Re: peer to peer messaging

"Chris Uppal" <chris.uppal@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:42960e8d$0$38044$bed64819@xxxxxxxxxxxxxxxxxxxx
>
> Since NAT is supposed to be transparent to both ends of the network
connection,

Eh?? Since when?? How can it be?? (Unless of coures you choose to restrict
yourself to protocols that you have checked that all the NAT boxes on the
path understand ... but of course the fact that you have to acquire such
knowledge is itself a breach of transparency.)

> it isn't obvious to me what the potential showstoppers might be ?

These days the IP address of any particular machine is different from
different places, and the machine itself probably won't know all the IP
addresses it can be referred to from all parts of the internet and private
subnets.

I'd have thought the potential showstoppers *were* obvious:

If machine A which knows its IP address is X can talk to machine B via IP
address Y then we have no way of knowing

(a) what IP address machine B thinks it has
(b) what IP address machine B should use to talk to machine A
(c) what IP address machine C should use to talk to machine B
(d) on which of its interfaces B would be best advised to listen for
connections from machine C

and so on and so on and so on.

All these things will work fine on singled homed machines on a LAN and most
of them will fall over with only one single simple NAT box in the way.

--
Tim Ward
Brett Ward Limited - www.brettward.co.uk


.

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