3com S7906E 설치 설명서

 

1-13 

z 

TTL threshold for multicast packet encapsulation in SA messages  

z 

Maximum number of (S, G) entries learned from the specified MSDP peer that the router can cache  

Some multicast sources send multicast data at an interval longer than the aging time of (S, G) entries. In 

this case, the source-side DR has to encapsulate multicast data packet by packet in register messages 

and send them to the source-side RP. The source-side RP transmits the (S, G) information to the 

remote RP through SA messages. Then the remote RP joins the source-side DR and builds an SPT. 

Since the (S, G) entries have timed out, remote receivers can never receive the multicast data from the 

multicast source.  

If the source-side RP is enabled to encapsulate register messages in SA messages, when there is a 

multicast packet to deliver, the source-side RP encapsulates a register message containing the 

multicast packet in an SA message and sends it out. After receiving the SA message, the remote RP 

decapsulates the SA message and delivers the multicast data contained in the register message to the 

receivers along the RPT.  

The MSDP peers deliver SA messages to one another. Upon receiving an SA message, a router 

performs RPF check on the message. If the router finds that the remote RP address is the same as the 

local RP address, it will discard the SA message. In the Anycast RP application, however, you need to 

configure RPs with the same IP address on two or more routers in the same PIM-SM domain, and 

configure these routers as MSDP peers to one another. Therefore, a logic RP address (namely the RP 

address on the logic interface) that is different from the actual RP address must be designated for SA 

messages so that the messages can pass the RPF check.  

Follow these steps to configure the SA message content:  

Enter system view 

— 

Enter public instance MSDP view or 
VPN instance MSDP view 

msdp [ vpn-instance 
vpn-instance-name ] 

— 

Enable encapsulation of a register 
message  

Optional 

Disabled by default  

Configure the interface address as 
the RP address in SA messages  

originating-rp interface-type 
interface-number 

Optional 

PIM RP address by default 

 

By default, upon receiving a new Join message, a router does not send an SA request message to any 

MSDP peer; instead, it waits for the next SA message from its MSDP peer. This will cause the receiver 

to delay obtaining multicast source information. To enable a new receiver to get the currently active 

multicast source information as early as possible, you can configure routers to send SA request 

messages to the designated MSDP peers upon receiving a Join message of a new receiver.  

Follow these steps to configure SA message transmission and filtering: