Re: [Ekiga-list] symmetric nat traversal

[Christopher Priest <christopherpriest yahoo com>]

> and a costly relay would have to be used to perform triangle routing.

My understanding of triangle routing has mobile device A sending to B directly but with a care/of return address of a mobile proxy that knows where A is now. C forwards the message. A is moving and it's IP changes as it crosses cells. Thus B sends care/of C which forwards to A. This forms a triangle.

I also thought that symmetric nat traversal requires an outbound proxy and that neither A or B communicate directly but both send packets to the outbound proxy which forwards all communication. This forms a V.

Am I correct or wrong?

Christopher Priest  ChristopherPriest yahoo com


--- On Fri, 11/28/08, yannick <sevmek free fr> wrote:

> From: yannick <sevmek free fr>
> Subject: Re: [Ekiga-list] symmetric nat traversal
> To: "Ekiga mailing list" <ekiga-list gnome org>
> Date: Friday, November 28, 2008, 1:40 PM
> Le vendredi 28 novembre 2008 à 19:15 +0100, Martin Uecker a
> écrit :
> > On Fri, Nov 28, 2008 at 04:17:35PM +0100, Piotr
> Morgwai Kotarbiński wrote:
> > > The document is 5 years old and last modification
> of the project page
> > > occurred also in 2003, so I'm not sure if
> anybody is working on it
> > > still... I'll try to contact the author or
> other members of the
> > > project and ask what's the status.
> > > 
> > > Thanks
> > > 
> > >   Morg
> > > 
> > 
> > It seems that Miredo [http://www.remlab.net/miredo/]
> has symmetric
> > NAT traversal support. It might be possible to acquire
> an IPv6
> > address using teredo (Miredo) on both clients and then
> communicate
> > with ipv6. In general, this would be a much more
> elegant solution
> > then to implement NAT traversal in each and every
> program. Since
> > Teredo is also supported on Windows, this might also
> work for
> > Windows users.
> > 
> 
> "Teredo is not compatible with all NAT devices. Using
> the terminology of
> RFC 3489, full cone, restricted and port-restricted NAT
> devices are
> supported, while symmetric NATs are not. National Chiao
> Tung University
> proposed SymTeredo which enhanced the original Teredo
> protocol to
> support symmetric NATs, and the Microsoft and Miredo
> implementations
> implement certain unspecified non-standard extensions to
> improve support
> for symmetric NATs. However, connectivity between a Teredo
> client behind
> a symmetric NAT, and a Teredo client behind a
> port-restricted or
> symmetric NAT remains seemingly impossible.
> 
> Indeed, Teredo assumes that when two clients exchange
> encapsulated IPv6
> packets, the mapped/external UDP port numbers used will be
> the same as
> those that were used to contact the Teredo server (and
> building the
> Teredo IPv6 address). Without this assumption, it would not
> be possible
> to establish a direct communication between the two
> clients, and a
> costly relay would have to be used to perform triangle
> routing. A Teredo
> implementation tries to detect the type of NAT at startup,
> and will
> refuse to operate if the NAT appears to be symmetric. (This
> limitation
> can sometimes be worked around by manually configuring a
> port forwarding
> rule on the NAT box, which requires administrative access
> to the
> device)."
> 
> http://en.wikipedia.org/wiki/Teredo_tunneling#Limitations
> 
> Well, according to wikipedia, it seems toredo has the same
> limitations
> as Ekiga currently has...
> 
> > 
> > Martin
> > 
> > 
> > _______________________________________________
> > ekiga-list mailing list
> > ekiga-list gnome org
> > http://mail.gnome.org/mailman/listinfo/ekiga-list
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