draft-ietf-pim-group-rp-mapping-10.txt   rfc6226.txt 
PIM Working Group B. Joshi Internet Engineering Task Force (IETF) B. Joshi
Internet-Draft Infosys Technologies Ltd. Request for Comments: 6226 Infosys Technologies Ltd.
Updates: 4601 (if approved) A. Kessler Updates: 4601 A. Kessler
Intended status: Standards Track Cisco Systems, Inc. Category: Standards Track Cisco Systems, Inc.
Expires: August 1, 2011 D. McWalter ISSN: 2070-1721 D. McWalter
January 28, 2011 May 2011
PIM Group-to-RP Mapping PIM Group-to-Rendezvous-Point Mapping
draft-ietf-pim-group-rp-mapping-10.txt
Abstract Abstract
Each PIM-SM router in a Protocol Independent Multicast (PIM) Domain Each Protocol Independent Multicast - Sparse Mode (PIM-SM) router in
which supports Any Source Multicast (ASM) maintains Group-to-RP a PIM domain that supports Any Source Multicast (ASM) maintains
mappings which are used to identify a Rendezvous Point(RP) for a Group-to-RP mappings that are used to identify a Rendezvous Point
specific multicast group. PIM-SM has defined an algorithm to choose (RP) for a specific multicast group. PIM-SM has defined an algorithm
a RP from the Group-to-RP mappings learned using various mechanisms. to choose a RP from the Group-to-RP mappings learned using various
This algorithm does not consider the PIM mode and the mechanism mechanisms. This algorithm does not consider the PIM mode and the
through which a Group-to-RP mapping was learned. mechanism through which a Group-to-RP mapping was learned.
This document defines a standard algorithm to deterministically This document defines a standard algorithm to deterministically
choose between several Group-to-RP mappings for a specific group. choose between several Group-to-RP mappings for a specific group.
This document first explains the requirements to extend the This document first explains the requirements to extend the Group-to-
Group-to-RP mapping algorithm and then proposes the new algorithm. RP mapping algorithm and then proposes the new algorithm.
Status of this Memo
This Internet-Draft is submitted in full conformance with the Status of This Memo
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This is an Internet Standards Track document.
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on August 1, 2011. 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/rfc6226.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ....................................................2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology .....................................................3
3. Existing algorithm . . . . . . . . . . . . . . . . . . . . . . 5 3. Existing Algorithm ..............................................4
4. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Assumptions .....................................................5
5. Common use cases . . . . . . . . . . . . . . . . . . . . . . . 7 5. Common Use Cases ................................................5
6. Proposed algorithm . . . . . . . . . . . . . . . . . . . . . . 8 6. Proposed Algorithm ..............................................6
7. Interpretation of MIB Objects . . . . . . . . . . . . . . . . 10 7. Interpretation of MIB Objects ...................................8
8. Clarification for MIB Objects . . . . . . . . . . . . . . . . 11 8. Clarification for MIB Objects ...................................8
9. Use of dynamic Group-to-RP mapping protocols . . . . . . . . . 12 9. Use of Dynamic Group-to-RP Mapping Protocols ....................9
10. Consideration for Bidirectional-PIM and BSR hash . . . . . . . 13 10. Considerations for Bidirectional-PIM and BSR Hash ..............9
11. Filtering Group-to-RP mappings at domain boundaries . . . . . 14 11. Filtering Group-to-RP Mappings at Domain Boundaries ............9
12. Security Consideration . . . . . . . . . . . . . . . . . . . . 15 12. Security Considerations .......................................10
13. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 16 13. Acknowledgements ..............................................10
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 14. Normative References ..........................................10
15. Normative References . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
Multiple mechanisms exist today to create and distribute Group-to-RP Multiple mechanisms exist today to create and distribute Group-to-RP
mappings. Each PIM-SM router may learn Group-to-RP mappings through mappings. Each PIM-SM router may learn Group-to-RP mappings through
various mechanisms as described in section 4. various mechanisms, as described in Section 4.
It is critical that each router select the same 'RP' for a specific It is critical that each router select the same 'RP' for a specific
multicast group address otherwise full multicast connectivity will multicast group address; otherwise, full multicast connectivity will
not be established. This is even true in the case of Anycast RP for not be established. This is true even when using an Anycast RP to
redundancy. This RP address may correspond to a different physical provide redundancy. This RP address may correspond to a different
router but it is one logical RP address and must be consistent across physical router, but it is one logical RP address and must be
the PIM domain. This is usually achieved by using the same algorithm consistent across the PIM domain. This is usually achieved by using
to select the RP in all the PIM routers in a domain. the same algorithm to select the RP in all the PIM routers in a
domain.
PIM-SM [RFC4601] has defined an algorithm to select a 'RP' for a PIM-SM [RFC4601] has defined an algorithm to select a 'RP' for a
given multicast group address but it is not flexible enough for an given multicast group address, but it is not flexible enough for an
administrator to apply various policies. Please refer to section 3 administrator to apply various policies. Please refer to Section 3
for more details. for more details.
PIM-STD-MIB [RFC5060] includes a number of objects to allow an The PIM-STD-MIB [RFC5060] includes a number of objects to allow an
administrator to set the precedence for Group-to-RP mappings which administrator to set the precedence for Group-to-RP mappings that are
are learned statically or dynamically and stored in the learned statically or dynamically and stored in the
'pimGroupMappingTable'. The Management Information Base (MIB) module 'pimGroupMappingTable'. The Management Information Base (MIB) module
also defines an algorithm that can be applied to the data contained also defines an algorithm that can be applied to the data contained
in the 'pimGroupMappingTable' to determine Group-to-RP mappings. in the 'pimGroupMappingTable' to determine Group-to-RP mappings.
However, this algorithm is not completely deterministic, because it However, this algorithm is not completely deterministic, because it
includes an implementation-specific 'precedence' value. includes an implementation-specific 'precedence' value.
Network Management stations will be able to deduce which RPs will be Network management stations will be able to deduce which RPs will be
selected by applying the algorithm from this document to the list of selected by applying the algorithm from this document to the list of
Group-to-RP mappings from the 'pimGroupMappingTable'. The algorithm Group-to-RP mappings from the 'pimGroupMappingTable'. The algorithm
provides MIB visibility into how routers will apply Group-to-RP provides MIB visibility into how routers will apply Group-to-RP
mappings and also fixes the protocol inconsistency with how different mappings and also fixes the inconsistency introduced by the way that
vendors select the Group-to-RP mappings to create multicast different vendors implement the selection of the Group-to-RP mappings
forwarding state. to create multicast forwarding state.
Embedded-RP as defined in section-7.1 of Embedded-RP address in IPv6 Embedded-RP, as defined in Section 7.1 of "Embedding the Rendezvous
Multicast address [RFC3956], mentions that to avoid loops and Point (RP) Address in an IPv6 Multicast Address" [RFC3956], specifies
inconsistencies, for addresses in the range FF70::/12, the the following: "To avoid loops and inconsistencies, for addresses in
Embedded-RP mapping must be considered the longest possible match and the range ff70::/12, the Embedded-RP mapping MUST be considered the
higher priority than any other mechanism. longest possible match and higher priority than any other mechanism".
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
This document also uses following terms:
This document also uses the following terms:
o PIM Mode o PIM Mode
PIM Mode is the mode of operation a particular multicast group is PIM Mode is the mode of operation for which a particular multicast
used for. Wherever this term is used in this document, it refers to group is used. Wherever this term is used in this document, it
either Sparse Mode or Bidirectional (BIDIR) Mode. refers to either Sparse Mode or Bidirectional (BIDIR) Mode.
o Dynamic group-to-RP mapping mechanisms o Dynamic Group-to-RP Mapping Mechanisms
The term Dynamic group-to-RP mapping mechanisms in this document The term "dynamic Group-to-RP mapping mechanisms" in this document
refers to Bootstrap Router (BSR) [RFC5059] and Auto-RP. refers to Bootstrap Router (BSR) [RFC5059] and Auto-RP.
o Dynamic mappings or Dynamically learned mappings o Dynamic Mappings and Dynamically Learned Mappings
The terms Dynamic mappings or Dynamically learned mappings refer to The terms "dynamic mappings" and "dynamically learned mappings"
group-to-RP mappings that have been learned by BSR or Auto-RP. refer to Group-to-RP mappings that have been learned by either BSR
Group-to-RP mappings that have been learned by embedded RP are or Auto-RP. Group-to-RP mappings that have been learned by
referred to as Embedded Group-to-RP mappings. Embedded-RP are referred to as Embedded Group-to-RP mappings.
o Filtering o Filtering
Filtering is selective discarding of dynamic Group-to-RP mapping Filtering is the selective discarding of dynamic Group-to-RP
information, based on the group address, the type of Group-to-RP mapping information, based on the group address, the type of
mapping message and the interface on which the mapping message was Group-to-RP mapping message, and the interface on which the
received. mapping message was received.
o Multicast Domain and Boundaries o Multicast Domain and Boundaries
The term multicast domain used in this document refers to a network The term "multicast domain" used in this document refers to a
topology that has a consistent set of Group-to-RP Mappings. The network topology that has a consistent set of Group-to-RP
interface between two or more multicast domains is a multicast domain mappings. The interface between two or more multicast domains is
boundary. The multicast boundaries are usually enforced by filtering a multicast domain boundary. The multicast boundaries are usually
the dynamic mapping messages and/or configuring different static RP enforced by filtering the dynamic mapping messages and/or
mappings. configuring different static RP mappings.
3. Existing algorithm 3. Existing Algorithm
The existing algorithm defined in PIM-SM (Section 4.7.1 in [RFC4601]) The existing algorithm defined in PIM-SM (Section 4.7.1 of [RFC4601])
does not consider following constraints: does not consider the following constraints:
o It does not consider the origin of a Group-to-RP mapping and o It does not consider the origin of a Group-to-RP mapping and
therefore will treat all of them equally. therefore will treat all of them equally.
o It does not provide the flexibility to give higher priority to a o It does not provide the flexibility to give higher priority to a
specific PIM mode. For example, an entry learned for PIM-BIDIR specific PIM mode. For example, an entry learned for the PIM-
mode is treated with same priority as an entry learned for PIM-SM. BIDIR Mode is treated with the same priority as an entry learned
for PIM-SM.
The algorithm defined in this document updates algorithm defined in The algorithm defined in this document updates the algorithm defined
PIM-SM ( Section 4.7.1 in [RFC4601]). The new algorithm is backward in PIM-SM (Section 4.7.1 of [RFC4601]). The new algorithm is
compatible and will produce the same result only if the Group-to-RP backward compatible and will produce the same result only if the
mappings are learned from a single mapping source. The full benefits Group-to-RP mappings are learned from a single mapping source. The
of the new algorithm will not be realized until it is widely full benefits of the new algorithm will not be realized until it is
deployed. widely deployed.
4. Assumptions 4. Assumptions
We have made following assumptions in defining this algorithm: We have made the following assumptions in defining this algorithm:
o A Group-to-RP mapping can be learned from various mechanisms. We o A Group-to-RP mapping can be learned from various mechanisms. We
assume that following list is in the decreasing preferences of assume that the following list is ordered by decreasing preference
these mechanism: for these mechanisms:
* Embedded Group-to-RP mappings * Embedded Group-to-RP mappings
* Dynamically learned mappings * Dynamically learned mappings
* Static configuration. * Static configuration
* Other mapping method * Other mapping method
o Embedded Group-to-RP mappings are special and always have the o Embedded Group-to-RP mappings are special and always have the
highest priority. They cannot be overridden either by static highest priority. They cannot be overridden by static
configuration or by dynamic Group-to-RP mappings. configuration or by dynamic Group-to-RP mappings.
o Dynamic mappings will override a static RP config if they have o Dynamic mappings will override a static RP configuration if they
overlapping ranges. However, it is possible to override dynamic have overlapping ranges. However, it is possible to override
Group-to-RP mappings with static configurations, either by dynamic Group-to-RP mappings with static configurations, either by
filtering, or by configuring longer static group addresses that filtering, or by configuring longer static group addresses that
override dynamic mappings when longest prefix matching is applied. override dynamic mappings when longest prefix matching is applied.
o A Group-to-RP mapping learned for PIM-BIDIR mode is preferred to o A Group-to-RP mapping learned for PIM-BIDIR Mode is preferred to
an entry learned for PIM-SM mode as stipulated by section 3.3 of an entry learned for PIM-SM Mode as stipulated in Section 3.3 of
[RFC5059]. [RFC5059].
o Dynamic group-to-RP mapping mechanisms are filtered at domain o Dynamic Group-to-RP mapping mechanisms are filtered at domain
boundaries or for policy enforcement inside a domain. boundaries or for policy enforcement inside a domain.
5. Common use cases 5. Common Use Cases
A network operator deploying IP Multicast will require a
deterministic way to select the precedence for Group-to-RP mappings
in the following use cases:
o Default static Group-to-RP mappings with dynamically learned o Default static Group-to-RP mappings with dynamically learned
entries entries
Many network operators will have a dedicated infrastructure for the Many network operators will have a dedicated infrastructure for
standard multicast group range (224/4) and so might be using the standard multicast group range (224/4) and so might be using
statically configured Group-to-RP mappings for this range. In this statically configured Group-to-RP mappings for this range. In
case, to support some specific applications, they might like to learn this case, to support some specific applications, they might want
Group-to-RP mappings dynamically using either BSR or Auto-RP to learn Group-to-RP mappings dynamically using either the BSR or
mechanism. In this case to select Group-to-RP mappings for these Auto-RP mechanism. In this case, to select Group-to-RP mappings
specific applications, a longer prefix match should be given for these specific applications, a longer prefix match should be
preference over statically configured Group-to-RP mappings. For given preference over statically configured Group-to-RP mappings.
example 239.100.0.0/16, an administratively scoped multicast address For example, 239.100.0.0/16, an administratively scoped multicast
range, could be learned for a corporate communications application. address range, could be learned for a corporate communications
Network operators may change the Group-to-RP mappings for these application. Network operators may change the Group-to-RP
applications more often and would need to be learned dynamically. mappings for these applications more often, and the mappings would
This is not an issue for IPv6 Multicast address ranges. need to be learned dynamically. This is not an issue for IPv6
Multicast address ranges.
o Migration situations o Migration situations
Network operators occasionally go through a migration due to an Network operators occasionally go through a migration due to an
acquisition or a change in their network design. In order to acquisition or a change in their network design. In order to
facilitate this migration there is a need to have a deterministic facilitate this migration, there is a need to have a deterministic
behaviour of Group-to-RP mapping selection for entries learned using behavior of Group-to-RP mapping selection for entries learned
BSR and Auto-RP mechanism. This will help in avoiding any unforeseen using the BSR and Auto-RP mechanisms. This will help in avoiding
interoperability issues between different vendor's network elements. any unforeseen interoperability issues between different vendors'
network elements.
o Use by management systems o Use by management systems
A network management station can determine the RP for a specific A network management station can determine the RP for a specific
group in a specific router by running this algorithm on the group in a specific router by running this algorithm on the Group-
Group-to-RP mapping table fetched using MIB objects. to-RP mapping table fetched using MIB objects.
6. Proposed algorithm 6. Proposed Algorithm
The following algorithm deterministically chooses between several The following algorithm deterministically chooses between several
Group-to-RP mappings for a specific group. It also addresses the Group-to-RP mappings for a specific group. It also addresses the
above mentioned shortcomings in the existing mechanism. above-mentioned shortcomings in the existing mechanism.
1. If the Multicast Group Address being looked up contains an 1. If the multicast group address being looked up contains an
embedded RP, the RP address extracted from the Group address is embedded RP, the RP address extracted from the group address is
selected as the Group-to-RP mapping. selected as the Group-to-RP mapping.
2. If the Multicast Group Address being looked up is in the Source 2. If the multicast group address being looked up is in the Source
Specific Multicast (SSM) range or is configured for Dense mode, Specific Multicast (SSM) range or is configured for Dense Mode,
no Group-to-RP mapping is selected, and this algorithm no Group-to-RP mapping is selected, and this algorithm
terminates. The fact that no Group-to-RP mapping has been terminates. The fact that no Group-to-RP mapping has been
selected can be represented in the PIM-STD-MIB module by setting selected can be represented in the PIM-STD-MIB module [RFC5060]
the address type of the RP to 'unknown' as described in Section by setting the address type of the RP to 'unknown', as described
8. in Section 8.
3. From the set of all Group-to-RP mapping entries, the subset 3. From the set of all Group-to-RP mapping entries, the subset
whose group prefix contains the multicast group that is being whose group prefix contains the multicast group that is being
looked up, is selected. looked up is selected.
4. If there are no entries available, then the Group-to-RP mapping 4. If there are no entries available, then the Group-to-RP mapping
is undefined and this algorithm terminates. is undefined, and this algorithm terminates.
5. A longest prefix match is performed on the subset of Group-to-RP 5. A longest prefix match is performed on the subset of Group-to-RP
Mappings. mappings.
* If there is only one entry available then that entry is * If there is only one entry available, then that entry is
selected as the Group-to-RP mapping. selected as the Group-to-RP mapping.
* If there are multiple entries available, we continue with the * If there are multiple entries available, the algorithm
algorithm with this smaller set of Group-to-RP Mappings. continues with this smaller set of Group-to-RP mappings.
6. From the remaining set of Group-to-RP Mappings we select the 6. From the remaining set of Group-to-RP mappings, we select the
subset of entries based on the preference for the PIM modes subset of entries based on the preference for the PIM modes to
which they are assigned. A Group-to-RP mapping entry with PIM which the multicast group addresses are assigned. A Group-to-RP
Mode 'BIDIR' will be preferred to an entry with PIM Mode mapping entry with PIM Mode 'BIDIR' will be preferred to an
'PIM-SM' entry with PIM Mode 'PIM-SM'.
* If there is only one entry available then that entry is * If there is only one entry available, then that entry is
selected as the Group-to-RP mapping. selected as the Group-to-RP mapping.
* If there are multiple entries available, we continue with the * If there are multiple entries available, the algorithm
algorithm with this smaller set of Group-to-RP Mappings continues with this smaller set of Group-to-RP mappings.
7. From the remaining set of Group-to-RP Mappings we select the 7. From the remaining set of Group-to-RP mappings, we select the
subset of the entries based on the origin. Group-to-RP mappings subset of the entries based on the origin. Group-to-RP mappings
learned dynamically are preferred over static mappings. If the learned dynamically are preferred over static mappings. If the
remaining dynamic Group-to-RP mappings are from BSR and Auto-RP remaining dynamic Group-to-RP mappings are from BSR and Auto-RP,
then the mappings from BSR is preferred. then the mappings from BSR are preferred.
* If there is only one entry available then that entry is * If there is only one entry available, then that entry is
selected as the Group-to-RP mapping. selected as the Group-to-RP mapping.
* If there are multiple entries available, we continue with the * If there are multiple entries available, the algorithm
algorithm with this smaller set of Group-to-RP Mappings. continues with this smaller set of Group-to-RP mappings.
8. If the remaining Group-to-RP mappings were learned through BSR 8. If the remaining Group-to-RP mappings were learned through BSR,
then the RP will be selected by comparing the RP Priority in the then the RP will be selected by comparing the RP Priority values
Candidate-RP-Advertisement messages. The RP mapping with the in the Candidate-RP-Advertisement messages. The RP mapping with
lowest value indicates the highest priority [RFC5059]. the lowest value indicates the highest priority [RFC5059].
* If more than one RP has the same highest priority value we * If more than one RP has the same highest priority (i.e., the
continue with the algorithm with those Group-to-RP mappings. same lowest value), the algorithm continues with those Group-
to-RP mappings.
* If the remaining Group-to-RP mappings were NOT learned from * If the remaining Group-to-RP mappings were NOT learned from
BSR we continue the algorithm with the next step. BSR, the algorithm continues with the next step.
9. If the remaining Group-to-RP mappings were learned through BSR 9. If the remaining Group-to-RP mappings were learned through BSR
and the PIM Mode of the Group is 'PIM-SM' then the hash function and the PIM Mode of the group is 'PIM-SM', then the hash
as defined in section 4.7.2 of [RFC4601] will be used to choose function as defined in Section 4.7.2 of [RFC4601] will be used
the RP. The RP with the highest resulting hash value will be to choose the RP. The RP with the highest resulting hash value
selected. Please look at section 10 for consideration of hash will be selected. Please see Section 10 for consideration of
for BIDIR-PIM and BSR. hash for BIDIR-PIM and BSR.
* If more than one RP has the same highest hash value we * If more than one RP has the same highest hash value, the
continue with the algorithm with those Group-to-RP mappings. algorithm continues with those Group-to-RP mappings.
* If the remaining Group-to-RP mappings were NOT learned from * If the remaining Group-to-RP mappings were NOT learned from
BSR we continue the algorithm with the next step. BSR, the algorithm continues with the next step.
10. From the remaining set of Group-to-RP Mappings we will select 10. From the remaining set of Group-to-RP mappings, the RP with the
the RP with the highest IP address (numerically greater). This highest IP address (numerically greater) will be selected. This
will serve as a final tiebreaker. will serve as a final tiebreaker.
7. Interpretation of MIB Objects 7. Interpretation of MIB Objects
As described in [RFC5060] the Group-to-RP mapping information is As described in [RFC5060], the Group-to-RP mapping information is
summarized in the pimGroupMappingTable. The precedence value is summarized in the pimGroupMappingTable. The precedence value is
stored in the 'pimGroupMappingPrecedence' object which covers both stored in the 'pimGroupMappingPrecedence' object, which covers both
the dynamically learned Group-to-RP mapping information as well as the dynamically learned Group-to-RP mapping information and the
the static configuration. For static configurations, the static configuration. For static configurations, the
'pimGroupMappingPrecedence' object uses the value of the 'pimGroupMappingPrecedence' object uses the value of the
'pimStaticRPPrecedence' object from the pimStaticRPTable table. 'pimStaticRPPrecedence' object from the pimStaticRPTable.
The algorithm defined in this document does not use the concept of The algorithm defined in this document does not use the concept of
precedence and therefore the values configured in the precedence, and therefore the values configured in the
'pimGroupMappingPrecedence' and 'pimStaticRPPrecedence' objects in 'pimGroupMappingPrecedence' and 'pimStaticRPPrecedence' objects in
the PIM-STD-MIB module [RFC5060] are not applicable to the new the PIM-STD-MIB module [RFC5060] are not applicable to the new
algorithm. The objects still retain their meaning for 'legacy' algorithm. The objects still retain their meaning for 'legacy'
implementations, but since the algorithm defined in this document is implementations, but since the algorithm defined in this document is
to be used in preference to that found in PIM-SM [RFC4601] and PIM- to be used in preference to those found in PIM-SM [RFC4601] and the
STD-MIB [RFC5060], the values of these objects will be ignored on PIM-STD-MIB [RFC5060], the values of these objects will be ignored on
implementations that support the new algorithm. implementations that support the new algorithm.
8. Clarification for MIB Objects 8. Clarification for MIB Objects
An implementation of this specification can continue to be managed An implementation of this specification can continue to be managed
using the PIM-STD-MIB [RFC5060]. When a Group-to-RP mapping entry is using the PIM-STD-MIB [RFC5060]. Group-to-RP mapping entries are
created in the pimGroupMappingTable with RP address type in the created in the pimGroupMappingTable for group ranges that are SSM or
pimGroupMappingRPAddressType object is set to unknown(0), and the PIM Dense mode. In these cases, the pimGroupMappingRPAddressType object
Mode in the pimGroupMappingPimMode object is set to either ssm(2) or is set to unknown(0), and the PIM Mode in the pimGroupMappingPimMode
dm(5) to represent group ranges for SSM or Dense mode. object is set to either ssm(2) or dm(5) to reflect the type of the
group range.
Also, all the entries which are already included in the SSM Range Also, all the entries that are already included in the SSM Range
table in the IP Mcast MIB [RFC5132] are copied to the table in the IP Multicast MIB [RFC5132] are copied to the
pimGroupMappingTable. Such entries have their type in the pimGroupMappingTable. Such entries have their type in the
pimGroupMappingOrigin object set to configSsm(3), and the RP address pimGroupMappingOrigin object set to configSsm(3) and the RP address
type in the pimGroupMappingRPAddressType object set to unknown(0) as type in the pimGroupMappingRPAddressType object set to unknown(0), as
described above. described above.
9. Use of dynamic Group-to-RP mapping protocols 9. Use of Dynamic Group-to-RP Mapping Protocols
It is not usually necessary to run several dynamic Group-to-RP It is not usually necessary to run several dynamic Group-to-RP
mapping mechanisms in one administrative domain. Specifically, mapping mechanisms in one administrative domain. Specifically,
interoperation of BSR and Auto-RP is OPTIONAL. interoperation of BSR and Auto-RP is OPTIONAL.
However, if a router does receive two overlapping sets of Group-to-RP However, if a router does receive two overlapping sets of Group-to-RP
mappings, for example from Auto-RP and BSR, then some algorithm is mappings, for example from Auto-RP and BSR, then some algorithm is
needed to deterministically resolve the situation. The algorithm in needed to deterministically resolve the situation. The algorithm in
this document MUST be used on all routers in the domain. This can be this document MUST be used on all routers in the domain. This can be
important at domain border routers, and is likely to avoid conflicts important at domain border routers, and is likely to avoid conflicts
under misconfiguration (when routers receive overlapping sets of caused by misconfiguration (when routers receive overlapping sets of
Group-to-RP mappings) and when configuration is changing. Group-to-RP mappings) and when configuration is changing.
An implementation of PIM that supports only one mechanism for An implementation of PIM that supports only one mechanism for
learning Group-to-RP mappings MUST also use this algorithm. The learning Group-to-RP mappings MUST also use this algorithm. The
algorithm has been chosen so that existing standard implementations algorithm has been chosen so that existing standard implementations
are already compliant. are already compliant.
10. Consideration for Bidirectional-PIM and BSR hash 10. Considerations for Bidirectional-PIM and BSR Hash
BIDIR-PIM [RFC5015] is designed to avoid any data driven events. BIDIR-PIM [RFC5015] is designed to avoid any data-driven events.
This is especially true in the case of a source only branch. The RP This is especially true in the case of a source-only branch. The RP
mapping is determined based on a group mask when the mapping is mapping is determined based on a group mask when the mapping is
received through a dynamic mapping protocol or statically configured. received through a dynamic mapping protocol or statically configured.
Therefore the hash in BSR is ignored for PIM-Bidir RP mappings based Therefore, based on the algorithm defined in this document, the hash
on the algorithm defined in this document. It is RECOMMENDED that in BSR is ignored for PIM-BIDIR RP mappings. It is RECOMMENDED that
network operators configure only one PIM-Bidir RP for each RP network operators configure only one PIM-BIDIR RP for each RP
Priority. Priority.
11. Filtering Group-to-RP mappings at domain boundaries 11. Filtering Group-to-RP Mappings at Domain Boundaries
An implementation of PIM SHOULD support configuration to filter An implementation of PIM SHOULD support configuration to filter
specific dynamic mechanism for a valid group prefix range. For specific dynamic mechanisms for a valid group prefix range. For
example, it should be possible to allow an administratively scoped example, it should be possible to allow an administratively scoped
address range, such as 239/8 range, for Auto-RP protocol but filter address range, such as 239/8, for the Auto-RP protocol, but to filter
out the BSR advertisement for the same range. Similarly it should be out the BSR advertisement for the same range. Similarly, it should
possible to filter out all Group-to-RP mappings learned from BSR or be possible to filter out all Group-to-RP mappings learned from BSR
Auto-RP protocol. or the Auto-RP protocol.
12. Security Consideration 12. Security Considerations
This document enhances an existing algorithm to deterministically This document enhances an existing algorithm to deterministically
choose between several Group-to-RP Mappings for a specific group. choose between several Group-to-RP mappings for a specific group.
Different routers may select a different Group-to-RP Mapping for the Different routers may select a different Group-to-RP mapping for the
same group if the Group-to-RP Mappings learned in these routers are same group if the Group-to-RP mappings learned in these routers are
not consistent. For example: let us assume that BSR is not enabled not consistent. For example, let us assume that BSR is not enabled
in one of the routers and so it does not learn any Group-to-RP in one of the routers, and so it does not learn any Group-to-RP
Mappings from BSR. Now the Group-to-RP Mappings learned in this mappings from BSR. Now the Group-to-RP mappings learned in this
router may not be consistent with other routers in the network, it router may not be consistent with other routers in the network; it
may select a different RP or may not select any RP for a given group. may select a different RP or may not select any RP for a given group.
Such situations can be avoided if the mechanisms used to learn Group- Such situations can be avoided if the mechanisms used to learn Group-
to-RP Mappings are secure and consistent across the network. Secure to-RP mappings are secure and consistent across the network. Secure
transport of the mapping protocols can be accomplished by using transport of the mapping protocols can be accomplished by using
authentication with IPsec as described in section 6.3 of [RFC4601]. authentication with IPsec, as described in Section 6.3 of [RFC4601].
13. IANA Consideration
This draft does not create any namespace for IANA to manage.
14. Acknowledgements 13. Acknowledgements
This draft is created based on the discussion occurred during the This document is created based on discussion that occurred during
PIM-STD-MIB [RFC5060] work. Many thanks to Stig Vennas, Yiqun Cai work on the PIM-STD-MIB [RFC5060]. Many thanks to Stig Venaas, Yiqun
and Toerless Eckert for providing useful comments. Cai, and Toerless Eckert for providing useful comments.
15. Normative References 14. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[RFC5060] Sivaramu, R., Lingard, J., McWalter, D., Joshi, B., and A.
Kessler, "Protocol Independent Multicast MIB", RFC 5060,
January 2008.
[RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous [RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous
Point (RP) Address in an IPv6 Multicast Address", Point (RP) Address in an IPv6 Multicast Address",
RFC 3956, November 2004. RFC 3956, November 2004.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano, [RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
"Bidirectional Protocol Independent Multicast (BIDIR- "Bidirectional Protocol Independent Multicast (BIDIR-
PIM)", RFC 5015, October 2007. PIM)", RFC 5015, October 2007.
[RFC5059] Bhaskar, N., Gall, A., Lingard, J., and S. Venaas, [RFC5059] Bhaskar, N., Gall, A., Lingard, J., and S. Venaas,
"Bootstrap Router (BSR) Mechanism for Protocol Independent "Bootstrap Router (BSR) Mechanism for Protocol Independent
Multicast (PIM)", RFC 5059, January 2008. Multicast (PIM)", RFC 5059, January 2008.
[RFC5060] Sivaramu, R., Lingard, J., McWalter, D., Joshi, B., and A.
Kessler, "Protocol Independent Multicast MIB", RFC 5060,
January 2008.
[RFC5132] McWalter, D., Thaler, D., and A. Kessler, "IP Multicast [RFC5132] McWalter, D., Thaler, D., and A. Kessler, "IP Multicast
MIB", RFC 5132, December 2007. MIB", RFC 5132, December 2007.
Authors' Addresses Authors' Addresses
Bharat Joshi Bharat Joshi
Infosys Technologies Ltd. Infosys Technologies Ltd.
44 Electronics City, Hosur Road 44 Electronics City, Hosur Road
Bangalore 560 100 Bangalore 560 100
India India
Email: bharat_joshi@infosys.com EMail: bharat_joshi@infosys.com
URI: http://www.infosys.com/ URI: http://www.infosys.com/
Andy Kessler Andy Kessler
Cisco Systems, Inc. Cisco Systems, Inc.
425 E. Tasman Drive 425 E. Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA USA
Email: kessler@cisco.com EMail: kessler@cisco.com
URI: http://www.cisco.com/ URI: http://www.cisco.com/
David McWalter David McWalter
Email: david@mcwalter.eu EMail: david@mcwalter.eu
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