[Asterisk-Users] OT: "Integrated Access T1" voice problems - is this possible?

[Mark Farver]

On Fri, 2004-12-17 at 16:26 -0600, Kristian Kielhofner wrote:
> 	We are getting pricing and one provider is telling us that they have 
> quality issues with the "Integrated Access" product.  From what they say 
> it sounds like you can have audio dropouts on the voice channels when 
> the data channels are being pushed to the max.  I have never heard of 
> this.  It doesn't seem possible to me, and if at all, probably more of a 
> limitation in the CSU/DSU than in the actual T.  Isn't that what TDM is 
> all about - giving each channel it's afforded bandwidth?
> 

There are a couple of ways of providing data + voice integrated.  

One of my providers uses a Lucent Cellpipe IAD.  As far as I can tell
the T1 coming into our building is ATM, the phone company actually
extends their internal packet network to the Lucent.  It breaks out the
data and voice streams.  (The data as ethernet, the voice as FXS ports,
no T1 voice) Since the voice is packetized and is prioritized on the
Lucent we never see any voice problems.. our data bandwidth decreases as
the number of open voice channels increases.  Now if the provider
forgets to set voice priority on the Cellpipe.. yeah then data can cause
voice dropouts.  We had some problems with using modems on the voice
channels that were resolved by decreasing compression settings on the
voice channels.  This system is nice becuase it is dynamic.. when all
the voice channels are idle we have a full T1 worth of bandwidth, (minus
protocol overhead)

The other method is to provision some of the 24 T1 channels as data,
some as voice.  This is not very dynamic and typically you can only have
one voice call per T1 channel.  So if your maximum number of active
calls is 12, only half the T1 can be used for data... idle voice
channels are wasted.

There is also some dynamic systems that still channelize the T1, but
idle channels are added and removed from a ppp connection in realtime.  

Basically.. there are lots of ways to provide integrated products, and
most phone companies support only one or two.  

In my area T1's are an expensive way to get data services.. its often
cheaper to get a separate DSL line for data, and a T1 for voice.  And up
to about 20 voice lines its cheaper to get copper pairs than a T1.
Wacky.

Of course.. the other solution is just use asterisk as a voip gateway,
buy a big data pipe and iax.cc service to terminate the Voip connection.

Integrated products are pretty new, a lot of the telcos are having a
rough time with them.  My Virginia installation of a Verizon Flexgrow
product took 8 months of back and forth with Verizon before I
surrendered and kept my twice as expensive PRI line.  (Of course they
billed me for Flexgrow the entire time, and I am still waiting for a
refund, or even confirmation the service was canceled)

Mark Farver