From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Furniss Date: Mon, 23 Aug 2004 22:58:51 +0000 Subject: Re: [LARTC] Question about htb class Message-Id: <412A76AB.2080709@dsl.pipex.com> List-Id: References: <20040822170027.2E61.EME@v003.vaio.ne.jp> In-Reply-To: <20040822170027.2E61.EME@v003.vaio.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lartc@vger.kernel.org Hideaki Nemoto wrote: > Hi everyone. > > I'm new to this list and I have some questions > regarding HTB class. > I was trying to see how tc sets the parameters for > HTB, but really couldnt understand them. > So, I thought that I might ask the wizards. > It's mainly from the source code. > > 1. What is the cell_log ? > (its everywhere in the code) > > 2. Why does htb calculate its burst(buffer) with > tc_xmit_time() ? Is opt.rate.buffer supposed to > have the time it takes to transmit the packet ? > (in q_htb.c around 223 lines) > 3. What does rtab and ctab arrays do ? > And what kind of value should be in there ? > (its set in tc_core.c tc_calc_rtable()) > > I'd really appreciate your help. > Thankyou very much in advance. I can't say about HTB, but I've been playing with Ed Wildgooses patch for DSL users - http://mailman.ds9a.nl/pipermail/lartc/2004q2/012752.html cell_log is used to look up the delay for a packet to be transmitted at a certain rate. A rate table is made using cell_log to give granularity - for me using htb it gets calculated with MTU 1600 which means it's 3. Three means the table has a dispatch time entry for every 8 bytes packet size, as a counter gets shifted left by cell_log to generate the table. HTB / whatever looks up the transmit time for a packet by shifting its' length right by cell_log and using the result as an index for the table. Andy. _______________________________________________ LARTC mailing list / LARTC@mailman.ds9a.nl http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/