3Com Switch 7750 Configuration Guide Guide

Configuring SA Message Transmission 447
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■ Before you configure an MSDP mesh group, make sure that the routers are
fully connected with one another.
■ The same group name must be configured on all the peers.
■ If you add the same MSDP peer to multiple mesh groups, only the latest
configuration takes effect.
Configuring MSDP Peer
Connection Control
The connection between MSDP peers can be flexibly controlled. You can disable
the MSDP peering relationships temporarily by shutting down the MSDP peers. As
a result, SA messages cannot be transmitted between these two peers. On the
other hand, when resetting an MSDP peering relationship between faulty MSDP
peers or bringing faulty MSDP peers back to work, you can adjust the retry interval
of establishing a peering relationship through the following configuration.
Configuring SA
Message Transmission
An SA message contains the IP address of the multicast source S, multicast group
address G, and RP address. In addition, it contains the first multicast data received
by the RP in the domain where the multicast source resides. For some burst
multicast data, if the multicast data interval exceeds the SA message hold time,
the multicast data must be encapsulated in the SA message; otherwise, the
receiver will never receive the multicast source information.
By default, when a new receiver joins, a router does not send any SA request
message to its MSDP peer but has to wait for the next SA message. This defers the
reception of the multicast information by the receiver. In order for the new receiver
to know about the currently active multicast source as quickly as possible, the
router needs to send SA request messages to the MSDP peer.
Generally, a router accepts all SA messages sent by all MSDP peers and sends all
SA messages to all MSDP peers. By configuring the rules for filtering SA messages
to receive/send, you can effectively control the transmission of SA messages
among MSDP peers. For forwarded SA messages, you can also configure a
Time-to-Live (TTL) threshold to control the range where SA messages carrying
encapsulated data are transmitted.
To reduce the delay in obtaining the multicast source information, you can cache
SA messages on the router. The number of SA messages cached must not exceed
the system limit. The more messages are cached, the more router memory is
occupied. You need to determine the number of cached SA messages as required.
Table 353 Configure MSDP peer connection control
Operation Command Description
Enter system view system-view -
Enter MSDP view msdp -
Shut down an MSDP peer shutdown peer-address Optional
Configure retry interval of
setting up an MSDP peer
connection
timer retry seconds
Optional
The default value is 30
seconds.