ECECNA - MODULE 15

Application Layer

It is the layer that provides the interface between the applications used to communicate, and the underlying network over which messages are transmitted.

Application Layer Protocol

Are used to exchange data between programs running on the source and destination hosts

Hypertext Transfer Protocol (HTTP)

File Transfer Protocol (FTP)

Trivial File Transfer Protocol (TFTP)

Internet Message Access Protocol (IMAP)

Domain Name System (DNS) protocol.

Some of the most widely known application layer protocols:

Formatting data for compatibility with the destination.

Compressing data for efficient transmission and decompression.

Encrypting for secure transmission and decrypting at receipt.

Presentation layer three primary functions:

Session Layer

This layer creates and maintains dialogs between source and destination applications.

Session Layer

It handles the exchange of information to initiate dialogs, keep them active, and to restart sessions that are disrupted or idle for a long period of time.

Client

In the client/server model, the device requesting the information is called

Server

The device responding to the request is called

Upload

Data transfer from a client to a server is referred to as

Download

Data transfer from a server to a client is referred to as

• BitTorrent

• Direct Connect

• eDonkey

• Freenet

Common P2P networks include:

Gnutella Protocol

Protocol where each user shares whole files with other users

μTorrent

BitComet

DC++

Deluge

emule

Gnutella client applications: