coffland@lll-lcc.llnl.gov (Douglas R. Coffland) (12/20/88)
We at Lawrence Livermore Natl. Laboratory are aware of significant price differences between Interlata Carriers, however, in some cases we feel that you may 'get what you pay for'. I am interested in finding out the performance differences between carriers. This is somewhat troublesome since I don't really know the questions to ask. For instance, various carriers have stated reference timing accuracy. This is fine but how can this data be used to determine the amount of noise or lost information on the long distance lines. In more general terms, what are the major performance concerns for long distance carriers, how are they quantified, and if not self explanatory how does the lack of them affect the user? Any references to literature, tips, or past experiences would be greatly appreciated. Thanks, Doug Coffland
w-colinp@microsoft.UUCP (Colin Plumb) (12/21/88)
One way to do a good test of the various interlata carriers is to get a couple of Telebit Trailblazers and let them measure the noise spectrum. They'll deliver 511 dB readings (to .1 dB, I don't know how much of that is significant) of line noise at about 7.5 Hz intervals, and a 0-100 "line quality index" for lower baud rates. Basically, a (realtively) cheap way of objectively measuring phone line quality. And if you're concerned for data transmission reasons, the mapping onto throughput is direct. If you want to do it seriously, make at least a dozen connections via each of the various carriers, to various places of interest and at various times of day. That should leave you with a feeling for who's best. -- -Colin (uunet!microsof!w-colinp)