North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: UUNET Routing issues
On Sat, 5 Oct 2002, Rafi Sadowsky wrote: > IvB> Obviously "some" packet loss and jitter are normal. But how much is > IvB> normal? Even at a few tenths of a percent packet loss hurts TCP > IvB> performance. The only way to keep jitter really low without dropping large > IvB> numbers of packets is to severely overengineer the network. That costs > IvB> money. So how much are customers prepared to pay to avoid jitter? > There may be better ways to keep "reasonable" jitter but that depends on > what is "really low" jitter - care to define numbers ? I don't use applications that have jitter requirements, so I'm not in the best position to comment on this. I'd say that with a line utilization of 50% or less, which leads to an average queue size of one packet or less, jitter is "really low". If the level of jitter introduced here is too high, then I don't think the application can successfully run over IP. > IvB> In any case, delays of 1000 ms aren't within any accepted definition of > IvB> "normal". > Ever used a satellite link ? > Practical RTT("normal" - end to end including the local loops at both > sides) starts at about 600msec So then a satellite link with a 1000 ms delay wouldn't be normal, would it? > >>> With these delays, high-bandwidth batch applications will > IvB> monopolize the links and interactive traffic suffers. > I'm assuming TCP since you didn't state otherwise > TCP extensions for "fat pipes"(such as window scaling and SACK) disabled > (as both sides of the TCP connection need to have them) > IIRC the maximum TCP(theoretical)session BW under these conditions > Is less than 1Mb/sec (for 600msec RTT) Ok, so "1 Mbps batch applications" will monopolize the links and interactive traffic suffers.
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