My guess is that it is a universal system as opposed to an integrated
system.
>
> 26.4K eh? This sounds familiar. This is the speed V.34 modems are reduced
> to if the telco is multiplexing lines on an SLC. There are two basic ways
> to use an SLC.
>
> Say the SLC handles 96 lines. You can run 4 T1 trunks into it (and a 5th for
> backup) and each line gets a DS0. In this case you have a full channel to
> use.
>
> OR, in areas suffering form trunk shortage, places the telco doesn't feel
> they'll make money, etc, you can run *2* T1 trunks (and a 3rd for backup)
> and MUX it so that there are 2 lines on each DS0. Each line gets only half
> a channel. The most commonly reported symptom of this is connect rates
> hit a 26.4K ceiling.
This is absolutely incorrect. This configuration would imply that it is
a mode 2 SLC-96. This is a SLC series 5.
When there are just 2 T1's feeding a SLC, there are only 48 channels
available to the 96 customers on the SLC. So, if all 96 subscribers were
to pick up their phones at the same time, only 48 of them would actually
get dial tone. Mode 2 SLC's function on the concept of Statistical Time
Division Multiplexing.
>
> If this is what the telco has done, you're basically out of luck. Because
> it is 100% legal, and completely within the tarriff. They provide voice
> connections - period - and this system works perfectly for voice calls.
I don't think there is a "mode 2" for SLC series 5.
>
> Of course it destoys any hope of a PCM modem connection (which the telco
> doesn't say they'll provide for anyway, and rightly so) and impacts V.34
> connections on the top end.
A PCM connection has more to do with whether the system is integrated
into the switch and what the ISP uses on their end than the mode the SLC
is running in.
>
> What can customers do for higher rates? Get ISDN if they'll provide it.
> They will guaruntee the throughput. And if it is in an area where DOSBS
> isn't charged per minute they can use ISDN DOSBS, or a modem on a POTS port,
> and get solid connections. Or, if it is somewhere ISDN is actually cost
> effective, just use ISDN.
>
> The telco is under NO obligation to improve this connection if they have
> it setup as above. It provides the service they are obligated to provide,
> and does so quite effectively. This happens a lot in areas with rapid
> growth. They can't bring in trunks fast enough, and MUXing doubles
> capacity immediately.
>
> They do this another way in some areas. In my new house I have 3 POTS
> lines and 1 BRI. There were only 2 pair coming into the house to start,
> that was used for the first POTS line and the ISDN. Well, I'm at the
> end of the line here (literally, one telephone pole up the phone cable is
> capped, end of this circuit run) and they are short on channels. So for
> the two new lines they put them on ONE pair. Ran a new pair to the house,
> and put a DSL box on the outside. They're running some form of DSL (I
> was reading the label in the box while the installer was doing something
> else - it refered to Digital Subscriber Line) down that pair to this box,
> which then splits off two POTS circuits here. Makes me kind of wonder
> if they're going to be offering any pure DSL services in this area...
We use them in our region. They are called UDC's (Universal Digital
Channel) and are built by Raychem. There is an A/D and back using this
box, so PCM connections will not work.
-- Kyle Platts Network Engineer !NTERPRISE Networking Services U S WEST Communications - To unsubscribe, email 'majordomo@livingston.com' with 'unsubscribe portmaster-users' in the body of the message. Searchable list archive: <URL:http://www.livingston.com/Tech/archive/>