TCP IP Illustrated

Because this reliable flow of data is provided by the

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: plication layer can ignore all these details. UDP, on the other hand, provides a much simpler service to the application layer. It just sends packets of data called datagrams from one host to the other, but there is no guarantee that the datagrams reach the other end. Any desired reliability must be added by the application layer. There is a use for each type of transport protocol, which we'll see when we look at the different applications that use TCP and UDP. 4. The application layer handles the details of the particular application. There are many common TCP/IP applications that almost every implementation provides: r Telnet for remote login, r FTP, the File Transfer Protocol, r SMTP, the Simple Mail Transfer protocol, for electronic mail, r SNMP, the Simple Network Management Protocol, and many more, some of which we cover in later chapters. If we have two hosts on a local area network (LAN) such as an Ethernet, both running FTP, Figure 1.2 shows the protocols involved. Figure 1.2 Two hosts on a LAN running FTP. We have labeled one application box the FTP client and the other the FTP server. Most network file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/introduc.htm (2 of 20) [12/09/2001 14.46.31] Chapter 1. Introduction applications are designed so that one end is the client and the other side the server. The server provides some type of service to clients, in this case access to files on the server host. In the remote login application, Telnet, the service provided to the client is the ability to login to the server's host. Each layer has one or more protocols for communicating with its peer at the same layer. One protocol, for example, allows the two TCP layers to communicate, and another protocol lets the two IP layers communicate. On the right side of Figure 1.2 we have noted that normally the application layer is a user process while the lower three layers are usually implemented in the kernel (the operating system). Although this isn't a requirement, it's typical and this is the way it's done und...
View Full Document

Ask a homework question - tutors are online