On Mon, 23 Aug 2004 23:58:51 +0100 Andy Furniss <andy.furniss@xxxxxxxxxxxxx> wrote: > 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. Thanks for the answer, Andy. I think I'm starting to understand. Does the "transmit time" here, mean "time the kernel should take in order to send out the packet" ? OK, so here's how I understood. Please correct me if I'm wrong. 1. When the kernel receives a packet, it gets the transmit time corresponding to the packet length. xmit_time = rtab[pkt_len>>cell_log]; 2. Then, the kernel sends that packet using xmit_time ? (If xmit_time was like 10 milli sec, it consumes 10 milli sec to sends the packet ? Or does it wait for xmit_time to send it) Is my understanding correct ? > > Andy. > > > > > > _______________________________________________ > LARTC mailing list / LARTC@xxxxxxxxxxxxxxx > http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/ Eme _______________________________________________ LARTC mailing list / LARTC@xxxxxxxxxxxxxxx http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
