Your dialup connection dies about half-way through a file transfer. Which OSI layer will help resume the transfer where it left off as soon as you re-connect to the network?

a. Data Link
b. Network
c. Physical
d. Presentation
e. Session
f. Transport

Cheers,
Ron

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Ron Steedman CCNP, CCNA, MCP, BS Computer Science
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Well, if you lost your connection, I have to assume you start from scratch, which would be your Physical Layer. But that's a gimmee, so I would say the answer is your Session Layer. Once the connections are re-established, the session should pick up where it left off, thus answering the question, "Which OSI layer will help resume the transfer where it left off as soon as you reconnect the network?".

I think it's e. Session.

(This is assuming that session has that capability... if not then you have to go all way up to Application, wherein the user starts the process again) Yeah I know I'm going around in circles.

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Yes - the answer is Session layer.

The Session layer helps an application to divide the file transfer into distinct parts called "dialogues".

At the end of each "dialogue", an FTP client and server record how much of the transfer is complete, a process called checkpointing.

If the Internet connection, ftp client, or ftp server fails - the client may resume the transfer from the last successful checkpoint!

Cheers,
Ron

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Ron Steedman CCNP, CCNA, MCP, BS Computer Science
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http://www.congonetworking.com/

Last edited by rsteedma on 05-15-02 at 06:50 PM

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