Protocolos nivel apicaçao

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Network Fundamentals, CCNA Exploration Companion Guide

specific peer-to-peer application, it invokes the required user interface and background services. After that, the devices can communicate directly.
Figure 3-10 Peer-to-Peer Applications

Instant Message Meeting tonight. I’ll be there. Good. Send Read Network

Instant Message Meeting tonight. I’ll be there. Good. Send Read

Client and Server Both phones: • Initiate a call • Receive a call

Client and Server Both phones simultaneously: • Send • Receive

A type of peer-to-peer application is the P2P hybrid system, which utilizes a centralized directory called an index server even though the files being shared are on the individual host machines. Each peer accesses the index server to get the location of a resource stored on another peer. The index server can also help connect two peers, but after they are connected, the communication takes place between the two peers without additional communication to the index server. Peer-to-peer applications can be used on peer-to-peer networks, in client/server networks, and across the Internet.

Application Layer Protocols and Services Examples
Now that you have a better understanding of how applications provide an interface for the user and provide access to the network, you will take a look at some specific commonly used protocols. As you will see later in this book, the transport layer uses an addressing scheme called a port number. Port numbers identify applications and application layer services that are the source and destination of data. Server programs generally use predefined port numbers that are commonly known by clients. As you examine the different TCP/IP application layer protocols and services, you will be referring to the TCP and UDP port numbers normally associated with these services. Some of these services are
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Domain Name System (DNS): TCP/UDP port 53 HTTP: TCP port 80

Chapter 3: Application Layer Functionality and