From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David S. Miller" Subject: Re: [PATCH, untested] Support for PPPOE on SMP Date: Wed, 25 Jun 2003 20:59:41 -0700 (PDT) Sender: netdev-bounce@oss.sgi.com Message-ID: <20030625.205941.41631020.davem@redhat.com> References: <20030625.143334.85380461.davem@redhat.com> <20030626035824.D68B62C147@lists.samba.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: paulus@samba.org, netdev@oss.sgi.com, fcusack@samba.org, carlson@workingcode.com Return-path: To: rusty@rustcorp.com.au In-Reply-To: <20030626035824.D68B62C147@lists.samba.org> Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org From: Rusty Russell Date: Thu, 26 Jun 2003 13:57:09 +1000 Frankly, I'm amazed anyone sees reordering in real life... Many paths on the internet are quite reordered, this is the first thing. In fact, I claim that any TCP stack that doesn't do reordering detection is busted performance wise. The second thing is that network cards can and do reorder packets. Some PCMCIA cards do this just for fun. And ethernet _DOES NOT_ guarentee non-reordering. At a minumum, a card can use QoS values to reorder receive of a given packet, it can also use this to reorder transmit. Our packet schedulers do this on a software level. If you need ordering, you need sequence numbers in your protocol if you wish to operate over these mediums. The case where SMP causes out-of-order packet delivery is just academic compared to the non-local sources of reordering mentioned above.