--- Greg Stark <gsstark@xxxxxxx> wrote: > > Ed Wildgoose <lists@xxxxxxxxxxxxxx> writes: > > > You need something which works at IP level or above. TCP (level > higher) has > > some stuff, but (I repeat) it basically involves dropping traffic > until the > > sender slows down. There are protocols like ECN, but they are broadly > > unsupported. ICMP stuff is frequently dropped by routers/firewalls > making it > > problematic (look at how difficult it is just to do MTU discovery!) > > ECN is largely there so that *non*-TCP protocols can implement > congestion > control like TCP does. > > The problem that was observed in DRUMS was that UDP based protocols like > the > various streaming audio/video protocols that have cropped up in recent > years > would push any TCP streams out of their way. Routers would drop UDP > packets > but most of them didn't throttle their bandwidth on dropped packets. And > congestion control using dropped packets required every protocol to > implement > its own acknowledgement and windowing infrastructure. The goal was to > have > something simple that could be supported at a lower level. > The problem is data in general, both UDP and TCP. Thought most ppl only have one computer connected to there modem, so high level protocols like ECN are overkill. I therefor recomend that any vendor that creates modems make sure they incoperate flow controle on ALL there inbound traffic. > ECN on TCP connections is a bit superfluous. It could be used to > throttle the > bandwidth being used before it led to dropped packets, but it's unclear > that > would help any. Traditional TCP congestion control is fairly effective > at > grabbing all the available bandwidth anyways. ECN would be accomplishing > largely the same thing that RED accomplishes at much greater expense on > the > router. > > Incidentally, ICMP Source Quench turned out to be a bad idea. Modern > RFCs say > hosts "SHOULD NOT" send them. The problem is that responding to > congestion by > sending more packets exacerbates the congestion. > What about ICMP TTL Expier? Also ECN's data WILL have the same effect? thought I know it's validated that both sides of the connection support ECN. When EVERY one is using it there will be the same type of traffic flow for the congestion state. > > -- > greg > > __________________________________ Do you Yahoo!? Yahoo! Mail Address AutoComplete - You start. We finish. http://promotions.yahoo.com/new_mail _______________________________________________ LARTC mailing list / LARTC@xxxxxxxxxxxxxxx http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
