RE: [P2PSIP] Choice of STUN peer or TURN peer

> -----Original Message-----
> From: JiangXingFeng [mailto:jiang.x.f@huawei.com] 
> Sent: Thursday, January 24, 2008 6:08 PM
> To: 'Dan Wing'; 'Bruce Lowekamp'
> Cc: 'P2PSIP Mailing List'
> Subject: RE: [P2PSIP] Choice of STUN peer or TURN peer
> 
> > 
> > The TURN server is responsible for obtaining a publicly-routable
> > address, and giving that address to the TURN client.  The TURN
> > specification, as currently written, expects the TURN server
> > itself to be on a publicly-routable network ("on the Internet").
> > 
> > If, however, the TURN server is behind a NAT, and we want the
> > TURN server to still be responsible for obtaining a
> > publicly-routable IP address, you could do that.  Here is a
> > new technique that could be used:  the TURN server could use
> > STUN (or NAT-PMP or UPnP, if there is only one NAT between
> > the TURN server and the Internet), and obtain a publicly-
> > routable mapping:
> > 
> > 
> >   TURN client         STUN server          NAT  TURN server
> >        |                   |                |      |
> >  1.    |------give me a TURN address------->|----->|
> >  2.    |                   |<--STUN Request--------|
> >  3.    |                   |-STUN Response->|----->|
> >  4.    |<-----here is your TURN address------------|
> > 
> > 
> > Messages 2-3 are normal STUN request/response messages, and
> > tell the TURN server a publicly-routable IP address and UDP
> > port.  The IP address and UDP port returned in in the STUN
> > Response (message 3) is the TURN server's publicly-routable
> > transport address, and is given to the TURN client in message
> > 4.
> > 
> > For the above message flow to work, the NAT has to be
> > p2p-friendly, of course -- that is a requirement for a
> > successful TURN server behind a NAT.
> 
> 
> If the NAT is nested, the location of the STUN server may 
> fail the above the
> method. For example, if the STUN server is also behind the 
> NAT and reflects
> the inner NAT mapping, not outer most NAT mapping, to the 
> TURN server, the
> relayed address will not be used for the TURN client to 
> contact with TURN
> server. In order to avoid this kind of failure, stun server's location
> should be learned by its clients.

Yep.  That is part of the qualification a p2p-sip TURN server 
would have to do before it declares itself a TURN server.

-d

> In china, due to the lack 
> of the IPv4
> address, nested NAT is not a rare situation. 
> Comments?
> 
> Regards!
> JiangXingFeng
> 

_______________________________________________
P2PSIP mailing list
P2PSIP@ietf.org
https://www1.ietf.org/mailman/listinfo/p2psip