Network Working Group V. Kamath
Internet-Draft VMware
Intended status: Standards Track R. Chokkanathapuram Sundaram
Expires: April 22, 2019 Cisco Systems, Inc.
October 19, 2018
PIM NULL Register packing
draft-ietf-pim-null-register-packing-00
Abstract
In PIM-SM networks PIM registers are sent from the first hop router
to the RP (Rendezvous Point) to signal the presence of Multicast
source in the network.There are periodic PIM Null registers sent from
first hop router to the RP to keep the state alive at the RP as long
as the source is active. The PIM null register packet carry
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 null register packet and the
interoperability between the PIM routers which do not understand the
packet format with multiple Multicast source and group details.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 22, 2019.
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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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions Used in This Document . . . . . . . . . . . . 2
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. PIM Register Stop format with capability option . . . . . . . 3
3. New PIM Null register format . . . . . . . . . . . . . . . . 4
4. New Packed PIM Register Stop format . . . . . . . . . . . . . 5
5. Protocol operation . . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
PIM Null registers are sent by First hop routers 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
increase, the number of PIM null register packets that are sent
increases at a given time. This results in more PIM packet
processing at RP and FHR. The control plane policing(COPP), monitors
the packets that gets processed by the control plane. Due to the
high rate at which NULL registers are received at the RP, this can
lead to COPP drops of Multicast PIM null register packets. This
draft proposes a method to efficiently pack multiple PIM null
registers and register stop into a single message as these packets
anyway don't contain data. The draft also proposes interoperability
with the 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", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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1.2. Terminology
RP: Rendezvous Point
RPF: Reverse Path Forwarding
SPT: Shortest Path Tree
FHR: First Hop Router, directly connected to the source
LHR: Last Hop Router, directly connected to the receiver
2. PIM Register Stop format with capability option
A router (FHR) can decide to pack multiple NULL registers based on
the capability received from the RP as part of Register Stop. This
ensures compatibility with routers that don't support processing of
the new format. The capability information can be indicated by the
RP via the PIM register stop message sent to the FHR. Thus a FHR
will switch to the new format only when it learns RP is capable of
handling the packed null register messages. Conversely, a FHR that
doesn't support the new format can continue generating the PIM NULL
register the usual way since they don't check for the capability
information present in the Register stop message. 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.
Figure 2: PIM Register Stop packet with capability option
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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PIM Version, Reserved, Type, Checksum, Group Address, Source Address
Same as RFC 7761 (Section 4.9.4)
P Capability bit used to indicate support for Packed NULL Register
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3. New PIM Null register format
PIM null-register packet format is enhanced to include the count of
the number of null-register records and pack multiple null-register
records in the same packet. Currently the data part in the NULL
register packet is a dummy IPv4 header which carries the source and
group information and the other fields are unused. To indicate that
the null register is in a new format the "Type" field in the PIM
register packet format is used. To indicate the number of null
register records a new field "record count" is introduced which can
hold 8 bit value (max 255 records can be packed) which can be based
on MTU. Even though null registers are supposed to be sent exactly
every 60s, its fine to send a null register earlier, so as to merge
the registers. When one register is sent, multiple registers can be
packed together which are close enough in time.
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Figure 1: New PIM NULL Register packet format
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 | Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record count | Reserved2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address[1] (Encoded-Group format) |
| Source Address[1] (Encoded-Unicast format) |
. .
. .
. .
. .
. Group Address[N] .
| Source Address[N] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PIM Version, Reserved, Checksum
Same as RFC 7761 (Section 4.9.3)
Type
The new packed NULL Register type value TBD
Record count
The count of the number of packed NULL register records.
A record consists of Group and Source Address
Group Address
IP address of the Multicast Group
Source Address
IP Address of the Multicast Source
4. New Packed PIM Register Stop format
The PIM register stop can be optimized to include multiple multicast
group and source information. The Record count can indicate the
number of S,G records that are packed and the Type value is used to
indicate the new format.
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Figure 3: New PIM Packed Register Stop packet formats
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 | Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record count | Reserved2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address[1] (Encoded-Group format) |
| Source Address[1] (Encoded-Unicast format) |
. .
. .
. .
. .
. Group Address[N] .
| Source Address[N] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PIM Version, Reserved, Checksum
Same as RFC 7761 (Section 4.9.3)
Type
The new packed Register Stop type value TBD
Record count
The count of the number of packed register stop records.
A record consists of Group and Source Address
Group Address
IP address of the Multicast Group
Source Address
IP Address of the Multicast Source
5. Protocol operation
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The following combinations exist -
FHR and RP both support the new PIM Register formats -
a. FHR sends the PIM register towards the RP when a new source is detected
b. RP sends a modified register stop towards the FHR that includes capability
information by setting the P bit (Figure 2)
c. Based on the receipt of the modified Register Stop, FHR will start packing
of NULL registers using the new packed register format (Figure 1)
d. RP processes the NULL registers and can generate Register Stop messages by
packing multiple S,Gs towards the same FHR (Figure 3)
FHR supports but RP doesn't support new PIM Register formats-
a. FHR sends the PIM register towards the RP
b. RP sends a normal register stop without any capability information
c. FHR then sends NULL registers in the old format
RP supports but FHR doesn't support the new PIM Register formats-
a. FHR sends the PIM register towards the RP
b. RP sends a modified register stop towards the FHR that includes
capability information
c. Since FHR doesn't support the new format, it sends NULL registers
in the old format
6. IANA Considerations
This document requires the assignment of 2 new PIM message types for
the packed pim register and pim register stop.
7. Acknowledgments
The authors would like to thank Stig Venaas and Umesh Dudani for
contributing to the original idea and also their very helpful
comments on the draft.
8. References
8.1. 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>.
[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>.
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8.2. Informative References
[RFC3973] Adams, A., Nicholas, J., and W. Siadak, "Protocol
Independent Multicast - Dense Mode (PIM-DM): Protocol
Specification (Revised)", RFC 3973, DOI 10.17487/RFC3973,
January 2005, <https://www.rfc-editor.org/info/rfc3973>.
Authors' Addresses
Vikas Ramesh Kamath
VMware
3401 Hillview Ave
Palo Alto CA 94304
USA
Email: vkamath@vmware.com
Ramakrishnan Chokkanathapuram Sundaram
Cisco Systems, Inc.
Tasman Drive
San Jose CA 95134
USA
Email: ramaksun@cisco.com
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