Subject: [Ieprep] a practical VoIP issue

From: RJ Atkinson <[email-masked]>
Date: Wed, 27 Nov 2002 06:55:44 -0500

It appears (according to Bill and others) that the biggest problem
with being able to deploy VoIP more widely might actually be NAT
devices.  Apparently VoIP systems use a wide range of dynamically 
assigned
UDP ports, which most firewalls block and which most NATs cannot cope
with properly.

	If one really wants to be able to use Internet infrastructure during
an emergency, designing a VoIP system that can do NAT/Firewall traversal
might be a pretty important component.

Ran

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From: Ken Carlberg <[email-masked]>
Date: Wed, 27 Nov 2002 12:28:40 +0000

> It appears (according to Bill and others) that the biggest
> problem with being able to deploy VoIP more widely might actually be NAT
> assigned UDP ports, which most firewalls block and which most NATs
> cannot cope with properly.
>

yes, a good point. and its actually being worked on in another group,
as well as industry.  

-ken

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From: Bill Woodcock <[email-masked]>
Date: Wed, 27 Nov 2002 10:04:19 -0800 (PST)

> yes, a good point. and its actually being worked on in another group,

STUN is a finger-in-the-dike which a) isn't yet deployable and b) will be
of _very_ little help in the general case.  It's a really ugly hack on top
of a really ugly hack.  The problem is the NAT, and it doesn't solve that.
It only lets you detect it.  To generalize, all of the other NAT traversal
schemes I know of fall into about the same bucket.  They do what they say
they do, but that basically amounts to the statically-configured traversal
of a specific, friendly NAT which you also have configuration access to.
And we can deal with those _without_ STUN and its ilk, so they're not
actually all that helpful.

                                -Bill