From: invalid@see.sig.telecom-digest.org   
      
   On 5/22/2022 10:41 PM, Bill Horne wrote:   
   > ...   
   >> ISDN Basic Rate Interface (BRI) is generally no longer available in   
   >> the US. Verizon and I think ATT long ago gave formal notice of   
   >> discontinuance or grandfathering. Maybe Qwest, pre-Century, didn't   
   >> bother, so it may still be on the books there. But few know how to   
   >> provision it. Many of the switches that provided it (mainly 5ESS   
   >> and DMS-100 in the US) no longer are in service. It was useful,   
   >> especially for broadcasters doing remote feeds. It was better than   
   >> a modem for Internet access, and that's what killed it as it was   
   >> coming out in the early 1990s -- the Bells hated the Internet,   
   >> which broke their locality-based business model, and while they   
   >> couldn't attack modem users per se, they could at least attack the   
   >> most obvious Internet user group, non-Centrex ISDN BRI users. Bell   
   >> Atlantic l/k/a Verizon was also fanatical in those days about   
   >> selling Centrex, and saw ISDN BRI as a tool for Centrex feature   
   >> phones, but that was about it. That business has faded out too.   
   >   
   > I don't often disagree with Fred on issues like ISDN, but I'm going to   
   > advance a different theory: I had a chance to test an ISDN line at my   
   > home near Boston, back around 1994 or so, and I was /very/ surprised to   
   > find that getting a 64Kbps connection on either of the "Bearer"   
   > channels was very difficult.   
   >   
   > It turned out that the only solution was to redial several times, and   
   > sooner or later I'd get a 64Kbps connection. After 15 or 20 minutes of   
   > dialing and redialing, I might end up with two 64Kbps "Bearer"   
   > connections to The Well, an ISP which served ISDN customers, and I   
   > could bind them together to obtain a 128 Kbps Internet connection.   
   >   
   > When I investigated, I quickly found out that almost all of the   
   > T-Carrier systems connecting the central office to its Tandems were   
   > not equipped for "8 bit clean" connections. In other words, the   
   > connections from the CO to Tandem offices were designed for the   
   > original T-Carrier "robbed bit" signalling paradigm, and were not   
   > capable of delivering 64Kbps data connections.   
   >   
   > I think Verizon - and probably the other Baby Bells - wanted to avoid   
   > the expense of retraining a unionized workforce to make use of the   
   > 8-bit-clean fiber-optic channels just being introduced at the   
   > time. The company would have had to retrain not only the "CO"   
   > technicians, but also the provisioning specialists responsible for   
   > specifying the number and type of trunks for each CO to use for each   
   > service. Even though ISDN data calls were billed per-minute, the   
   > accountants most likely projected more cost than revenue.   
      
   The 64-kbit data bearer service was, as you note, not widely   
   available.  For it to work, both the transmission systems and the   
   switching systems needed to implement the B8ZS fix to the T1 carrier   
   system specification.  And yes, NYNEX was full of old line cards that   
   only did the not-clean old AMI format. They had upgraded some of the   
   switches to have ISDN but didn't update the trunk network. Also, the   
   inbound ports needed ISDN PRI, which they were initially slow to roll   
   out. They treated ISDN data as "Switched 56", an older data service   
   that accommodated robbed-bit signaling. That was where their tariff   
   came from too, at 8c/minute for data calls.   
      
   There was a work-around, though. I always used "data over voice bearer   
   service" (DOVBS), wherein the network was told it was a voice call and   
   the terminal gear only used the clean 7 bits, for a 56k connection.   
   That not only worked well, but took advantage of the flat rate voice   
   calls on residential lines. Those calls could also terminate into a   
   modem pool that was not on ISDN PRI, just on the older robbed-bit T1   
   trunk service.  When I was setting up DEC's ISDN trial circa 1993,   
   they actually told us to do that, as they had no other way to deliver   
   the calls.   
      
   --   
   Fred R. Goldstein      k1io     fred "at" ionary.com   
     +1 617 795 2701   
      
      
   ***** Moderator's Note *****   
      
   For some reason, "DOSBS" (Data Over Speech Bearer Service) was a taboo   
   subject by 1994: the ISP's that supported ISDN connections all   
   pretended that they had never heard of it, and "bonding," even with 56   
   Kbps *DATA* calls, was likewise a mystery.   
      
   Bill Horne   
   Moderator   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)