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On 2/19/2011 10:11 AM, kmedcalf at dessus.com wrote:
> And that has nothing to do with whether a protocol is a peer protocol or not.
> IP is a peer-to-peer protocol.  As SMTP is implemented over IP, it is also a
> peer-to-peer protocol.

At each layer of an architecture, the question of whether a mechanism is peer to
peer can be newly defined.  Even within a layer it can be, depending upon
configuration choices.

IP is typically /not/ peer to peer, since getting from the originating host to
the target host is typically mediated by many routers.  That is the essence of
/not/ being peer to peer.

One layer up, we find that TCP typically /is/ peer-to-peer.

"SMTP" as a one-hop email transmission protocol is peer-to-peer from the SMTP
client to the corresponding SMTP server.  However email exchange from an
author's MUA to a recipient's MUA is, again, the essence of /not/ being peer to
peer.  It is typically massively mediated by lots of different email servers.

One could configure two MUAs to talk with each other 'directly' using SMTP, but 
that's never done.

Instant message services similarly are not peer-to-peer technical terms.



   Dave Crocker
   Brandenburg InternetWorking