Internet Engineering Task Force (IETF) L. Zheng
Request for Comments: 7063 Huawei Technologies
Category: Informational Z. Zhang
ISSN: 2070-1721 Juniper Networks
R. Parekh
Cisco Systems
November 2013
Survey Report on Protocol Independent Multicast - Sparse Mode (PIM-SM)
Implementations and Deployments
Abstract
This document provides supporting documentation to advance the IETF
stream's Protocol Independent Multicast - Sparse Mode (PIM-SM)
protocol from
IETF Proposed Standard to an Internet Standard.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7063.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Overview of PIM-SM . . . . . . . . . . . . . . . . . . . 2
1.2. Requirements of RFCs 2026 and 6410 . . . . . . . . . . . 2
2. Survey on Implementations and Deployments . . . . . . . . . . 3
2.1. Methodology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Operator Responses . . . . . . . . . . . . . . . . . . . 3
2.2.1. Description of PIM-SM Deployments . . . . . . . . . . 3 4
2.2.2. PIM-SM Deployment with Other Multicast Technologies . 4
2.2.3. PIM-SM Rendezvous Points (RPs) and RP Discovery
Mechanisms . . . . . . . . . . . . . . . . . . . . . 4
2.3. Vendor Responses . . . . . . . . . . . . . . . . . . . . 4
2.3.1. Implementations Based on RFCs 4601 and 2362 . . . . . 4
2.3.2. Lack of (*,*,RP) and PMBR Implementations . . . . . . 5
2.3.3. Implementations of Other Features of RFC 4601 . . . . 5
2.4. Key Findings . . . . . . . . . . . . . . . . . . . . . . 5
3. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Normative References . . . . . . . . . . . . . . . . . . 6
5.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Questionnaire . . . . . . . . . . . . . . . . . . . 7
A.1. PIM Survey for Operators . . . . . . . . . . . . . . . . 7
A.2. PIM Survey for Implementors . . . . . . . . . . . . . . . 8 9
1. Motivation
1.1. Overview of PIM-SM
Protocol Independent Multicast - Sparse Mode (PIM-SM) was first
published as [RFC2117] in 1997. This version was then obsoleted by
[RFC2362] in 1998. The protocol was classified as Experimental in
both documents. The protocol specification was then rewritten in
whole and advanced to Proposed Standard as [RFC4601] in 2006.
Considering its multiple independent implementations developed and
sufficient successful operational experience gained, the PIM WG
decided to advance the PIM-SM protocol to Internet Standard. The
conducted survey and this document are part of the work.
1.2. Requirements of RFCs 2026 and 6410
[RFC2026] defines the stages in the standardization process, the
requirements for moving a document between stages, and the types of
documents used during this process. Section 4.1.2 of [RFC2026]
states that:
The requirement for at least two independent and interoperable
implementations applies to all of the options and features of the
specification. In cases in which one or more options or features
have not been demonstrated in at least two interoperable
implementations, the specification may advance to the Draft
Standard level only if those options or features are removed.
[RFC6410] updates the IETF Standards Process defined in [RFC2026].
Primarily, it reduces the Standards Process from three Standards
Track maturity levels to two. The second maturity level is a
combination of Draft Standard and Standard as specified in [RFC2026].
Section 2.2 of [RFC6410] states that:
(1) There are at least two independent interoperating
implementations with widespread deployment and successful
operational experience.
(2)...
(3) There are no unused features in the specification that greatly
increase implementation complexity.
Optional features that do not meet the aforesaid criteria have been
identified by the PIM Working Group and will be removed. This
document provides supporting documentation to advance the PIM-SM IETF
stream's Protocol Independent Multicast - Sparse Mode (PIM-SM)
protocol from IETF Proposed Standard to Internet Standard.
2. Survey on Implementations and Deployments
2.1. Methodology
A questionnaire was issued by the PIM WG co-chairs and announced
widely to the vendors and operational community to obtain information
on PIM-SM implementations and deployments. The survey concluded on
22 Oct 2012. The responses remain confidential and only combined
results are published here, while responders chose whether to keep
their affiliations confidential. The raw questionnaire is shown in
Appendix A, and a compilation of the responses is included in the
following section.
2.2. Operator Responses
Nine operators responded to the survey. They are SWITCH, National
Research Council Canada, South Dakota School of Mines and Technology,
Motorola Solutions, and five anonymous operators.
2.2.1. Description of PIM-SM Deployments
Since 1998, PIM-SM has been deployed for a wide variety of
applications: Campus, Enterprise, Research and WAN networks,
Broadband ISP, and Digital TV. There are five deployments based on
[RFC4601] implementations and two on [RFC2362] implementations. PIM-
SM for IPv6 has been deployed by three operators. Out of the nine
operators, six have deployed PIM-SM implementations from multiple
vendors.
Operators reported minor interoperability issues and these were
addressed by the vendors. There was no major interoperability
concern reported by the operators.
2.2.2. PIM-SM Deployment with Other Multicast Technologies
Except for one deployment of PIM-SM with Multicast Extensions to OSPF
(MOSPF), all other operators have deployed PIM-SM exclusively. No
operators acknowledged deployments of either (*,*,RP) or PIM
Multicast Border Route (PMBR) for interconnection between PIM-SM and
other multicast domains.
2.2.3. PIM-SM Rendezvous Points (RPs) and RP Discovery Mechanisms
The number of PIM-SM RPs deployed by operators ranges from a few (up
to
(e.g., sixteen) to a massively scaled number (four hundred). Both
static configuration and Bootstrap Router (BSR) have been deployed as
RP discovery mechanisms.
Anycast-RP has been deployed for RP redundancy. Two operators have
deployed Anycast-RP using the Multicast Source Discovery Protocol
(MSDP) [RFC3446]. Three operators have deployed Anycast-RP using
both MSDP [RFC3446] and PIM [RFC4610] for different scenarios. The
best common practice seems to be to use static-RP configuration with
Anycast-RP for redundancy.
2.3. Vendor Responses
Eight vendors reported PIM-SM implementations. They are XORP, Huawei
Technologies, Cisco Systems, Motorola Solutions, Juniper Networks,
and three other anonymous vendors.
2.3.1. Implementations Based on RFCs 4601 and 2362
Four vendors reported PIM-SM implementations based on [RFC4601] and
two reported PIM-SM implementations based on [RFC2362]. Two other
reported implementations are hybrids.
Minor interoperability issues have been addressed by the vendors over
the years and no concerns were reported by any vendor.
2.3.2. Lack of (*,*,RP) and PMBR Implementations
Most vendors have not implemented (*,*,RP) state as specified in
[RFC4601] either due to lack of deployment requirements or due to
security concerns. Similarly, most vendors have also not implemented
PMBR due to lack of deployment requirements or because it was
considered too complex and non-scalable.
Only one vendor, XORP, reported (*,*,RP) and PMBR implementation and
they were implemented just because these were part of the [RFC4601]
specification.
2.3.3. Implementations of Other Features of RFC 4601
Most vendors have implemented all of the following from the [RFC4601]
specification:
o Source-Specific Multicast (SSM)
o Join suppression
o Explicit tracking
o Register mechanism
o shortest path tree Shortest Path Tree (SPT) switchover at last-hop router
o Assert mechanism
o Hashing of group to RP mappings
Some vendors do not implement explicit tracking and SSM.
2.4. Key Findings
PIM-SM has been widely implemented and deployed for different
applications. The protocol is sufficiently well specified in
[RFC4601] resulting in interoperable implementation deployed by
operators.
There are no deployments and only one known implementation of
(*,*,RP) and PMBR as specified in [RFC4601]. Hence, it is necessary
to remove these features from the specification as required by
[RFC2026] and [RFC6410].
3. Security Considerations
The PIM WG is aware of at least three (and believes there are more)
PIM-SM implementations that support the use of IPsec to protect PIM
messages. For at least one of them, IPsec is not part of the PIM
implementation itself -- one just configures IPsec with Security
Policy Databases (SPDs) where interface, the ALL_PIM_ROUTERS
multicast address, etc., can be used as selectors, according to
[RFC5796].
4. Acknowledgements
The authors would like to thank Tim Chown and Bill Atwood, who helped
to collect and anonymize the responses as the neutral third party.
Special thanks are also given to Alexander Gall, William F F. Maton
Sotomayor, Steve Bauer, Sonum Mathur, Pavlin Radoslavov, Shuxue Fan,
Sameer Gulrajani, and to the anonymous responders.
5. References
5.1. Normative References
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996.
[RFC6410] Housley, R., Crocker, D., and E. Burger, "Reducing the
Standards Track to Two Maturity Levels", BCP 9, RFC 6410,
October 2011.
5.2. Informative References
[RFC2117] Estrin, D., Farinacci, D., Helmy, A., Thaler, D., Deering,
S., Handley, M., Jacobson, V., Liu, C., Sharma, P., and L.
Wei, "Protocol Independent Multicast-Sparse Mode (PIM-SM):
Protocol Specification", RFC 2117, June 1997.
[RFC2362] Estrin, D., Farinacci, D., Helmy, A., Thaler, D., Deering,
S., Handley, M., and V. Jacobson, "Protocol Independent
Multicast-Sparse Mode (PIM-SM): Protocol Specification",
RFC 2362, June 1998.
[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, January 2003.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[RFC4610] Farinacci, D. and Y. Cai, "Anycast-RP Using Protocol
Independent Multicast (PIM)", RFC 4610, August 2006.
[RFC5796] Atwood, W., Islam, S., and M. Siami, "Authentication and
Confidentiality in Protocol Independent Multicast Sparse
Mode (PIM-SM) Link-Local Messages", RFC 5796, March 2010.
Appendix A. Questionnaire
This section provides copies of the questionnaires exactly as
distributed to operators and implementors.
A.1. PIM Survey for Operators
Introduction:
PIM-SM was first published as RFC2117 in 1997 and then again as
RFC2362 in 1998. The protocol was classified as Experimental in
both of these documents. The PIM-SM protocol specification was then
rewritten in whole and advanced to Proposed Standard as RFC4601 in
2006. Considering the multiple independent implementations developed
and the successful operational experience gained, the IETF has
decided to advance the PIM-SM routing protocol to Draft Standard.
This survey intends to provide supporting documentation to advance
the Protocol Independent Multicast - Sparse Mode (PIM-SM) routing
protocol from IETF Proposed Standard to Draft Standard. (Due to
RFC6410, now the intention is to progress it to Internet Standard.
Draft Standard is no longer used.)
This survey is issued on behalf of the IETF PIM Working Group.
The responses will be collected by a neutral third-party and kept
strictly confidential if requested in the response; only the final
combined results will be published. Tim Chown and Bill Atwood have
agreed to anonymize the response to this Questionnaire. They have a
long experience with multicast but have no direct financial interest
in this matter, nor ties to any of the vendors involved. Tim is
working at University of Southampton, UK, and he has been active in
the IETF for many years, including the mboned working group, and he
is a co-chair of the 6renum working group. Bill is at Concordia
University, Montreal, Canada, and he has been an active participant
in the IETF pim working group for over ten years, especially in the
area of security.
Please send questionnaire responses addressed to them both. The
addresses are tjc@ecs.soton.ac.uk and william.atwood@concordia.ca.
Please include the string "RFC4601 bis Questionnaire" in the subject
field.
Before answering the questions, please complete the following
background information.
Name of the Respondent:
Affiliation/Organization:
Contact Email:
Provide description of PIM deployment:
Do you wish to keep the information provided confidential:
Questions:
1 Have you deployed PIM-SM in your network?
2 How long have you had PIM-SM deployed in your network? Do you know
if your deployment is based on the most recent RFC4601?
3 Have you deployed PIM-SM for IPv6 in your network?
4 Are you using equipment with different (multi-vendor) PIM-SM
implementations for your deployment?
5 Have you encountered any inter-operability or backward-
compatibility issues amongst differing implementations? If yes,
what are your concerns about these issues?
6 Have you deployed both dense mode and sparse mode in your network?
If yes, do you route between these modes using features such as
*,*,RP or PMBR?
7 To what extent have you deployed PIM functionality, like BSR, SSM,
and Explicit Tracking?
8 Which RP mapping mechanism do you use: Static, AutoRP, or BSR?
9 How many RPs have you deployed in your network?
10 If you use Anycast-RP, is it Anycast-RP using MSDP (RFC 3446) or
Anycast-RP using PIM (RFC4610)?
11 Do you have any other comments on PIM-SM deployment in your
network?
A.2. PIM Survey for Implementors
Introduction:
PIM-SM was first published as RFC2117 in 1997 and then again as
RFC2362 in 1998. The protocol was classified as Experimental in both
of these documents. The PIM-SM protocol specification was then
rewritten in whole and advanced to Proposed Standard as RFC4601 in
2006. Considering the multiple independent implementations developed
and the successful operational experience gained, the IETF has
decided to advance the PIM-SM routing protocol to Draft Standard.
This survey intends to provide supporting documentation to advance
the Protocol Independent Multicast - Sparse Mode (PIM-SM) routing
protocol from IETF Proposed Standard to Draft Standard. (Due to
RFC6410, now the intention is to progress it to Internet Standard.
Draft Standard is no longer used.)
This survey is issued on behalf of the IETF PIM Working Group.
The responses will be collected by a neutral third-party and kept
strictly confidential if requested in the response; only the final
combined results will be published. Tim Chown and Bill Atwood have
agreed to anonymize the response to this Questionnaire. They have a
long experience with multicast but have no direct financial interest
in this matter, nor ties to any of the vendors involved. Tim is
working at University of Southampton, UK, and he has been active in
the IETF for many years, including the mboned working group, and he
is a co-chair of the 6renum working group. Bill is at Concordia
University, Montreal, Canada, and he has been an active participant
in the IETF pim working group for over ten years, especially in the
area of security.
Please send questionnaire responses addressed to them both. The
addresses are tjc@ecs.soton.ac.uk and william.atwood@concordia.ca.
Please include the string "RFC 4601 bis Questionnaire" in the subject
field.
Before answering the questions, please complete the following
background information.
Name of the Respondent:
Affiliation/Organization:
Contact Email:
Provide description of PIM implementation:
Do you wish to keep the information provided confidential:
Questions:
1 Have you implemented PIM-SM?
2 Is the PIM-SM implementation based on RFC2362 or RFC4601?
3 Have you implemented (*,*, RP) state of RFC4601? What is the
rationale behind implementing or omitting (*,*,RP)?
4 Have you implemented the PMBR as specified in RFC4601 and RFC2715?
What is the rationale behind implementing or omitting PMBR?
5 Have you implemented other features and functions of RFC4601:
- SSM
- Join Suppression
- Explicit tracking
- Register mechanism
- SPT switchover at last-hop router
- Assert mechanism
- Hashing of group to RP mappings
6 Does your PIM-SM implementation support IPv6?
7 Have you encountered any inter-operability issues with other PIM
implementations in trials or in the field?
8 Do you have any other comments or concerns about PIM-SM as
specified in RFC4601?
Authors' Addresses
Lianshu Zheng
Huawei Technologies
China
EMail: vero.zheng@huawei.com
Zhaohui Zhang
Juniper Networks
USA
EMail: zzhang@juniper.net
Rishabh Parekh
Cisco Systems
USA
EMail: riparekh@cisco.com