2.13 Protocol Usage by Common Internet Applications

Figure 2.19 summarizes the protocol usage of various common Internet applications.

The first two applications, ping and traceroute, are diagnostic applications that use ICMP. traceroute builds its own UDP packets to send and reads ICMP replies.

The three popular routing protocols demonstrate the variety of transport protocols used by routing protocols. OSPF uses IP directly, employing a raw socket, while RIP uses UDP and BGP uses TCP.

The next five are UDP-based applications, followed by seven TCP applications and four that use both UDP and TCP. The final five are IP telephony applications that use SCTP exclusively or optionally UDP, TCP, or SCTP.