North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical RE: Cisco PPP DS-3 limitations - 42.9Mbpbs?
If you are just doing testing, then sending a stream of UDP echos across, using something like a Digital Lightwave is the easiest way of testing, provided your target system will take the traffic (this is a good way to crash most windows boxes, for example). PPP and HDLC both have very little in the way of overhead. The same can be said for c-bit framing. You should be getting something like 96% efficiency, which gets you to the 42.9mb/sec number. PPP has something like 7 bytes of overhead per frame. Various forms of DS3 framing are discussed here: http://www.dl.com/ResearchCenter/Training/t3/t3fund.pdf. ATM, for comparison, will usually max at around 36mb/sec for a DS3. YMMV of course, and in actual operation, due to peaks and 5 minute sampling, you will see lower bit rates. - Daniel Golding > -----Original Message----- > From: [email protected] [mailto:[email protected]]On Behalf Of > Stephen J. Wilcox > Sent: Wednesday, February 20, 2002 11:09 AM > To: Randy Bush > Cc: [email protected] > Subject: Re: Cisco PPP DS-3 limitations - 42.9Mbpbs? > > > > Hmm, reasonable explanation.. > > presumably this can be improved (a little) with increased interface > buffers.. ? and possibly non fifo queuing eg custom queuing in favour of > TCP rathen than UDP/ICMP etc which wont have the backoffs > > Cheers > > Steve > > On Wed, 20 Feb 2002, Randy Bush wrote: > > > > we run HDLC on DS3 and we max at about 40.something too > > > > if you're using five min (or three min) samples, and you're seeing 70%, > > peaks are likely much higher and some users' packets are being dropped. > > by 80%, enough packets are being dropped that users are likely to see > > the effects of exponential backoff. things do not improve above 80%. > > > > randy > > > > -- > Stephen J. Wilcox > IP Services Manager, Opal Telecom > http://www.opaltelecom.co.uk/ > Tel: 0161 222 2000 > Fax: 0161 222 2008 >
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