Huawei Quidway S9300 Configuration Manual - Multicast page 195

Quidway S9300 Terabit Routing Switch
Configuration Guide - Multicast
Configurable Parameters for Connecting MSDP Peers
You can enable and disable MSDP on an S9300. In addition, you can configure the interval for
sending TCP connection requests to remote MDSP peers.
Configurable the SA cache
By default, SA caching is enabled on the S9300. The S9300 can locally store the (S, G)
information contained in SA messages. When the S9300 needs to receive messages, it can obtain
useful (S, G) information from the SA cache.
You can set the maximum number of (S, G) entries to efficiently protect the S9300 against Deny
of Service (DoS) attacks.
SA caching can be disabled on the S9300. After SA caching is disabled, the S9300 does not
locally store the (S, G) information contained in SA messages. When the S9300 needs to receive
messages, it must wait for the SA messages sent by the MSDP peer during the next period. This
postpones the time for the receiver to obtain the information from multicast sources.
Controllable SA Requests
Some multicast routers and multicast switches do not support SA caching or the capacity of the
SA cache is set to a small value. When they need to receive messages, they must wait for the
SA message sent by the MSDP peer in the next period instead of obtaining valid (S, G)
information immediately.
If SA caching is enabled on a remote MSDP peer and the capacity of the SA cache is set to a
great value, you can configure the local S9300 to send SA request messages. Therefore, the time
that the receiver waits to obtain the information about the multicast source is shortened.
In addition, you can configure the rule for filtering received SA request messages on remote
MSDP peers.
Transmitting Burst Multicast Data
If the interval at which a multicast source sends multicast data is greater than the timeout period
of the (S, G) entry and if burst multicast data needs to be sent, the source DR must encapsulate
the multicast data in Register messages and sends them to the source RP. The source RP transmits
the (S, G) information through SA messages to the remote RP. Then the remote RP sends an (S,
G) Join message to the source and creates an SPT. If the (S, G) entry times out, the remote users
cannot receive the multicast data sent by S.
The S9300 can transmit burst multicast data. After you enable the function of encapsulating a
multicast packet in an SA message on the source RP, the source RP encapsulates a multicast
packet into an SA message and sends the SA message out. After receiving the SA message, the
remote RP decapsulates it and transmits the multicast packet along RPT to the users in the local
domain.
In addition, you can set the TTL threshold to limit the transmission range of the multicast packet
encapsulated in the SA message. After receiving the SA message that contains the multicast
packet, the MSDP peer checks the TTL value of the IP header of the multicast packet. If the
TTL value of the multicast packet is smaller than or equal to the threshold, the MSDP peer does
not forward the packet to the specific remote peer. If the TTL value of the multicast packet is
greater than the threshold, the MSDP peer subtracts 1 from the TTL value and sends the SA
message with the multicast packet.
Issue 01 (2009-07-28) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
5 MSDP Configuration
5-3