From owner-freebsd-questions Fri Sep 6 12:24:29 2002 Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 71A6037B400 for ; Fri, 6 Sep 2002 12:24:25 -0700 (PDT) Received: from boris.st.hmc.edu (boris.ST.HMC.Edu [134.173.63.11]) by mx1.FreeBSD.org (Postfix) with ESMTP id EB12543E72 for ; Fri, 6 Sep 2002 12:24:24 -0700 (PDT) (envelope-from jeff@unixconsults.com) Received: from boris.st.hmc.edu (localhost [127.0.0.1]) by boris.st.hmc.edu (8.12.3/8.12.3) with ESMTP id g86JOMgS049475; Fri, 6 Sep 2002 12:24:22 -0700 (PDT) Received: from localhost (jeff@localhost) by boris.st.hmc.edu (8.12.3/8.12.3/Submit) with ESMTP id g86JOLdx049472; Fri, 6 Sep 2002 12:24:21 -0700 (PDT) (envelope-from jeff@unixconsults.com) X-Authentication-Warning: boris.st.hmc.edu: jeff owned process doing -bs Date: Fri, 6 Sep 2002 12:24:21 -0700 (PDT) From: Jeff Jirsa X-X-Sender: jeff@boris.st.hmc.edu To: Linh Pham Cc: "Marc G. Fournier" , Subject: Re: Netcraft no longer sees FreeBSD ... ? In-Reply-To: <20020906115715.J39314-100000@q.closedsrc.org> Message-ID: <20020906121720.R49440-100000@boris.st.hmc.edu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Virus-Scanned: by amavisd-milter on boris.st.hmc.edu Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Fri, 6 Sep 2002, Linh Pham wrote: > # Does anyone know what Netcraft uses to determine uptime? > > My guess is that it periodically queries your machine once enough > requests have been made. If it gets a host unreachable, connection > refused or something like that... then it will mark that the server as > "down". Yeah... it doesn't make as much sense as using 'uptime' since > sites behind load balancers can really inflate the numbers. No. Netcraft (like many scanning tools) uses characteristics of the tcp responses to determine how long a system has been up. It's far more difficult to forge uptime than the webserver information (check out walmart.com's info for an example of webserver forging). For more information on uptime calculation and system identification in general, read the FAQ: http://uptime.netcraft.com/up/accuracy.html - Jeff -- Jeff Jirsa jeff@unixconsults.com -- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message