Internet DRAFT - draft-ietf-pim-null-register-packing
draft-ietf-pim-null-register-packing
Network Working Group V. Kamath
Internet-Draft VMware
Intended status: Standards Track R. Chokkanathapuram Sundaram
Expires: 14 September 2023 Cisco Systems, Inc.
R. Banthia
Apstra
A. Gopal
Cisco Systems, Inc.
13 March 2023
PIM Null-Register packing
draft-ietf-pim-null-register-packing-16
Abstract
In PIM-SM networks, PIM Null-Register messages are sent by the
Designated Router (DR) to the Rendezvous Point (RP) to signal the
presence of Multicast sources in the network. There are periodic PIM
Null-Registers sent from the DR to the RP to keep the state alive at
the RP as long as the source is active. The PIM Null-Register
message carries information about a single Multicast source and
group.
This document defines a standard to send multiple Multicast source
and group information in a single PIM message. This document refers
to the new messages as the PIM Packed Null-Register message and PIM
Packed Register-Stop message.
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 14 September 2023.
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Copyright Notice
Copyright (c) 2023 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 Revised BSD License text as
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Packed Null-Register Packing Capability . . . . . . . . . . . 3
3. PIM Packed Null-Register message format . . . . . . . . . . . 3
4. PIM Packed Register-Stop message format . . . . . . . . . . . 4
5. Protocol operation . . . . . . . . . . . . . . . . . . . . . 5
6. Operational Considerations . . . . . . . . . . . . . . . . . 6
6.1. PIM Anycast RP Considerations . . . . . . . . . . . . . . 6
6.2. Interoperability between different versions . . . . . . . 6
6.3. Disabling PIM Packed Message Support at RP and/or DR . . 6
7. Fragmentation Considerations . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
11. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
The DR periodically sends PIM Null-Registers to keep the state of
existing multicast sources active on the RP. As the number of
multicast sources increases, the number of PIM Null-Register messages
that are sent also increases. This results in more PIM packet
processing at the RP and the DR.
This document specifies a method to efficiently pack the content of
multiple PIM Null-Register and Register-Stop messages [RFC7761] into
a single message.
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The document also discusses interoperability between PIM routers that
support PIM Packed Null-Registers and PIM Packed Register-Stops and
PIM routers that do not.
1.1. Conventions used in this document
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.
1.2. Terminology
RP: Rendezvous Point
DR: Designated Router
2. Packed Null-Register Packing Capability
The RP indicates its ability to receive PIM Packed Null-Register
messages (Section 3) and send PIM Packed Register-Stop messages
(Section 4) with a Packing Capability bit (P-bit) in the PIM
Register-Stop message. The P-bit is allocated in Section 9.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PIM Ver| Type |P|6 5 4 3 2 1 0| Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address (Encoded-Group format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address (Encoded-Unicast format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: PIM Register-Stop message with Packing Capability option
The fields in the PIM Register-Stop message are defined in
Section 4.9.4 of [RFC7761], and the common header in
[I-D.venaas-pim-rfc8736bis].
Packing Capability bit (P-bit / Flag Bit TBD1): When set, it
indicates the ability of the RP to receive PIM Packed Null-Register
messages, and send PIM Packed Register-Stop messages.
3. PIM Packed Null-Register message format
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PIM Ver| Type |Subtype| FB | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address[1] (Encoded-Group format) |
| Source Address[1] (Encoded-Unicast format) |
. .
. .
. .
. .
. Group Address[N] .
| Source Address[N] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: PIM Packed Null-Register message format
The fields in the PIM Packed Null-Register message are defined in
Section 4.9.4 of [RFC7761], and the common header in
[I-D.venaas-pim-rfc8736bis]
Type, Subtype: The PIM Packed Null-Register Type value TBD2.
[I-D.venaas-pim-rfc8736bis]
N: The total number of records; A record consists of a Group Address
and Source Address pair.
After parsing the PIM common header, individual records are then
parsed one by one until the length of the PIM Packed Null-Register
message. This length is inferred from the IP layer.
Sending or receiving a PIM Packed Null-Register message is the
equivalent, for all purposes, of sending or receiving an individual
Null-Register message for each record represented in the PIM Packed
Null-Register message.
4. PIM Packed Register-Stop message format
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PIM Ver| Type |Subtype| FB | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address[1] (Encoded-Group format) |
| Source Address[1] (Encoded-Unicast format) |
. .
. .
. .
. .
. Group Address[N] .
| Source Address[N] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: PIM Packed Register-Stop message format
The fields in the PIM Packed Register-Stop message are defined in
Section 4.9.4 of [RFC7761], and the common header in
[I-D.venaas-pim-rfc8736bis]
Type, Subtype: The PIM Packed Register-Stop Type TBD3
N: The total number of records; A record consists of a Group Address
and Source Address pair.
After parsing the PIM common header, individual records are then
parsed one by one until the length of the PIM Packed Register-Stop
message. This length is inferred from the IP layer.
Sending or receiving a PIM Packed Register-Stop message is the
equivalent, for all purposes, of sending or receiving an individual
Null-Register message for each record represented in the PIM Packed
Register-Stop.
5. Protocol operation
As specified in [RFC7761], the DR sends PIM Register messages towards
the RP when a new source is detected.
When this feature is enabled/configured, an RP supporting this
specification MUST set the P-bit (Flag bit TBD1) in all Register-Stop
messages.
When a Register-Stop message with the P-bit set is received, the DR
SHOULD send PIM Packed Null-Register messages (Section 3) to the RP
instead of multiple Register messages with the N-bit set [RFC7761].
The DR MAY use a mixture of PIM Packed Null-Register messages and
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Register messages. The decision is up to the implementation and out
of the scope of this document. However, it is RECOMMENDED to stick
to the PIM Packed Null-Register and PIM Packed Register-Stop formats
as long as the RP and DR have the feature enabled.
The RP, after receiving a PIM Packed Null-Register message, SHOULD
start sending PIM Packed Register-Stop messages (Section 4) to the
corresponding DR instead of individual Register-Stop messages. The
RP MAY use a mixture of PIM Packed Register-Stop messages and
individual Register-Stop messages. The decision is up to the
implementation and out of the scope of this document. However, it is
RECOMMENDED to stick to the PIM Packed Null-Register and PIM Packed
Register-Stop formats as long as the RP and DR have the feature
enabled.
6. Operational Considerations
6.1. PIM Anycast RP Considerations
The PIM Packed Null-Register packet format should be enabled only if
it is supported by all the routers in the Anycast-RP set [RFC4610].
This consideration applies to PIM Anycast RP with MSDP [RFC3446] as
well.
6.2. Interoperability between different versions
A router (DR) can decide to use the PIM Packed Null-Register message
format based on the Packing Capability received from the RP as part
of the PIM Register-Stop. This ensures compatibility with routers
that do not support processing of the new packet format. The Packing
Capability information MUST be indicated by the RP via the PIM
Register-Stop message sent to the DR. Thus, a DR will switch to the
new packet format only when it learns that the RP is capable of
handling the PIM Packed Null-Register messages.
Conversely, a DR that does not support the packed format can continue
generating the PIM Null-Register as defined in [RFC7761]
(Section 4.4).
6.3. Disabling PIM Packed Message Support at RP and/or DR
Consider a PIM RP router that supports PIM Packed Null-Registers and
PIM Packed Register-Stops. In scenarios where this router now no
longer supports this feature, for example, in case of a software
downgrade, it will not send a PIM Register-Stop message to the DR in
response to a PIM Packed Null-Register message.
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When the DR switches to Data Registers from Null-Registers, it MUST
start a Packed_Register_Probe_Time timer. If no PIM Packed Register-
Stop or Register-Stop with the P-bit set is received within
Packed_Register_Probe_Time seconds, the DR can decide that the RP no
longer supports PIM Packed Null-Registers. The
Packed_Register_Probe_Time timer is configurable; its default value
is 60 seconds.
When Packed_Register_Probe_Time expires, The DR MAY also send an
unpacked PIM Null-Register and check the PIM Register-Stop to see if
the P-bit is set or not. If it is not set then the DR will continue
sending unpacked PIM Null-Register messages.
In case the network manager disables the Packing Capability at the
RP, or in other words, disables the feature from the RP, the router
MUST NOT advertise the Packing Capability. However, an
implementation MAY choose to still parse any packed registers if they
are received. This may be particularly useful in the transitional
period after the network manager disables it.
7. Fragmentation Considerations
As explained in Section 4.4.1 of [RFC7761], the DR may perform Path
MTU Discovery to the RP before sending PIM Packed Null-Register
messages. Similarly, the RP may perform Path MTU Discovery to the DR
before sending PIM Packed Register-Stop messages. In both cases, the
number of records in a message should be limited such that it can fit
within the Path MTU.
8. Security Considerations
The Security Considerations from [RFC7761] apply to this document.
In particular, the effect of forging a PIM Packed Null-Register or
Register-Stop message would be amplified to all the records included
instead of just one.
By forging a PIM Register-Stop message and setting the P-bit, an
attacker can trigger the use of PIM Packed Null-Register messages by
a DR thus creating unnecessary churn in the network.
9. IANA Considerations
When this document is published, IANA is asked to assign a Packing
Capability bit (TBD1) in the PIM Register-Stop Common Header from the
PIM Message Types registry.
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When this document is published, IANA is asked to assign a PIM
message type (TBD2) for the PIM Packed Null-Register from the PIM
Message Types registry. The Flag Bits (0-3) for PIM message type
(TBD2) are requested to be "Unassigned".
When this document is published, IANA is asked to assign a PIM
message type (TBD3) for the PIM Packed Register-Stop from the PIM
Message Types registry. The Flag Bits (0-3) for PIM message type
(TBD3) are requested to be "Unassigned".
10. Acknowledgments
The authors would like to thank Stig Venaas, Alvaro Retana, Anish
Peter, Zheng Zhang and Umesh Dudani for their helpful comments on the
document.
11. 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>.
[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>.
[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>.
[RFC4610] Farinacci, D. and Y. Cai, "Anycast-RP Using Protocol
Independent Multicast (PIM)", RFC 4610,
DOI 10.17487/RFC4610, August 2006,
<https://www.rfc-editor.org/info/rfc4610>.
[I-D.venaas-pim-rfc8736bis]
Venaas, S. and A. Retana, "PIM Message Type Space
Extension and Reserved Bits", Work in Progress, Internet-
Draft, draft-venaas-pim-rfc8736bis-00, 1 March 2023,
<https://datatracker.ietf.org/doc/html/draft-venaas-pim-
rfc8736bis-00>.
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[RFC3446] Kim, D., Meyer, D., Kilmer, H., and D. Farinacci, "Anycast
Rendevous Point (RP) mechanism using Protocol Independent
Multicast (PIM) and Multicast Source Discovery Protocol
(MSDP)", RFC 3446, DOI 10.17487/RFC3446, January 2003,
<https://www.rfc-editor.org/info/rfc3446>.
Authors' Addresses
Vikas Ramesh Kamath
VMware
3401 Hillview Ave
Palo Alto, CA 94304
United States of America
Email: vkamath@vmware.com
Ramakrishnan Chokkanathapuram Sundaram
Cisco Systems, Inc.
Tasman Drive
San Jose, CA 95134
United States of America
Email: ramaksun@cisco.com
Raunak Banthia
Apstra
333 Middlefield Rd STE 200
Menlo Park, CA 94025
United States of America
Email: rbanthia@apstra.com
Ananya Gopal
Cisco Systems, Inc.
Tasman Drive
San Jose, CA 95134
United States of America
Email: ananygop@cisco.com
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