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S Live layers. a livuel includes o layers that matter so that we only need to PDITSPA The application layer is responsible for handling the application data that is sent FTP, and Gnutella. from host to host. Examples of application layer protocols include HTTP, SMTP, The transport layer deals with logical end-to-end transport of the data. The transport layer protocols of interest are TCP and UDP. The network layer routes the data through the network. IP is the network layer protocol that matters to us. The link layer handles the transferring of data over each individual link of the network. There are many link layer protocols hut train ether- nat and ADD The physical layer sends the bits over the physical media. If you want to k about the physical layer, study electrical engineering. data nasses down the protocol stack ve and then Conceptually, a par back up the protocol stack at the destination. Routers in the core of the network must process data up to the network layer in order to know where to route a packet. This is illustrated in Figure 14.2. Suppose that X is a packet of application data at the source. As X goes down protocol arch nrotocol adds a header, which includes the information required by that particu- diastian laver Then the application layer