From owner-freebsd-net Wed Aug 2 9:52:51 2000 Delivered-To: freebsd-net@freebsd.org Received: from bubba.whistle.com (bubba.whistle.com [207.76.205.7]) by hub.freebsd.org (Postfix) with ESMTP id 8E64137B971; Wed, 2 Aug 2000 09:52:47 -0700 (PDT) (envelope-from archie@whistle.com) Received: (from archie@localhost) by bubba.whistle.com (8.9.3/8.9.3) id JAA81974; Wed, 2 Aug 2000 09:52:46 -0700 (PDT) (envelope-from archie) From: Archie Cobbs Message-Id: <200008021652.JAA81974@bubba.whistle.com> Subject: Re: Improved PPTP support for libalias(3) In-Reply-To: <20000802194901.D36141@sunbay.com> from Ruslan Ermilov at "Aug 2, 2000 07:49:01 pm" To: Ruslan Ermilov Date: Wed, 2 Aug 2000 09:52:46 -0700 (PDT) Cc: Archie Cobbs , Charles Mott , Erik Salander , net@FreeBSD.ORG, Julian Elischer , Brian Somers , Eivind Eklund X-Mailer: ELM [version 2.4ME+ PL68 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org Ruslan Ermilov 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 > > > > . 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. ^^^^^^^^^^^^^^^^^ this is why ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > This is all right, except libalias(3) is supposed to intercept > > > outgoing PPTP call requests messages and alias CallID to be unique, > > > see AliasHandlePptpOut(). > > > > Sorry, I don't understand your point... libalias already does this fine, > > that's not the problem. > > > > The problem is that two internal clients connecting to the same > > external server at the same time will result in two TCP connections > > to the same server seeming to come from the same IP address, which > > violates the protocol. > > Sorry, I misinterpreted your explanation. But I still do not understand > why there is such a limitation in PPTP, can you see any sense here? Because there can be only one "controlling authority" for each IP address.. see above. -Archie ___________________________________________________________________________ Archie Cobbs * Whistle Communications, Inc. * http://www.whistle.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message