Introduction to MSDP protocol

The premise for multicast to communicate normally is to set up a multicast tree, multicast tree to normal establishment, RP must know the multicast source and group members, if the same PIM-SM domain, the RP want to know all the multicast source and group members is very easy, but the RP has no way to know the other PIM-SM domain multicast source. To solve this problem let a pim-sm in the domain of the RP to know the multicast source information to the other PIM-SM domain of the RP, so we have to find ways to allow the RP between different PIM-SM can share and exchange multicast source information, this information is called source Active (SA), this protocol is the multicast source Discovery Protocol (MSDP), the Multicast Sources Discovery protocol.

The function and purpose of the MSDP protocol is only one, is to send the multicast source information (SA) in a PIM-SM domain to the RP of other PIM-SM domains, so that the multicast communication between the PIM-SM domains is normal, MSDP just send a message between the PIM-SM domain. As for the following multicast is not pass, is not the responsibility of MSDP.

Pim-sm to communicate within a single domain are established (*,g) entries, and if communication between PIM-SM domains is established, the (S,G) entry is equivalent to the path of the distance vector.

Advantages of using MSDP:

1. There is no third party (Third-party) resource-dependent RP within the domain.

2. The PIM-SM domain relies only on its own RP.

3. Receiving-end domain: Domains with only the receiving end can obtain data without the global notification group members. MSDP can be used with other non-PIM-SM protocols.

MSDP uses TCP639 ports to establish Peer-to-peer connections (high IP listening, low IP connectivity, as with BGP, peer-to-peer connections must be explicitly configured, and when PIMDR registers the source in the RP, the RP sends the source activation message to all MSDP peers, and then the other MSDP routers will flood the SA to prevent loopback , now check MBGP, and then check BGP message-type.

This article is from the "Network Engineer" blog, please be sure to keep this source http://692344.blog.51cto.com/682344/1062217