Network Working Group IJ. Wijnands
Internet-Draft S. Venaas
Intended status: Experimental Cisco Systems, Inc.
Expires: June 23, 2018 M. Brig
Aegis BMD Program Office
A. Jonasson
Swedish Defence Material Administration (FMV)
December 20, 2017
PIM flooding mechanism and source discovery
draft-ietf-pim-source-discovery-bsr-07
Abstract
PIM Sparse-Mode uses a Rendezvous Point and shared trees to forward
multicast packets from new sources. Once last hop routers receive
packets from a new source, they may join the Shortest Path Tree for
the source for optimal forwarding. This draft defines a new
mechanism that provides a way to support PIM Sparse Mode (SM) without
the need for PIM registers, RPs or shared trees. Multicast source
information is flooded throughout the multicast domain using a new
generic PIM flooding mechanism. This allows last hop routers to
learn about new sources without receiving initial data packets.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 23, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Testing and deployment experiences . . . . . . . . . . . . . 4
3. A generic PIM flooding mechanism . . . . . . . . . . . . . . 4
3.1. PFM message format . . . . . . . . . . . . . . . . . . . 6
3.2. Administrative boundaries . . . . . . . . . . . . . . . . 7
3.3. Originating PFM messages . . . . . . . . . . . . . . . . 7
3.4. Processing PFM messages . . . . . . . . . . . . . . . . . 8
3.4.1. Initial checks . . . . . . . . . . . . . . . . . . . 9
3.4.2. Processing and forwarding of PFM messages . . . . . . 9
4. Distributing Source Group Mappings . . . . . . . . . . . . . 10
4.1. Group Source Holdtime TLV . . . . . . . . . . . . . . . . 10
4.2. Originating Group Source Holdtime TLVs . . . . . . . . . 11
4.3. Processing GSH TLVs . . . . . . . . . . . . . . . . . . . 11
4.4. The first packets and bursty sources . . . . . . . . . . 12
4.5. Resiliency to network partitioning . . . . . . . . . . . 13
5. Security Considerations . . . . . . . . . . . . . . . . . . . 13
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 14
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
PIM Sparse-Mode uses a Rendezvous Point (RP) and shared trees to
forward multicast packets to Last Hop Routers (LHR). After the first
packet is received by a LHR, the source of the multicast stream is
learned and the Shortest Path Tree (SPT) can be joined. This draft
defines a new mechanism that provides a way to support PIM Sparse
Mode (SM) without the need for PIM registers, RPs or shared trees.
Multicast source information is flooded throughout the multicast
domain using a new generic PIM flooding mechanism. By removing the
need for RPs and shared trees, the PIM-SM procedures are simplified,
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improving router operations, management and making the protocol more
robust. Also the data packets are only sent on the SPTs, providing
optimal forwarding.
This document defines a generic flooding mechanism for distributing
information throughout a PIM domain. While the forwarding rules are
largely similar to Bootstrap Router mechanism (BSR) [RFC5059], any
router can originate information, and it allows for flooding of any
kind of information. Each message contains one or more pieces of
information encoded as TLVs (type, length and value). This document
defines one TLV used for distributing information about active
multicast sources. Other documents may define additional TLVs.
Note that this document is experimental. While the flooding
mechanism is largely similar to BSR, there are some concerns about
scale as there can be multiple routers distributing information, and
potentially larger amount of data that needs to be processed and
stored. Distributing knowledge of active sources in this way is new,
and there are some concerns, mainly regarding potentially large
amounts of source states that need to be distributed. While there
has been some testing in the field, we need to learn more about the
forwarding efficiency, both the amount of processing per router, and
propagation delay, and the amount of state that can be distributed.
In particular, how many active sources one can support without
consuming too many resources. There are also parameters that can be
tuned regarding how frequently information is distributed, and it is
not clear what parameters are useful for different types of networks.
1.1. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
1.2. Terminology
RP: Rendezvous Point
BSR: Bootstrap Router
RPF: Reverse Path Forwarding
SPT: Shortest Path Tree
FHR: First Hop Router, directly connected to the source
LHR: Last Hop Router, directly connected to the receiver
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PFM: PIM Flooding Mechanism
PFM-SA: PFM Source Announcement
SG Mapping: Multicast source group mapping
2. Testing and deployment experiences
A prototype of this specification has been implemented and there has
been some limited testing in the field. The prototype was tested in
a network with low bandwidth radio links. The network has frequent
topology changes, including frequest link or router failures.
Previously existing mechanisms like PIM-SM and PIM-DM were tested.
With PIM-SM the existing RP election mechanisms were found to be too
slow. With PIM-DM, issues were observed with new multicast sources
starving low bandwidth links even when there are no receivers, in
some cases such that there was no bandwidth left for prune message.
For the PFM-SA prototype tests, all routers were configured to send
PFM-SA for directly connected source and to cache received
announcements. Applications such as SIP with multicast subscriber
discovery, multicast voice conferencing, position tracking and NTP
were successfully tested. The tests went quite well. Packets were
rerouted as needed and there were no unnecessary forwarding of
packets. Ease of configuration was seen as a plus.
3. A generic PIM flooding mechanism
The Bootstrap Router mechanism (BSR) [RFC5059] is a commonly used
mechanism for distributing dynamic Group to RP mappings in PIM. It
is responsible for flooding information about such mappings
throughout a PIM domain, so that all routers in the domain can have
the same information. BSR as defined, is only able to distribute
Group to RP mappings. This document defines a more generic mechanism
that can flood any kind of information. Administrative boundaries
Section 3.2 may be configured to limit to which parts of a network
the information is flooded.
The forwarding rules are identical to BSR, except that one can
control whether routers should forward unsupported data types. For
some types of information it is quite useful that it can be
distributed without all routers having to support the particular
type, while there may also be types where it is necessary for every
single router to support it. The mechanism includes an originator
address which is used for RPF checking to restrict the flooding, and
prevent loops, just like BSR. Like BSR, messages are forwarded hop
by hop. Note that there is no equivalent to the BSR election
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mechanism;, there can be multiple originators. This mechanism is
named the PIM Flooding Mechanism (PFM).
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3.1. PFM message format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PIM Ver| Type |N| Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator Address (Encoded-Unicast format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type 1 | Length 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value 1 |
| . |
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . |
| . |
| Type n | Length n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value n |
| . |
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PIM Version, Reserved and Checksum: As specified in [RFC7761].
Type: PIM Message Type. Value (pending IANA) for a PFM message.
[N]o-Forward bit: When set, this bit means that the PFM message is
not to be forwarded. This bit is defined to prevent Bootstrap
message forwarding in [RFC5059].
Originator Address: The address of the router that originated the
message. This can be any address assigned to the originating
router, but MUST be routable in the domain to allow successful
forwarding. The format for this address is given in the Encoded-
Unicast address in [RFC7761].
Type 1..n: A message contains one or more TLVs, in this case n
TLVs. The Type specifies what kind of information is in the
Value. The type range is from 0 to 65535. A TLV with a type in
the range from 32768 to 65535 is never to be forwarded by an
implementation not supporting the type, see Section 3.4.2.
Length 1..n: The length of the the value field in octets.
Value 1..n: The value associated with the type and of the specified
length.
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3.2. Administrative boundaries
PFM messages are generally forwarded hop by hop to all PIM routers.
However, similar to BSR, one may configure administrative boundaries
to limit the information to certain domains or parts of the network.
Implementations MUST have a way of defining a set of interfaces on a
router as administrative boundaries for all PFM messages, or
optionally for certain TLVs, allowing for different boundaries for
different TLVs. Usually one wants boundaries to be bidirectional,
but an implementation MAY also provide unidirectional boundaries.
When forwarding a message, a router MUST NOT send it out an interface
that is an outgoing boundary, including bidirectional boundary, for
all PFM messages. If an interface is an outgoing boundary for
certain TLVs, the message MUST NOT be sent out the interface if it is
a boundary for all the TLVs in the message. Otherwise the router
MUST remove all the boundary TLVs from the message and send the
message with the remaining TLVs. Also, when receiving a PFM message
on an interface, the message MUST be discarded if the interface is an
incoming boundary, including bidirectional boundary, for all PFM
messages. If the interface is an incoming boundary for certain TLVs,
the router MUST ignore all boundary TLVs. If all the TLVs in the
message are boundary TLVs, then the message is effectively ignored.
Note that when forwarding an incoming message, the boundary is
applied before forwarding. If the message was discarded or all the
TLVs were ignored, then no message is forwarded. When a message is
forwarded, it MUST NOT contain any TLVs for which the incoming
interface is an incoming, or bidirectional, boundary.
3.3. Originating PFM messages
A router originates a PFM message when it needs to distribute
information using a PFM message to other routers in the network.
When a message is originated depends on what information is
distributed. For instance this document defines a TLV to distribute
information about active sources. When a router has a new active
source, a PFM message should be sent as soon as possible. Hence a
PFM message should be sent every time there is a new active source.
However, the TLV also contains a holdtime and PFM messages need to be
sent periodically. Generally speaking, a PFM message would typically
be sent when there is a local state change, causing information to be
distributed with PFM to change. Also, some information may need to
be sent periodically. These messages are called triggered and
periodic messages, respectively. Each TLV definition will need to
define when a triggered PFM message needs to be originated, and also
whether to send periodic messages, and how frequent.
Unless otherwise specified by the TLV definitions, there is no
relationship between different TLVs, and an implementation can choose
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whether to combine TLVs in one message or across separate messages.
It is RECOMMENDED to combine multiple TLVs in one message, to reduce
the number of messages, but it is also RECOMMENDED that the message
is small enough to avoid fragmentation at the IP layer. When a
triggered PFM message needs to be sent due to a state change, a
router MAY send a message containing only the information that
changed. If there are many changes occuring at about the same time,
it might be possible to combine multiple changes in one message. In
the case where periodic messages are also needed, an implementation
MAY include periodic PFM information in a triggered PFM. E.g., if
some information needs to be sent every 60 seconds and a triggered
PFM is about to be sent 20 seconds before the next periodic PFM was
scheduled, the triggered PFM might include the periodic information
and the next periodic PFM can then be scheduled 60 seconds after
that, rather than 20 seconds later.
When a router originates a PFM message, it puts one of its own
addresses in the originator field. An implementation MUST allow an
administrator to configure which address is used. For a message to
be received by all routers in a domain, all the routers need to have
a route for this address due to the RPF based forwarding. Hence an
administrator needs to be careful which address to choose. When this
is not configured, an implementation MUST NOT use a link-local
address. It is RECOMMENDED to use an address of a virtual interface
such that the originator can remain unchanged and routable
independent of which physical interfaces or links may go down.
The No-Forward bit MUST NOT be set, except for the case when a router
receives a PIM Hello from a new neighbor, or a PIM Hello with a new
GenID is received from an existing neighbor. In that case an
implementation MAY send PFM messages containing relevant information
so that the neighbor can quickly get the correct state. The
definition of the different PFM message TLVs need to specify what, if
anything, needs to be sent in this case. If such a PFM message is
sent, the No-Forward bit MUST be set, and the message must be sent
within 60 seconds after the neighbor state change. The processing
rules for PFM messages will ensure that any other neighbors on the
same link ignores the message.
3.4. Processing PFM messages
A router that receives a PFM message MUST perform the initial checks
specified here. If the checks fail, the message MUST be dropped. An
error MAY be logged, but otherwise the message MUST be dropped
silently. If the checks pass, the contents is processed according to
the processing rules of the included TLVs.
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3.4.1. Initial checks
In order to do further processing, a message MUST meet the following
requirements. The message MUST be from a directly connected PIM
neighbor, the destination address MUST be ALL-PIM-ROUTERS. Also, the
interface MUST NOT be an incoming, nor bidirectional, administrative
boundary for PFM messages Section 3.2. If No-Forward is not set, the
message MUST be from the RPF neighbor of the originator address. If
No-Forward is set, this system, the router doing these checks, MUST
have restarted within 60 seconds. In pseudo-code the algorithm is as
follows:
if ((DirectlyConnected(PFM.src_ip_address) == FALSE) OR
(PFM.src_ip_address is not a PIM neighbor) OR
(PFM.dst_ip_address != ALL-PIM-ROUTERS) OR
(Incoming interface is admin boundary for PFM)) {
drop the message silently, optionally log error.
}
if (PFM.no_forward_bit == 0) {
if (PFM.src_ip_address !=
RPF_neighbor(PFM.originator_ip_address)) {
drop the message silently, optionally log error.
}
} else if (more than 60 seconds elapsed since startup)) {
drop the message silently, optionally log error.
}
Note that src_ip_address is the source address in the IP header of
the PFM message. Originator is the originator field inside the PFM
message, and is the router that originated the message. When the
message is forwarded hop by hop, the originator address never
changes, while the source address will be an address belonging to the
router that last forwarded the message.
3.4.2. Processing and forwarding of PFM messages
When the message is received, the initial checks above must be
performed. If it passes the checks, then for each included TLV,
perform processing according to the specification for that TLV.
After processing, the messsage is forwarded. Unless otherwise
specified by the type specification, the TLVs in the forwarded
message are identical to the TLVs in the received message. However,
if the most significant bit in the type field is set (the type value
is larger than 32767) and this system does not support the type, then
that particular type should be omitted from the forwarded messages.
The message is forwarded out of all interfaces with PIM neighbors
(including the interface it was received on).
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4. Distributing Source Group Mappings
The generic flooding mechanism (PFM) defined in the previous section
can be used for distributing source group mappings about active
multicast sources throughout a PIM domain. A Group Source Holtime
(GSH) TLV is defined for this purpose.
4.1. Group Source Holdtime TLV
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address (Encoded-Group format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Src Count | Src Holdtime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Src Address 1 (Encoded-Unicast format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Src Address 2 (Encoded-Unicast format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . |
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Src Address m (Encoded-Unicast format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: This TLV has type 0.
Length: The length of the value in octets.
Group Address: The group that sources are to be announced for. The
format for this address is given in the Encoded-Group format in
[RFC7761].
Src Count: How many unicast encoded sources address encodings
follow.
Src Holdtime: The Holdtime (in seconds) for the corresponding
source(s).
Src Address: The source address for the corresponding group. The
format for these addresses is given in the Encoded-Unicast address
in [RFC7761].
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4.2. Originating Group Source Holdtime TLVs
A PFM message MAY contain one or more Group Source Holdtime (GSH)
TLVs. This is used to flood information about active multicast
sources. Each FHR that is directly connected to an active multicast
source originates PFM messages containing GSH TLVs. How a multicast
router discovers the source of the multicast packet and when it
considers itself the FHR follows the same procedures as the
registering process described in [RFC7761]. When a FHR has decided
that a register needs to be sent per [RFC7761], the SG is not
registered via the PIM SM register procedures, but the SG mapping is
included in an GSH TLV in a PFM message. Note, only the SG mapping
is distributed in the message, not the entire packet as would have
been done with a PIM register. The PFM messages containing the GSH
TLV are periodically sent for as long as the multicast source is
active, similar to how PIM registers are periodically sent. The
default announcement period is 60 seconds, which means that as long
as the source is active, it is included in a PFM message originated
every 60 seconds. The holdtime for the source is by default 210
seconds. Other values MAY be configured, but the holdtime MUST be
either zero, or larger than the announcement period. It is
RECOMMENDED to be 3.5 times the announcement period. A source MAY be
announced with a holdtime of zero to indicate that the source is no
longer active.
If an implementation supports originating GSH TLVs with different
holdtimes for different sources, it can if needed send multiple TLVs
with the same group address. Due to the format, all the sources in
the same TLV have the same holdtime.
When a new source is detected, an implementation MAY send a PFM
message containing just that particular source. However, it MAY also
include information about other sources that were just detected, so
sources that are scheduled for periodic announcement later, or other
types of information. See Section 3.3 for details.
When a new PIM neighbor is detected, or an existing neighbor changes
GenID, an implementation MAY send a triggered PFM message containing
GSH TLVs for any Source Group mappings it has learned by receiving
PFM GSH TLVs as well as any active directly connected sources. See
Section 3.3 for further details.
4.3. Processing GSH TLVs
A router that receives a PFM message containing GSH TLVs MUST parse
the GSH TLVs and store each of the GSH TLVs as SG mappings with a
holdtimer started with the advertised holdtime, unless the
implementation specifically does not support GSH TLVs, the router is
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configured to ignore GSH TLVs in general, or to ignore GSH TLVs for
certain sources or groups. In particular, an administrator might
configure a router to not process GSH TLVs if the router is known to
never have any directly connected receivers.
For each group that has directly connected receivers, this router
SHOULD send PIM (S,G) joins for all the SG mappings advertised in the
message for the group. Generally joins are sent, but there could for
instance be administrative policy limiting which sources and groups
to join. The SG mappings are kept alive for as long as the holdtimer
for the source is running. Once the holdtimer expires a PIM router
MAY send a PIM (S,G) prune to remove itself from the tree. However,
when this happens, there should be no more packets sent by the
source, so it may be desirable to allow the state to time out rather
than sending a prune.
Note that a holdtime of zero has a special meaning. It is to be
treated as if the source just expired, and state to be removed.
Source information MUST NOT be removed due to the source being
omitted in a message. For instance, if there is a large number of
sources for a group, there may be multiple PFM messages, each message
containing a different list of sources for the group.
4.4. The first packets and bursty sources
The PIM register procedure is designed to deliver Multicast packets
to the RP in the absence of a Shortest Path Tree (SPT) from the RP to
the source. The register packets received on the RP are decapsulated
and forwarded down the shared tree to the LHRs. As soon as an SPT is
built, multicast packets would flow natively over the SPT to the RP
or LHR and the register process would stop. The PIM register process
ensures packet delivery until an SPT is in place reaching the FHR.
If the packets were not unicast encapsulated to the RP they would be
dropped by the FHR until the SPT is setup. This functionality is
important for applications where the initial packet(s) must be
received for the application to work correctly. Another reason would
be for bursty sources. If the application sends out a multicast
packet every 4 minutes (or longer), the SPT is torn down (typically
after 3:30 minutes of inactivity) before the next packet is forwarded
down the tree. This will cause no multicast packet to ever be
forwarded. A well behaved application should be able to deal with
packet loss since IP is a best effort based packet delivery system.
But in reality this is not always the case.
With the procedures defined in this document the packet(s) received
by the FHR will be dropped until the LHR has learned about the source
and the SPT is built. That means for bursty sources or applications
sensitive for the delivery of the first packet this solution would
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not be very applicable. This solution is mostly useful for
applications that don't have strong dependency on the initial
packet(s) and have a fairly constant data rate, like video
distribution for example. For applications with strong dependency on
the initial packet(s) using PIM Bidir [RFC5015] or SSM [RFC4607] is
recommended. The protocol operations are much simpler compared to
PIM SM, it will cause less churn in the network and both guarantee
best effort delivery for the initial packet(s).
4.5. Resiliency to network partitioning
In a PIM SM deployment where the network becomes partitioned, due to
link or node failure, it is possible that the RP becomes unreachable
to a certain part of the network. New sources that become active in
that partition will not be able to register to the RP and receivers
within that partition are not able to receive the traffic. Ideally
you would want to have a candidate RP in each partition, but you
never know in advance which routers will form a partitioned network.
In order to be fully resilient, each router in the network may end up
being a candidate RP. This would increase the operational complexity
of the network.
The solution described in this document does not suffer from that
problem. If a network becomes partitioned and new sources become
active, the receivers in that partitioned will receive the SG
Mappings and join the source tree. Each partition works
independently of the other partition(s) and will continue to have
access to sources within that partition. Once the network has
healed, the periodic flooding of SG Mappings ensures that they are
re-flooded into the other partition(s) and other receivers can join
to the newly learned sources.
5. Security Considerations
When it comes to general PIM message security, see [RFC7761]. PFM
messages MUST only be accepted from a PIM neighbor, but as discussed
in [RFC7761], any router can become a PIM neighbor by sending a Hello
message. To control from where to accept PFM packets, one can limit
which interfaces PIM is enabled, and also one can configure
interfaces as administrative boundaries for PFM messages, see
Section 3.2. The implications of forged PFM messages depend on which
TLVs they contain. Documents defining new TLVs will need to discuss
the security considerations for the specific TLVs. In general
though, the PFM messages are flooded within the network, and by
forging a large number of PFM messages one might stress all the
routers in the network.
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If an attacker can forge PFM messages, then such messages may contain
arbitrary GSH TLVs. An issue here is that an attacker might send
such TLVs for a huge amount of sources, potentially causing every
router in the network to store huge amounts of source state. Also,
if there is receiver interest for the groups specified in the GSH
TLVs, routers with directly connected receivers will build Shortest
Path Trees for the announced sources, even if the sources are
actually active. Building such trees will consume additional
resources on routers that the trees pass through.
6. IANA considerations
This document requires the assignment of a new PIM message type for
the PIM Flooding Mechanism (PFM). IANA is also requested to create a
registry for PFM TLVs, with type 0 assigned to the "Source Group
Holdtime" TLV. Values in the range from 1 to 65535 are "Unassigned".
Assignments for the registry are to be made according to the policy
"IETF Review" as defined in [RFC8126].
7. Acknowledgments
The authors would like to thank Arjen Boers for contributing to the
initial idea, and Yiqun Cai and Dino Farinacci for their comments on
the draft.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5059] Bhaskar, N., Gall, A., Lingard, J., and S. Venaas,
"Bootstrap Router (BSR) Mechanism for Protocol Independent
Multicast (PIM)", RFC 5059, DOI 10.17487/RFC5059, January
2008, <https://www.rfc-editor.org/info/rfc5059>.
[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>.
Wijnands, et al. Expires June 23, 2018 [Page 14]
Internet-Draft PIM flooding mechanism and source discovery December 2017
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
8.2. Informative References
[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, DOI 10.17487/RFC4607, August 2006,
<https://www.rfc-editor.org/info/rfc4607>.
[RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
"Bidirectional Protocol Independent Multicast (BIDIR-
PIM)", RFC 5015, DOI 10.17487/RFC5015, October 2007,
<https://www.rfc-editor.org/info/rfc5015>.
Authors' Addresses
IJsbrand Wijnands
Cisco Systems, Inc.
De kleetlaan 6a
Diegem 1831
Belgium
Email: ice@cisco.com
Stig Venaas
Cisco Systems, Inc.
Tasman Drive
San Jose CA 95134
USA
Email: stig@cisco.com
Michael Brig
Aegis BMD Program Office
17211 Avenue D, Suite 160
Dahlgren VA 22448-5148
USA
Email: michael.brig@mda.mil
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Internet-Draft PIM flooding mechanism and source discovery December 2017
Anders Jonasson
Swedish Defence Material Administration (FMV)
Loennvaegen 4
Vaexjoe 35243
Sweden
Email: anders@jomac.se
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