RE: Port preservation

Jonathan,
This was merely an example. 

For clarity, common server ports in this example would be HTTP, SMTP,
FTP, etc. This is a common enterprise deployment use for static
translations that I was describing earlier.

Most developers of well behaved protocols will implement the capability
to listen on the same port they send on, or provide the capability to
configure this. Firewall/NAT vendors typically provide the capability to
configure the static IP/PORT NAT translations for these types of
services, which is why I used this as a possible reason, to answer the
question raised below.

The use described is in no way definitive, but it does provide a
practical use scenario that you will see quite often in the real world.

The capability to perform this type of configuration is essential to
providing secure access policies, a feature that I wish VoIP and other
peer-to-peer protocol developers would have modeled (Some do, but the
standard doesn't require this, which doesn't help security). 

Chris

-----Original Message-----
From: Jonathan Rosenberg [mailto:[email protected]] 
Sent: Monday, April 26, 2004 11:44 PM
To: [email protected]
Cc: 'Cullen Jennings'; 'Yutaka Takeda'; 'Midcom'; [email protected]
Subject: Re: [midcom] Port preservation



Christopher A. Martin wrote:

> Hi all,
> The only reason that I can think of, that may be a good reason, is to
> provide the appearance that a client is communicating directly with a
> server on a standard server port (for that professional, I'm a big
> organization look and feel). Some applications do check for this for
> paranoid security reasons, but they are less common.

For what application does the protocol expect the SOURCE port to be a 
standard server port? None that I can think of.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                600 Lanidex Plaza
Chief Technology Officer                    Parsippany, NJ 07054-2711
dynamicsoft
[email protected]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com