From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martijn Lievaart Subject: Re: using packet filtering to discover TCP end-to-end latency Date: Mon, 21 May 2007 19:25:05 +0200 Message-ID: <4651D5F1.2080701@rtij.nl> References: Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: netfilter-bounces@lists.netfilter.org Errors-To: netfilter-bounces@lists.netfilter.org Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Rohit Grover Cc: netfilter@lists.netfilter.org Rohit Grover wrote: > Hello, > > I need to discover the TCP end-to-end latency between web clients and > servers transparently (i.e. without altering the clients or the > servers in any way). I have squid running as a proxy server on a linux > box, sitting between the clients and the servers. I can have the > clients change their proxy settings to have requests pass through > squid. Squid can measure latencies between itself and the web servers. > The problem is to measure the network latency when squid tries to > forward the server responses back to clients. > > Can packet filtering help me with this? Can I, for example, filter for > the client ACK of the last bit of data sent from squid back to the > client? > > Also, I still need to device a solution to measure network latency > experienced by the client's SYN sent to the squid box. Any ideas? > I would hire a packeteer for this. Expensive, but is perfect for this job. Otherwise, capture with wireshark (formerly Ethereal), export to csv, write a small program. (I don't think wireshark has a plugin for exactly this). I would NOT do this with packet filtering unless I need (near) realtime analysis. And even then. HTH, M4