Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750888AbWITJyv (ORCPT ); Wed, 20 Sep 2006 05:54:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750891AbWITJyv (ORCPT ); Wed, 20 Sep 2006 05:54:51 -0400 Received: from mx1.suse.de ([195.135.220.2]:56709 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S1750886AbWITJyv (ORCPT ); Wed, 20 Sep 2006 05:54:51 -0400 To: "Stuart MacDonald" Cc: linux-kernel@vger.kernel.org Subject: Re: TCP stack behaviour question References: <87wt802hd9.fsf@willow.rfc1149.net> <006301c6dbf4$035a71c0$294b82ce@stuartm> From: Andi Kleen Date: 20 Sep 2006 11:54:44 +0200 In-Reply-To: <006301c6dbf4$035a71c0$294b82ce@stuartm> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1120 Lines: 21 "Stuart MacDonald" writes: > > > *** I found arp(7) and read up on it while I was typing. And now I see > something interesting in the tcpdump; my app is actually talking on > two TCP connections at the same time. Both are in retransmit phase, > and the first arp is 5 seconds (delay_first_probe_time) after an > _aggregate total_ of 15 retransmits (being the two original unanswered > packets and 7 and 6 retransmits of each). > > My reading of tcp(7)'s documentation of tcp_retries2 is that > tcp_retries2 is a per-TCP packet count. My tcpdump seems to show that > it is in fact a global count. Which is correct? The ARP layer keeps track of what neighbours are reachable and doesn't transmit packets to unreachable ones before they answer unicast or broadcast ARP. This is a state machine borrowed from IPv6. There is nothing global. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/