Re: Telstra/Uni Lines

Roland Turner (raz@nospam.arrakis.com.au)
Wed, 31 Jul 1996 14:19:53 +1000

At 02:01 PM 7/31/96 +1000, Peter Meric wrote:
>On Wed, 31 Jul 1996, Roland Turner wrote:
>
>> This isn't quite how it works.
>>
>> PSTN (analogue) calls cross the intelligent network as single B-channels
>> (64Kbps). It makes no difference at all whose network it crosses, 64Kbps is
>> 64Kbps, pretty much error free. (Incidentally, this is why V.34 is the end
>> of the road for analogue modems. The Shannon liomit means that the
>> underlying carrier must have at least twice the bandwidth of the signal
>> being carried, thus for PSTN that limit is half of 64Kbps which is 32Kbps.
>> Allowing for a few losses here and there, 28.8kbps is about the limit.)
>
>I don't presume to know all that much about this subject. However, I do
>believe that it makes a difference which carrier you use. If Optus is
>using slower or more utilised switches, then the traffic across that
>network is going to be slower, no?

No. You are confusing routers with switches.

A switched circuit is a switched circuit. If you have a 64Kbps circuit, then
this means that you can move 64Kbps through that circuit. Period.

>This will at least explain why the
>time taken to create a connection (get the other end to start ringing)
>takes longer.
>I'm not sure if this would affect the bandwidth available
>for the connection (I happen to think not).

Call routing time and packet switching time are unrelated in switching
environments.

>As for UTS, I wouldn't think their equipment has changed at all. In fact,
>I'd be shocked to hear that their equipment has changed. The changes should
>not affect UTS' PABX at all--if it did, how would they handle the changeover
>period?

Same way anyone does when they replace PABX equipment.

I have heard conflicting reports on this. Somewhere I had gained the
impression that UTS's external phone connection was already optical, but
someone else suggested that they've only just made the change.

Additionally, Optus doesn't do ISDN. Assuming that the PABX is (and has been
for a while) entirely digital, and further assuming that an intelligent TA
has been handling the ISDN connection, then the only change in switching to
Optus would be the disconnection of Telstra's NTU (ISDN box) and the TA
(roughly, ISDN equivalent of a modem) and the connection of Optus's link
(which is a straightforward serial port).

(Hmm. Problem. If Optus doesn't do ISDN still, then I don't follow how the B
channels are seperated out. The above may be wrong.)

>> The line that you are dialling in with is analogue only to the first
>> optimux/exchange. It is generally safe to assume that it will have the same
>> (analogue) characteristics from call to call, so if you are seeing different
>> characteristics for two different paths into the same modem, the problem is
>> almost certainly arising at the UTS end. Because 9514 is digitial all the
>> way into UTS's premises (I believe) the problem (if indeed it exists) is
>> actually with the equipment on UTS's premises. At a guess, this equipment
>> belongs to UTS and is therefore the domain of ITD.
>
>I agree, up until the UTS bits. The 330 should be digital all the way
>into UTS. If it isn't, and the 9514 is, then surely that's a sad
>indictment on the new service.

Not on the service, on the customer equipment at UTS's end. But possibly
this isn't the case.

- Raz

"It often upsets a man's God fantasies to have (Misquoted? from )
someone shoot down one of his helicopters." (Ben Elton's "Stark" )