What protocol does MSDP use to communicate?

A.
UDP 639

B.
TCP 389

C.
IP protocol 90

D.
TCP 639

E.
IP protocol 87

F.
UDP 389

Explanation:
https://tools.ietf.org/html/rfc3618
MSDP uses TCP as its transport protocol. In a peering relationship, one MSDP peer listens for new TCP connections on the well-known port 639.
https://en.wikipedia.org/wiki/Multicast_Source_Discovery_Protocol
Router# clear ip msdp peer [peer-address | peer-name]
Clears the TCP connection to the specified MSDP peer, resetting all MSDP message
counters.