PIM Null-Register packing
draft-ietf-pim-null-register-packing-11
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9465.
|
|
|---|---|---|---|
| Authors | Vikas Ramesh Kamath , Ramakrishnan Cokkanathapuram Sundaram , Raunak Banthia , Ananya Gopal | ||
| Last updated | 2022-12-20 (Latest revision 2021-11-07) | ||
| Replaces | draft-ramki-pim-null-register-packing | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
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||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Mike McBride | ||
| Shepherd write-up | Show Last changed 2020-02-24 | ||
| IESG | IESG state | Became RFC 9465 (Proposed Standard) | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Alvaro Retana | ||
| Send notices to | Mike McBride <mmcbride7@gmail.com>, aretana.ietf@gmail.com |
draft-ietf-pim-null-register-packing-11
Network Working Group V. Kamath
Internet-Draft VMware
Intended status: Standards Track R. Chokkanathapuram Sundaram
Expires: 11 May 2022 Cisco Systems, Inc.
R. Banthia
Apstra
A. Gopal
Cisco Systems, Inc.
7 November 2021
PIM Null-Register packing
draft-ietf-pim-null-register-packing-11
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 Packed Null-Register message.
We will refer to the new packed formats as the PIM Packed Null-
Register format and PIM Packed Register-Stop format throughout the
document. This document also discusses interoperability between the
PIM routers which do not understand the PIM Packed Null-Register
format and routers which do understand it.
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 11 May 2022.
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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 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
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Packed Null-Register Capability . . . . . . . . . . . . . . . 3
3. PIM Packed Null-Register message format . . . . . . . . . . . 4
4. PIM Packed Register-Stop message format . . . . . . . . . . . 5
5. Protocol operation . . . . . . . . . . . . . . . . . . . . . 6
6. Operational Considerations . . . . . . . . . . . . . . . . . 7
7. PIM Anycast RP Considerations . . . . . . . . . . . . . . . . 7
8. PIM RP router version downgrade . . . . . . . . . . . . . . . 7
9. Fragmentation Considerations . . . . . . . . . . . . . . . . 7
10. Security Considerations . . . . . . . . . . . . . . . . . . . 8
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
13.1. Normative References . . . . . . . . . . . . . . . . . . 8
13.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
PIM Null-Registers are sent by the DR periodically for Multicast
streams to keep the states active on the RP, as long as the multicast
source is alive. 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.
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The control plane policing (COPP), monitors the packets that are
processed by the control plane. The high rate at which Null-
Registers are received at the RP can lead to COPP drops of Multicast
PIM Null-Register messages. This draft proposes a method to
efficiently pack multiple PIM Null-Registers [RFC7761] (Section 4.4)
and Register-Stops [RFC7761](Section 3.2) into a single message as
these packets anyway do not contain encapsulated data.
The draft also discusses interoperability with PIM routers that do
not understand the new packet format.
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 Capability
A router (DR) can decide to pack multiple Null-Register messages
based on the 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 format. The capability information can
be indicated by the RP via the PIM Register-Stop message sent to the
DR. Thus a DR will switch to the new 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). To exchange the capability information in the
Register-Stop message, the "Reserved" field can be used to indicate
this capability in those Register-Stop messages. One bit of the
Reserved field is used to indicate the "packing" capability (P bit).
The rest of the bits in the "Reserved" field will be retained for
future use.
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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 |P| Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address (Encoded-Group format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address (Encoded-Unicast format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: PIM Register-Stop message with capability option
PIM Version, Type, Checksum, Group Address, Source Address:
Same as [RFC7761] (Section 4.9.4)
P:
Capability bit (flag bit 7) used to indicate support for the
Packed Null-Register Capability
3. PIM Packed Null-Register message format
PIM Packed Null-Register message format includes a count to indicate
the number of Null-Register records in the message.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Count | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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
PIM Version, Reserved, Checksum:
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Same as [RFC7761] (Section 4.9.3)
Type, SubType:
The new packed Null-Register Type and SubType values TBD.
[RFC8736]
Count:
The number of packed Null-Register records. A record consists of
a Group Address and Source Address pair.
Group Address, Source Address:
Same as [RFC7761] (Section 4.9.4)
4. PIM Packed Register-Stop message format
The PIM Packed Register-Stop message includes a count to indicate the
number of records that are present in the message.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Count | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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
PIM Version, Reserved, Checksum:
Same as [RFC7761] (Section 4.9.4)
Type:
The new Register Stop Type and SubType values TBD
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Count:
The number of PIM packed Register-Stop records. A record consists
of a Group Address and Source Address pair.
Group Address, Source Address:
Same as [RFC7761] (Section 4.9.4)
5. Protocol operation
The following combinations exist -
1. DR and RP both support the PIM Packed Null-Register and PIM
Packed Register-Stop formats:
* As specified in [RFC7761], the DR sends PIM Register messages
towards the RP when a new source is detected.
* An RP supporting this specification MUST set the P-bit in the
corresponding 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 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.
2. DR supports but RP does not support the PIM Packed Null-Register
and PIM Packed Register-Stop formats:
* As specified in [RFC7761], DR sends PIM Null-Registers towards
the RP.
* After receiving DR's PIM Null-Register message, RP sends a
normal Register-Stop without any capability information.
* DR then sends PIM Null-Registers in the unpacked format
[RFC7761].
3. RP supports but DR does not support the PIM Packed Null-Register
and PIM Packed Register-Stop formats:
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* As specified in [RFC7761], DR sends the PIM Null-Register
towards the RP.
* After receiving DR's PIM Null-Register message, RP sends a PIM
Packed Register-Stop towards the DR that includes capability
information.
* Since DR does not support the new format, it sends PIM Null-
Registers in the unpacked format [RFC7761].
6. Operational Considerations
In case the network manager disables the packed capability at the RP,
the router should not advertise the 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. PIM Anycast RP Considerations
The PIM Packed Null-Register format should be enabled only if it is
supported by all PIM Anycast RP [RFC4610] members in the RP set for
the RP address. This consideration applies to PIM Anycast RP with
MSDP [RFC3446] as well.
8. PIM RP router version downgrade
Consider a PIM RP router that supports PIM Packed Null-Registers and
PIM Packed Register-Stops. When this router downgrades to a software
version which does not support PIM Packed Null-Registers and PIM
Packed Register-Stops, the DR that sends the PIM Packed Null-Register
message will not get a PIM Register-Stop message back from the RP.
In such scenarios the DR can send an unpacked PIM Null-Register and
check the PIM Register-Stop to see if the capability bit (P-bit) for
PIM Packed Null-Register is set or not. If it is not set then the DR
will continue sending unpacked PIM Null-Register messages.
9. Fragmentation Considerations
When building a PIM Packed Null-Register message or PIM Packed
Register-Stop message, a router should include as many records as
possible based on the path MTU towards RP, if path MTU discovery is
done. Otherwise, the number of records should be limited by the MTU
of the outgoing interface.
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10. Security Considerations
General Register messages security considerations from [RFC7761]
apply. As mentioned in [RFC7761], PIM Null-Register messages and
Register-Stop messages are forwarded by intermediate routers to their
destination using normal IP forwarding. Without data origin
authentication, an attacker who is located anywhere in the network
may be able to forge a Null-Register or Register-Stop message. We
next consider the effect of a forgery of each of these messages. By
forging a Register message, an attacker can cause the RP to inject
forged traffic onto the shared multicast tree.
By forging a Register-Stop message, an attacker can prevent a
legitimate DR from registering packets to the RP. This can prevent
local hosts on that LAN from sending multicast packets. The above
two PIM messages are not changed by intermediate routers and need
only be examined by the intended receiver. Thus, these messages can
be authenticated end-to-end. Attacks on Register and Register-Stop
messages do not apply to a PIM-SSM-only implementation, as these
messages are not used in PIM-SSM.
There is another case where a spoofed Register-Stop can be sent to
make it appear that is from the RP, and that the RP supports this new
packed capability when it does not. This can cause Null-Registers to
be sent to an RP that doesnt support this packed format. But
standard methods to prevent spoofing should take care of this case.
For example, uRPF can be used to filter out packets coming from the
outside from addresses that belong to routers inside.
11. IANA Considerations
This document requires the assignment of Capability bit (P-bit),
flag bit 7 in the PIM Register-Stop message.
This document requires the assignment of 2 new PIM message types
for the PIM Packed Null-Register and PIM Packed Register-Stop.
12. Acknowledgments
The authors would like to thank Stig Venaas, Anish Peter, Zheng Zhang
and Umesh Dudani for their helpful comments on the draft.
13. References
13.1. Normative References
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[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>.
[RFC8736] Venaas, S. and A. Retana, "PIM Message Type Space
Extension and Reserved Bits", RFC 8736,
DOI 10.17487/RFC8736, February 2020,
<https://www.rfc-editor.org/info/rfc8736>.
13.2. Informative References
[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
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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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