On 23 Nov, 14:47, "Clive D. W. Feather" cl...@on-the-
train.demon.co.uk wrote:

Mizter T writes

Overlays sound like a pretty ugly 'solution', I'm glad it sounds like
they're probably off the cards.

They're a lot better than the alternatives (area splits, like the London
01 - 071+081, and length changing, like Reading 01734-0118), both of
which affect existing customers as well.

But one could argue that overlays will affect everyone in the area in
that they'll force people into dialling an 11 digit number for some
local calls. Indeed in the US I've read that the FCC mandates 11 digit
dialling in areas where there are overlays so as to ensure that no
telco has a competitive advantage over any others simply because they
can offer new subscribers numbers in the the older established area
code.

Changing area codes shouldn't be done lightly, but my gut feeling is
that it's preferable to overlays.


I wonder whether the earlier projections for a squeeze on available
numbers aren't a bit out now. I'd think there's far less demand for
second residential lines nowadays, as people don't want dedicated
lines for fax machines or dial-up internet access. Of course, business
still likes direct-dial numbers which certainly has driven demand for
new numbers in certain locations.

The overwhelming cause of number shortages is new telephone companies,
because numbers are allocated in blocks of 1000 (formerly 10,000). So if
five new VoIP providers start up and want numbers in Cambridge, that's
5,000 numbers gone just like that (and a couple of years ago, 50,000
gone just like that).


May I enquire what the forthcoming central portability database is all
about?

Let's suppose you started with a BT line, but then moved to Virgin Media
while keeping your number. At present, when somebody calls you, the call
is sent to the BT exchange handling your old (now removed) line. This
notes that you're a ported customer, sticks a prefix (say 527724) on the
front of your number, and re-injects the call into the trunk network.
This prefix means that it's now routed to the VM exchange handling your
line, which can deliver the call to you. This technique is called
"onward routeing" and is relatively inefficient.

Yes, I'd heard about this method.


The new database will contain every telephone number in the UK together
with a code indicating which exchange it is connected to. When someone
calls you, *their* telephone exchange looks up your number in the
database and adds the code on the front. The rest of the network will
then route on the basis of the code, not your number.

OK. It's almost like each exchange will have the equivalent of their
own DNS server.


One effect of this is that ported calls are routed more efficiently. It
also means that numbers don't need to be allocated in blocks - there are
no problems with giving consecutive numbers to different telephone
companies. And, finally, it makes it trivial to port your number to a
different place.

Does this mean that say a London number could be ported to Cambridge
when someone moves? Would that actually be allowed?

I've certainly lost numbers when moving in London, between different
exchange areas. It'd have been handy to have kept the number - but
that would have broken the number/place linkage, and I also find it
most useful being able to have a broad idea of which area a particular
phone number relates to. Of course, with VOIP, there's no guarantee
that a number relates to any particular place these days - especially
as one can now port a geographic landline number to a VOIP provider -
but nonetheless it is still broadly true that much of the time the
number relates to a farily specific area (especially with regards to
BT geographic numbers).

I'm almost of the opinion that VOIP numbers should all occupy their
own number range (such as 04), rather than masquerade as geographic
numbers. Perhaps this ultimately shows that I'm living in the past,
and any notion of a firm link between telephone numbers and an area is
now old hat!

Anyway, thanks for your reply Clive.

On Fri, 23 Nov 2007, Clive D. W. Feather wrote:

In article
, Mizter T
writes

May I enquire what the forthcoming central portability database is all
about?

Let's suppose you started with a BT line, but then moved to Virgin Media
while keeping your number. At present, when somebody calls you, the call
is sent to the BT exchange handling your old (now removed) line. This
notes that you're a ported customer, sticks a prefix (say 527724) on the
front of your number, and re-injects the call into the trunk network.
This prefix means that it's now routed to the VM exchange handling your
line, which can deliver the call to you. This technique is called
"onward routeing" and is relatively inefficient.

Hang on, what is it that gets re-routed? Do the ATM cells carrying the
actual audio signal go to the old exchange and get forwarded, or is it
some kind of initial handshake that gets forwarded, with the audio then
travelling over a sensible path? I can see that the former would indeed be
very inefficient, but the latter doesn't seem to bad.

If it is the former, is this central database the right solution? How
about a redirection, like the HTTP 3xx status codes, where the old
exchange responds to the call setup handshake by saying "sorry old bean,
that number's now at exchange 527724", and the initiator then gets in
touch with the right exchange directly? I suppose that would still mean
the old exchange gets bothered by lots of annoying requests, which the
centralised approach avoids, but i imagine the aggregate cost would be
similar to that of using the database - less, in fact, since the majority
of calls will avoid the redirection step, whereas with the database, every
call makes a round-trip to it.

Although the database approach is more general and elegant, and probably
makes more sense long-term. It's basically adopting the internet's model
of having domain names sit on top of IP numbers with the DNS in the
middle. As the old computer scientists' proverb goes, there's no problem
that can't be solved with one more layer of abstraction.

tom

--
The whole of science is nothing more than a refinement of everyday
thinking. -- Albert Einstein

In article
,
Mizter T writes
But one could argue that overlays will affect everyone in the area in
that they'll force people into dialling an 11 digit number for some
local calls.

But I already dial an 11 digit number for some local calls. Not all
local calls are in the same area code.

These overlays will clearly be different area codes, so there's no
problem there. To that extent, it would be no different to splitting an
area code, except everyone with an existing line will be on one side of
the split.

Indeed in the US I've read that the FCC mandates 11 digit
dialling in areas where there are overlays so as to ensure that no
telco has a competitive advantage over any others simply because they
can offer new subscribers numbers in the the older established area
code.

Yes, but in the US it's usually the case that the local call area is
smaller than the area code, not bigger.

The new database will contain every telephone number in the UK together
with a code indicating which exchange it is connected to. When someone
calls you, *their* telephone exchange looks up your number in the
database and adds the code on the front. The rest of the network will
then route on the basis of the code, not your number.
OK. It's almost like each exchange will have the equivalent of their
own DNS server.

In fact, it may be done through DNS.

One effect of this is that ported calls are routed more efficiently. It
also means that numbers don't need to be allocated in blocks - there are
no problems with giving consecutive numbers to different telephone
companies. And, finally, it makes it trivial to port your number to a
different place.
Does this mean that say a London number could be ported to Cambridge
when someone moves? Would that actually be allowed?

Possible, yes. Allowed? Would depend on the provider of the line in
Cambridge. It's legal to have an out-of-area number *if* the subscriber
explicitly asks.

I'm almost of the opinion that VOIP numbers should all occupy their
own number range (such as 04),

055 is allocated for this purpose.

rather than masquerade as geographic
numbers. Perhaps this ultimately shows that I'm living in the past,
and any notion of a firm link between telephone numbers and an area is
now old hat!

As I said above, you're allowed a (say) 01223 number if you're *in*
Cambridge or *want to be presented* as being in Cambridge.

--
Clive D.W. Feather | Home:
Tel: +44 20 8495 6138 (work) | Web: http://www.davros.org
Fax: +44 870 051 9937 | Work:
Please reply to the Reply-To address, which is:

In article , Tom
Anderson writes
This technique is called "onward routeing" and is relatively
inefficient.
Hang on, what is it that gets re-routed? Do the ATM cells carrying the
actual audio signal go to the old exchange and get forwarded,

Yes, except it's not ATM cells, but a timeslot in a PDH or SDH line.

If it is the former, is this central database the right solution? How
about a redirection, like the HTTP 3xx status codes, where the old
exchange responds to the call setup handshake by saying "sorry old
bean, that number's now at exchange 527724", and the initiator then
gets in touch with the right exchange directly?

That would be another approach, yes. But it would require a new protocol
to be added to the existing signalling, which is not an easy job. The
lookup can be done as an add-on.

In addition, technology changes mean that, in the future, the call
control is being done elsewhere than the local exchange anyway. So a
lookup is taking place already.

I suppose that would still mean the old exchange gets bothered by lots
of annoying requests, which the centralised approach avoids, but i
imagine the aggregate cost would be similar to that of using the
database - less, in fact, since the majority of calls will avoid the
redirection step, whereas with the database, every call makes a
round-trip to it.

The central database also solves something called the "Atlantic Telecom
problem".

Suppose that Joe Bloggs sets up a new telephone company and strings
cables around the town. He gets a number block and assigns numbers to
customers. He's cheap, so you decide to use him.

After a while you get fed up with the bad line quality and customer
service, so you decide to move to BT. You don't want to have to tell
everyone a new phone number, so you port to BT. All your incoming calls
go via Joe Bloggs Telecom (or, with your idea, involve a message back
from JBT), but that doesn't affect you.

Then Joe goes bust. The electricity gets cut off and his telephone
exchange stops working. You're not a customer, so you don't care. Right?
Wrong! You stop getting phone calls, because they all route towards the
JBT exchange and hit a dead end.

This actually happened some years ago with a company called Atlantic
Telecom. Their former-but-ported-away business customers were *not*
happy with the results.

A central database solves this problem.

--
Clive D.W. Feather | Home:
Tel: +44 20 8495 6138 (work) | Web: http://www.davros.org
Fax: +44 870 051 9937 | Work:
Please reply to the Reply-To address, which is:

On Fri, 23 Nov 2007 23:00:24 +0000, "Clive D. W. Feather"
wrote:

In article
,
Mizter T writes
But one could argue that overlays will affect everyone in the area in
that they'll force people into dialling an 11 digit number for some
local calls.

But I already dial an 11 digit number for some local calls. Not all
local calls are in the same area code.

These overlays will clearly be different area codes, so there's no
problem there. To that extent, it would be no different to splitting an
area code, except everyone with an existing line will be on one side of
the split.

Indeed in the US I've read that the FCC mandates 11 digit
dialling in areas where there are overlays so as to ensure that no
telco has a competitive advantage over any others simply because they
can offer new subscribers numbers in the the older established area
code.

Yes, but in the US it's usually the case that the local call area is
smaller than the area code, not bigger.

The new database will contain every telephone number in the UK together
with a code indicating which exchange it is connected to. When someone
calls you, *their* telephone exchange looks up your number in the
database and adds the code on the front. The rest of the network will
then route on the basis of the code, not your number.
OK. It's almost like each exchange will have the equivalent of their
own DNS server.

In fact, it may be done through DNS.

One effect of this is that ported calls are routed more efficiently. It
also means that numbers don't need to be allocated in blocks - there are
no problems with giving consecutive numbers to different telephone
companies. And, finally, it makes it trivial to port your number to a
different place.
Does this mean that say a London number could be ported to Cambridge
when someone moves? Would that actually be allowed?

Possible, yes. Allowed? Would depend on the provider of the line in
Cambridge.

They can't usually get out of it, providing it has been a requirement
since 2002-ish :-
http://www.ofcom.org.uk/telecoms/ioi...num_port_info/

It's legal to have an out-of-area number *if* the subscriber
explicitly asks.

IIRC it is an "out of area" number (and thus chargeable) if it
involves a new line and a "foreign" number which has not been brought
in by a removing subscriber, otherwise it is merely a use of the
number portability facility.

I'm almost of the opinion that VOIP numbers should all occupy their
own number range (such as 04),

055 is allocated for this purpose.

rather than masquerade as geographic
numbers. Perhaps this ultimately shows that I'm living in the past,
and any notion of a firm link between telephone numbers and an area is
now old hat!

As I said above, you're allowed a (say) 01223 number if you're *in*
Cambridge or *want to be presented* as being in Cambridge.

In article , Charles Ellson
writes
Does this mean that say a London number could be ported to Cambridge
when someone moves? Would that actually be allowed?
Possible, yes. Allowed? Would depend on the provider of the line in
Cambridge.
They can't usually get out of it, providing it has been a requirement
since 2002-ish :-
http://www.ofcom.org.uk/telecoms/ioi...num_port_info/

If you work your way through the actual definitions in the regulations,
you'll find that "portability" applies *at the same location* as the
original number.

--
Clive D.W. Feather | Home:
Tel: +44 20 8495 6138 (work) | Web: http://www.davros.org
Fax: +44 870 051 9937 | Work:
Please reply to the Reply-To address, which is:

On Fri, 23 Nov 2007 01:48:57 -0800 (PST), John B
wrote:

Landlines are only an issue because the numbers after "01" and "02"
mean something, which means you can't (e.g.) fill the demand for new
numbers in London by using the spare capacity in the 01620 range (I'm
guessing there are rather fewer than a million landlines in North
Berwick...).

Well, you *could*. All you'd need to do, assuming the modern
exchanges can be modified to cope, is to do away with STD codes.
They're of limited relevance these days anyway, as I recall another
poster said earlier in the thread.

Neil

--
Neil Williams
Put my first name before the at to reply.

In article ,
(Clive D. W. Feather) wrote:

rather than masquerade as geographic
numbers. Perhaps this ultimately shows that I'm living in the past,
and any notion of a firm link between telephone numbers and an area
is now old hat!

As I said above, you're allowed a (say) 01223 number if you're *in*
Cambridge or *want to be presented* as being in Cambridge.

Until Cambridge runs out of numbers and we get an overlay!

--
Colin Rosenstiel

Mizter T wrote:
On 23 Nov, 14:47, "Clive D. W. Feather" cl...@on-the-
train.demon.co.uk wrote:
Mizter T writes

Overlays sound like a pretty ugly 'solution', I'm glad it sounds like
they're probably off the cards.
They're a lot better than the alternatives (area splits, like the London
01 - 071+081, and length changing, like Reading 01734-0118), both of
which affect existing customers as well.

But one could argue that overlays will affect everyone in the area in
that they'll force people into dialling an 11 digit number for some
local calls. Indeed in the US I've read that the FCC mandates 11 digit
dialling in areas where there are overlays so as to ensure that no
telco has a competitive advantage over any others simply because they
can offer new subscribers numbers in the the older established area
code.

pedantIt's only 10 digits to make a local call in the states, 3 digit
area code plus 7 digit number. The "1" to access the long-distance
network may be omitted when making local calls from a land line (and
must be omitted in Texas,) and may be omitted on any call from a
mobile./pedant

Some of this is that there is no segregation between mobile, voIP, and
land line numbering in the American system, so as more and more people
get mobiles, the crunch is continuing.

Until overlays started, the standard was 7 digits (or fewer, in some
small towns) for local calls, "1"+10 for long-distance. (And "1"+7 for a
while for long-distance calls within the area code.) Where local calling
areas crossed area code lines, pains were taken to prevent the same
prefix being used in the same local calling area. This got to be
troublesome in places where a major metropolitan area straddled an area
code line (usually because of a state line running through the
metropolitan area; codes are specific to one and only one state.)

It's a bit of a hodgepodge now. If one's local calling area is entirely
within a single area code, without overlays, 7 digits is still the
minimum to dial a call. If there is an overlay, or in some places where
local calling includes two or more area codes, 10 digits are required
for all local calls. In some places with a geographic split only, and no
overlay, it's 7 digits within your area code and 10 outside (e.g., calls
in Kansas City, Missouri must be dialed xxx-xxxx, but calls to Kansas
City, Kansas side must be 913-xxx-xxxx.)

With the university crowd, everyone's main phone is their mobile and the
numbers are almost universally from "back home," so 10 digits is pretty
much the standard for them. But I'm not looking forward to the
inevitable day North America has to add a digit to their phone numbers,
since it's been using the relatively rigid (xxx) xxx-xxxx format since
intercity direct dialing was introduced.

John Rowland wrote:

I'll keep an eye out for more fanshafts and email you when I find
them.

I found an impressive beast today... I thought it was an abservatory
telescope housing when I first saw it. I'm not sure if it's a substation or
a fanshaft.

http://maps.live.com/default.aspx?v=...9243&encType=1