Reliable Transport Protocol

EIGRP can provide guaranteed and reliable delivery of its various packets, whereas other routing protocols rely on other mechanisms, such as time, to determine whether a packet needs to be retransmitted. EIGRP uses the Reliable Transport Protocol (RTP) to provide reliable delivery of its own packets.

RTP is a transport layer (OSI Layer-4) protocol that correlates to the functions found in TCP (Transmission Control Protocol) and UDP (User Datagram Protocol); however, RTP is not an open protocol standard.

RTP is responsible for guaranteed ordered delivery of EIGRP packets and is used to transport all EIGRP messages through an internetwork. RTP supports unicasting and multicasting, even simultaneously for different peers.