Hi Russ,
thank you for your thorough review, thoughtful and helpful suggestions. Please find my notes in-lined below under the GIM>> tag. I've attached the new working version and the diff.
Regards,
Greg
On Tue, Sep 21, 2021 at 9:17 AM Russ Housley via Datatracker <noreply@xxxxxxxx> wrote:
Reviewer: Russ Housley
Review result: Has Issues
I reviewed this document as part of the Security Directorate's ongoing
effort to review all IETF documents being processed by the IESG. These
comments were written primarily for the benefit of the Security Area
Directors. Document authors, document editors, and WG chairs should
treat these comments just like any other IETF Last Call comments.
Document: draft-ietf-pim-bfd-p2mp-use-case-07
Reviewer: Russ Housley
Review Date: 2021-09-21
IETF LC End Date: 2021-09-28
IESG Telechat date: Unknown
Summary: Has Issues
Major Concerns: None
Minor Concerns:
General: All of the field names in this document use camel case, except
one. I think the document would be easier to read if My Discriminator
were to use the same convention. Also, HeadDiscriminator would be
more descriptive.
GIM>> Thank you for pointing this out to me. I agree with the proposed update of the field name, The remaining in the text references to My Discriminator use the convention of RFC 5880. I hope that is acceptable.
Section 2.1 says:
The head MUST include the BFD Discriminator option in its Hello
messages.
This MUST statement cold me much more complete:
The head MUST include the BFD Discriminator option in its Hello
messages, and it MUST include a 4-byte My Discriminator with a
value other than zero.
GIM>> Thank you, I agree with the proposed text with a minor modification based on re-naming of the field to HeadDiscriminator. Below is the update:
OLD TEXT:
The head MUST include the BFD Discriminator option in its Hello
messages.
NEW TEXT:
The head MUST include the BFD Discriminator option in its Hello
messages, and it MUST include a 4-byte HeadDiscriminator with a value
other than zero.
Section 2.3: s/must set/MUST set/
GIM>> Thank you. Done.
Nits:
Section 1, para 1 could be more clear and more forceful. I suggest:
Faster convergence in the control plane minimizes the periods of
traffic blackholing, transient routing loops, and other situations
that may negatively affect service data flow. Faster convergence
in the control plane is beneficial to unicast and multicast routing
protocols.
GIM>> Thank you for the suggested text. Accepted.
Section 1, para 2: s/DR is to act on behalf/DR acts on behalf/
GIM>> Thank you. Done.
Section 1, para 3: The first sentence is very unclear. I cannot offer
an improvement because it is too hard to parse.
GIM>> Would the following update make it clearer:
OLD TEXT:
Bidirectional Forwarding Detection (BFD) [RFC5880] had been
originally defined to detect a failure of point-to-point (p2p) paths
- single-hop [RFC5881], multihop [RFC5883].
NEW TEXT:
Bidirectional Forwarding Detection (BFD) [RFC5880] had been
originally defined to detect a failure of a point-to-point (p2p)
path, single-hop [RFC5881] or multihop [RFC5883].
Section 1, para 3: s/networks precisely/networks, and it precisely/
GIM>> Thank you. Accepted.
Section 1.1.1: s/familiarity/Familiarity/
GIM>> Done.
PIM Working Group G. Mirsky
Internet-Draft Ericsson
Intended status: Standards Track J. Xiaoli
Expires: March 25, 2022 ZTE Corporation
September 21, 2021
Fast Failover in Protocol Independent Multicast - Sparse Mode (PIM-SM)
Using Bidirectional Forwarding Detection (BFD) for Multipoint Networks
draft-ietf-pim-bfd-p2mp-use-case-08
Abstract
This document specifies how Bidirectional Forwarding Detection for
multipoint networks can provide sub-second failover for routers that
participate in Protocol Independent Multicast - Sparse Mode (PIM-SM).
An extension to the PIM Hello message used to bootstrap a point-to-
multipoint BFD session is also defined in this document.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 25, 2022.
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
Mirsky & Xiaoli Expires March 25, 2022 [Page 1]
Internet-Draft BFD P2MP Use in PIM-SM September 2021
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
2. BFD Discriminator PIM Hello Option . . . . . . . . . . . . . 3
2.1. Using P2MP BFD in PIM Router Monitoring . . . . . . . . . 4
2.2. P2MP BFD in PIM DR Load Balancing . . . . . . . . . . . . 5
2.3. Multipoint BFD Encapsulation . . . . . . . . . . . . . . 5
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Faster convergence in the control plane minimizes the periods of
traffic blackholing, transient routing loops, and other situations
that may negatively affect service data flow. Faster convergence in
the control plane is beneficial to unicast and multicast routing
protocols.
[RFC7761] is the current specification of the Protocol Independent
Multicast - Sparse Mode (PIM-SM) for IPv4 and IPv6 networks. A
conforming implementation of PIM-SM elects a Designated Router (DR)
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
acts on behalf of directly connected hosts in the context of the PIM-
SM protocol. Failure of the DR impacts the quality of the multicast
services it provides to directly connected hosts because the default
failure detection interval for PIM-SM routers is 105 seconds.
Bidirectional Forwarding Detection (BFD) [RFC5880] had been
originally defined to detect a failure of a point-to-point (p2p)
path, single-hop [RFC5881] or multihop [RFC5883]. In some PIM-SM
deployments, a p2p BFD can be used to detect a failure and enable
faster failover. [RFC8562] extends the BFD base specification
[RFC5880] for multipoint and multicast networks, and it precisely
characterizes deployment scenarios for PIM-SM over a LAN segment.
Among specific characteristics of p2mp BFD that particularly benefit
PIM-SM over a LAN segment is a faster transition to the Up state of
Mirsky & Xiaoli Expires March 25, 2022 [Page 2]
Internet-Draft BFD P2MP Use in PIM-SM September 2021
the p2mp BFD session due to avoidance of the three-way handshake
required in p2p BFD [RFC5880]. Also, because the router that
transmits BFD Control messages uses the BFD Demand mode [RFC5880], it
maintains less BFD state than the Asynchronous mode. Point-to-
multipoint (p2mp) BFD can enable faster detection of PIM-SM router
failure and thus minimize multicast service disruption. The
monitored PIM-SM router acts as the head and other routers as tails
of a p2mp BFD session. This document defines the monitoring of a
PIM-SM router using p2mp BFD. The document also defines the
extension to PIM-SM [RFC7761] to bootstrap a PIM-SM router to join in
p2mp BFD session over shared media segment.
1.1. Conventions used in this document
1.1.1. Terminology
This document uses terminology defined in [RFC5880], [RFC8562], and
[RFC7761]. Familiarity with these specifications and the terminology
used is expected.
1.1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. 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.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OptionType | OptionLength |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HeadDiscriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: BFD Discriminator PIM Hello Option
where new fields are interpreted as:
OptionType: TBA.
OptionLength: MUST be set to 4.
Mirsky & Xiaoli Expires March 25, 2022 [Page 3]
Internet-Draft BFD P2MP Use in PIM-SM September 2021
HeadDiscriminator: equals the value of My Discriminator
([RFC5880]) allocated by the head.
If the value of the OptionLength field is not equal to 4, the BFD
Discriminator PIM Hello option is considered malformed, and the
receiver MUST stop processing PIM Hello options. If the value of the
HeadDiscriminator field equals zero, then the BFD Discriminator PIM
Hello option MUST be considered invalid, and the receiver MUST ignore
it. The receiver SHOULD log a notification regarding the malformed
or invalid BFD Discriminator Hello option under the control of a
throttling logging mechanism.
2.1. Using P2MP BFD in PIM Router Monitoring
The head MUST create a BFD session of type MultipointHead [RFC8562].
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
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, 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
BFD, referred to through this document as 'tail', receives a PIM-
Hello packet with the BFD Discriminator PIM Hello option, the tail
MAY create a p2mp BFD session of type MultipointTail, as defined in
[RFC8562].
The node that includes the BFD Discriminator PIM Hello option
transmits BFD Control packets periodically. For the tail to
correctly demultiplex BFD [RFC8562], the source address, and My
Discriminator values of the BFD packets MUST be the same as those of
the HeadDiscriminator 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 is, the head of the p2mp BFD session, though the
regular PIM-SM mechanisms remain fully operational.
If the tail detects a MultipointHead failure [RFC8562], it MUST
delete the corresponding neighbor state and follow procedures defined
in [RFC7761].
If the head ceases to include the BFD Discriminator PIM Hello option
in its PIM-Hello message, tails MUST close the corresponding
MultipointTail BFD session without affecting the PIM state in any
way. Thus the tail stops using BFD to monitor the head and reverts
to the procedures defined in [RFC7761].
Mirsky & Xiaoli Expires March 25, 2022 [Page 4]
Internet-Draft BFD P2MP Use in PIM-SM September 2021
2.2. P2MP BFD in PIM DR Load Balancing
[RFC8775] specifies the PIM Designated Router Load Balancing (DRLB)
functionality. Any PIM router that advertises the DRLB-Cap Hello
Option can become the head of a p2mp BFD session, as specified in
Section 2.1. The head router administratively sets the
bfd.SessionState to Up in the MultipointHead session [RFC8562] only
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
GDR, then it MUST shut down following the procedures described in
Section 5.9 [RFC8562]. For each GDR Candidate that includes BFD
Discriminator option in its PIM Hello, the PIM DR creates a
MultipointTail session [RFC8562]. PIM DR demultiplexes BFD sessions
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
remove that router from the GDR Candidate list and immediately
transmit a new DRLB-List option.
2.3. Multipoint BFD Encapsulation
The MultipointHead of a p2mp BFD session when transmitting BFD
Control packets:
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
and 'ff02::d' for IPv6) as destination IP address
3. IANA Considerations
IANA is requested to allocate a new OptionType value from PIM-Hello
Options registry according to:
+-------+--------+--------------------------+---------------+
| Value | Length | Name | Reference |
+-------+--------+--------------------------+---------------+
| TBA | 4 | BFD Discriminator Option | This document |
+-------+--------+--------------------------+---------------+
Table 1: BFD Discriminator option type
4. Security Considerations
The security considerations discussed in [RFC7761], [RFC5880],
[RFC8562], and [RFC8775] apply to this document.
Mirsky & Xiaoli Expires March 25, 2022 [Page 5]
Internet-Draft BFD P2MP Use in PIM-SM September 2021
5. Acknowledgments
The authors cannot say enough to express their appreciation of the
comments and suggestions we received from Stig Venaas. The authors
greatly appreciate the comments and suggestions by Alvaro Retana that
improved the clarity of the document.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
DOI 10.17487/RFC5881, June 2010,
<https://www.rfc-editor.org/info/rfc5881>.
[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8562] Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky,
Ed., "Bidirectional Forwarding Detection (BFD) for
Multipoint Networks", RFC 8562, DOI 10.17487/RFC8562,
April 2019, <https://www.rfc-editor.org/info/rfc8562>.
[RFC8775] Cai, Y., Ou, H., Vallepalli, S., Mishra, M., Venaas, S.,
and A. Green, "PIM Designated Router Load Balancing",
RFC 8775, DOI 10.17487/RFC8775, April 2020,
<https://www.rfc-editor.org/info/rfc8775>.
Mirsky & Xiaoli Expires March 25, 2022 [Page 6]
Internet-Draft BFD P2MP Use in PIM-SM September 2021
6.2. Informative References
[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>.
Authors' Addresses
Greg Mirsky
Ericsson
Email: gregimirsky@xxxxxxxxx
Ji Xiaoli
ZTE Corporation
No.50 Software Avenue, Yuhuatai District
Nanjing
China
Email: ji.xiaoli@xxxxxxxxxx
Mirsky & Xiaoli Expires March 25, 2022 [Page 7]
<<< text/html; charset="UTF-8"; name="Diff_ draft-ietf-pim-bfd-p2mp-use-case-07.txt - draft-ietf-pim-bfd-p2mp-use-case-08.txt.html": Unrecognized >>>
-- last-call mailing list last-call@xxxxxxxx https://www.ietf.org/mailman/listinfo/last-call
