This document discusses and compares three transport layer protocols: UDP, TCP, and SCTP. It provides details on the services, features, header formats, and operation of each protocol. UDP is a connectionless and unreliable protocol that uses a simple 8-byte header with fields for source/destination ports and length. TCP is connection-oriented and reliable, using sequence numbers and acknowledgments to ensure delivery. It establishes connections for data transfer and teardown. SCTP combines features of UDP and TCP, with support for multiple streams, multihoming, and reliability.