From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phillip Susi Subject: Re: [PATCH 0/2] NET: Accurate packet scheduling for ATM/ADSL Date: Wed, 14 Jun 2006 10:27:13 -0400 Message-ID: <44901CC1.60403@cfl.rr.com> References: <1150278004.26181.35.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Stephen Hemminger , Jamal Hadi Salim , netdev@vger.kernel.org, lartc@mailman.ds9a.nl, russell-tcatm@stuart.id.au, hawk@diku.dk, linux-kernel@vger.kernel.org Return-path: Received: from iriserv.iradimed.com ([69.44.168.233]:34164 "EHLO iradimed.com") by vger.kernel.org with ESMTP id S964978AbWFNO21 (ORCPT ); Wed, 14 Jun 2006 10:28:27 -0400 To: Jesper Dangaard Brouer In-Reply-To: <1150278004.26181.35.camel@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Jesper Dangaard Brouer wrote: > The Linux traffic's control engine inaccurately calculates > transmission times for packets sent over ADSL links. For > some packet sizes the error rises to over 50%. This occurs > because ADSL uses ATM as its link layer transport, and ATM > transmits packets in fixed sized 53 byte cells. > I could have sworn that DSL uses its own framing protocol that is similar to the frame/superframe structure of HDSL ( T1 ) lines and over that you can run ATM or ethernet. Or is it typically ethernet -> ATM -> HDSL? In any case, why does the kernel care about the exact time that the IP packet has been received and reassembled on the headend?