They can block access by denying outgoing requests that have a destination
port of xxxx.
Neil
"RAUNIYAR RAJEEV" <[EMAIL PROTECTED]> wrote in message
Pine.GSO.4.21.0010020923090.17297-100000@taiwan">news:Pine.GSO.4.21.0010020923090.17297-100000@taiwan...
>
> HI all,
>
> That has helped me visualized the whole port concept a lot better now. I
> now understand how a local application chooses ats source port
> etc... however I still dont know how a local network can close some of its
> OWN port and effectively block entrance to a remote network/server.
>
> I gave an example of colleges blocking Napster. Suppose Napter keeps a
> well-known port open... maybe 80. all you have to do to log in is teh
> specify the destination port of 80 and bingo, you're in. the source port
> is randomly picked from teh lists of ephemeral ports you have
> available. to in theory, a college cannot block access to a remote server
> without blocking ALL remote access (closing all out-going ports). i know
> that im wrong somewhere, since that HAS been done before. i just need you
> to explain to me which part have i misunderstood.
>
> thanks for the long reply, btw. it really did help me clear up a lot of
> things.
>
> Joe
>
>
>
>
>
>
>
>
>
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