RE: [midcom] Port preservation
"Christopher A. Martin" <chris@sip1.com> Mon, 26 April 2004 21:29 UTC
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Reply-To: Chris@sip1.com
From: "Christopher A. Martin" <chris@sip1.com>
To: 'Cullen Jennings' <fluffy@cisco.com>, 'Yutaka Takeda' <takeday@pcrla.com>, 'Midcom' <midcom@ietf.org>, stun@www.vovida.org
Subject: RE: [midcom] Port preservation
Date: Mon, 26 Apr 2004 15:28:42 -0500
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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. We typically call this a static port translation, irregardless of vendor, and it can be configured on many of the popular enterprise class firewalls. The other common type of configuration used for the same reason would be a static IP NAT translation, which provides the server with a whole range of ports that it can be listening on. Chris -----Original Message----- From: midcom-admin@ietf.org [mailto:midcom-admin@ietf.org] On Behalf Of Cullen Jennings Sent: Monday, April 26, 2004 3:42 PM To: Yutaka Takeda; Midcom; stun@www.vovida.org Subject: Re: [midcom] Port preservation There may be many but the two reasons I have heard are below - neither of which make much sense to me. Makes debugging easier by not switching the port traffic is on. This allows network sniffers and such guess the type of traffic from the port. (Personally I find this argument a little hard to buy given it is the source port that is being preserved and using ports for traffic type determination is usually based on the destination port) Higher odds of interoperability for protocols. The argument goes that A sends though a NAT to B. B may reply expecting to go to a certain port number so if that does not change life will be better. I suspect that most applications that reply to the correct IP, are likely to also reply to port the packet came from but who knows. The most common answer I get to this questions and the one that seems most believable ... "Because vendor X's NAT worked that way so we made ours do the same" I don't know - it is a good questions. Can others provide any insight into this? On 4/23/04 11:19 AM, "Yutaka Takeda" <takeday@pcrla.com> wrote: > > Does anyone know what the real motivation for NAT designers to > implement the port preservation[1] is? Is there an actual service > or application that depends on this behavior? I just realized that > I know such NATs exist but why... > > [1] > http://www.ietf.org/internet-drafts/draft-jennings-midcom-stun-results-0 0.txt > > Yutaka > > _______________________________________________ > midcom mailing list > midcom@ietf.org > https://www1.ietf.org/mailman/listinfo/midcom > _______________________________________________ midcom mailing list midcom@ietf.org https://www1.ietf.org/mailman/listinfo/midcom _______________________________________________ midcom mailing list midcom@ietf.org https://www1.ietf.org/mailman/listinfo/midcom
- [midcom] Port preservation Yutaka Takeda
- Re: [midcom] Port preservation Pyda Srisuresh
- RE: [midcom] Port preservation Yutaka Takeda
- Re: [midcom] Port preservation Cullen Jennings
- RE: [midcom] Port preservation Pyda Srisuresh
- RE: [midcom] Port preservation Christopher A. Martin
- Re: [midcom] Port preservation Jonathan Rosenberg
- RE: [midcom] Port preservation Christopher A. Martin
- RE: [midcom] Port preservation Christopher A. Martin
- Re: [midcom] Port preservation Cullen Jennings
- Re: [stun] Re: [midcom] Port preservation Cullen Jennings
- RE: [midcom] Port preservation Christopher A. Martin
- RE: [midcom] Port preservation Christopher A. Martin
- Re: [midcom] Port preservation Jonathan Rosenberg
- RE: [midcom] Port preservation Christopher A. Martin
- RE: [midcom] Port preservation Christopher A. Martin
- RE: [midcom] Port preservation Yutaka Takeda