Network Working Group Dino Farinacci
INTERNET DRAFT Procket Networks
Yakov Rekhter
David Meyer
Cisco Systems
Peter Lothberg
Sprint
Hank Kilmer
Jeremy Hall
UUnet
Category Standards Track
Decemeber, 1999
Multicast Source Discovery Protocol (MSDP)
<draft-ietf-msdp-spec-00.txt>
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC Internet-Drafts.
2026 are working documents of the Internet Engineering Task Force
(IETF), its areas, and its working groups. Note that other groups
may also distribute working documents as Internet- Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
The Multicast Source Discovery Protocol, MSDP, describes a mechanism
to connect multiple PIM-SM domains together. Each PIM-SM domain uses
it's own independent RP(s) and do not have to depend on RPs in other
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domains.
2. Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
3. Introduction
The Multicast Source Discovery Protocol, MSDP, describes a mechanism
to connect multiple PIM-SM domains together. Each PIM-SM domain uses
its own independent RP(s) and does not have to depend on RPs in other
domains.
Advantages of this approach include:
3.1. No Third-party resource dependencies on RP
PIM-SM domains can rely on their own RPs only.
3.2. Receiver only Domains
Domains with only receivers get data without globally advertising
group membership.
3.3. Global Source State
Global source state is not required, since a router need not cache
Source Active (SA) messages (see below). MSDP is a periodic protocol.
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4. Overview
An RP (or other MSDP SA originator) in a PIM-SM domain will have a
MSDP peering relationship with an RP in another domain. The peering
relationship will be made up of a TCP connection in which control
information is primarily exchanged. Each domain will have a
connection to this virtual topology.
The purpose of this topology is to have domains discover multicast
sources from other domains. If the multicast sources are of interest
to a domain which has receivers, the normal source-tree building
mechanism in PIM-SM will be used to deliver multicast data over an
inter-domain distribution tree.
We envision this virtual topology will essentially be congruent to
the existing BGP topology used in the unicast-based Internet today.
That is the TCP connections between RPs can be realized by the
underlying BGP routing system.
5. Procedure
A source in a PIM-SM domain originates traffic to a multicast group.
The PIM DR which is directly connected to the source sends the data
encapsulated in a PIM Register message to the RP in the domain.
The RP will construct a "Source-Active" (SA) message and send it to
its MSDP peers. The SA message contains the following fields:
o Source address of the data source.
o Group address the data source sends to.
o IP address of the RP.
Each MSDP peer receives and forwards the message away from the RP
address in a "peer-RPF flooding" fashion. The notion of peer-RPF
flooding is with respect to forwarding SA messages. The BGP routing
table is examined to determine which peer is the next hop towards the
originating RP of the SA message. Such a peer is called an "RPF
peer". See the section on "MSDP Peer-RPF Forwarding" for more
details.
If the MSDP peer receives the SA from a non-RPF peer towards the
originating RP, it will drop the message. Otherwise, it forwards the
message to all it's MSDP peers.
The flooding can be further constrained to children of the peer by
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interrogating BGP reachability information. That is, if a BGP peer
advertises a route (back to you) and you are the next to last AS in
the AS-path, the peer is using you as the next-hop. In this case, an
implementation SHOULD forward an SA message (which was originated
from the RP address covered by that route) to the peer. This is known
in other circles as Split-Horizon with Poison Reverse.
When an MSDP peer which is also an RP for its own domain receives an
SA message, it determines if it has any group members interested in
the group which the SA message describes. That is, the RP checks for
an (*,G) entry with a non-empty outgoing interface list; this implies
that the domain is interested in the group. In this case, the RP
triggers an (S,G) join event towards the data source as if a
Join/Prune message was received addressed to the RP itself (See [1]
Section 3.2.2). This sets up a branch of the source-tree to this
domain. Subsequent data packets arrive at the RP which are forwarded
down the shared-tree inside the domain. If leaf routers choose to
join the source-tree they have the option to do so according to
existing PIM-SM conventions. Finally, if an RP in a domain receives
a PIM Join message for a new group G, and it is caching SA's, then
the RP should trigger an (S,G) join event for each SA for that group
in its cache.
This procedure has been affectionately named flood-and-join because
if any RP is not interested in the group, they can ignore the SA
message. Otherwise, they join a distribution tree.
6. Controlling State
While RPs which receive SA messages are not required to keep MSDP
(S,G) state, an RP SHOULD cache SA messages by default. The advantage
of caching is that newly formed MSDP peers can get MSDP (S,G) state
sooner and therefore reduce join latency for new joiners. In
addition, caching greatly aids in diagnosis and debugging of various
problems.
6.1. Timers
The main timers for MSDP are: SA Advertisement period, SA Hold-down
period, the SA Cache timeout period, KeepAlive, HoldTimer, and
ConnectRetry. Each is described below.
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6.1.1. SA Advertisement Period
RPs which originate SA messages do it periodically as long as there
is data being sent by the source. The SA Advertisement Period MUST be
60 seconds. An RP will not send more than one SA message for a given
(S,G) within an SA Advertisment period. Originating periodic SA
messages is important so that new receivers who join after a source
has been active can get data quickly via the receiver's own RP when
it is not caching SA state. Finally, if an RP in a domain receives a
PIM Join message for a new group G, and it is caching SAs, then the
RP should trigger an (S,G) join for each SA for that group in its
cache.
6.1.2. SA Hold-down Period
A caching MSDP speaker SHOULD NOT forward a SA message it has
received in the last SA-Hold-down period. The SA-Hold-down period
SHOULD be set 30 seconds.
6.1.3. SA Cache Timeout
A caching MSDP speaker times out it's SA cache at SA-State-Timer.
The SA-State-Timer MUST NOT be less than 90 seconds minutes.
6.1.4. KeepAlive, HoldTimer, and ConnectRetry
The KeepAlive, HoldTimer, and ConnectRetry timers are defined in
RFC1771 [3].
6.2. Intermediate MSDP Speakers
Intermediate RPs do not originate periodic SA messages on behalf of
sources in other domains. In general, an RP MUST only originate an SA
for its own sources.
6.3. SA Filtering
As the number of (S,G) pairs increases in the Internet, an RP may
want to filter which sources it describes in SA messages. Also,
filtering may be used as a matter of policy which at the same time
can reduce state. Only the RP colocated in the same domain as the
source can restrict SA messages. Other MSDP peers in transit domains
should not filter or the flood-and-join model does not guarantee that
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sources will be known throughout the Internet. An exception occurs at
an administrative scope [13] boundary. In particular, a SA message
for an (S,G) MUST NOT be sent to peers which are on the other side of
an administrative scope boundary for G.
6.4. Caching
If an MSDP peer decides to cache SA state, it may accept SA-Requests
from other MSDP peers. When a MSDP peer receives an SA-Request for a
group range, it will respond to the peer with a set of SA entries, in
a SA-Response message, for all active sources sending to the group
range requested in the SA-Request message. The peer that sends the
request will not flood the responding SA-Response message to other
peers.
If an implementation receives an SA-Request message and is not
caching SA messages, it sends a notification with Error code 7
subcode 1, as defined in section 11.2.7.
7. Encapsulated Data Packets
For bursty sources, the RP may encapsulate multicast data from the
source. An interested RP may decapsulate the packet, which SHOULD be
forwarded as if a PIM register encapsulated packet was received. That
is, if packets are already arriving over the interface toward the
source, then the packet is dropped. Otherwise, if the outgoing
interface list is non-null, the packet is forwarded appropriately.
Note that when doing data encapsulation, an implementation MUST bound
the number of packets from the source which are encapsulated.
This allows for small bursts to be received before the multicast tree
is built back toward the source's domain. For example, an
implementation SHOULD encapsulate at least the first packet to
provide service to bursty sources.
Finally, if an implementation supports an encapsulation of SA data
other than default TCP encapsulation, then it MUST support GRE
encapsulation. In addition, an implementation MUST learn about not
TCP encapsulations via capability advertisment (see section 11.2.5).
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8. Other Scenarios
MSDP is not limited to deployment across different routing domains.
It can be used within a routing domain when it is desired to deploy
multiple RPs for different group ranges. As long as all RPs have a
interconnected MSDP topology, each can learn about active sources as
well as RPs in other domains. Another example is the Anycast RP
mechanism [8].
9. MSDP Peer-RPF Forwarding
The MSDP Peer-RPF Forwarding rules are used for forwarding SA
messages throughout an MSDP enabled internet. An SA message
originated by a MSDP originator R and received by a MSDP router from
MSDP peer N in AS A is accepted if any of the following are true:
(i). If N is R.
(ii). If A is the first AS in the AS-Path of the BGP
route towards R.
(iii). If N is the iBGP advertiser of the BGP route
towards R.
(iv). If N is the MSDP default-peer.
If none of the conditions above is met, the SA message is discarded.
This is the case where the SA message was received on a redundant
MSDP peering path.
Note that these rules are evaluated in the order shown here. This
selects a "peer-RPF neighbor" for the SA message, and allows for the
construction of diagnostic tools such as MSDP-traceroute [7].
9.1. MSDP default-peer semantics
A MSDP default-peer is much like a default route. It is intended to
be used in those cases where a stub network isn't running BGP or
MBGP. In this case, the MSDP speaker accepts all SA messages from the
default-peer. Of course, if multiple default peers are configured,
the possibility of looping exists, so care must be taken. Finally, a
router running BGP or multiprotol BGP [4] SHOULD NOT allow
configuration of default peers.
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10. MSDP Connection Establishment
MSDP speakers establish peering sessions according to the following
state machine:
Deconfigured or
disabled
+-------------------------------------------+
| |
+-----|--------->+----------+ |
| | +->| INACTIVE |----------------+ |
| | | +----------+ | |
Deconf'ed | | | /|\ /|\ | Timer + Higher Address
or | | | | | | |
disabled | | | | | \|/ |
| | | | | | +-------------+
| | | | | +---------------| CONNNECTING |
| | | | | Timeout or +-------------+
| | | | | Router ID Change |
\|/ \|/ | | | |
+----------+ | | | |
| DISABLED | | | +---------------------+ | TCP Established
+----------+ | | | |
/|\ /|\ | | Connection Timeout or | |
| | | | Router ID change or | |
| | | | Authorization Failure | |
| | | | | |
| | | | | \|/
| | | | +-------------+
| | Router ID | | Timer + | ESTABLISHED |
| | Change | | Low Addresss +-------------+
| | | \|/ /|\ |
| | | +--------+ | |
| | +--| LISTEN |--------------------+ |
| | +--------+ TCP Accept |
| | | |
| | | |
| +---------------+ |
| Deconfigured or |
| disabled |
| |
+------------------------------------------------------+
Deconfigured or
disabled
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11. Packet Formats
MSDP messages will be encapsulated in a TCP connection using well-
known port 639. One side of the MSDP peering relationship will listen
on the well-known port and the other side will do an active connect
on the well-known port. The side with the higher IP address will do
the listen. This connection establishment algorithm avoids call
collision. Therefore, there is no need for a call collision
procedure. It should be noted, however, that the disadvantage of this
approach is that it may result in longer startup times at the passive
end.
Finally, if an implementation receives a TLV that has length that is
longer than expected, the TLV SHOULD be accepted. Any additional data
SHOULD be ignored.
11.1. MSDP messages will be encoded in TLV format:
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 | Length | Value .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type (8 bits)
Describes the format of the Value field.
Length (16 bits)
Length of Type, Length, and Value fields in octets. Minimum
length required is 3 octets.
Value (variable length)
Format is based on the Type value. See below. The length of
the value field is Length field minus 3.
11.2. The following TLV Types are defined:
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Code Type
================================================================
1 IPv4 Source-Active
2 IPv4 Source-Active Request
3 IPv4 Source-Active Response
4 KeepAlive
5 Encapsulation Capability Advertisement
6 Encapsulation Capability Request
7 Notification
8 GRE Encapsulation
Each TLV is described below.
11.2.1. IPv4 Source-Active TLV
The maximum size SA message that can be sent is 1400 bytes. If an
MSDP peer needs to originate a message with information greater than
1400 bytes, it sends successive 1400-byte messages. The 1400 byte
size does not include the TCP, IP, layer-2 headers.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | x + y | Entry Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Gprefix Len | Sprefix Len | \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \
| Group Address Prefix | ) z
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ /
| Source Address Prefix | /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
IPv4 Source-Active TLV is type 1.
Length x
Is the length of the control information in the message. x is
8 octets (for the first two 32-bit quantities) plus 12 times
Entry Count octets.
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Length y
If 0, then there is no data encapsulated. Otherwise an IPv4
packet follows and y is the length of the total length field
of the IPv4 header encapsulated. If there are multiple SA TLVs
in a message, and data is also included, y must be 0 in all SA
TLVs except the last one. And the last SA TLV must reflect the
source and destination addresses in the IP header of the
encapsulated data.
Entry Count
Is the count of z entries (note above) which follow the RP
address field. This is so multiple (S,G)s from the same domain
can be encoded efficiently for the same RP address.
RP Address
The address of the RP in the domain the source has become
active in.
Gprefix Len and Sprefix Len
The route prefix length associated with the group address
prefix and source address prefix, respectively.
Group Address Prefix
The group address the active source has sent data to.
Source Address Prefix
The route prefix associated with the active source.
Multiple SA TLVs MAY appear in the same message and can be batched
for efficiency at the expense of data latency. This would typically
occur on intermediate forwarding of SA messages.
11.2.2. IPv4 Source-Active Request TLV
Used to request SA-state from a caching MSDP peer. If an RP in a
domain receives a PIM Join message for a group, creates (*,G) state
and wants to know all active sources for group G, and it has been
configured to peer with an SA-state caching peer, it may send an SA-
Request message for the group.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2 | 8 | Gprefix Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
IPv4 Source-Active Request TLV is type 2.
Gprefix Len
The route prefix length associated with the group address prefix.
Group Address Prefix
The group address prefix the MSDP peer is requesting.
11.2.3. IPv4 Source-Active Response TLV
Sent in response to a Source-Active Request message. The Source-
Active Response message has the same format as a Source-Active
message but does not allow encapsulation of multicast data.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 | x | .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
IPv4 Source-Active Response TLV is type 3.
Length x
Is the length of the control information in the message. x is 8
octets (for the first two 32-bit quantities) plus 12 times Entry
Count octets.
11.2.4. KeepAlive TLV
Sent to an MSDP peer if and only if there were no MSDP messages sent
to the peer after a period of time. This message is necessary for the
active connect side of the MSDP connection. The passive connect side
of the connection knows that the connection will be reestablished
when a TCP SYN packet is sent from the active connect side. However,
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the active connect side will not know when the passive connect side
goes down. Therefore, the KeepAlive timeout will be used to reset the
TCP connection.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4 | 3 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The length of the message is 3 bytes which encompasses the 1-byte
Type field and the 2-byte Length field.
11.2.5. Encapsulation Capability Advertisement TLV
This TLV implements encapsulation capability advertisement. This TLV
is sent by an MSDP speaker to advertise its ability to receive data
packets encapsulated as described by the TLV (in addition to the
default TCP encapsulation).
A MSDP speaker receiving this TLV can choose to either default TCP
encapsulation, or may send a IPv4 Encapsulation Request to change to
the advertised encapsulation type.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 | 8 | ENCAP_TYPE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
IPv4 Encapsulation Advertisement TLV is type 5.
Length
Length is a two byte field with value 8.
ENCAP_TYPE
The following data encapsulation types are defined for MSDP:
Value Meaning
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-------------------------------------
0 TCP Encapsulation
1 UDP Encapsulation [10]
2 GRE Encapsulation [9]
Soure Port
Port for use by the requester.
Note that since the TLV does not carry endpoint addresses for the GRE
or UDP tunnels, an implementation using these encapsulations MUST use
the endpoints that are used for the MSDP peering.
11.2.6. Encapsulation Capability Request TLV
This TLV implements encapsulation capability request. This TLV should
be sent in response to a capability advertisement.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 6 | 4 | ENCAP_TYPE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
IPv4 Encapsulation Request TLV is type 6.
Length
Length is a two byte field with value 4.
ENCAP_TYPE
ENCAP_TYPE is described above.
A requester MAY also provide a source port, in which case
the TLV has the following form:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 6 | 8 | ENCAP_TYPE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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11.2.7. NOTIFICATION TLV
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 7 | x + 5 | Error Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error subcode | ... |
+-+-+-+-+-+-+-+-+ |
| Data |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
The Notification TLV is type 7.
Length
Length is a two byte field with value x + 5, where x is
the length of the notification data field.
Error code
See [3]. In addition, Error code 7 indicates an
a SA-Request Error.
Error subcode
See [3]. In addition, Error code 7 subcode 1 indicates
the receipt of a SA-Request message by a non-caching
MSDP speaker.
Data
See [3]. In addition, for Error code 7 subcode 1 (receipt of
a SA-Request message by a non-caching MSDP speaker), the TLV
has the follwing form:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 7 | 20 | 7 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | Reserved | Gprefix Len | Sprefix Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising RP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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See [3] for NOTIFICATION error handling.
11.2.8. Encapsulation Capability State Machine
The active connect side of an MSDP peering SHALL begin in ADVERTISING
state, and the passive side of the TCP connection begins in DEFAULT
state. This will cause the state machine to behave deterministically.
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+-------+
| | Receive TLV which isn't
| | understood or
| | Receive Request (TLV 6) or
| | Receive Advertisement (TLV 5)
\|/ | that isn't understood
+---------+----+
| DEFAULT |----------------+
+---------+ |
|
+-------------+ |
| ADVERTISING | |
+-------------+ |
| |
Timeout +--------+ | |
+-------->| FAILED | | Send Advertisement | Receive Advertisement
| +--------+ | (TLV 5) | (TLV 5)
| | |
| | |
| | |
| | |
| Receive non-matching | |
| Request (TLV 6) | |
| +----+ | |
| | | | |
| | | | |
| | \|/ | \|/
| | +------+ | +----------+
| +-| SENT |<-------------+ | RECEIVED |
+---+------+ +----------+
| \|/
| |
| Receive matching | Send matching
| Request (TLV 6) | Request (TLV 6)
| +--------+ |
+------------>| AGREED |<------------------+
+--------+
Note that if an advertiser transitions into the FAILED state, it
SHOULD assume that it has an old-style peer which can only support
TCP encapsulation. If an implementation wishes to be backwardly
compatible, it SHOULD support TCP encapsulation. In addition, a
requester in any state other than AGREED MUST only encapsulate data
in the TCP stream.
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11.2.9. UDP Data Encapsulation
When using UDP encapsulation, the UDP psuedo-header has the following
form:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port | Dest Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Origin RP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Source Port
When using UDP encapsulation, a capability requester
uses the advertiser's Source Port as its destination
port. The advertiser MUST provide a Source Port.
o Destination Port
When using UDP encapsulation, a capability advertiser
uses the well known port 639 as the destination port.
A capability requester MUST listen on this well-known
port. The requester MAY provide a Source Port in it's
reply to the advertiser.
o Length is the length in octets of this user datagram
including this header and the data. The minimum value
of the length is twelve.
o Checksum is computed according to RFC768 [10].
o Originating RP Address is the address of the RP sending
the encapsulated data.
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Internet Draft draft-ietf-msdp-spec-03.txt Decemeber, 1999
11.2.10. GRE Encapsulation TLV
A TLV is defined to describe GRE encapsulated data packets. The TLV
has the following form:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 8 | 8 + x | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originating RP IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (S,G) Data Packet ....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
GRE encapsulated data packet TLV is type 8.
Length
Length is a two byte field with value 8 + x, where
x is the length of the (S,G) Data packet.
The entire GRE header, then, will have the following form:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Delivery Headers ..... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| Reserved | Ver | Protocol Type |\
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GRE Header
| Checksum (optional) | Reserved |/
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\
| 8 | 8 + x | Reserved | \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Payload
| Originating RP IPv4 Address | /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .
| (S,G) Data Packet .... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Internet Draft draft-ietf-msdp-spec-03.txt Decemeber, 1999
11.3. MTU Exeeded
If the outbound link MTU is execeeded by the newly encapsulated
packet, the packet SHOULD be dropped.
12. Security Considerations
A MSDP implementation MAY use IPsec [11] or keyed MD5 [12] to secure
control messages. Encapsulated data packets rely on the underlying
security model.
13. Acknowledgments
The authors would like to thank Dave Thaler, Bill Fenner, Bill
Nickless, John Meylor, Liming Wei, Manoj Leelanivas, Mark Turner, and
John Zwiebel for their design feedback and comments.
14. Author's Address:
Dino Farinacci
Procket Networks
Email: dino@procket.com
Yakov Rehkter
Cisco Systems, Inc.
170 Tasman Drive
San Jose, CA, 95134
Email: yakov@cisco.com
David Meyer
Cisco Systems, Inc.
170 Tasman Drive
San Jose, CA, 95134
Email: dmm@cisco.com
Peter Lothberg
Sprint
VARESA0104
12502 Sunrise Valley Drive
Reston VA, 20196
Email: roll@sprint.net
Hank Kilmer
Email: hank@rem.com
Farinacci, Rekhter, Meyer, Lothberg, Kilmer, Hall [Page 20]
Internet Draft draft-ietf-msdp-spec-03.txt Decemeber, 1999
Jeremy Hall
UUnet Technologies
3060 Williams Drive
Fairfax, VA 22031
Email: jhall@uu.net
15. REFERENCES
[1] Estrin D., et al., "Protocol Independent Multicast - Sparse Mode
(PIM-SM): Protocol Specification", RFC 2362, June 1998.
[2] Thaler, D., Estrin, D., Meyer, D., "Border Gateway Multicast Protocol
(BGMP): Protocol Specification", draft-ietf-idmr-gum-01.txt,
October 30, 1997.
[3] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 (BGP-4)",
RFC 1771, March 1995.
[4] Bates, T., Chandra, R., Katz, D., and Y. Rekhter., "Multiprotocol
Extensions for BGP-4", RFC 2283, February 1998.
[5] Deering, S., "Multicast Routing in a Datagram Internetwork", PhD
thesis, Electric Engineering Dept., Stanford University, December
1991.
[6] Pusateri, T., "Distance Vector Multicast Routing Protocol",
draft-ietf-idmr-dvmrp-v3-09.txt, October 1997.
[7] Meyer, et. al, "MSDP Traceroute",
draft-ietf-msdp-traceroute-00.txt, November, 1999.
[8] Meyer, et. al, "Anycast RP mechanism using PIM and MSDP",
draft-ietf-mboned-anycast-rp-04.txt, November, 1999.
[9] Farinacci, D., at el., "Generic Routing Encapsulation (GRE)",
draft-ietf-meyer-gre-update-01.txt, December, 1999.
[10] Postel, J. "User Datagram Protocol", RFC768, August, 1980.
[11] Atkinson, R., "Security architecture for the internet protocol",
RFC1825, August, 1995.
[12] P. Metzger and W. Simpson, "IP Authentication using Keyed
MD5", RFC 1828, August, 1995.
[13] Meyer, D. "Administratively Scoped IP Multicast", RFC2365,
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July, 1998.
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