The protocols that operate at the transport layer of the Open Systems Interconnection (OSI) reference model work with the network layer protocols to provide a unified quality of service that is suitable for the applications using them. Both the Transmission Control Protocol/Internet Protocol (TCP/IP) and the Internetwork Packet Exchange (IPX) suites have multiple protocols at the transport layer, which provide various levels of service. This chapter examines the options available to applications at this layer and describes the mechanisms used by the protocols to provide the services they supply.
This chapter requires a basic understanding of the OSI reference model, as described in Chapter 1, "Networking Basics," as well as familiarity with the network layer protocols discussed in Chapter 5, "Network Layer Protocols."