tailieunhanh - The Illustrated Network- P32

The Illustrated Network- P32:In this chapter, you will learn about the protocol stack used on the global public Internet and how these protocols have been evolving in today’s world. We’ll review some key basic defi nitions and see the network used to illustrate all of the examples in this book, as well as the packet content, the role that hosts and routers play on the network, and how graphic user and command line interfaces (GUI and CLI, respectively) both are used to interact with devices. | CHAPTER Transmission Control Protocol 11 What You Will Learn In this chapter you will learn about the TCP transport layer protocol which is the connection-oriented more reliable companion of UDP. We ll talk about all the fields in the TCP header which are many and how TCP s distinctive three-way handshake works. You will learn how TCP operates during the data transfer and disconnect phase as well as some of the options that have been established to extend TCP s use for today s networking conditions. The Transmission Control Protocol TCP is as complex as UDP is simple. Some of the same concepts apply to both because both TCP and UDP are end-to-end protocols. Sockets and ports well-known dynamic and private apply to both. TCP is IP protocol 6 but the ports are usually the same as UDP and run from 0 to 65 535. The major difference between UDP and TCP is that TCP is connection oriented. And that makes all the difference. Internet specifications variously refer to connections as virtual circuits flows or packet-switched services depending on the context. These subtle variations are unnecessary for this book and we simply use the term connection. A connection is a logical relationship between two endpoints hosts on a network. Connections can be permanent although the proper term is semipermanent or on demand often called switched . Permanent connections are usually set up by manual configuration of the network nodes. On the Internet this equates to a series of very specific static routes. On-demand connections require some type of signaling protocol to establish connections on the fly node by node through the network from the source the caller host to the destination the callee host. Permanent connections are like intercoms You can talk right away or at any time and know the other end is there. However you can only talk to that specific endpoint on that connection. On-demand connections are like telephone calls You have to wait until the other end answers before you talk