From: Lars Poulsen <[email protected]> Subject: Re: ADSL, SDSL... Sources of Information
Stephen Phillips asks: >"Any info. or sources of info. for worldwide PTT >requirements, and any info. on this technology >itself, for - ADSL, SDSL, etc., would be greatly >appreciated. Thanks. " > At 02:07 AM 6/10/97 -0400, David Drori wrote: >I will not even attempt to describe and compare the various DSL >technologies because the following references do the job perfectly. >... Okay, so he did say "about the technology itself". To me, however, the real question is not "what is xDSL", but "out of the myriad of variations for which there is circuitry available, which versions are actually being deployed, and to the extent that such deployment happens under the wings of telecom administrations, what are the specifications to which they require compliance ?" You do get a little bit into this: >I should mention that HDSL is specified in ETSI document RTR/TM-0306 (Our >copy is version 5, dated June 1996), and in a Bellcore Technical Advisory >(our copy is dated October 1991): TA-NWT-001210 "Generic Requirements for >High-Bit-Rate Subscriber Lines" (a module of TSGR, FR-NWT-000440). My reading is that in the US, total chaos reigns. A few local exchange carriers are conducting some very limited field tests to gauge: - what is the subscriber community's real level of interest, (of course they want it if it's free, but will they pay the same for an HDSL loop as for a T1 ?) - what are the compatibility issues ? (Is the backchannel really useable or do you need to throw away the slow backchannel and use two loops ? If you do, do you need the same split-pair rules as for T1 to limit near-end crosstalk ? Do you have ingress and noise pollution problems if you just throw these pairs into residential bundles ?) - what kind of packaged services would it make marketing sense to build on this technology ? Meanwhile some value-added operators (ISPs, for example) are building services based on leasing dry copper from the local exchange carriers and running ADSL over them. This practice would probably be illegal in Europe and many other parts of the world. I think this list has people who have some experience in this area, and I, too, would be interested in learning from their work, but I'd not be surprised if they are holding on to what is certainly valuable competitive information at this time. / Lars Poulsen [email protected] +1-805-562-3158 OSICOM Technologies (Internet Business Unit) (formerly RNS) 7402 Hollister Avenue Manager of Remote Access Engineering Goleta, CA 93117 Internets designed while you wait
