Cell Relay Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] Re: Acceptable Cell Loss
In article <D789C4.H2I@sci.kun.nl>, johnk@cs.kun.nl says... > >Let's not mix up cell loss ratio on one operational link, which should indeed >be very low (say << 10^-12), and the cell loss ratio on the end-to-end >connection which can widely vary, depending on the chosen QoS or traffic >class. >Also mind the difference in rate (events per second) and ratio (fraction). >Finally, since cells count hundreds of bits, the bit error ratio and cell loss >ratio will differ in general. > >Depending on the details of the terminal adapter, cell loss ratios up in the >percents (!) seem to be acceptable for phone. > I agree that it depends on the application wheter a loss rate is acceptable or not. But ATM was designed to work on high reliable media, with a very low error rate. Otherwise, in those applications which are sensitive to errors, one bit error leads to retransmitting a complete frame (a lot of cells). Of course, one bit error in plain video or audio signals wouldn't do much harm, but bear in mind that most of the video and audio signals are compressed before sending. A bit error in compressed signals leads to unacceptable noise in the signal (we want to have a clear noise free connection, don't we ?) And because those signals can't be retransmitted, bit errors are even more a burden then within data. BTW: A cell loss ratio of percents is certainly not what we expect from ATM. John -- ____________________________________________________________________________ John Lasschuit Aranea Consult BV tel:+31(0)73441415 j.lasschuit@aranea.nl Reitscheweg 5b fax:+31(0)73441691 5232 BX 's-Hertogenbosch The Netherlands Tele- and Datacommunication Consultancy ____________________________________________________________________________ |
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