Path: utzoo!attcan!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!apple!sun-barr!texsun!pollux!killer!vector!telecom-gateway From: westmark!dave@rutgers.edu (Dave Levenson) Newsgroups: comp.dcom.telecom Subject: Re: Modems and LD Carriers Message-ID: Date: 13 May 89 02:42:34 GMT Sender: news@vector.Dallas.TX.US Organization: Westmark, Inc., Warren, NJ, USA Lines: 30 Approved: telecom-request@vector.dallas.tx.us X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@vector.dallas.tx.us X-TELECOM-Digest: volume 9, issue 162, message 5 of 12 In article , gould@pilot.njin.net (Brian Jay Gould) writes: > I have seen numerous comparisons by carriers, of their noise levels (dropping > pins and such). The modem manufacturers specify data rates based upon > noise free lines. > > So... has anyone ever attempted to chart data rate versus carrier? > (for several modem types) We have used three different LD carriers in recent years. Our experience is that each of these (SBS Skyline, MCI, and AT&T) shows significant variation between different calls to the same place, using the same carrier. The variation in data transmission quality varies even more among calls placed over the same carrier to different destinations. The variation between these carriers was no more than the variation between different calls using the same carrier. We also find plenty of noisey intra-lata calls. If the local carrier cannot deliver a clean dial-up circuit across town, how can they be expected to provide a uniformly clean interface to any of the inter-lata carriers? It doesn't matter much how good the toll carrier is if the local carrier is bad. A given circuit is as good as its weakest link, isn't it? -- Dave Levenson {uunet | rutgers | att}!westmark!dave ...the man in the mooney