Subj : Packet Vs Circuit Switch
To   : Andy Ball
From : Bo Simonsen
Date : Fri Oct 22 2004 12:25 am

Hello Andy!

Monday October 18 2004 08:54, you wrote to me:

AB>> Out-of-order packet reception springs to mind.

BS>> Hm. Please explain, not familear with that expression.

AB> On a circuit-switched link (such as a dial-up call between my modem
AB> and yours) all the data sent from my end to your end take the same
AB> route and arrive in the same order that they were sent.

Yes,

AB> On a
AB> packet-switched network (such as the Internet), it is possible for
AB> packets to take different routes to reach you, and for a packet to
AB> arrive ahead of one that was sent before it was (arriving out of
AB> order).

AB> Thinking about it though, Telnet works over TCP which almost certainly
AB> re-orders packets that it receives in the wrong order before passing
AB> them up to Telnet, so although it's a valid difference between
AB> circuit-switched and packet- switched networks, it's sort of
AB> irrelevent from Telnet's point of view.  :-)

But if we see in the OSI model, it's not really the application layers job to
make scure the data is valid. Which we actually do anyhow, with fx. CRC check
in Zmodem and brothers.

Bo
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