Date: Sat, 19 Aug 2000 10:41:28 +0100 From: Brian Somers <brian@Awfulhak.org> To: Archie Cobbs <archie@whistle.com> Cc: Brian Somers <brian@Awfulhak.org>, Brian Somers <brian@FreeBSD.ORG>, cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG, brian@Awfulhak.orgg, brian@Awfulhak.org Subject: Re: cvs commit: src/usr.sbin/ppp README.changes mp.c Message-ID: <200008190941.e7J9fSF94932@hak.lan.Awfulhak.org> In-Reply-To: Message from Archie Cobbs <archie@whistle.com> of "Fri, 18 Aug 2000 08:49:38 PDT." <200008181549.IAA07643@bubba.whistle.com>
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> Brian Somers writes: > > > Mixing MP frames with non-MP frames is slightly dangerous. The > > > problem is that the PPP link layer is required to deliver packets > > > in order. When you go from MP encapsulating packets to not MP > > > encapsulating packets (or vice-versa) you can't guarantee that the > > > peer will deliver the packets in the same order that you sent them > > > without being careful. This is mainly a problem when going from 1 > > > -> 2 links I believe... or when mixing MP and non-MP over multiple > > > links. > > > > It should only ever be possible to deliver out-of-order network layer > > frames here, and even then, only a single frame can be out of order > > at the time of the second link opening. > > > > I think the reason behind the link layer being required to deliver in > > order is so that the control protocol packets don't make a mess of > > the peers state machine (out of order IPCP frames for example). > > > > As ppp currently only does IP as an NCP, and IP packets are allowed > > to be delivered out-of-order, I think this is ok. > > If you're doing Van Jacobson header compression, for example, > with connection ID compression, out of order packets can really > screw things up. True, but as ppp will only ever generate one out-of-order packet under normal circumstances, this just means that if the two packets in question are from the same tcp stream, the first will get dropped. Perhaps it would be better if PROTO_IP packets were only sent when there's only one link open *AND* no other links are in any sort of trying-to-open state ? > -Archie > > ___________________________________________________________________________ > Archie Cobbs * Whistle Communications, Inc. * http://www.whistle.com -- Brian <brian@Awfulhak.org> <brian@[uk.]FreeBSD.org> <http://www.Awfulhak.org>; <brian@[uk.]OpenBSD.org> Don't _EVER_ lose your sense of humour ! To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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