Re: IP: Pac Bell says Net use may collapse phone system

["Fred R. Goldstein" <fgoldstein@bbn.com>]

  At 12:05 AM 10/27/96 -0400, James Love wrote:
  
  fg>> I suspect it's around 30-40 hours of originating local calls per month
  for a
  >> flat rate resi subscriber.  But I don't have the real numbers; they're
  >> included in some rate filings, though.  Resi busy hour is the evening.
  
  >                Hours of originating calls?  What I was asking for 
  >was some type of measure of the *capacity* of the switch..   Hours of
  >calls seems not very relevant...   If there are 100 POTS lines hooked
  >up to a switch, how many can pick up the line at one time?
  
  It's not all that simple to roll up into one number.  Capacity can run out
  anywhere.  Telco provisions for some value, but can of course adjust to the
  current requirements.  (Not for free, but for a lot less than they want.)
  
  Residence lines are *typically*, so far as I know, provisioned at around 3-4
  CCS apiece, where 36 CCS means in use all the time.  But switch capacity has
  many dimensions.  In a 5E, for instance, resi POTS lines go onto a line
  concentration module that allows some percentage of lines to be in use at
  once. This was designed for typical voice use, though high-traffic variants
  are now available. Then there are the trunks, which are more likely to run
  out; trunks are typically run to nearby COs with a lot of local traffic, and
  trunks to the toll office, and in a metro area, trunks to the tandem office.
  These can run out too.
  
  Individual business lines and small hunts are provisioned like resi lines.
  Large ISPs more often use ISDN PRI or Channelized T1, which come off of the
  trunk side of the switch.  There can be some intra-switch limits between
  modules, for instance, but trunk ports are assumed, for engineering
  purposes, to be busy almost all the time. Note that different telcos have
  different tariff and installation policies here; some seem to handle this
  better than others.
  
  Off-peak, capacity sits idle. The cost to telco of off-peak usage is bo
  diddley. Not zero, but probably around a mill a minute, if that.  (A "mill",
  of course, is a tenth of a cent.)  Lest we get too smug, though, resi data
  usage has done wonders to create an evening busy hour to complement the
  voice daytime busy hour.  Different COs have different busy hours.
  ---
  Fred R. Goldstein     k1io    fgoldstein@bbn.com   +1 617 873 3850
  Opinions are mine alone.  Sharing requires permission.