From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Furniss Date: Sun, 02 Jan 2005 01:07:28 +0000 Subject: Re: [LARTC] Shaping traffic on heavily oversubscribed links? Message-Id: <41D74950.5010407@dsl.pipex.com> List-Id: References: <41A5A31B.8010901@expertron.co.za> In-Reply-To: <41A5A31B.8010901@expertron.co.za> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lartc@vger.kernel.org Dimitris Kotsonis wrote: > Justin Schoeman wrote: > >> Hi all, >> >> I am having some fun with traffic shaping, and have run into an >> interesting situation. Here is South Africa, most internet links are >> heavily oversubscribed, which means that in most cases the local link >> is _not_ the bottleneck, and shaping on the local link does not help >> that much... >> > > We have the same problem in DSL lines here in Greece. > > I have found that while the average efective speed on such lines varies, > tha average rate of packets is more or less constant. I have a theory > for this. I believe that the routers that forward the traffic on > congested lines - on ISPs and on the ATM circuits at the telcoms - don't > take the extra time needed to calculate the size of the packets and > distribute the traffic on a per packet basis. This leads to a 'fairness' > among the end receivers based on packets/sec instead of bandwidth. > > To be more specific. In my ADSL line I usually achieve between 20-30 pps > (measured with MRTG). With an average packet size of 1500 this is 20-45 > kbytes/sec. But packets sizes close to the MTU are found on single > ftp/http connections and pretty much nowehere else. Packet sizes of 400 > to 500 are more realistic, especially when p2p programs are involved. > 20-30 packets give 8-10kbytes/sec. You can expect even less when using > voip programs which utilize smaller packets. > > If you find that single a FTP session tends to get more bandwidth thatn > p2p programs or multiuser traffic then you have a simillar problem to > our own. I would suggest that you setup MRTG to monitor packets to > research further into this. It is normal for an FTP download to take over from p2ps the latter are likely to be higher latency, so TCP will let a lower latency FTP grab more bandwidth. Try shaping with HTB and sfq - It should help. > > > >> Does anybody have some tips on shaping such links? How can you get >> interractive traffic if you don't know how much bandwidth to reserve >> for it? How can you give fair access to a link if you don't know what >> the link capacity is? >> > > Well, I am working on one. Since I can't shape bandwidth because it > flactuates erratically with time and usage I decided to shape packets. I > have created a new queueing discipline based on TBF which uses packets > instead of bytes for its tokens and I am allocating a constant > packet/sec rate on each user of my ADSL line. A better solution would be > to create an HTB alike packet-based qdisc for dynamic shaping. > > If you find that you have the some problem as me and you want to > experiment with a packet-based TBF qdisc I can send you a patch for > linux-2.6.8 and iproute2 in this list. > > I would like to here your thought on this anyway ... > > Dimitris > > > > _______________________________________________ > LARTC mailing list / LARTC@mailman.ds9a.nl > http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/ > _______________________________________________ LARTC mailing list / LARTC@mailman.ds9a.nl http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/