From owner-freebsd-ipfw@FreeBSD.ORG Fri May 23 03:50:34 2003 Return-Path: Delivered-To: freebsd-ipfw@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0F19D37B401 for ; Fri, 23 May 2003 03:50:34 -0700 (PDT) Received: from epita.fr (hermes.epita.fr [163.5.255.10]) by mx1.FreeBSD.org (Postfix) with ESMTP id D44E443FA3 for ; Fri, 23 May 2003 03:50:32 -0700 (PDT) (envelope-from le-hen_j@epita.fr) Received: from carpediem (carpediem.epita.fr [10.42.42.5]) by epita.fr id h4NAoVq01327 for ipfw@freebsd.org EPITA Paris France Fri, 23 May 2003 12:50:31 +0200 (MEST) Date: Fri, 23 May 2003 12:50:30 +0200 From: jeremie le-hen To: ipfw@freebsd.org Message-ID: <20030523105030.GA24992@carpediem.epita.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4i Subject: Understanding queue size X-BeenThere: freebsd-ipfw@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: IPFW Technical Discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 23 May 2003 10:50:34 -0000 Hi, ipfw(8) manual page, section "TRAFFIC SHAPER (DUMMYNET) CONFIGURATION" tells: queue {slots | sizeKbytes} Queue size, in slots or KBytes. Default value is 50 slots, which is the typical queue size for Ethernet devices. Note that for slow speed links you should keep the queue size short or your traffic might be affected by a significant queueing delay. E.g., 50 max- sized ethernet packets (1500 bytes) mean 600Kbit or 20s of queue on a 30Kbit/s pipe. Even worse effect can result if you get packets from an interface with a much larger MTU, e.g. the loopback inter- face with its 16KB packets. I understand that if the queue size is too large, then it will imply large delays. But what if the queue is too short ? Does anyone can point me a detailed document which talks about queues ? Or maybe it exists a simple general rule explaining all this stuff... Regards, -- Jeremie aka TtZ/TataZ jeremie.le-hen@epita.fr