🚀 go-pugleaf

In article <2066@brl-adm.ARPA> G.MDP@score.stanford.edu (Mike Peeler) writes:
>In article <975@chinet.UUCP> magik@chinet.UUCP (Ben Liberman) writes:
>>Seem that I recall a figure like 20% trunkage.  If you have 100 subscriber,
>>no more that 20 can be calling out of the exchange (no more than 40 within
>>the exchange - 20 trunks).
>
>The local phone company estimates its average and peak loads and
>allocates capacity as a business decision.
    True.  It's a business decision based on telephone calling pattern
    history.  The decision tends to be made company-wide;  that is, the
    decision is embodied in a standard that says the probability
    of your call being blocked due to no more capacity.  A "typical"
    such standard might be:
    Less than 1% blocking during the busy hour of the ten busiest
    days of the year.

>The percentage of
>calls that can be trunk calls thus varies from place to place.
    Close.  The 20% figure above is, as you correctly imply, a number
    that varies from place to place.  However, it accounts for not only
    the percentage of calls that are interoffice (trunk) calls, but
    also the fraction of subscribers that have a connection RIGHT NOW.
    For instance, where the number is 20%, this could arise from:
    1. Everybody talks all the time; 20% of them are on interoffice calls.
    2. Subscribers talk only 20% of the time, but always call
       other offices.
    3. Some linear mix of (1) and (2).

>
>Trunk capacity increases exponentially with the number of trunk
>lines, not linearly, as at first you might expect.  Figure out
>how much traffic a highway can bear as a function of its width
>in lanes.  That's basically the same thing, and some fancy math
>helps (if you think statistical analysis is fancy math).
    Not really true.
    The highway analogy deals with a very small number of servers
    in the queueing system (say, 1 to 3).  In this range, I agree that
    small increases in servers give large increases in capacity, IF
    your standard is based on blocking probability.  (I noted above
    that this IS the standard used by phone companies.  But it's
    not the only one possible, and probably isn't the one used
    by highway engineers.  If, for instance, you used an average
    server occupancy as your standard, capacity would vary linearly
    with number of servers, for ALL server sizes.)

    In any event, interoffice telephone trunk groups are much larger
    (tens to hundreds of servers).  For this size of group, capacity
    varies pretty nearly linearly with number of servers, for any
    required blocking probability.

>
>Cheers,
>   Mike
Likewise, and Happy New Year!
    Dave