From owner-freebsd-net  Fri Jul 28 12:41:54 2000
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From: Archie Cobbs <archie@whistle.com>
Message-Id: <200007281941.MAA26153@bubba.whistle.com>
Subject: Re: Improved PPTP support for libalias(3)
In-Reply-To: <200007281735.KAA25478@bubba.whistle.com> from Archie Cobbs at "Jul
 28, 2000 10:35:23 am"
To: Archie Cobbs <archie@whistle.com>
Date: Fri, 28 Jul 2000 12:41:34 -0700 (PDT)
Cc: Charles Mott <cmott@scientech.com>,
	Erik Salander <erik@whistle.com>, net@FreeBSD.ORG,
	Ruslan Ermilov <ru@FreeBSD.ORG>,
	Julian Elischer <julian@elischer.org>,
	Brian Somers <brian@Awfulhak.org>, Eivind Eklund <perhaps@yes.no>
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Archie Cobbs writes:
> > Is this a limitation of a specific server implementation, or
> > a limitation of the PPTP standard?
> 
> It's simply a limitation in our address translation module for PPTP. 
> There's nothing implied wrong with the standard itself or the server
> implementation.
> 
> This limitation could be eliminated with more coding, but it's
> somewhat ugly (you have to make two TCP streams appear as one).

Sorry, I may have misinterpreted your question...

It is inherent in the PPTP standard that there be at most ONE
PPTP TCP control connection between any two IP addresses.

If you think about it for a second you can see why: when a machine
receives a GRE packet, it identifies the call using the pair
<sourceIP, CallID>. That means that there can be at most ONE entity
living at sourceIP doling out CallID's for calls to the local
machine/IP address.. otherwise CallID's would not be guaranteed
to be unique.

-Archie

___________________________________________________________________________
Archie Cobbs   *   Whistle Communications, Inc.  *   http://www.whistle.com


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