From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lennier.cc.vt.edu (lennier.cc.vt.edu [198.82.162.213]) (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 06A9121F510 for ; Sat, 31 May 2014 04:54:37 -0700 (PDT) Received: from mr2.cc.vt.edu (mr2.cc.vt.edu [198.82.163.74]) by lennier.cc.vt.edu (8.13.8/8.13.8) with ESMTP id s4VBrUEO031698; Sat, 31 May 2014 07:53:30 -0400 Received: from auth1.smtp.vt.edu (auth1.smtp.vt.edu [198.82.161.152] (may be forged)) by mr2.cc.vt.edu (8.14.4/8.14.4) with ESMTP id s4VBrPYU025335; Sat, 31 May 2014 07:53:30 -0400 Received: from turing-police.cc.vt.edu ([IPv6:2601:8:1f80:663:28bc:56b8:dc5d:9190]) (authenticated bits=0) by auth1.smtp.vt.edu (8.14.4/8.14.4) with ESMTP id s4VBrNsE002693 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sat, 31 May 2014 07:53:24 -0400 X-Mailer: exmh version 2.8.0 04/21/2012 with nmh-1.6+dev To: Dave Taht In-Reply-To: Your message of "Fri, 30 May 2014 23:05:24 -0700." From: Valdis.Kletnieks@vt.edu References: Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1401537202_3092P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Sat, 31 May 2014 07:53:22 -0400 Message-ID: <29775.1401537202@turing-police.cc.vt.edu> X-Spam-Status: No, score=-0.7 required=5.0 tests=MIME_QP_LONG_LINE, RP_MATCHES_RCVD autolearn=disabled version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mr2.cc.vt.edu Cc: "cerowrt-devel@lists.bufferbloat.net" Subject: Re: [Cerowrt-devel] measuring bandwidth and latency with snmp X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 31 May 2014 11:54:38 -0000 --==_Exmh_1401537202_3092P Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable On Fri, 30 May 2014 23:05:24 -0700, Dave Taht said: > There's no need to do ping.You can just measure the > time it takes to issue and get the snmp query response. > > Am I missing something obvious? For devices with separate control and data planes, it's quite possible to have 3 different numbers: 1) The time it takes for the data plane to receive and forward a packet. 2) The time it takes for the data or control plane to generate an ICMP response 3) The time it takes for the control plane to do slowpath handling of a relatively heavy SNMP packet. It's why traceroute often gives you wonky timing numbers and reports RTTs to a middle hop are higher than to the destination. It's because the router was able to forward packets much faster than the slowpath to generate the ICMP TTL Exceeded reply.... For longer hauls, there's the added fun that the source and destination may not be in the same administrative domain - I have smokeping running on a Raspberry Pi to measure from local Comcast to work. My personal device and the work box in a different group are *never* going to speak SNMP to each other. :) --==_Exmh_1401537202_3092P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Exmh version 2.5 07/13/2001 iQIVAwUBU4nCsgdmEQWDXROgAQLBhA/+M+0K9DpAFzowJB9css/XJGk97wKL85Jg EnZCjeWF+lgko3Rq+Dq/4rBzhqPTL+o3KAOfJdTeJxBo/OB3tqo/3SE+tuCjV/5J h4ouCyBOvPb1w+WvEbXTqAKHbAda0g72OnQpeNLKN4Lhvxa2A+CCc8atPZVASfsI zKe5pNDUlJZ+0LWbvhcPysSjwtNmtMRs4B2UNn+K4Pg/SKNNwB5XDfWjWiZsnJEe q3waKpTkpYWD3PIbhGtgFc8NFw3nAr78np7+niFg8uDp4RM+m6lFqzFTp7CcHQlr oV9m/fyx8XFg8WBEhlIcRI4IlProCePYDeZ9+n5FIuZC2Cfeyvh8KfMJEj2zHwhz sgoUWxp04GgBdW4zGeU9Jtj1J5p65cFKgYA0Zyi/Dg5AtU03UJYuAcF3Sc+9DN3H zN3594CvZ/9YFJfWHKJrirvlqpJKqhGodq/KArrMwi3A/CeV0M/YjmJmyFbF9cKl /OyCAyGr6mU+otZaqw4iP0LM+cq8c5OaaZns95UE/Nq6audLIil9oBIFu0n3gmRd 1nvWIIjWmwWHtimlUgpFDw/6QmAh4WWWZvZHiayBVm0KPUYJlVAHqWaPOEuBBTe3 5zV0NqXzifQmd4dyzWvKbzk3iZH6mqbCK5y5dKXyY7b49qLmzr1SqPGAyMUwtXg2 t9Hz23w/S6E= =w5y0 -----END PGP SIGNATURE----- --==_Exmh_1401537202_3092P--