TELECOM Digest OnLine - Sorted: Re: Phone Call Routing

Re: Phone Call Routing

John Schmerold (
Sat, 10 Mar 2007 23:37:44 -0600

To date, no one has been able to explain this to me. I'm not afraid of
Google, I have a hunch no one really knows how this works, in fact for
all the reasons Lisa identified (thanks Lisa), it has become a
remarkable feat to get a call connected.

Part of the answer seems to be: Neustar, it seems they serve the same
role as a ICANN plays regarding IP addresses and domains. I've sent a
note to Neustar to see what service they offer to end users wanting to
protect one of their important assets - their phone number.
Ultimately all I'm really after is the knowledge that is required to
help our clients get their number back if they sign with a
Norvergence, then find 1/2 their inbound calls aren't making it
through to order entry.

> On Mar 7, 8:51 am, Sam Spade <> wrote:

>> The switched public network has been around in its present form
>> since the 1950s. There has been huge amounts of material published
>> on the technical workings of the telephone system

> Actually, the question is very reasonable. Since the 1980s the nature
> of the public switched network has drastically changed and much of
> that material is obsolete. Here's why:

> 1) Expense: The "trunk" (physical connection) between two central
> offices was extremely expensive. It consisted of (a) switchgear on
> the front end, (b) the physical wire, and (c) switchgear on the rear
> end. Accordingly, trunks between offices rationed and carefully
> planned -- just enough to meet demand but not more so. The phone
> company worked hard to maximize capacity of the physical wire (carrier
> circuits) and switchgear.

> But after the 1980s the costs dropped dramatically. The head and
> rear terminal equipment became cheap. Fiber optic with very high
> capacity replaced copper and coax. Suddenly capacity was not a big an
> issue anymore. Everything was so cheap there could be waste.

> 2) Politics: The old model had the Bell System handling everything.
> The 1983 model had the local Bell companies handing off toll calls to
> dedicated toll carriers (AT&T, MCI, Sprint, etc.)

> But further deregulation allowed local companies access, too. Bell
> (that is, successors to Bell) might own the physical line between your
> house and the C.O., but once inside it was immediately handed off to a
> new company that did the switching instead. (Bell had to spend a
> fortune building extensions to C.O.s to house lockable rooms for new
> switchers).

> Non-Bell companies might lease lines and switching from Bell or own
> their own. Bell might lease stuff from non-Bell companies, indeed,
> they often now sub-contract out repair and installation work. (If you
> see a plain truck with a small stick-on Bell company sign instead of
> fully painted, that's probably a sub contractor.)

> 3) Many people use their cell phone or cableTV phone as their line.
> The routing is completely different for those systems.

> 4) New services: We have new stuff like DSL and FIOS.

> So, the question of routing methods today is quite reasonable and
> realistic. With so much deregulation, it is also relevant to know if
> a given carrier, even a "main" one, is good to use.

>> You would learn a lot more my doing a bit of research

> Where would you suggest to research to get _current_ information
> appropriate for a lay person?

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