From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from potemkin.univ-paris7.fr (potemkin.univ-paris7.fr [IPv6:2001:660:3301:8000::1:1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id 844D521F1EE for ; Mon, 1 Jul 2013 17:02:41 -0700 (PDT) Received: from mailhub.math.univ-paris-diderot.fr (mailhub.math.univ-paris-diderot.fr [81.194.30.253]) by potemkin.univ-paris7.fr (8.14.4/8.14.4/relay2/38117) with ESMTP id r6202QYa017827; Tue, 2 Jul 2013 02:02:26 +0200 Received: from mailhub.math.univ-paris-diderot.fr (localhost [127.0.0.1]) by mailhub.math.univ-paris-diderot.fr (Postfix) with ESMTP id D1A5F4F44B; Tue, 2 Jul 2013 02:02:26 +0200 (CEST) X-Virus-Scanned: amavisd-new at math.univ-paris-diderot.fr Received: from mailhub.math.univ-paris-diderot.fr ([127.0.0.1]) by mailhub.math.univ-paris-diderot.fr (mailhub.math.univ-paris-diderot.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id ZlBVnizwe_g4; Tue, 2 Jul 2013 02:02:26 +0200 (CEST) Received: from pirx.pps.jussieu.fr (bob75-6-82-238-73-9.fbx.proxad.net [82.238.73.9]) (Authenticated sender: jch) by mailhub.math.univ-paris-diderot.fr (Postfix) with ESMTPSA id ECE114F441; Tue, 2 Jul 2013 02:02:25 +0200 (CEST) Received: from localhost ([127.0.0.1] helo=pirx.pps.jussieu.fr) by pirx.pps.jussieu.fr with esmtp (Exim 4.80) (envelope-from ) id 1Uto37-00016M-I7; Tue, 02 Jul 2013 02:02:25 +0200 Date: Tue, 02 Jul 2013 02:02:25 +0200 Message-ID: <871u7hesmm.wl%jch@pps.univ-paris-diderot.fr> From: Juliusz Chroboczek To: Baptiste Jonglez In-Reply-To: <20130701164607.GB12090@ens-lyon.fr> References: <20130701164607.GB12090@ens-lyon.fr> User-Agent: Wanderlust/2.15.9 MIME-Version: 1.0 (generated by SEMI 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (potemkin.univ-paris7.fr [194.254.61.141]); Tue, 02 Jul 2013 02:02:27 +0200 (CEST) Cc: babel-users@lists.alioth.debian.org, bloat@lists.bufferbloat.net Subject: Re: [Bloat] [Babel-users] RTT stability inside a GRE tunnel X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 02 Jul 2013 00:02:42 -0000 > While experimenting with the RTT-aware branch of babeld, I ran into an > odd but interesting behaviour: between two given hosts reachable over > the Internet, the RTT is more stable inside a GRE tunnel than outside. The RTT is around 300 ms for both kinds of packets. GRE packets have virtually no jitter, while ICMP packets have some 15ms jitter, which would appear to be completely random. My guess would be that there might be a router in the way that handles GRE packets in hardware, and ICMP packets in software. The extra 15 ms is the CPU time spent on processing the ICMP packets. Still, the nondeterminacy is weird. Anybody seen anything similar? -- Juliusz