From owner-freebsd-ipfw@FreeBSD.ORG Mon May 9 20:35:05 2011 Return-Path: Delivered-To: freebsd-ipfw@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 523BB106566B for ; Mon, 9 May 2011 20:35:05 +0000 (UTC) (envelope-from luigi@onelab2.iet.unipi.it) Received: from onelab2.iet.unipi.it (onelab2.iet.unipi.it [131.114.59.238]) by mx1.freebsd.org (Postfix) with ESMTP id 17F0B8FC17 for ; Mon, 9 May 2011 20:35:04 +0000 (UTC) Received: by onelab2.iet.unipi.it (Postfix, from userid 275) id D399173027; Mon, 9 May 2011 22:50:29 +0200 (CEST) Date: Mon, 9 May 2011 22:50:29 +0200 From: Luigi Rizzo To: quamar niyaz Message-ID: <20110509205029.GC39097@onelab2.iet.unipi.it> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i Cc: freebsd-ipfw@freebsd.org Subject: Re: DummyNet configuration for opportunistic Links for emulating DTN X-BeenThere: freebsd-ipfw@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: IPFW Technical Discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 09 May 2011 20:35:05 -0000 On Mon, May 09, 2011 at 10:16:43PM +0530, quamar niyaz wrote: > Hi, > > I am working on a application which is meant for Delay Tolerant Network. I > want to emulate the opportunistic link availability for the data sending > nodes using dummyNet . One scenario, suppose from source node to > destination node let's say a data link is available at around 9 a.m. morning > and the latency of the link from source node to destination node is 1hr. So > if a request for upload comes around 8 a.m. at the sending node then the > data should start reaching to the destination node after 10 a.m. as the link > between the nodes comes at 9 and the latency is 1 hr so delivery time at the > destination node(9 a.m. +1hr. = 10.am.). In other words sending node should > hold the data in its buffer till 10 a.m as the nodes are actually in my 100 > Mbps LAN so for emulating this the sender must start sending the data after > 10 a.m. > > Can the buffer holds such large amount of data e.g. 500 MB for an hour. Or I > have to modify the buffer size if yes, to which file i have to modify and > then build dummynet. Or simply writing a batch scripts is fine for this. > Please let me know. Thanks in advance this kind of stuff belongs to the application layer, not in the link layer. It is not just a matter of buffering, but the fact that your application will likely want to choose what to send when the link becomes available. cheers luigi