[Dshield] Question on Skype

Valdis.Kletnieks@vt.edu Valdis.Kletnieks at vt.edu
Fri Feb 17 18:08:36 GMT 2006


On Fri, 17 Feb 2006 12:02:59 EST, Kenton Smith said:
> My concern with Skype is that it is a P2P technology.
> As far as I know that means that your machine could be
> being used as a node in the network even if you aren't
> using it.

P2P simply means 'Peer To Peer' - meaning that the machines that
want to talk do so directly, rather than the more usual 'client server'
model (where if 2 arbitrary machines wanted to communicate, they'd do
so by sending to a central server, which would then forward to the other
machine).

"node in the network" is mostly for file-sharing systems where the data
is fetched from one or more "best available copies".  Obviously, if you're
trying to do a phone call, sending the data to some other "node" is incredibly
silly (as you're then adding the round trip time to/from that node to the
total round trip, and your RTT and jitter values go *all* to hell...)

For the record, the Internet was always *designed* to be a P2P network
(anybody doubting that should read figure 8 on page 32 of RFC793, regarding
simultaneous opens).  And in the early years, *every* host had the ability to
provide essentially *all* services - its own mail server, and so on.  It was
only with the advent of Windows and Macs and similar dumbed-down systems that
required outside assistance to survive on the net that the client-server
model took hold (for instance, the only reason POP exists is because some
systems didn't have the ability to run their own mail server, and as a result
the MUA needs to download the mail from a more capable machine)....
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