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Old 27th August 2012
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jggimi jggimi is offline
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Default Chapter 5: Layer 7: Applications

We jump now to the last layer -- the protocols which manage communications at the application layer -- HTTP was mentioned above in Chapter 1, and there are other protocols at this layer you may be familiar with: such as FTP, SSH, and P2P protocols like BitTorrent.

The network model permits the applications to operate separately from protocols in other layers. This approach permits some of the protocols at this layer to choose between multiple lower level protocols as needed, or as the admin chooses. As an example of an automatic protocol switch, the Domain Name System protocol uses UDP for requests and responses that are relatively short, and uses TCP for longer length queries or for database maintenance actions between and among Domain Name Servers.

The separation of protocols into layers impacts application design. For example, the HTTP protocol uses TCP as an underlying transport mechanism. HTTP is stateless, yet HTTP takes advantage of TCP's state management and automated error handling.

Last edited by jggimi; 4th September 2012 at 12:01 AM.
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