From owner-freebsd-net@FreeBSD.ORG Thu Jan 27 15:07:29 2005 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id AF8B616A4CE for ; Thu, 27 Jan 2005 15:07:29 +0000 (GMT) Received: from smtp-1.dlr.de (smtp-1.dlr.de [195.37.61.185]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8566743D2F for ; Thu, 27 Jan 2005 15:07:28 +0000 (GMT) (envelope-from Hartmut.Brandt@dlr.de) Received: from beagle.kn.op.dlr.de ([129.247.173.6]) by smtp-1.dlr.de over TLS secured channel with Microsoft SMTPSVC(5.0.2195.6713); Thu, 27 Jan 2005 16:07:26 +0100 Date: Thu, 27 Jan 2005 16:10:59 +0100 (CET) From: Harti Brandt X-X-Sender: brandt_h@beagle.kn.op.dlr.de To: Jose M Rodriguez In-Reply-To: <200501271600.42408.josemi@freebsd.jazztel.es> Message-ID: <20050127160658.K55581@beagle.kn.op.dlr.de> References: <200501271600.42408.josemi@freebsd.jazztel.es> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-OriginalArrivalTime: 27 Jan 2005 15:07:26.0858 (UTC) FILETIME=[E9BB36A0:01C50481] cc: net@freebsd.org Subject: Re: [OT] aal5 pdu CRC X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: Harti Brandt List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 Jan 2005 15:07:29 -0000 On Thu, 27 Jan 2005, Jose M Rodriguez wrote: JMR>Hi, JMR> JMR>get some free time to work in uadsl, but have a problem. Hope someone that JMR>can read ITU I.363 can answer this. JMR> JMR>Every usb adsl modem implementation I see doesn't obey aal5 pdu encoding JMR>standards, which requires that the PDU trailer come at the begin of a fresh JMR>cell. That is not true. The trailer must be on the END of a cell. Before the trailer there will be padding bytes so that this happens. If, for example, you have a one byte PDU the AAL5 PDU will consist of 1 byte information, 39 bytes padding and 8 bytes trailer. JMR> JMR>So, I think that the modem must rework this and generate two cells on the JMR>wire. Due how this modems works, I doubt that the modem recalculate PDU CRC JMR>itself, So... JMR> JMR>Can someone confir if the CRC covers the PAD? I'm begin to think that the CRC JMR>only covers the playload and the pdu-trailer. The CRC covers everything but the CRC. The PAD must be filled with zeros though. harti