Subject: RE: [midcom] More than one NAT in Network-friendlier Midcom

From: "Cedric Aoun" <[email-masked]>
Date: Fri, 7 Dec 2001 00:02:11 -0000

yes :-). I've been troubled with this issue as well as the discovery
problem.
Using the application client registration process is the best way to reach
the clients (while maintaining the bind by a keep alive of course) but we
need to reach the application servers first.
This is not a tough problem in enterprise since you can afford putting 1 or
2 call agents in the DMZ.

Unfortunately when we look at a VoIP service provider handling several
hundred thousands (or probably millions) calls, several 10s of call agent
processing entities will be required. 
In case full cone NATs where used all times, one could potentially think of
using stateless registration servers; most enterprises still use symmetric
NAT for security reasons. So this solution doesn't work, we can't minimize
the number of servers in the DMZ.

It is no longer a couple of servers hosted in the DMZ of a service provider.

This is a problem that I've been noticing in the VoIP carrier space, and not
all service providers could afford giving up these groups of registered
addresses.
Using static binds doesn't scale and is a nightmare to maintain.
Potentially the solution could use DNS SRV with an embedded DNS ALG on the
service provider MBs.
Any comments/inputs? 

-----Original Message-----
From: Scott Brim [mailto:[email-masked]]
Sent: Thursday, December 06, 2001 8:15 PM
To: midcom
Subject: Re: [midcom] More than one NAT in Network-friendlier Midcom

On Thu, Dec 06, 2001 01:29:09PM -0500, Melinda Shore wrote:
> First, a deployment in which a server does not have a
> public address but is intended to be globally reachable
> is just asking for trouble.  

There's a message I can't find in the archives, in which iirc Cedric
Aoun claimed that at least some voice service providers would be placing
voice agents behind NATs.  It's been complicating everything for me.
Cedric, are you there?

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From: Keith Moore <[email-masked]>
Date: Thu, 06 Dec 2001 20:06:51 -0500

> Potentially the solution could use DNS SRV with an embedded DNS ALG on the

please don't pollute DNS in an effort to try to solve the NAT problem.
NATs cause enough problems as it is without making DNS worse.

Keith