosts in the context of the to act on behalf of directly connected hosts in the context of the
PIM-SM protocol. Failure of the DR impacts the quality of the PIM-SM protocol. Failure of the DR impacts the quality of the
multicast services it provides to directly connected hosts because multicast services it provides to directly connected hosts because
the default failure detection interval for PIM-SM routers is 105 the default failure detection interval for PIM-SM routers is 105
seconds. Introduction of Backup DR (BDR) seconds.
([I-D.ietf-pim-dr-improvement]) improves convergence time in PIM-SM
over shared-media segment but still depends on a long failure
detection interval.
Bidirectional Forwarding Detection (BFD) [RFC5880] had been Bidirectional Forwarding Detection (BFD) [RFC5880] had been
originally defined to detect failure of point-to-point (p2p) paths - originally defined to detect a failure of point-to-point (p2p) paths
single-hop [RFC5881], multihop [RFC5883]. In some PIM-SM - single-hop [RFC5881], multihop [RFC5883]. In some PIM-SM
deployments, a p2p BFD can be used to detect a failure and enable deployments, a p2p BFD can detect a failure and enable faster
faster conversion. [RFC8562] extends the BFD base specification failover. [RFC8562] extends the BFD base specification [RFC5880] for
[RFC5880] for multipoint and multicast networks precisely multipoint and multicast networks precisely characterizes deployment
characterizes deployment scenarios for PIM-SM over a LAN segment. scenarios for PIM-SM over a LAN segment. Among specific
Among specific characteristics of p2mp BFD that particularly benefit characteristics of p2mp BFD that particularly benefit PIM-SM over a
PIM-SM over a LAN segment is a faster transition to the Up state of LAN segment is a faster transition to the Up state of the p2mp BFD
the p2mp BFD session due to avoidance of the three-way handshake session due to avoidance of the three-way handshake required in p2p
required in p2p BFD [RFC5880]. Also, because the router that BFD [RFC5880]. Also, because the router that transmits BFD Control
transmits BFD Control messages uses the BFD Demand mode [RFC5880], it messages uses the BFD Demand mode [RFC5880], it maintains less BFD
maintains less BFD state comparing to the Asynchronous mode. Point- state than the Asynchronous mode. Point-to-multipoint (p2mp) BFD can
to-multipoint (p2mp) BFD can enable faster detection of PIM-SM router enable faster detection of PIM-SM router failure and thus minimize
failure and thus minimize multicast service disruption. The multicast service disruption. The monitored PIM-SM router acts as
monitored PIM-SM router acts as the head and other routers as tails the head and other routers as tails of a p2mp BFD session. This
of a p2mp BFD session. This document defines the monitoring of PIM- document defines the monitoring of a PIM-SM router using p2mp BFD.
SM DR and BDR using p2mp BFD. Other cases of using p2mp BFD in PIM- The document also defines the extension to PIM-SM [RFC7761] to
SM are outside the scope of this specification. The document also bootstrap a PIM-SM router to join in p2mp BFD session over shared
defines the extension to PIM-SM [RFC7761] to bootstrap a PIM-SM media segment.
router to join in p2mp BFD session over shared-media link.
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
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OptionLength: MUST be set to 4. OptionLength: MUST be set to 4.
My Discriminator: My Discriminator ([RFC5880]) value allocated by My Discriminator: My Discriminator ([RFC5880]) value allocated by
the head. 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 My Discriminator 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 the 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 DR/BDR 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. The head MUST include the BFD head of a p2mp BFD session. To control the volume of BFD control
Discriminator option in its Hello messages. traffic on a shared media segment, an operator should carefully
select PIM-SM routers configured as a head of a p2mp BFD session.
The head MUST include the BFD Discriminator option in its Hello
messages.
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 PIM-Hello BFD, referred to through this document as 'tail', receives a PIM-
packet with BFD Discriminator PIM Hello option, the tail MAY create a Hello packet with the BFD Discriminator PIM Hello option, the tail
p2mp BFD session of type MultipointTail, as defined in [RFC8562]. MAY create a p2mp BFD session of type MultipointTail, as defined in
[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
used in the PIM Hello message. If that is not the case, the tail BFD used in the PIM Hello message. If that is not the case, the tail BFD
node would not be able to monitor the state of the PIM-SM node, that node would not be able to monitor the state of the PIM-SM node, that
is the head of the p2mp BFD session, though the regular PIM-SM is, the head of the p2mp BFD session, though the regular PIM-SM
mechanisms remain fully operational. 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. If the failed head was the delete the corresponding neighbor state and follow procedures defined
DR (or BDR), the DR (or BDR) election mechanism in [RFC7761] or in [RFC7761].
[I-D.ietf-pim-dr-improvement] is followed.
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. Thus the tail stops using BFD to monitor MultipointTail BFD session without affecting the PIM state in any
the head and reverts to the procedures defined in [RFC7761] and way. Thus the tail stops using BFD to monitor the head and reverts
[I-D.ietf-pim-dr-improvement]. to the procedures defined in [RFC7761].
2.2. P2MP BFD in PIM DR Load Balancing 2.2. P2MP BFD in PIM DR Load Balancing
[RFC8775] specifies the PIM Designated Router Load Balancing (DRLB) [RFC8775] specifies the PIM Designated Router Load Balancing (DRLB)
functionality. Any PIM router that advertises the DRLB-Cap Hello functionality. Any PIM router that advertises the DRLB-Cap Hello
Option can become the head of a p2mp BFD session, as specified in Option can become the head of a p2mp BFD session, as specified in
Section 2.1. The head router administratively sets the Section 2.1. The head router administratively sets the
bfd.SessionState to Up in the MultipointHead session [RFC8562] only bfd.SessionState to Up in the MultipointHead session [RFC8562] only
if it is a Group Designated Router (GDR) Candidate, as specified in if it is a Group Designated Router (GDR) Candidate, as specified in
Sections 5.5 and 5.6 of [RFC8775]. If the router is no longer the Sections 5.5 and 5.6 of [RFC8775]. If the router is no longer the
skipping to change at page 5, line 37 skipping to change at page 5, line 40
Discriminator option in its PIM Hello, the PIM DR creates a Discriminator option in its PIM Hello, the PIM DR creates a
MultipointTail session [RFC8562]. PIM DR demultiplexes BFD sessions MultipointTail session [RFC8562]. PIM DR demultiplexes BFD sessions
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 packet: 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:
+=============+================+===================+===============+ +=======+========+==========================+===============+
| Value Name | Length Number | Name Protocol | Reference | | Value | Length | Name | Reference |
+=============+================+===================+===============+ +=======+========+==========================+===============+
| TBA | 4 | BFD Discriminator | This document | | TBA | 4 | BFD Discriminator Option | This document |
| | | Option | | +-------+--------+--------------------------+---------------+
+-------------+----------------+-------------------+---------------+
Table 1: BFD Discriminator option type Table 1: BFD Discriminator option type
4. Security Considerations 4. Security Considerations
The security considerations discussed in [RFC7761], [RFC5880], The security considerations discussed in [RFC7761], [RFC5880],
[RFC8562], [RFC8775], and [I-D.ietf-pim-dr-improvement] apply to this [RFC8562], and [RFC8775] apply to this document.
document.
An implementation that supports this specification SHOULD use a
mechanism to control the maximum number of BFD sessions that can be
active at the same time.
5. Acknowledgments 5. Acknowledgments
The authors cannot say enough to express their appreciation of the The authors cannot say enough to express their appreciation of the
comments and suggestions we received from Stig Venaas. The authors comments and suggestions we received from Stig Venaas. The authors
greatly appreciate the comments and suggestions by Alvaro Retana that greatly appreciate the comments and suggestions by Alvaro Retana that
improved the clarity of the document. improved the clarity of the document.
6. References 6. References
6.1. Normative References 6.1. Normative References
[I-D.ietf-pim-dr-improvement]
Zhang, Z., Hu, F., Xu, B., and M. Mishra, "Protocol
Independent Multicast - Sparse Mode (PIM-SM) Designated
Router (DR) Improvement", Work in Progress, Internet-
Draft, draft-ietf-pim-dr-improvement-11, 17 February 2021,
<https://www.ietf.org/archive/id/draft-ietf-pim-dr-
improvement-11.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[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>.
[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>.
[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>. 2016, <https://www.rfc-editor.org/info/rfc7761>.
[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>.
skipping to change at page 7, line 27 skipping to change at page 7, line 17
Multipoint Networks", RFC 8562, DOI 10.17487/RFC8562, Multipoint Networks", RFC 8562, DOI 10.17487/RFC8562,
April 2019, <https://www.rfc-editor.org/info/rfc8562>. April 2019, <https://www.rfc-editor.org/info/rfc8562>.
[RFC8775] Cai, Y., Ou, H., Vallepalli, S., Mishra, M., Venaas, S., [RFC8775] Cai, Y., Ou, H., Vallepalli, S., Mishra, M., Venaas, S.,
and A. Green, "PIM Designated Router Load Balancing", and A. Green, "PIM Designated Router Load Balancing",
RFC 8775, DOI 10.17487/RFC8775, April 2020, RFC 8775, DOI 10.17487/RFC8775, April 2020,
<https://www.rfc-editor.org/info/rfc8775>. <https://www.rfc-editor.org/info/rfc8775>.
6.2. Informative References 6.2. Informative References
[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>.
[RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883, (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
June 2010, <https://www.rfc-editor.org/info/rfc5883>. June 2010, <https://www.rfc-editor.org/info/rfc5883>.
Authors' Addresses Authors' Addresses
Greg Mirsky Greg Mirsky
ZTE Corp. Ericsson
Email: gregimirsky@gmail.com Email: gregimirsky@gmail.com
Ji Xiaoli Ji Xiaoli
ZTE Corporation ZTE Corporation
No.50 Software Avenue, Yuhuatai District No.50 Software Avenue, Yuhuatai District
Nanjing, Nanjing,
China China
Email: ji.xiaoli@zte.com.cn Email: ji.xiaoli@zte.com.cn
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