Subject: [midcom] Proxy + Traversal => FANTOM

From: "Pete Cordell" <[email-masked]>
Date: Thu, 22 Nov 2001 16:05:10 -0000

Bob,

This addresses another of the threads you raised.

Steve Davies wrote:
>> In this case the FANTOM client would have to handle
>> multiple simultaneous call setups and cleardowns. We judged a single
>> persistant tunnel for all call control from the FANTOM client to FANTOM
>> server was the most efficient use of resources.

To which Bob replied:
> Isn't this really the same as putting a proxy in the exterprise and having
> it connect to the proxy in the public network over TCP? Why is FANTOM
> better than adding a proxy? If FANTOM is present in the terminal, you have
> a tunnel for every terminal. If you have a FANTOM client, then all the
terminals
> need to send signalling to the FANTOM client. Doesn't that make it a
proxy?

The problem is that a proxy on its own is not sufficient to traverse the
firewall and NAT combination.  What you need is proxy + traversal solution.
In our case, proxy + traversal solution => FANTOM (as does client +
traversal solution => FANTOM).

This is why we multiplex the control channel.  We need both the native
signalling protocol (e.g. SIP) and the out-of-band traversal control
protocol (see previous e-mail for why we have it out-of-band) to pass
between the private and public proxies.  Muxing them over the same
connection reduces the number of rules required in the firewall, and saves
resources.  As the TCP connection will have already been established to make
the call, then there is also no over-head associated with establishing a new
TCP connection for the traversal control protocol.

Pete.

=============================================
Pete Cordell
Tech-Know-Ware
[email-masked]
+44 1473 635863
=============================================

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