22 Transmission Control Protocol and User Datagram Protocol

This chapter covers

  • How the Transmission Control Protocol and User Datagram Protocol provide Layer 4 addressing and session multiplexing
  • How TCP provides features like reliable communication and flow control
  • Comparing TCP and UDP, and the situations in which each is preferred

In chapter 3 of this book, we covered physical cables, connectors, and ports—Layer 1 of the TCP/IP model. In other chapters, we covered the Data Link Layer (Layer 2): MAC addresses, frame switching, VLANs, STP, and other related topics. We have also spent many pages on the Network Layer (Layer 3): IPv4 and IPv6 addressing, subnetting, packet forwarding, static and dynamic routing, first-hop redundancy protocols, etc. In this chapter, we will venture beyond those first three layers and take a look at Layer 4 of the TCP/IP model: the Transport Layer. Specifically, we will examine the two major Layer 4 protocols: Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), which are exam topic 1.5: Compare TCP to UDP.

22.1 The role of Layer 4

In chapter 4 of this book, we took a high-level look at the role of each layer of the TCP/IP model. For review, figure 22.1 summarizes the role of each layer.

22.1.1 Port numbers

22.1.2 Session multiplexing

22.2 TCP and UDP

22.2.1 Transmission Control Protocol

22.2.2 User Datagram Protocol

22.2.3 Comparing TCP and UDP

Summary