draft-ietf-idmr-pim-sm-spec-04.txt   draft-ietf-idmr-pim-sm-spec-05.txt 
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Network Working Group Steven Deering (XEROX) Network Working Group Steven Deering (XEROX)
Internet Draft Deborah Estrin (USC) Internet Draft Deborah Estrin (USC)
Dino Farinacci (CISCO) Dino Farinacci (CISCO)
Mark Handley (UCL) Mark Handley (UCL)
Ahmed Helmy (USC) Ahmed Helmy (USC)
Van Jacobson (LBL) Van Jacobson (LBL)
Chinggung Liu (USC) Chinggung Liu (USC)
Puneet Sharma (USC) Puneet Sharma (USC)
David Thaler (UMICH) David Thaler (UMICH)
Liming Wei (CISCO) Liming Wei (CISCO)
Expire in six months
Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol
Specification Specification
Status of This Memo Status of This Memo
This document is an Internet Draft. Internet Drafts are working This document is an Internet Draft. Internet Drafts are working
documents of the Internet Engineering Task Force (IETF), its Areas, documents of the Internet Engineering Task Force (IETF), its Areas,
and its Working Groups. (Note that other groups may also distribute and its Working Groups. (Note that other groups may also distribute
working documents as Internet Drafts). working documents as Internet Drafts).
Internet Drafts are draft documents valid for a maximum of six Internet Drafts are draft documents valid for a maximum of six
months. Internet Drafts may be updated, replaced, or obsoleted by months. Internet Drafts may be updated, replaced, or obsoleted by
other documents at any time. It is not appropriate to use Internet other documents at any time. It is not appropriate to use Internet
Drafts as reference material or to cite them other than as a Drafts as reference material or to cite them other than as a
``working'' draft'' or ``work in progress.'' ``working'' draft'' or ``work in progress.''
Please check the I-D abstract listing contained in each Internet Please check the I-D abstract listing contained in each Internet
Draft directory to learn the current status of this or any other Draft directory to learn the current status of this or any other
Internet Draft. Internet Draft.
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1 Introduction 1 Introduction
This document describes a protocol for efficiently routing to This document describes a protocol for efficiently routing to
multicast groups that may span wide-area (and inter-domain) multicast groups that may span wide-area (and inter-domain)
internets. We refer to the approach as Protocol Independent internets. We refer to the approach as Protocol Independent
Multicast--Sparse Mode (PIM-SM) because it is not dependent on any Multicast--Sparse Mode (PIM-SM) because it is not dependent on any
particular unicast routing protocol, and because it is designed to particular unicast routing protocol, and because it is designed to
support sparse groups as defined in [1][2]. This document describes support sparse groups as defined in [1][2]. This document describes
the protocol details. For the motivation behind the design and a the protocol details. For the motivation behind the design and a
description of the architecture, see [1][2]. Section 2 summarizes description of the architecture, see [1][2]. Section 2 summarizes
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on which explicit joins have been received. on which explicit joins have been received.
A Designated Router (DR) sends periodic Join/Prune messages toward a A Designated Router (DR) sends periodic Join/Prune messages toward a
group-specific Rendezvous Point (RP) for each group for which it has group-specific Rendezvous Point (RP) for each group for which it has
active members. Each router along the path toward the RP builds a active members. Each router along the path toward the RP builds a
wildcard (any-source) forwarding state. for the group and sends wildcard (any-source) forwarding state. for the group and sends
_________________________ _________________________
[*] All routers mentioned in this document are assumed [*] All routers mentioned in this document are assumed
to be PIM-SM capable, unless otherwise specified. to be PIM-SM capable, unless otherwise specified.
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messages on toward the RP. We use the term entry to refer to the messages on toward the RP. We use the term entry to refer to the
forwarding state maintained in a router to represent the distribution forwarding state maintained in a router to represent the distribution
tree. Each entry includes such things as the incoming interface from tree. Each entry includes such things as the incoming interface from
which packets are accepted, the list of outgoing interfaces to which which packets are accepted, the list of outgoing interfaces to which
packets are sent, timers, flag bits, etc. The wildcard forwarding packets are sent, timers, flag bits, etc. The wildcard forwarding
entry's incoming interface points toward the RP; the outgoing entry's incoming interface points toward the RP; the outgoing
interfaces point to the neighboring downstream routers that have sent interfaces point to the neighboring downstream routers that have sent
Join/Prune messages toward the RP. This forwarding state creates a Join/Prune messages toward the RP. This forwarding state creates a
shared, RP-centered, distribution tree that reaches all group shared, RP-centered, distribution tree that reaches all group
members. When a data source first sends to a group, its DR unicasts members. When a data source first sends to a group, its DR unicasts
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specified in [4], IGMP Host-Membership-Report messages are sent in specified in [4], IGMP Host-Membership-Report messages are sent in
response to a directly-connected router's IGMP Host-Membership-Query response to a directly-connected router's IGMP Host-Membership-Query
message (see figure 1) [*] From this point on we refer to such a message (see figure 1) [*] From this point on we refer to such a
host as a receiver, R, (or member) of the group G. host as a receiver, R, (or member) of the group G.
_________________________ _________________________
[*] All figures used in this section are for illustra- [*] All figures used in this section are for illustra-
tion and are not intended to be complete. For complete tion and are not intended to be complete. For complete
and detailed protocol action see Section 3 . and detailed protocol action see Section 3 .
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Fig. 1 Example: how a receiver joins, and sets up shared tree Fig. 1 Example: how a receiver joins, and sets up shared tree
When a DR receives an IGMP Host-Membership-Report for a new group, G, When a DR receives an IGMP Host-Membership-Report for a new group, G,
the DR looks up the associated RP. The DR (e.g., router A in figure the DR looks up the associated RP. The DR (e.g., router A in figure
1) creates a wildcard multicast forwarding entry for the group, 1) creates a wildcard multicast forwarding entry for the group,
referred to here as a (*,G) entry; if there is no more specific match referred to here as a (*,G) entry; if there is no more specific match
for a particular source, the packet will be forwarded according to for a particular source, the packet will be forwarded according to
this entry. this entry.
The RP address is included in a special field in the forwarding entry The RP address is included in a special field in the forwarding entry
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sources via this (shared tree) path; WC stands for wildcard sources via this (shared tree) path; WC stands for wildcard
[*] [*]
Each upstream router creates or updates its multicast forwarding Each upstream router creates or updates its multicast forwarding
_________________________ _________________________
[*] Note that the term RPT-bit is used to refer to both [*] Note that the term RPT-bit is used to refer to both
the RPT-bit flags associated with forwarding entries, the RPT-bit flags associated with forwarding entries,
and the RPT-bit included in each encoded address in a and the RPT-bit included in each encoded address in a
Join/Prune message. Join/Prune message.
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entry for (*,G) when it receives a Join/Prune with the RPT-bit and entry for (*,G) when it receives a Join/Prune with the RPT-bit and
WC-bit set. The interface on which the Join/Prune message arrived is WC-bit set. The interface on which the Join/Prune message arrived is
added to the list of outgoing interfaces (oifs) for (*,G). Based on added to the list of outgoing interfaces (oifs) for (*,G). Based on
this entry each upstream router between the receiver and the RP sends this entry each upstream router between the receiver and the RP sends
a Join/Prune message in which the join list includes the RP. The a Join/Prune message in which the join list includes the RP. The
packet payload contains Multicast-Address=G, Join=RP,WC-bit,RPT-bit, packet payload contains Multicast-Address=G, Join=RP,WC-bit,RPT-bit,
Prune=NULL. Prune=NULL.
2.3 Hosts sending to a group 2.3 Hosts sending to a group
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when (and so long as) it receives Register-Stop messages from the RP. when (and so long as) it receives Register-Stop messages from the RP.
The RP triggers Register-Stop messages in response to Registers, if The RP triggers Register-Stop messages in response to Registers, if
the RP has no downstream receivers for the group (or for that the RP has no downstream receivers for the group (or for that
particular source), or if the RP has already joined the (S,G) tree particular source), or if the RP has already joined the (S,G) tree
_________________________ _________________________
[*] This decision is a local policy established at the [*] This decision is a local policy established at the
RP. For example, when the Register rate exceeds a con- RP. For example, when the Register rate exceeds a con-
figured threshold at the RP, this may warrant the use figured threshold at the RP, this may warrant the use
of the SPT. of the SPT.
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and is receiving the data packets natively. Each source's DR and is receiving the data packets natively. Each source's DR
maintains, per (S,G), a Register-bit and a Register-bit timer. The maintains, per (S,G), a Register-bit and a Register-bit timer. The
Register-bit timer is started by the Register-Stop message; upon Register-bit timer is started by the Register-Stop message; upon
expiration, the Register-bit is set to 1 and the source's DR resumes expiration, the Register-bit is set to 1 and the source's DR resumes
sending data packets encapsulated in Register messages. sending data packets encapsulated in Register messages.
2.4 Switching from shared tree (RP-tree) to shortest path tree (SP- 2.4 Switching from shared tree (RP-tree) to shortest path tree (SP-
tree) tree)
When a router has directly-connected members, it first joins the When a router has directly-connected members, it first joins the
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this path. Note that (S,G) state must be maintained in each last-hop this path. Note that (S,G) state must be maintained in each last-hop
router that is responsible for initiating and maintaining an SP-tree. router that is responsible for initiating and maintaining an SP-tree.
[*] [*]
_________________________ _________________________
[*] In more complicated scenarios, other entries in the [*] In more complicated scenarios, other entries in the
router have to be considered. For details see Section 3. router have to be considered. For details see Section 3.
[*] By last-hop router we mean the router that delivers [*] By last-hop router we mean the router that delivers
the packets to their ultimate end-system destination. the packets to their ultimate end-system destination.
This is the router that monitors if there is group This is the router that monitors if there is group
membership and joins or prunes the appropriate distri- membership and joins or prunes the appropriate distri-
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Even when (*,G) and (S,G) overlap, both states are needed to trigger Even when (*,G) and (S,G) overlap, both states are needed to trigger
the source-specific Join/Prune messages. (S,G) state is kept alive by the source-specific Join/Prune messages. (S,G) state is kept alive by
data packets arriving from that source. A timer, S-timer, is set for data packets arriving from that source. A timer, S-timer, is set for
the (S,G) entry and this timer is restarted whenever a data packet the (S,G) entry and this timer is restarted whenever a data packet
for (S,G) is forwarded out at least one oif. When the S-timer expires for (S,G) is forwarded out at least one oif. When the S-timer expires
the state is deleted. the state is deleted.
Only the RP and routers with local members can initiate switching to Only the RP and routers with local members can initiate switching to
the SP-tree; intermediate routers do not. Consequently, last-hop the SP-tree; intermediate routers do not. Consequently, last-hop
routers create (S,G) state in response to data packets from the routers create (S,G) state in response to data packets from the
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the last-hop router in place of the DR. the last-hop router in place of the DR.
[*] For example, to implement the policy that source- [*] For example, to implement the policy that source-
specific trees are only setup for high-data rate specific trees are only setup for high-data rate
source, a last-hop router might not create a (S,G) en- source, a last-hop router might not create a (S,G) en-
try until it has received m data packets from the try until it has received m data packets from the
source within some interval of n seconds. source within some interval of n seconds.
[*] As in DVMRP, each PIM multicast forwarding entry [*] As in DVMRP, each PIM multicast forwarding entry
has an associated incoming interface on which packets has an associated incoming interface on which packets
are expected to arrive. are expected to arrive.
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as an (S,G)RPT-bit entry. This notational distinction is useful to as an (S,G)RPT-bit entry. This notational distinction is useful to
point out the different actions taken for (S,G) entries depending on point out the different actions taken for (S,G) entries depending on
the setting of the RPT-bit flag. Note that a router can have no more the setting of the RPT-bit flag. Note that a router can have no more
than one (S,G) entry for any particular S and G, at any particular than one (S,G) entry for any particular S and G, at any particular
time; whether the RPT-bit flag is set or not. In other words, a time; whether the RPT-bit flag is set or not. In other words, a
router never has both an (S,G) and an (S,G)RPT-bit entry for the same router never has both an (S,G) and an (S,G)RPT-bit entry for the same
S and G at the same time. The Join/Prune message payload contains S and G at the same time. The Join/Prune message payload contains
Multicast-Address=G, Join=NULL, Prune=S,RPT-bit. Multicast-Address=G, Join=NULL, Prune=S,RPT-bit.
A new receiver may join an existing RP-tree on which source-specific A new receiver may join an existing RP-tree on which source-specific
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packets using the periodic refresh mechanism. packets using the periodic refresh mechanism.
2.6 Obtaining RP information 2.6 Obtaining RP information
To obtain the RP information, all routers within a PIM domain collect To obtain the RP information, all routers within a PIM domain collect
RP-Set messages. RP-Set messages are sent hop-by-hop within the RP-Set messages. RP-Set messages are sent hop-by-hop within the
domain; the domain's bootstrap router (BSR) is responsible for domain; the domain's bootstrap router (BSR) is responsible for
originating the RP-set messages. The BSR is elected dynamically originating the RP-set messages. The BSR is elected dynamically
within each domain. within each domain.
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[*] [*]
Routers then use the set of RPs to get the proper Group to RP Routers then use the set of RPs to get the proper Group to RP
mapping. Details are as follows: mapping. Details are as follows:
A (small) set of routers, within a domain, are configured as A (small) set of routers, within a domain, are configured as
candidate bootstrap routers. Initially, each of these candidates candidate bootstrap routers. Initially, each of these candidates
includes its address in `RP-set' messages. Through a simple election includes its address in `RP-set' messages. Through a simple election
mechanism, a single bootstrap router (BSR) is elected for that domain mechanism, a single bootstrap router (BSR) is elected for that domain
(see Section 3.6). (see Section 3.6).
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and removed from the list of RPs over which the hash algorithm acts. and removed from the list of RPs over which the hash algorithm acts.
Each router continues to use the contents of the most recently Each router continues to use the contents of the most recently
received RP-set message until it receives a new RP-set message. received RP-set message until it receives a new RP-set message.
_________________________ _________________________
[*] A domain in this context is a contiguous set of [*] A domain in this context is a contiguous set of
routers that all implement PIM and are configured to routers that all implement PIM and are configured to
operate within a common boundary defined by PIM Multi- operate within a common boundary defined by PIM Multi-
cast Border Routers (PMBRs). PMBRs connect each PIM cast Border Routers (PMBRs). PMBRs connect each PIM
domain to the rest of the internet. domain to the rest of the internet.
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2.7 Interoperation with dense mode protocols such as DVMRP 2.7 Interoperation with dense mode protocols such as DVMRP
In order to interoperate with networks that run dense-mode, In order to interoperate with networks that run dense-mode,
broadcast and prune, protocols, such as DVMRP, all packets generated broadcast and prune, protocols, such as DVMRP, all packets generated
within a PIM-SM region must be pulled down to that region's PIM within a PIM-SM region must be pulled down to that region's PIM
Multicast Border Routers (PMBRs) and injected (i.e., broadcast) into Multicast Border Routers (PMBRs) and injected (i.e., broadcast) into
the DVMRP network. [*] the DVMRP network. [*]
To achieve this capability, a special entry type, referred to as To achieve this capability, a special entry type, referred to as
(*,*,RP), must be supported by all PIM routers. For this reason we (*,*,RP), must be supported by all PIM routers. For this reason we
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exists, then a (*,*,RP) entry match is attempted as follows: the exists, then a (*,*,RP) entry match is attempted as follows: the
router hashes on G to identify the RP for group G, and looks for a router hashes on G to identify the RP for group G, and looks for a
_________________________ _________________________
[*] A PMBR is a router that sits at the boundary of a [*] A PMBR is a router that sits at the boundary of a
PIM-SM domain and interoperates with other types of PIM-SM domain and interoperates with other types of
multicast routers such as those that run DVMRP. Gen- multicast routers such as those that run DVMRP. Gen-
erally a PMBR would speak both protocols and implement erally a PMBR would speak both protocols and implement
interoperability functions not required by regular PIM interoperability functions not required by regular PIM
routers. routers.
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(*,*,RP) entry that has this RP address associated with it. If none (*,*,RP) entry that has this RP address associated with it. If none
of the above exists, then the packet is dropped. If a state is of the above exists, then the packet is dropped. If a state is
matched, the router compares the interface on which the packet matched, the router compares the interface on which the packet
arrived to the incoming interface field in the matched forwarding arrived to the incoming interface field in the matched forwarding
entry. If the iif check fails the packet is dropped, otherwise the entry. If the iif check fails the packet is dropped, otherwise the
packet is forwarded to all interfaces listed in the outgoing packet is forwarded to all interfaces listed in the outgoing
interface list. interface list.
Some special actions are needed to deliver packets continuously while Some special actions are needed to deliver packets continuously while
switching from the shared to shortest-path tree. In particular, when switching from the shared to shortest-path tree. In particular, when
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matching (*,G) or (*,*,RP) entry. IF the iif is the matching (*,G) or (*,*,RP) entry. IF the iif is the
same as one of those, the packet is forwarded to the same as one of those, the packet is forwarded to the
oif-list of the matching entry. oif-list of the matching entry.
3 Otherwise the iif does not match any entry for G and 3 Otherwise the iif does not match any entry for G and
the packet is discarded. the packet is discarded.
Data packets never trigger prunes. However, data packets may Data packets never trigger prunes. However, data packets may
trigger actions that in turn trigger prunes. For example, when trigger actions that in turn trigger prunes. For example, when
router B in figure 3 decides to switch to SP-tree at step 3, it router B in figure 3 decides to switch to SP-tree at step 3, it
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creates a (S,G) entry with SPT-bit set to 0. When data packets creates a (S,G) entry with SPT-bit set to 0. When data packets
from S arrive at interface 2 of B, B sets the SPT-bit to 1 from S arrive at interface 2 of B, B sets the SPT-bit to 1
since the iif for (*,G) is different than that for (S,G). This since the iif for (*,G) is different than that for (S,G). This
triggers the sending of prunes towards the RP. triggers the sending of prunes towards the RP.
2.9 Operation over Multi-access Networks 2.9 Operation over Multi-access Networks
This section describes a few additional protocol mechanisms This section describes a few additional protocol mechanisms
needed to operate PIM over multi-access networks: Designated needed to operate PIM over multi-access networks: Designated
Router election, Assert messages to resolve parallel paths, and Router election, Assert messages to resolve parallel paths, and
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Using Assert messages addressed to `224.0.0.13' (ALL-PIM-ROUTERS Using Assert messages addressed to `224.0.0.13' (ALL-PIM-ROUTERS
group) on the LAN, upstream routers can resolve which one will group) on the LAN, upstream routers can resolve which one will
act as the forwarder. Downstream routers listen to the Asserts act as the forwarder. Downstream routers listen to the Asserts
so they know which one was elected, and therefore where to send so they know which one was elected, and therefore where to send
_________________________ _________________________
[*] IGMP Queries are sent by a PIMv2 DR if it supports [*] IGMP Queries are sent by a PIMv2 DR if it supports
IGMPv1. If a PIMv2 router is using IGMPv2 then Host IGMPv1. If a PIMv2 router is using IGMPv2 then Host
queries are not sent by the PIMv2 DR but by the IGMP queries are not sent by the PIMv2 DR but by the IGMP
querier. querier.
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subsequent Joins. Typically this is the same as the downstream subsequent Joins. Typically this is the same as the downstream
router's RPF (Reverse Path Forwarding) neighbor; but there are router's RPF (Reverse Path Forwarding) neighbor; but there are
circumstances where this might not be the case, e.g., when using circumstances where this might not be the case, e.g., when using
different unicast protocols. [*] different unicast protocols. [*]
The upstream router elected is the one that has the shortest The upstream router elected is the one that has the shortest
distance to the source. Therefore, when a packet is received on distance to the source. Therefore, when a packet is received on
an outgoing interface a router sends an Assert message on the an outgoing interface a router sends an Assert message on the
multi-access LAN indicating what metric it uses to reach the multi-access LAN indicating what metric it uses to reach the
source of the data packet. The router with the smallest source of the data packet. The router with the smallest
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would otherwise be carried over the LAN. would otherwise be carried over the LAN.
In case the packet, or the Assert message, matches on oif for In case the packet, or the Assert message, matches on oif for
_________________________ _________________________
[*] The RPF neighbor for a particular source (or RP) is [*] The RPF neighbor for a particular source (or RP) is
the next-hop router to which packets are forwarded en the next-hop router to which packets are forwarded en
route to that source (or RP); and therefore is con- route to that source (or RP); and therefore is con-
sidered a good path via which to accept packets from sidered a good path via which to accept packets from
that source. that source.
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(*,*,RP) entry, a (*,G) entry is created, and asserts take place (*,*,RP) entry, a (*,G) entry is created, and asserts take place
as if the matching state were (*,G). as if the matching state were (*,G).
The DR may lose the (*,G) Assert process to another router on The DR may lose the (*,G) Assert process to another router on
the LAN if there are multiple paths to the RP through the LAN. the LAN if there are multiple paths to the RP through the LAN.
From then on, the DR is no longer the last-hop router for local From then on, the DR is no longer the last-hop router for local
receivers and removes the LAN from its (*,G) oif list. The receivers and removes the LAN from its (*,G) oif list. The
winning router becomes the last-hop router and is responsible winning router becomes the last-hop router and is responsible
for sending (*,G) join messages to the RP. Asserts are rate for sending (*,G) join messages to the RP. Asserts are rate
limited. limited.
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routers or are timed out due to lack of appropriate Join/Prune routers or are timed out due to lack of appropriate Join/Prune
messages. If the router has a (S,G) entry with the SPT-bit set, messages. If the router has a (S,G) entry with the SPT-bit set,
and the updated iif(S,G) does not differ from iif(*,G) or and the updated iif(S,G) does not differ from iif(*,G) or
iif(*,*,RP), then the router resets the SPT-bit. iif(*,*,RP), then the router resets the SPT-bit.
The router must send a Join/Prune message with S in the Join The router must send a Join/Prune message with S in the Join
list out its new incoming interface to inform upstream routers list out its new incoming interface to inform upstream routers
that it expects multicast datagrams over the interface. It may that it expects multicast datagrams over the interface. It may
also send a Join/Prune message with S in the Prune list out the also send a Join/Prune message with S in the Prune list out the
old incoming interface, if the link is operational, to inform old incoming interface, if the link is operational, to inform
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upstream routers that this part of the distribution tree is upstream routers that this part of the distribution tree is
going away. going away.
2.11 PIM-SM for Inter-Domain Multicast 2.11 PIM-SM for Inter-Domain Multicast
Future documents will address the use of PIM-SM as a backbone Future documents will address the use of PIM-SM as a backbone
inter-domain multicast routing protocol. Design choices center inter-domain multicast routing protocol. Design choices center
primarily around the distribution and usage of RP information primarily around the distribution and usage of RP information
for wide area, inter-domain groups. for wide area, inter-domain groups.
2.12 Security 2.12 Security
All PIM control messages may use [5] to address security All PIM control messages may use [5] to address security
concerns. Security mechanisms are likely to be enhanced in the concerns. Security mechanisms are likely to be enhanced in the
near future. near future.
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3 Detailed Protocol Description 3 Detailed Protocol Description
This section describes the protocol operations from the This section describes the protocol operations from the
perspective of an individual router implementation. In perspective of an individual router implementation. In
particular, for each message type we describe how it is particular, for each message type we describe how it is
generated and processed. generated and processed.
3.1 Query 3.1 Query
Query messages are sent so neighboring routers can discover each Query messages are sent so neighboring routers can discover each
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3.1.3 Timing out neighbor entries 3.1.3 Timing out neighbor entries
A periodic process is run to time out PIM neighbors that have A periodic process is run to time out PIM neighbors that have
not sent queries. If the DR has gone down, a new DR is chosen by not sent queries. If the DR has gone down, a new DR is chosen by
scanning all neighbors on the interface and selecting the new DR scanning all neighbors on the interface and selecting the new DR
to be the one with the highest IP address. If an interface has to be the one with the highest IP address. If an interface has
gone down, the router may optionally time out all PIM neighbors gone down, the router may optionally time out all PIM neighbors
associated with the interface. associated with the interface.
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3.2 Join/Prune 3.2 Join/Prune
Join/Prune messages are sent to join or prune a branch off of Join/Prune messages are sent to join or prune a branch off of
the multicast distribution tree. A single message contains both the multicast distribution tree. A single message contains both
a join and prune list, either one of which may be null. Each a join and prune list, either one of which may be null. Each
list contains a set of source addresses, indicating the source- list contains a set of source addresses, indicating the source-
specific trees or shared tree that the router wants to join or specific trees or shared tree that the router wants to join or
prune. prune.
3.2.1 Sending Join/Prune Messages 3.2.1 Sending Join/Prune Messages
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1 The Join/Prune message is being sent to the RPF 1 The Join/Prune message is being sent to the RPF
neighbor toward the RP for an active (*,G) or (*,*,RP) neighbor toward the RP for an active (*,G) or (*,*,RP)
entry, and entry, and
_________________________ _________________________
[*] In the future we will introduce mechanisms to [*] In the future we will introduce mechanisms to
rate-limit this control traffic on a hop by hop basis, rate-limit this control traffic on a hop by hop basis,
in order to avoid excessive overhead on small links. in order to avoid excessive overhead on small links.
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2 The outgoing interface list in the (*,G) or (*,*,RP) 2 The outgoing interface list in the (*,G) or (*,*,RP)
entry is non-NULL, or the router is the DR on the same entry is non-NULL, or the router is the DR on the same
interface as the RPF neighbor. interface as the RPF neighbor.
2 A particular source address, S, is included in the join 2 A particular source address, S, is included in the join
list with the RP and WC bits cleared under the following list with the RP and WC bits cleared under the following
conditions: conditions:
1 The Join/Prune message is being sent to the RPF 1 The Join/Prune message is being sent to the RPF
neighbor toward S, and neighbor toward S, and
skipping to change at page 19, line 4 skipping to change at line 774
4 A particular source address, S, is included in the prune 4 A particular source address, S, is included in the prune
list with the RPT-bit set and the WC bit cleared under the list with the RPT-bit set and the WC bit cleared under the
following conditions: following conditions:
1 The Join/Prune message is being sent to the RPF 1 The Join/Prune message is being sent to the RPF
neighbor toward the RP and there exists a (S,G) entry neighbor toward the RP and there exists a (S,G) entry
with the RPT-bit flag set and null oif list, or with the RPT-bit flag set and null oif list, or
2 The Join/Prune message is being sent to the RPF 2 The Join/Prune message is being sent to the RPF
[Page 18]
neighbor toward the RP, there exists a (S,G) entry neighbor toward the RP, there exists a (S,G) entry
with the RPT-bit flag cleared and SPT-bit set, and the with the RPT-bit flag cleared and SPT-bit set, and the
incoming interface toward S is different than the incoming interface toward S is different than the
incoming interface toward the RP, or incoming interface toward the RP, or
3 The Join/Prune message is being sent to the RPF 3 The Join/Prune message is being sent to the RPF
neighbor toward the RP, and there exists a (*,G) entry neighbor toward the RP, and there exists a (*,G) entry
and (S,G) entry for a directly connected source. and (S,G) entry for a directly connected source.
5 The RP address (with RP and WC bits set) is included in the 5 The RP address (with RP and WC bits set) is included in the
skipping to change at page 20, line 5 skipping to change at line 817
sends a Join/Prune message towards the RP with the RP sends a Join/Prune message towards the RP with the RP
address and RPT-bit and WC-bits set in the join list. address and RPT-bit and WC-bits set in the join list.
A timer is initiated for each interface in the oif A timer is initiated for each interface in the oif
list. Or, list. Or,
2 If the (*,G) already exists, the interface upon which 2 If the (*,G) already exists, the interface upon which
the IGMP Host-Membership-Report was received is added the IGMP Host-Membership-Report was received is added
to the oif list (if it was not included already) and to the oif list (if it was not included already) and
the timer for that interface is restarted. the timer for that interface is restarted.
[Page 19]
2 Receipt of a Join/Prune message for (S,G), (*,G) or 2 Receipt of a Join/Prune message for (S,G), (*,G) or
(*,*,RP) will cause building or modifying corresponding (*,*,RP) will cause building or modifying corresponding
state, and subsequent triggering of upstream Join/Prune state, and subsequent triggering of upstream Join/Prune
messages, in the following cases: messages, in the following cases:
1 When there is no current forwarding entry, the RP 1 When there is no current forwarding entry, the RP
address included in the Join/Prune message is checked address included in the Join/Prune message is checked
against the local RP-Set information. If it matches, against the local RP-Set information. If it matches,
an entry will be created. If the router has no RP-Set an entry will be created. If the router has no RP-Set
information it may discard the message, or optionally information it may discard the message, or optionally
skipping to change at page 21, line 4 skipping to change at line 857
4 When a Join/Prune message is received for a group G, the 4 When a Join/Prune message is received for a group G, the
prune list is checked. If it contains a source for which prune list is checked. If it contains a source for which
the receiving router has a corresponding active (S,G), the receiving router has a corresponding active (S,G),
(*,G) or (*,*,RP) entry, and whose iif is that on which (*,G) or (*,*,RP) entry, and whose iif is that on which
the Join/Prune was received, then a join for (S,G), (*,G) the Join/Prune was received, then a join for (S,G), (*,G)
or (*,*,RP) is triggered to override the prune, or (*,*,RP) is triggered to override the prune,
respectively. (This is necessary in the case of parallel respectively. (This is necessary in the case of parallel
downstream routers connected to a multi-access network.) downstream routers connected to a multi-access network.)
5 When the RP fails, the RP will not be included in the RP- 5 When the RP fails, the RP will not be included in the RP-
[Page 20]
Set messages sent to all routers in that domain. This Set messages sent to all routers in that domain. This
triggers the DRs to send (*,G) Join/Prune messages towards triggers the DRs to send (*,G) Join/Prune messages towards
the new RP for the group, as determined by the RP-Set and the new RP for the group, as determined by the RP-Set and
the hash function [*] the hash function [*]
We do not trigger prunes onto interfaces for SM groups based on We do not trigger prunes onto interfaces for SM groups based on
data packets. Data packets that arrive on the wrong incoming data packets. Data packets that arrive on the wrong incoming
interface for an SM group are silently dropped. interface for an SM group are silently dropped.
3.2.1.3 Fragmentation 3.2.1.3 Fragmentation
skipping to change at page 22, line 5 skipping to change at line 904
actions are taken: actions are taken:
1 If Sj is not the same as the receiving router's RP 1 If Sj is not the same as the receiving router's RP
mapping for G, the receiving router may ignore the mapping for G, the receiving router may ignore the
_________________________ _________________________
[*] As described earlier, PMBRs trigger (*,*,RP) joins [*] As described earlier, PMBRs trigger (*,*,RP) joins
towards each RP in the RP-Set. towards each RP in the RP-Set.
[*] If the router is connected to a multiaccess LAN, [*] If the router is connected to a multiaccess LAN,
the message could be intended for a different router. the message could be intended for a different router.
[Page 21]
Join/Prune message with respect to that group entry. Join/Prune message with respect to that group entry.
If the router does not have any RP-Set information, it If the router does not have any RP-Set information, it
may use the address Sj included in the Join/Prune may use the address Sj included in the Join/Prune
message as the RP for the group. message as the RP for the group.
2 If Sj is the same as the receiving router's RP mapping 2 If Sj is the same as the receiving router's RP mapping
for G, the receiving router adds I to the outgoing for G, the receiving router adds I to the outgoing
interface list of the (*,G) forwarding entry and sets interface list of the (*,G) forwarding entry and sets
the timer for that interface (if there is no (*,G) the timer for that interface (if there is no (*,G)
entry, the router creates one first). If a (*,*,RP) entry, the router creates one first). If a (*,*,RP)
skipping to change at page 23, line 4 skipping to change at line 946
2 For each address, Sj, in the join list whose RPT-bit and 2 For each address, Sj, in the join list whose RPT-bit and
WC-bit are not set, and for which there is no existing WC-bit are not set, and for which there is no existing
(Sj,G) forwarding entry, the router initiates one. (Sj,G) forwarding entry, the router initiates one.
[*] [*]
_________________________ _________________________
[*] A `*' in the group field of the Join/Prune is [*] A `*' in the group field of the Join/Prune is
represented by a group address 224.0.0.0 and a group represented by a group address 224.0.0.0 and a group
mask length of 4, indicating a (*,*,RP) Join. mask length of 4, indicating a (*,*,RP) Join.
[*] The router creates a (S,G) entry and copies all [*] The router creates a (S,G) entry and copies all
[Page 22]
1 The outgoing interface for (Sj,G) is set to I. The 1 The outgoing interface for (Sj,G) is set to I. The
incoming interface for (Sj,G) is set to the interface incoming interface for (Sj,G) is set to the interface
used to send unicast packets to Sj (i.e., the RPF used to send unicast packets to Sj (i.e., the RPF
neighbor). neighbor).
2 If the interface, I, used to reach Sj, is the same as 2 If the interface, I, used to reach Sj, is the same as
the outgoing interface being initialized, this the outgoing interface being initialized, this
represents an error (or a unicast routing change) and represents an error (or a unicast routing change) and
the Join/Prune should not be processed. the Join/Prune should not be processed.
skipping to change at page 24, line 5 skipping to change at line 987
down the shortest path tree. down the shortest path tree.
_________________________ _________________________
outgoing interfaces from the (S,G)RPT-bit entry, if it outgoing interfaces from the (S,G)RPT-bit entry, if it
exists. If there is no (S,G) entry, the oif list is exists. If there is no (S,G) entry, the oif list is
copied from the (*,G) entry; and if there is no (*,G) copied from the (*,G) entry; and if there is no (*,G)
entry, the oif list is copied from the (*,*,RP) entry, entry, the oif list is copied from the (*,*,RP) entry,
if it exists. In all cases, the iif of the (S,G) entry if it exists. In all cases, the iif of the (S,G) entry
is always excluded from the oif list. is always excluded from the oif list.
[Page 23]
For each Sp in the prune list of the Join/Prune message: For each Sp in the prune list of the Join/Prune message:
1 For each address, Sp, in the prune list whose RPT-bit and 1 For each address, Sp, in the prune list whose RPT-bit and
WC-bit are cleared: WC-bit are cleared:
1 If there is an existing (Sp,G) forwarding entry, the 1 If there is an existing (Sp,G) forwarding entry, the
router schedules a deletion of I from the list of router schedules a deletion of I from the list of
outgoing interfaces by lowering that oif timer to 5 outgoing interfaces by lowering that oif timer to 5
seconds (unless it is already lower). The deletion is seconds (unless it is already lower). The deletion is
not executed until this timer expires, allowing for not executed until this timer expires, allowing for
skipping to change at page 25, line 4 skipping to change at line 1027
2 If the router has a current (*,G), or (*,*,RP), 2 If the router has a current (*,G), or (*,*,RP),
forwarding entry, and if the existing (Sp,G) entry has forwarding entry, and if the existing (Sp,G) entry has
its RPT-bit flag set to 1, then this (Sp,G)RPT-bit its RPT-bit flag set to 1, then this (Sp,G)RPT-bit
entry is maintained (not deleted) even if its outgoing entry is maintained (not deleted) even if its outgoing
interface list is null. interface list is null.
3 If (*,G), or corresponding (*,*,RP), state exists, but 3 If (*,G), or corresponding (*,*,RP), state exists, but
there is no (Sp,G) entry, an (Sp,G)RPT-bit entry is there is no (Sp,G) entry, an (Sp,G)RPT-bit entry is
created . The outgoing interface list is copied from created . The outgoing interface list is copied from
[Page 24]
the (*,G), or (*,*,RP), entry, with the interface, I, the (*,G), or (*,*,RP), entry, with the interface, I,
on which the prune was received, is deleted. Packets on which the prune was received, is deleted. Packets
from the pruned source, Sp, match on this state and from the pruned source, Sp, match on this state and
are not forwarded toward the pruned receivers. are not forwarded toward the pruned receivers.
4 If there exists a (Sp,G) entry, with or without the 4 If there exists a (Sp,G) entry, with or without the
RPT-bit set, the iif on which the prune was received, RPT-bit set, the iif on which the prune was received,
I, is deleted from the oif list, and the entry I, is deleted from the oif list, and the entry
timer is restarted. timer is restarted.
skipping to change at page 26, line 4 skipping to change at line 1066
3 If there exists a (*,G) entry, the interface on which 3 If there exists a (*,G) entry, the interface on which
the prune was received, I, is deleted from the oif the prune was received, I, is deleted from the oif
list, and the entry timer is restarted. list, and the entry timer is restarted.
For any new (S,G), (*,G) or (*,*,RP) entry created by an For any new (S,G), (*,G) or (*,*,RP) entry created by an
incoming Join/Prune message, the Joiner-bit is initialized incoming Join/Prune message, the Joiner-bit is initialized
to 1 and the SPT-bit is cleared. to 1 and the SPT-bit is cleared.
If the received Join/Prune does not indicate the router as its If the received Join/Prune does not indicate the router as its
target, then if the Join/Prune matches an existing (S,G), (*,G), target, then if the Join/Prune matches an existing (S,G), (*,G),
[Page 25]
or (*,*,RP) entry and the Join/Prune arrived on the iif for or (*,*,RP) entry and the Join/Prune arrived on the iif for
that entry, then the router compares the IP address of the that entry, then the router compares the IP address of the
generator of the Join/Prune, to its own IP address and sets the generator of the Join/Prune, to its own IP address and sets the
Joiner-bit as follows. Joiner-bit as follows.
1 If its own IP address is higher, the Joiner-bit in the 1 If its own IP address is higher, the Joiner-bit in the
entry is set. entry is set.
2 If its own IP address is lower, the Joiner-bit in the entry 2 If its own IP address is lower, the Joiner-bit in the entry
is cleared, and the Joiner-bit timer is activated. is cleared, and the Joiner-bit timer is activated.
skipping to change at page 27, line 5 skipping to change at line 1108
1 If there is no corresponding (S,G) entry, and the 1 If there is no corresponding (S,G) entry, and the
_________________________ _________________________
[*] When a PMBR (e.g., a router that connects the PIM- [*] When a PMBR (e.g., a router that connects the PIM-
SM region to a dense mode region running DVMRP or PIM- SM region to a dense mode region running DVMRP or PIM-
DM) receives a packet from a source in the dense mode DM) receives a packet from a source in the dense mode
region, the router treats the packet as if it were from region, the router treats the packet as if it were from
a directly connected source. A separate document will a directly connected source. A separate document will
describe the details of interoperabiity. describe the details of interoperabiity.
[Page 26]
router has RP-Set information, the DR creates one with router has RP-Set information, the DR creates one with
the Register-bit set to 1 and the RP address set the Register-bit set to 1 and the RP address set
according to the hash function mapping for the according to the hash function mapping for the
corresponding group. The Register-bit-timer is corresponding group. The Register-bit-timer is
initialized to zero; the Register-bit-timer is non- initialized to zero; the Register-bit-timer is non-
zero only when the Register-bit is set to 0. zero only when the Register-bit is set to 0.
2 If there is a (S,G) entry in existence, the DR simply 2 If there is a (S,G) entry in existence, the DR simply
restarts the corresponding S-timer (entry timer). restarts the corresponding S-timer (entry timer).
skipping to change at page 28, line 5 skipping to change at line 1147
packets in Register messages. packets in Register messages.
3.3.2 Receiving Register Messages and Sending Register-Stops 3.3.2 Receiving Register Messages and Sending Register-Stops
When a router (i.e., the RP) receives a Register message, the When a router (i.e., the RP) receives a Register message, the
router does the following: router does the following:
1 Decapsulates the data packet, and checks for a 1 Decapsulates the data packet, and checks for a
corresponding (S,G) entry. corresponding (S,G) entry.
[Page 27]
1 If a (S,G) entry exists, the packet is forwarded but 1 If a (S,G) entry exists, the packet is forwarded but
the SPT bit is left cleared (0). If the SPT bit is 1, the SPT bit is left cleared (0). If the SPT bit is 1,
the packet is dropped, and Register-Stop messages are the packet is dropped, and Register-Stop messages are
triggered. Register-Stops are rate limited. [*] triggered. Register-Stops are rate limited. [*]
2 If there is no (S,G) entry, but there is a (*,G) 2 If there is no (S,G) entry, but there is a (*,G)
entry, or a (*,*,RP) entry with the RP corresponding entry, or a (*,*,RP) entry with the RP corresponding
to G, the packet is forwarded according to that entry. to G, the packet is forwarded according to that entry.
3 If there is a (*,*,RP) entry but no (*,G) entry, a 3 If there is a (*,*,RP) entry but no (*,G) entry, a
skipping to change at page 29, line 5 skipping to change at line 1188
_________________________ _________________________
[*] Register-Stops should be rate limited so that no [*] Register-Stops should be rate limited so that no
more than a few are sent per round trip time. This more than a few are sent per round trip time. This
prevents a high datarate stream of packets from prevents a high datarate stream of packets from
triggering a large number of Register-stop messages triggering a large number of Register-stop messages
between the time that the first packet is received and between the time that the first packet is received and
the time when the source receives the first Register- the time when the source receives the first Register-
Stop. Stop.
[Page 28]
2 If the `PMBR' field for the corresponding (S,G) 2 If the `PMBR' field for the corresponding (S,G)
entry matches the source of the Register packet, entry matches the source of the Register packet,
the decapsulated packet is forwarded to the oif the decapsulated packet is forwarded to the oif
list of that entry, else list of that entry, else
3 The packet is dropped, and a Register-stop is 3 The packet is dropped, and a Register-stop is
triggered towards the source of the Register. triggered towards the source of the Register.
The (S,G) state timer is restarted by Registers arriving The (S,G) state timer is restarted by Registers arriving
from that source to that group. from that source to that group.
skipping to change at page 30, line 5 skipping to change at line 1229
entry causes the RP to send a Join/Prune message for the entry causes the RP to send a Join/Prune message for the
indicated group towards the source of the register message. indicated group towards the source of the register message.
If the (S,G) oif list becomes null, Join/Prune messages If the (S,G) oif list becomes null, Join/Prune messages
will not be sent towards the source, S. will not be sent towards the source, S.
3.4 Multicast Data Packet Forwarding 3.4 Multicast Data Packet Forwarding
Processing a multicast data packet involves the following steps: Processing a multicast data packet involves the following steps:
[Page 29]
1 Lookup forwarding state based on a longest match of the 1 Lookup forwarding state based on a longest match of the
source address, and an exact match of the destination source address, and an exact match of the destination
address in the data packet. If neither S, nor G, find a address in the data packet. If neither S, nor G, find a
longest match entry, and the RP for the packet's longest match entry, and the RP for the packet's
destination group address has a corresponding (*,*,RP) destination group address has a corresponding (*,*,RP)
entry, then the longest match does not require an exact entry, then the longest match does not require an exact
match on the destination group address. In summary, the match on the destination group address. In summary, the
longest match is performed in the following order: (1) longest match is performed in the following order: (1)
(S,G), (2) (*,G). If neither is matched, then a lookup is (S,G), (2) (*,G). If neither is matched, then a lookup is
performed on (*,*,RP) entries. performed on (*,*,RP) entries.
skipping to change at page 31, line 5 skipping to change at line 1270
sends it to the RP. sends it to the RP.
This covers the common case of a packet arriving on the RPF This covers the common case of a packet arriving on the RPF
interface to the source or RP and being forwarded to all interface to the source or RP and being forwarded to all
joined branches. It also detects when packets arrive on the joined branches. It also detects when packets arrive on the
SP-tree, and triggers their pruning from the RP-tree. If it SP-tree, and triggers their pruning from the RP-tree. If it
_________________________ _________________________
[*] Optionally, the (S,G) timer may be restarted by [*] Optionally, the (S,G) timer may be restarted by
periodic checking of the matching packet count. periodic checking of the matching packet count.
[Page 30]
is the DR for the source, it sends data packets is the DR for the source, it sends data packets
encapsulated in Registers to the RPs. encapsulated in Registers to the RPs.
3 If the packet matches to an entry but did not arrive on the 3 If the packet matches to an entry but did not arrive on the
interface found in the entry's iif field, check the interface found in the entry's iif field, check the
SPT-bit of the entry. If the SPT-bit is set, drop the SPT-bit of the entry. If the SPT-bit is set, drop the
packet. If the SPT-bit is cleared, then lookup the (*,G), packet. If the SPT-bit is cleared, then lookup the (*,G),
or (*,*,RP), entry for G. If the packet arrived on the or (*,*,RP), entry for G. If the packet arrived on the
iif found in (*,G), or the corresponding (*,*,RP), iif found in (*,G), or the corresponding (*,*,RP),
forward the packet to the oif list of the matching forward the packet to the oif list of the matching
skipping to change at page 32, line 4 skipping to change at line 1313
trees. trees.
One proposed example is to do so based on data rate. For One proposed example is to do so based on data rate. For
example, when a (*,G), or corresponding (*,*,RP), entry is example, when a (*,G), or corresponding (*,*,RP), entry is
created, a data rate counter may be initiated at the last-hop created, a data rate counter may be initiated at the last-hop
routers. The counter is incremented with every data packet routers. The counter is incremented with every data packet
received for directly connected members of an SM group, if the received for directly connected members of an SM group, if the
longest match is (*,G) or (*,*,RP). If and when the data rate longest match is (*,G) or (*,*,RP). If and when the data rate
for the group exceeds a certain configured threshold (t1), the for the group exceeds a certain configured threshold (t1), the
router initiates `source-specific' data rate counters for the router initiates `source-specific' data rate counters for the
[Page 31]
following data packets. Then, each counter for a source, is following data packets. Then, each counter for a source, is
incremented when packets matching on (*,G), or (*,*,RP), are incremented when packets matching on (*,G), or (*,*,RP), are
received from that source. If the data rate from the particular received from that source. If the data rate from the particular
source exceeds a configured threshold (t2), a (S,G) entry is source exceeds a configured threshold (t2), a (S,G) entry is
created and a Join/Prune message is sent towards the source. If created and a Join/Prune message is sent towards the source. If
the RPF interface for (S,G) is the RPF interface for (S,G) is
not the same as that for (*,G) -or (*,*,RP), then the SPT-bit not the same as that for (*,G) -or (*,*,RP), then the SPT-bit
is cleared in the (S,G) entry. is cleared in the (S,G) entry.
Other configured rules may be enforced to cause or prevent Other configured rules may be enforced to cause or prevent
skipping to change at page 33, line 5 skipping to change at line 1353
2 If route is not found, use metric preference of 0x7fffffff 2 If route is not found, use metric preference of 0x7fffffff
and metric 0xffffffff. and metric 0xffffffff.
When an assert is sent for a (*,G) entry, the first bit in the When an assert is sent for a (*,G) entry, the first bit in the
metric preference (the RPT-bit) is set to 1, indicating the data metric preference (the RPT-bit) is set to 1, indicating the data
packet is routed down the RP-tree. packet is routed down the RP-tree.
Asserts are rate-limited by the router. Asserts are rate-limited by the router.
[Page 32]
3.5.2 Receiving Asserts 3.5.2 Receiving Asserts
When an assert is received the router performs a longest match When an assert is received the router performs a longest match
on the source and group address in the assert message. The on the source and group address in the assert message. The
router checks the first bit of the metric preference (RPT-bit). router checks the first bit of the metric preference (RPT-bit).
1 If the RPT-bit is set, the router first does a match on 1 If the RPT-bit is set, the router first does a match on
(*,G), or (*,*,RP), entries; if no matching entry is found, (*,G), or (*,*,RP), entries; if no matching entry is found,
the router matches (S,G) entries. the router matches (S,G) entries.
skipping to change at page 34, line 4 skipping to change at line 1391
preference should be treated as the high-order part of an preference should be treated as the high-order part of an
assert metric comparison. If the value in the assert is assert metric comparison. If the value in the assert is
less than the router's value, delete the interface from the less than the router's value, delete the interface from the
entry. If the value is the same, compare IP addresses, if entry. If the value is the same, compare IP addresses, if
the routers address is less than the assert sender, delete the routers address is less than the assert sender, delete
the interface. the interface.
3 If the router has won the election and there are directly 3 If the router has won the election and there are directly
connected members on the multi-access LAN, the router keeps connected members on the multi-access LAN, the router keeps
the interface in its outgoing interface list. It acts as the interface in its outgoing interface list. It acts as
[Page 33]
the forwarder for the LAN. the forwarder for the LAN.
4 If the router won the election but there are no directly 4 If the router won the election but there are no directly
connected members on the multi-access LAN, the router connected members on the multi-access LAN, the router
schedules to delete the interface. The LAN might be a stub schedules to delete the interface. The LAN might be a stub
LAN with no members (and no downstream routers). If no LAN with no members (and no downstream routers). If no
subsequent Join/Prunes are received, the router deletes the subsequent Join/Prunes are received, the router deletes the
interface from the outgoing interface list; otherwise it interface from the outgoing interface list; otherwise it
keeps the interface in its outgoing interface and acts as keeps the interface in its outgoing interface and acts as
the forwarder for the LAN. the forwarder for the LAN.
skipping to change at page 35, line 5 skipping to change at line 1435
This will cause the upstream forwarder to cancel its This will cause the upstream forwarder to cancel its
_________________________ _________________________
[*] This is important so that downstream routers send [*] This is important so that downstream routers send
subsequent Joins/Prunes (in SM) to the correct neigh- subsequent Joins/Prunes (in SM) to the correct neigh-
bor. An Assert timer is initiated when changing the RPF bor. An Assert timer is initiated when changing the RPF
neighbor to the Assert winner. When the timer expires neighbor to the Assert winner. When the timer expires
the router resets its RPF neighbor according to its un- the router resets its RPF neighbor according to its un-
icast routing tables to capture failures of the Assert icast routing tables to capture failures of the Assert
winner. winner.
[Page 34]
scheduled deletion of the interface. scheduled deletion of the interface.
3.6 Candidate-RP-Advertisements and RP-Set messages 3.6 Candidate-RP-Advertisements and RP-Set messages
Candidate-RP-Advertisements (C-RP-Advs) are periodic PIM Candidate-RP-Advertisements (C-RP-Advs) are periodic PIM
messages unicast by those routers that are configured as messages unicast by those routers that are configured as
Candidate-RPs (C-RPs). Candidate-RPs (C-RPs).
RP-Set messages are periodic PIM messages originated by the RP-Set messages are periodic PIM messages originated by the
Bootstrap router (BSR) within a domain, and forwarded hop-by-hop Bootstrap router (BSR) within a domain, and forwarded hop-by-hop
skipping to change at page 36, line 5 skipping to change at line 1459
Candidate BSR (C-BSR) with the highest BSR-priority and IP Candidate BSR (C-BSR) with the highest BSR-priority and IP
address (referred to as the preferred BSR) is elected as the BSR address (referred to as the preferred BSR) is elected as the BSR
for the domain [*] Sections 3.6.2 and 3.6.3 describe the for the domain [*] Sections 3.6.2 and 3.6.3 describe the
combined function of RP-Set messages as the vehicle for BSR combined function of RP-Set messages as the vehicle for BSR
election and RP-Set distribution. election and RP-Set distribution.
_________________________ _________________________
[*] We recommend that each router configured as a C-RP [*] We recommend that each router configured as a C-RP
also be configured as a C-BSR. also be configured as a C-BSR.
[Page 35]
3.6.1 Sending Candidate-RP-Advertisements 3.6.1 Sending Candidate-RP-Advertisements
C-RPs periodically unicast C-RP-Advs to the BSR for that domain. C-RPs periodically unicast C-RP-Advs to the BSR for that domain.
The interval for sending these messages is subject to local The interval for sending these messages is subject to local
configuration at the C-RP. A recommended default value is 60 configuration at the C-RP. A recommended default value is 60
seconds. seconds.
Candidate-RP-Advertisements carry group address and group mask Candidate-RP-Advertisements carry group address and group mask
fields. This enables the advertising router to limit the fields. This enables the advertising router to limit the
advertisement to certain prefixes or scopes of groups. The advertisement to certain prefixes or scopes of groups. The
skipping to change at page 37, line 5 skipping to change at line 1505
group. In steady state, the BSR originates RP-Set messages every group. In steady state, the BSR originates RP-Set messages every
60 seconds. At startup, the RP-Set timer is initialized to 180 60 seconds. At startup, the RP-Set timer is initialized to 180
seconds, causing the first RP-Set message to be originated after seconds, causing the first RP-Set message to be originated after
180 seconds, when/if the timer expires. For timer details see 180 seconds, when/if the timer expires. For timer details see
Section 3.6.3. A DR unicasts an RP-Set message to new PIM Section 3.6.3. A DR unicasts an RP-Set message to new PIM
neighbors starting up, after receiving their Query messages. neighbors starting up, after receiving their Query messages.
_________________________ _________________________
[*] The BSR may apply a local policy to limit the [*] The BSR may apply a local policy to limit the
number of Candidate RPs included in the RP-Set message. number of Candidate RPs included in the RP-Set message.
[Page 36]
(since after DR election the new neighbor may become the new (since after DR election the new neighbor may become the new
DR.) DR.)
The RP-Set message is subdivided into sets of group-prefix,RP- The RP-Set message is subdivided into sets of group-prefix,RP-
Count,RP-addresses. The format of the RP-Set message allows Count,RP-addresses. The format of the RP-Set message allows
`semantic fragmentation', if the length of the original RP-Set `semantic fragmentation', if the length of the original RP-Set
message exceeds the packet maximum boundaries (see Section 4). message exceeds the packet maximum boundaries (see Section 4).
However, we recommend against configuring a large number of However, we recommend against configuring a large number of
routers as C-RPs, to reduce the semantic fragmentation required. routers as C-RPs, to reduce the semantic fragmentation required.
skipping to change at page 38, line 4 skipping to change at line 1549
PIM interfaces, excluding the one over which the PIM interfaces, excluding the one over which the
message arrived, to `ALL-PIM-ROUTERS' group, with a message arrived, to `ALL-PIM-ROUTERS' group, with a
TTL of 1. TTL of 1.
3 If the RP-Set message includes a BSR address that is 3 If the RP-Set message includes a BSR address that is
preferred over, or equal to, the currently active BSR, the preferred over, or equal to, the currently active BSR, the
router resets its RP-Set timer to 180 seconds, and stores router resets its RP-Set timer to 180 seconds, and stores
the BSR address and RP-Set information. The RP-Set message the BSR address and RP-Set information. The RP-Set message
is then forwarded out all PIM interfaces, excluding the one is then forwarded out all PIM interfaces, excluding the one
over which the message arrived, to `ALL-PIM-ROUTERS' group, over which the message arrived, to `ALL-PIM-ROUTERS' group,
[Page 37]
with a TTL of 1. with a TTL of 1.
4 If the receiving router has no current RP set information 4 If the receiving router has no current RP set information
and the RP-set was unicast to it from a directly connected and the RP-set was unicast to it from a directly connected
neighbor, the router stores the information as its new RP- neighbor, the router stores the information as its new RP-
set. This covers the startup condition when a newly booted set. This covers the startup condition when a newly booted
router obtains the RP-Set and BSR address from its DR. router obtains the RP-Set and BSR address from its DR.
When a router receives a new RP-Set it checks if each of the RPs When a router receives a new RP-Set it checks if each of the RPs
referred to by existing state (i.e., by (*,G), (*,*,RP), or referred to by existing state (i.e., by (*,G), (*,*,RP), or
skipping to change at page 39, line 5 skipping to change at line 1595
Set, whose Group-prefix covers G, compute a value: Set, whose Group-prefix covers G, compute a value:
Value(G,M,Ci) = Value(G,M,Ci) =
1103515245 ((1103515245 (G&M)+12345) XOR Ci)+ 12345 mod 2^31 1103515245 ((1103515245 (G&M)+12345) XOR Ci)+ 12345 mod 2^31
where M is a hash-mask included in RP-Set messages. where M is a hash-mask included in RP-Set messages.
This hash-mask allows a small number of This hash-mask allows a small number of
consecutive groups (e.g., 4) to always hash to the same RP. consecutive groups (e.g., 4) to always hash to the same RP.
For instance, hierarchically-encoded data can be sent on For instance, hierarchically-encoded data can be sent on
consecutive group addresses to get the same delay and consecutive group addresses to get the same delay and
fate-sharing characteristics. fate-sharing characteristics.
[Page 38]
In standard C, this corresponds to: In standard C, this corresponds to:
srand(G & M); srand(G & M);
srand(rand() ^ Ci); srand(rand() ^ Ci);
value = rand(); value = rand();
2 The candidate with the highest resulting value is then 2 The candidate with the highest resulting value is then
chosen as the RP for that group, and its identity and hash chosen as the RP for that group, and its identity and hash
value are stored with the entry created. value are stored with the entry created.
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timer has reached zero. timer has reached zero.
In many cases, the values for timers come from Holdtime fields In many cases, the values for timers come from Holdtime fields
in PIM control messages, in which case the default values used in PIM control messages, in which case the default values used
in these Holdtime fields are shown in the tables below. in these Holdtime fields are shown in the tables below.
Otherwise, the default value used when setting the timer is Otherwise, the default value used when setting the timer is
shown. In general, the default timeout value for state shown. In general, the default timeout value for state
information is three times the refresh period. For example, information is three times the refresh period. For example,
Queries refresh Neighbor state and the default Query-timer Queries refresh Neighbor state and the default Query-timer
period is 30 seconds, so a default Neighbor-timer duration of 90 period is 30 seconds, so a default Neighbor-timer duration of 90
[Page 39]
seconds is included in the Holdtime field of the Queries. seconds is included in the Holdtime field of the Queries.
In this version of the spec we suggest particular numerical In this version of the spec we suggest particular numerical
timer settings. A future version of the specification will timer settings. A future version of the specification will
specify a mechanism for timers to be set as a function of the specify a mechanism for timers to be set as a function of the
outgoing link bandwidth. outgoing link bandwidth.
3.8.1 Timers related to tree maintenance 3.8.1 Timers related to tree maintenance
Each (S,G), (*,G), and (*,*,RP) entry has multiple timers Each (S,G), (*,G), and (*,*,RP) entry has multiple timers
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_________________________ _________________________
[*] If there are sources in the prune list of the (*,G) [*] If there are sources in the prune list of the (*,G)
join, then the timers for the arriving interface will join, then the timers for the arriving interface will
first be reset for those sources, and then this inter- first be reset for those sources, and then this inter-
face will be deleted from these same entries; producing face will be deleted from these same entries; producing
a correct result, even though the updating of the ti- a correct result, even though the updating of the ti-
mers was unnecessary. An implementation could optimize mers was unnecessary. An implementation could optimize
this by checking the prune list before processing the this by checking the prune list before processing the
join list. join list.
[Page 40]
Timer DefVal Notes Timer DefVal Notes
Joiner-bit 90 Started : When Joiner bit is cleared Joiner-bit 90 Started : When Joiner bit is cleared
per route entry Reset by: Receiving Join from higher-IP neighbor on iif per route entry Reset by: Receiving Join from higher-IP neighbor on iif
Action : Set Joiner bit Action : Set Joiner bit
Join/Prune 60 Started : When booting Join/Prune 60 Started : When booting
Reset by: Nothing Reset by: Nothing
Action : Send Join/Prune to each RPF neighbor, restart timer Action : Send Join/Prune to each RPF neighbor, restart timer
skipping to change at page 42, line 4 skipping to change at line 1724
(S,G) entry 180 Started : When entry is created (S,G) entry 180 Started : When entry is created
aka S-timer Restarted by: Forwarding data packet, aka S-timer Restarted by: Forwarding data packet,
per (S,G) receiving Register, receiving (S,G)RPT-bit per (S,G) receiving Register, receiving (S,G)RPT-bit
prune, restarting timer on any oif, prune, restarting timer on any oif,
or receiving an Assert without RPT-bit set. or receiving an Assert without RPT-bit set.
Action : Delete entry Action : Delete entry
Register-bit 60 Started : When Register bit is cleared by Register-bit 60 Started : When Register bit is cleared by
per (S,G) receiving a Register-Stop per (S,G) receiving a Register-Stop
Restarted by: Receiving Register-Stop Restarted by: Receiving Register-Stop
[Page 41]
Action : Set Register bit Action : Set Register bit
Assert 180 Started : Receiving an Assert where the Assert 180 Started : Receiving an Assert where the
per (S,G) upstream RPF neighbor is not your unicast RPF per (S,G) upstream RPF neighbor is not your unicast RPF
and (*,G) neighbor. and (*,G) neighbor.
Restarted by: Receiving an Assert where the Restarted by: Receiving an Assert where the
upstream RPF neighbor is not your unicast upstream RPF neighbor is not your unicast
RPF neighbor. RPF neighbor.
Action : Change RPF neighbor to unicast RPF neighbor Action : Change RPF neighbor to unicast RPF neighbor
skipping to change at page 43, line 4 skipping to change at line 1754
Query 30 Started : When booting Query 30 Started : When booting
Restarted by: Nothing Restarted by: Nothing
Action : Send Query on all ifaces, restart timer Action : Send Query on all ifaces, restart timer
Neighbor 90 Started : When receive first Query from neighbor Neighbor 90 Started : When receive first Query from neighbor
per neighbor Restarted by: When receive subsequent Queries per neighbor Restarted by: When receive subsequent Queries
Action : Delete neighbor entry Action : Delete neighbor entry
3.8.3 Timers relating to RP information 3.8.3 Timers relating to RP information
[Page 42]
Timer DefVal Notes Timer DefVal Notes
C-RP-Adv 60 Started : When booting if you're a Cand-RP C-RP-Adv 60 Started : When booting if you're a Cand-RP
Restarted by: Nothing Restarted by: Nothing
Action : Send C-RP-Adv, restart C-RP-Adv timer Action : Send C-RP-Adv, restart C-RP-Adv timer
RP 180 Started : When adding an RP to the RP-Set if RP 180 Started : When adding an RP to the RP-Set if
per RP you are BSR per RP you are BSR
Restarted by: Receiving C-RP-Adv Restarted by: Receiving C-RP-Adv
Action : Remove RP from RP-Set Action : Remove RP from RP-Set
skipping to change at page 44, line 5 skipping to change at line 1798
the path indicated corresponds to the RP tree. the path indicated corresponds to the RP tree.
SPT (S,G) entry Packets have arrived on the iif towards S, SPT (S,G) entry Packets have arrived on the iif towards S,
and the iif is different from the (*,G) iif. and the iif is different from the (*,G) iif.
WC Join Included address is an RP and the receiver expects to WC Join Included address is an RP and the receiver expects to
receive packets from all sources via this (shared tree) receive packets from all sources via this (shared tree)
path. Thus, the Join/Prune applies to a (*,G) entry. path. Thus, the Join/Prune applies to a (*,G) entry.
WC Route entry Wildcard entry; if there is no more specific match for WC Route entry Wildcard entry; if there is no more specific match for
a particular source, packets will be forwarded according a particular source, packets will be forwarded according
to this entry. to this entry.
[Page 43]
3.10 Security 3.10 Security
Editors Note: this section is to be completed. Editors Note: this section is to be completed.
All PIM control messages may use [5] to address security All PIM control messages may use [5] to address security
concerns. concerns.
[Page 44]
4 Packet Formats 4 Packet Formats
This section describes the details of the packet formats for PIM This section describes the details of the packet formats for PIM
control messages. control messages.
All PIM control messages have protocol number 103. All PIM control messages have protocol number 103.
Basically, PIM messages are either unicast (e.g. Registers and Basically, PIM messages are either unicast (e.g. Registers and
Register-Stop), or multicast hop-by-hop to `ALL-PIM-ROUTERS' Register-Stop), or multicast hop-by-hop to `ALL-PIM-ROUTERS'
group `224.0.0.13' (e.g. Join/Prune, Asserts, etc.). group `224.0.0.13' (e.g. Join/Prune, Asserts, etc.).
skipping to change at page 46, line 5 skipping to change at line 1844
5 = Assert 5 = Assert
6 = Graft (used in PIM-DM only) 6 = Graft (used in PIM-DM only)
7 = Graft-Ack (used in PIM-DM only) 7 = Graft-Ack (used in PIM-DM only)
8 = Candidate-RP-Advertisement 8 = Candidate-RP-Advertisement
Addr length Addr length
Address length in bytes. Throughout this section this Address length in bytes. Throughout this section this
would indicate the number of bytes in the Address field of would indicate the number of bytes in the Address field of
an address, including unicast and group addresses. an address, including unicast and group addresses.
[Page 45]
Checksum Checksum
The checksum is the 16-bit one's complement of the one's The checksum is the 16-bit one's complement of the one's
complement sum of the entire PIM message, (excluding the complement sum of the entire PIM message, (excluding the
data portion in the Register message). For computing the data portion in the Register message). For computing the
checksum, the checksum field is zeroed. checksum, the checksum field is zeroed.
[Page 46]
4.1 Encoded Source and Group Address formats 4.1 Encoded Source and Group Address formats
1 Unicast address: Only the address is included. The length 1 Unicast address: Only the address is included. The length
of the unicast address in bytes is specified in the `Addr of the unicast address in bytes is specified in the `Addr
length' field in the header. length' field in the header.
2 Encoded-Group-Address: Takes the following format: 2 Encoded-Group-Address: Takes the following format:
0 1 2 3 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 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
skipping to change at page 48, line 5 skipping to change at line 1885
Addr length * 8. If the message is sent for a single Addr length * 8. If the message is sent for a single
group then the Mask length should equal Addr length * group then the Mask length should equal Addr length *
8 (i.e. 32 for IPv4 and 128 for IPv6). 8 (i.e. 32 for IPv4 and 128 for IPv6).
Group multicast Address Group multicast Address
contains the group address, and has number of bytes contains the group address, and has number of bytes
equal to that specified in the Addr length field. equal to that specified in the Addr length field.
3 Encoded-Source-Address: Takes the following format: 3 Encoded-Source-Address: Takes the following format:
[Page 47]
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Rsrvd |S|W|R| Mask Len | Source Address ... | | Rsrvd |S|W|R| Mask Len | Source Address ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... Source Address | | ... Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+~+~+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+~+~+-+
Reserved Reserved
Transmitted as zero, ignored on receipt. Transmitted as zero, ignored on receipt.
skipping to change at page 49, line 5 skipping to change at line 1914
sent for a single source then the Mask length should sent for a single source then the Mask length should
equal Addr length * 8. In version 2 of PIM, it is equal Addr length * 8. In version 2 of PIM, it is
strongly recommended that this field be set to 32 for strongly recommended that this field be set to 32 for
IPv4. IPv4.
Source Address Source Address
The address length is indicated from the Addr length The address length is indicated from the Addr length
field at the beginning of the header. For IPv4, the field at the beginning of the header. For IPv4, the
address length is 4 octets. address length is 4 octets.
[Page 48]
4.2 Query Message 4.2 Query Message
It is sent periodically by routers on all interfaces. It is sent periodically by routers on all interfaces.
0 1 2 3 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 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 | Addr length | Checksum | |PIM Ver| Type | Addr length | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Holdtime | | Reserved | Holdtime |
skipping to change at page 50, line 5 skipping to change at line 1937
PIM Version, Type, Addr length, Checksum PIM Version, Type, Addr length, Checksum
Described above. Described above.
Reserved Reserved
Transmitted as zero, ignored on receipt. Transmitted as zero, ignored on receipt.
Holdtime Holdtime
The amount of time a receiver should keep the neighbor The amount of time a receiver should keep the neighbor
reachable, in seconds. reachable, in seconds.
[Page 49]
4.3 Register Message 4.3 Register Message
It is sent by the Designated Router (DR) to the RP when a It is sent by the Designated Router (DR) to the RP when a
multicast packet needs to be transmitted on the RP-tree. Source multicast packet needs to be transmitted on the RP-tree. Source
IP address is set to the address of the DR, destination IP IP address is set to the address of the DR, destination IP
address is to the RP's address. address is to the RP's address.
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 51, line 5 skipping to change at line 1969
is done only on the PIM header, excluding the data packet is done only on the PIM header, excluding the data packet
portion. portion.
B The Border bit. Set to zero by all DRs. Set to `1' by the B The Border bit. Set to zero by all DRs. Set to `1' by the
PIM Multicast Border Routers, when registering for external PIM Multicast Border Routers, when registering for external
sources. sources.
Multicast data packet Multicast data packet
The original packet sent by the source. The original packet sent by the source.
[Page 50]
4.4 Register-Stop Message 4.4 Register-Stop Message
A Register-Stop is unicast from the RP to the sender of the A Register-Stop is unicast from the RP to the sender of the
Register message. Source IP address is the address to which the Register message. Source IP address is the address to which the
register was addressed. Destination IP address is the source register was addressed. Destination IP address is the source
address of the register message. address of the register message.
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 52, line 5 skipping to change at line 2001
Format described above. Note that for Register-Stops the Format described above. Note that for Register-Stops the
Mask Len field should contain Addr length * 8 (32 for Mask Len field should contain Addr length * 8 (32 for
IPv4), if the message is sent for a single group. IPv4), if the message is sent for a single group.
Unicast-Source Address Unicast-Source Address
IP host address of source from multicast data packet in IP host address of source from multicast data packet in
register. The length of this field in bytes is specified in register. The length of this field in bytes is specified in
the Addr length field. A special wild card value (0.0.0.0), the Addr length field. A special wild card value (0.0.0.0),
can be used to indicate any source. can be used to indicate any source.
[Page 51]
4.5 Join/Prune Message 4.5 Join/Prune Message
It is sent by routers towards upstream sources and RPs. A join It is sent by routers towards upstream sources and RPs. A join
creates forwarding state and a prune destroys forwarding state. creates forwarding state and a prune destroys forwarding state.
Joins are sent to build shared trees (RP trees) or source trees Joins are sent to build shared trees (RP trees) or source trees
(SPT). Prunes are sent to prune source trees when members leave (SPT). Prunes are sent to prune source trees when members leave
groups as well as sources that do not use the shared tree. groups as well as sources that do not use the shared tree.
[Page 52]
0 1 2 3 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 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 | Addr length | Checksum | |PIM Ver| Type | Addr length | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unicast-Upstream Neighbor Address | | Unicast-Upstream Neighbor Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Num groups | Holdtime | | Reserved | Num groups | Holdtime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encoded-Multicast Group Address-1 | | Encoded-Multicast Group Address-1 |
skipping to change at page 54, line 4 skipping to change at line 2058
| . | | . |
| . | | . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encoded-Joined Source Address-n | | Encoded-Joined Source Address-n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encoded-Pruned Source Address-1 | | Encoded-Pruned Source Address-1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . | | . |
| . | | . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
[Page 53]
| Encoded-Pruned Source Address-n | | Encoded-Pruned Source Address-n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PIM Version, Type, Addr length, Checksum PIM Version, Type, Addr length, Checksum
Described above. Described above.
Upstream Neighbor Address Upstream Neighbor Address
The IP address of the RPF or upstream neighbor. The IP address of the RPF or upstream neighbor.
Reserved Reserved
skipping to change at page 55, line 5 skipping to change at line 2101
This list contains the sources that the sending router This list contains the sources that the sending router
will forward multicast datagrams for if received on the will forward multicast datagrams for if received on the
interface this message is sent on. interface this message is sent on.
See format section 4.1. The fields explanation for the See format section 4.1. The fields explanation for the
Encoded-Source-Address format follows: Encoded-Source-Address format follows:
Reserved Reserved
Described above. Described above.
[Page 54]
S The Sparse bit is a 1 bit value, set to 1 for PIM-SM. S The Sparse bit is a 1 bit value, set to 1 for PIM-SM.
It is used for PIM v.1 compatability. It is used for PIM v.1 compatability.
W The WC bit is a 1 bit value. If 1, the join or prune W The WC bit is a 1 bit value. If 1, the join or prune
applies to the (*,G) or (*,*,RP) entry. If 0, the join applies to the (*,G) or (*,*,RP) entry. If 0, the join
or prune applies to the (S,G) entry where S is Source or prune applies to the (S,G) entry where S is Source
Address. Joins and prunes sent towards the RP should Address. Joins and prunes sent towards the RP should
have this bit set. have this bit set.
R The RPT-bit is a 1 bit value. If 1, the information R The RPT-bit is a 1 bit value. If 1, the information
skipping to change at page 56, line 4 skipping to change at line 2148
Number of Pruned Sources Number of Pruned Sources
Number of prune source addresses listed for a group. Number of prune source addresses listed for a group.
Prune Source Address-1 .. n Prune Source Address-1 .. n
This list contains the sources that the sending router This list contains the sources that the sending router
does not want to forward multicast datagrams for when does not want to forward multicast datagrams for when
received on the interface this message is sent on [*] received on the interface this message is sent on [*]
_________________________ _________________________
[*] If the Join/Prune message boundary exceeds the max- [*] If the Join/Prune message boundary exceeds the max-
[Page 55]
4.6 RP-Set 4.6 RP-Set
The RP-Set messages are multicast to `ALL-PIM-ROUTERS' group, The RP-Set messages are multicast to `ALL-PIM-ROUTERS' group,
out all interfaces having PIM neighbors (excluding the one over out all interfaces having PIM neighbors (excluding the one over
which the message was received). RP-Set messages are sent with which the message was received). RP-Set messages are sent with
TTL value of 1. RP-Set messages originate at the BSR, and are TTL value of 1. RP-Set messages originate at the BSR, and are
forwarded by intermediate routers. forwarded by intermediate routers.
RP-Set message is divided up into `semantic fragments', if the RP-Set message is divided up into `semantic fragments', if the
original message exceeds the maximum packet size boundaries. original message exceeds the maximum packet size boundaries.
The semantics of a single `fragment' is given below: The semantics of a single `fragment' is given below:
_________________________ _________________________
imum packet size, then the join and prune lists for the imum packet size, then the join and prune lists for the
same group must be included in the same packet. same group must be included in the same packet.
[Page 56]
0 1 2 3 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 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 | Addr length | Checksum | |PIM Ver| Type | Addr length | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Fragment Tag | Hash Mask len | BSR-priority | | Fragment Tag | Hash Mask len | BSR-priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unicast-BSR-Address | | Unicast-BSR-Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encoded-Group Address-1 | | Encoded-Group Address-1 |
skipping to change at page 58, line 4 skipping to change at line 2210
| . | | . |
| . | | . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unicast-RP-Address-m | | Unicast-RP-Address-m |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PIM Version, Type, Addr length, Checksum PIM Version, Type, Addr length, Checksum
Described above. Described above.
Fragment Tag Fragment Tag
[Page 57]
A randomly generated number, acts to distinguish the A randomly generated number, acts to distinguish the
fragments belonging to different RP-Set messages; fragments fragments belonging to different RP-Set messages; fragments
belonging to same RP-Set message carry the same `Fragment belonging to same RP-Set message carry the same `Fragment
Tag'. Tag'.
Hash Mask len Hash Mask len
The length (in bits) of the mask to use in the hash The length (in bits) of the mask to use in the hash
function. For IPv4 we recommend a value of 30. For IPv6 we function. For IPv4 we recommend a value of 30. For IPv6 we
recommend a value of 126. recommend a value of 126.
skipping to change at page 59, line 5 skipping to change at line 2257
The address of the Candidate RPs, for the corresponding The address of the Candidate RPs, for the corresponding
_________________________ _________________________
[*] A router does not replace its old RP-Set for a [*] A router does not replace its old RP-Set for a
given group prefix until/unless it receives `RP-Count' given group prefix until/unless it receives `RP-Count'
addresses for that prefix; the addresses could be car- addresses for that prefix; the addresses could be car-
ried over several fragments. If only part of the RP-Set ried over several fragments. If only part of the RP-Set
for a given group prefix was received, the router dis- for a given group prefix was received, the router dis-
cards it, without updating that specific group prefix's cards it, without updating that specific group prefix's
RP-Set. RP-Set.
[Page 58]
group prefix. The length of this field in bytes is group prefix. The length of this field in bytes is
specified in Addr length. specified in Addr length.
[Page 59]
4.7 Assert Message 4.7 Assert Message
The Assert message is sent when a multicast data packet is The Assert message is sent when a multicast data packet is
received on an outgoing interface corresponding to the (S,G) or received on an outgoing interface corresponding to the (S,G) or
(*,G) associated with the source. (*,G) associated with the source.
0 1 2 3 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 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 | Addr length | Checksum | |PIM Ver| Type | Addr length | Checksum |
skipping to change at page 61, line 5 skipping to change at line 2307
tree, then the RPT-bit is 1; if the IP multicast datagram tree, then the RPT-bit is 1; if the IP multicast datagram
is routed down the SPT, it is 0. is routed down the SPT, it is 0.
Metric Preference Metric Preference
Preference value assigned to the unicast routing protocol Preference value assigned to the unicast routing protocol
that provided the route to Host address. that provided the route to Host address.
Metric The unicast routing table metric. The metric is in units Metric The unicast routing table metric. The metric is in units
applicable to the unicast routing protocol used. applicable to the unicast routing protocol used.
[Page 60]
4.8 Graft Message 4.8 Graft Message
Used in dense-mode. Refer to PIM dense mode specification. Used in dense-mode. Refer to PIM dense mode specification.
4.9 Graft-Ack Message 4.9 Graft-Ack Message
Used in dense-mode. Refer to PIM dense mode specification. Used in dense-mode. Refer to PIM dense mode specification.
[Page 61]
4.10 Candidate-RP-Advertisement 4.10 Candidate-RP-Advertisement
Candidate-RP-Advertisements are periodically unicast from the Candidate-RP-Advertisements are periodically unicast from the
C-RPs to the BSR. C-RPs to the BSR.
0 1 2 3 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 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 | Addr length | Checksum | |PIM Ver| Type | Addr length | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 63, line 4 skipping to change at line 2359
information, the C-RP puts a default value of `0' in this information, the C-RP puts a default value of `0' in this
field. field.
Holdtime Holdtime
The amount of time the advertisement is valid. This field The amount of time the advertisement is valid. This field
allows advertisements to be aged out. allows advertisements to be aged out.
Unicast-RP-Address Unicast-RP-Address
The address of the interface to advertise as a Candidate The address of the interface to advertise as a Candidate
RP. The length of this field in bytes is specified in Addr RP. The length of this field in bytes is specified in Addr
[Page 62]
length. length.
Encoded-Group Address-1..n Encoded-Group Address-1..n
The group prefixes for which the C-RP is advertising. The group prefixes for which the C-RP is advertising.
Format previously described. Format previously described.
[Page 63]
5 Appendix I: Major Changes and Updates to the Spec 5 Appendix I: Major Changes and Updates to the Spec
This appendix populates the major changes in the specification This appendix populates the major changes in the specification
document as compared to `draft-ietf-idmr-pim-spec-01.ps,txt'. document as compared to `draft-ietf-idmr-pim-spec-01.ps,txt'.
5.1 Major Changes 5.1 Major Changes
List of changes since March '96 IETF: List of changes since March '96 IETF:
1. (*,*,RP) Joins state and data forwarding check; replaces (*,G- 1. (*,*,RP) Joins state and data forwarding check; replaces (*,G-
skipping to change at page 65, line 5 skipping to change at line 2405
5.2 Packet Format Changes 5.2 Packet Format Changes
Packet Format incurred updates to accommodate different address Packet Format incurred updates to accommodate different address
lengths, and address aggregation. lengths, and address aggregation.
1 The `Addr length' field was added to the PIM fixed header 1 The `Addr length' field was added to the PIM fixed header
to specify the address length in bytes of the underlying to specify the address length in bytes of the underlying
protocol, see section 4. protocol, see section 4.
[Page 64]
2 The Encoded source and group address formats were 2 The Encoded source and group address formats were
introduced, with the use of a `Mask length' field to allow introduced, with the use of a `Mask length' field to allow
aggregation, section 4.1. aggregation, section 4.1.
3 Packet formats are no longer IGMP messages; rather PIM 3 Packet formats are no longer IGMP messages; rather PIM
messages. messages.
PIM message types and formats were also modified: PIM message types and formats were also modified:
[ Note: most changes were made to the May 95 version, unless [ Note: most changes were made to the May 95 version, unless
skipping to change at page 67, line 4 skipping to change at line 2440
(a) Candidate-RP-Advertisement [change made in October 95] (a) Candidate-RP-Advertisement [change made in October 95]
RP-Set [Feb. 96] RP-Set [Feb. 96]
3 Modified messages: 3 Modified messages:
(a) Join/Prune [Feb. 96] (a) Join/Prune [Feb. 96]
(b) Register [Feb. 96] (b) Register [Feb. 96]
(c) Register-Stop [Feb. 96] (c) Register-Stop [Feb. 96]
[Page 65]
[Page 66]
6 Acknowledgments 6 Acknowledgments
Tony Ballardie, Scott Brim, Jon Crowcroft, Bill Fenner, Paul Tony Ballardie, Scott Brim, Jon Crowcroft, Bill Fenner, Paul
Francis, Joel Halpern, Horst Hodel, Polly Huang, Stephen Francis, Joel Halpern, Horst Hodel, Polly Huang, Stephen
Ostrowski, and Lixia Zhang provided detailed comments on Ostrowski, and Lixia Zhang provided detailed comments on
previous drafts. The authors of [6] and membership of the IDMR previous drafts. The authors of [6] and membership of the IDMR
WG provided many of the motivating ideas for this work and WG provided many of the motivating ideas for this work and
useful feedback on design details. useful feedback on design details.
This work was supported by the National Science Foundation, This work was supported by the National Science Foundation,
skipping to change at line 2393 skipping to change at line 2478
Protocol specification. Internet Draft, November 1995. Protocol specification. Internet Draft, November 1995.
4. S.Deering. Host extensions for ip multicasting, aug 1989. 4. S.Deering. Host extensions for ip multicasting, aug 1989.
RFC1112. RFC1112.
5. R.Atkinson. Security architecture for the internet protocol, 5. R.Atkinson. Security architecture for the internet protocol,
August 1995. RFC-1825. August 1995. RFC-1825.
6. A.J. Ballardie, P.F. Francis, and J.Crowcroft. Core based trees. 6. A.J. Ballardie, P.F. Francis, and J.Crowcroft. Core based trees.
In Proceedings of the ACM SIGCOMM, San Francisco, 1993. In Proceedings of the ACM SIGCOMM, San Francisco, 1993.
[Page 67]
 End of changes. 

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