asterisk users - Dec 2004 - T-1 vs channelised T-1?

OK. Now I show my ignorance.

What's the difference between a T-1 and a channelised T-1? I see that
Covad's voip service (formerly GoBeam) requires a channelised T-1. Then
I read recently on the list that many T-1s being installed are actually
HDSL....which would be not a T-1 at all...right?

Michael
--
Michael Graves                           mgraves@pixelpower.com
Sr. Product Specialist                          www.pixelpower.com
Pixel Power Inc.                                 mgraves@mstvp.com

o713-861-4005
o800-905-6412
c713-201-1262

A T1 is made up of 24 64kbps channels (actually they are just timing
slots on a single channel). When used for data you can use all channels
or just a few, the CSU/DSU is the device that is configured for what
channels are used.

In voice you can use CAS t1, where each 64 channel has inband signaling,
or PRI (more common in the US) where 23 channels are data stream only
and 1 channels is used for signaling for all of the other channels.

With some integrated access you dedicated some channels for voice, and
others for data, not dynamically allocated bandwidth. In this scenario
the voice is usually TDM, not VoIP, although it can be done with voip if
you wish to prevent data from interfering with the voip traffic, but
there are better ways to accomplish that.

Many telcos now us HDSL to provision DS1 (T1) level service, while the
data stream between the NIU and the CO are different, the customer
interface at the Telco are identical, so HDSL and DS1 and T1 are all
synonymous in this example. There are other uses for HDSL, not just T1
provisioning.

This is all background info, and does not answer the question about what
covad is requiring, and I can not imagine why they would specify
channelized T1, as far as I know you have to have a Covad data T1, so it
really does not matter anyways. Am I wrong here?
> -----Original Message-----
> From: asterisk-users-bounces@lists.digium.com 
> [mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of 
> Michael Graves
> Sent: Friday, December 17, 2004 4:45 PM
> To: Asterisk Users Mailing List - Non-Commercial Discussion
> Subject: [Asterisk-Users] T-1 vs channelised T-1?
> 
> OK. Now I show my ignorance.
> 
> What's the difference between a T-1 and a channelised T-1? I 
> see that Covad's voip service (formerly GoBeam) requires a 
> channelised T-1. Then I read recently on the list that many 
> T-1s being installed are actually HDSL....which would be not 
> a T-1 at all...right?
> 
> Michael
> --
> Michael Graves                           mgraves@pixelpower.com
> Sr. Product Specialist                          www.pixelpower.com
> Pixel Power Inc.                                 mgraves@mstvp.com
> 
> o713-861-4005
> o800-905-6412
> c713-201-1262
> 
> 
> 
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>

> In part I'm trying to figure out at extactly what point it 
> might make sense for a small office to consider a T-1 vs DSL 
> incombination with POTS or BRI. Also, I'm just very curious.
> 
> Michael
> --
> Michael Graves                           mgraves@pixelpower.com
> Sr. Product Specialist                          www.pixelpower.com
> Pixel Power Inc.                                 mgraves@mstvp.com
> 
> o713-861-4005
> o800-905-6412
> c713-201-1262
> 
Keep in mind that a 1.5mbps T1 is a full duplex circuit, 1.5 up and 1.5
down at the same time, you need a 3mbps DSL line to get 1.5mbps up and
1.5mbps down at the same time. Voip traffic requires 2 way data streams,
wheras TYPICAL internet use is more down than up.

I see by your 713 area code you are in houston, cbeyond offers a 5
line/1.5mbps integrated voip solution over t1 for ~$500/month. That is
about the same cost as a dedicated data t1 from most providers.