E1 and DSP resources

Answered Question
Feb 15th, 2012

Hi

I have a cme 8.6 implementation, it uses 2 E1 lines to connect to PSTN, the first E1 is configured with no problems, but when i configured the second with the command "pri time-slots 1-31" got a error that says that i have not enough DSP resourses, that i only have enough resources for 8 slots, so i used 8 (pri time-slots 1-8).

however we need 9 numbers in this line, and i don't want have to buy another DSP chip just for 1 line. My question is if in the E1 line the channels are associated statically with lines? for example:

CH1 ->5551001

CH2 ->5551001

....so on

or the channel and lines are associated dinamically?, and the unique limitation in my setup is that i wont be able to establish a call with the 9 lines at time?

Many thanks.

I have this problem too.
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Correct Answer by babatunde_sanda about 2 years 2 months ago

From PRI experience, I can tell you this channels are allocated dynamically.  And I want to say the same will likely apply for an E1.

If you were to think about it really.  The number of available channels will not necessarily equate the available phone numbers.  Say for instance your carrier allocates 100 TNs or even maybe just 20 TNs to you.  Either ways all the available chanels on your media (E1/T1) will be availble to you except you get something like a fractional T1/E1 but still you will be able to get calls for any of the numbers since the provider will send it to your available connection.  The channels are just transport mediums for your 64k calls.  You wouldn't buy/get 4 E1 connections to get your 100 numbers routed to you.

Moreover that is why it is digital connection.  It is not circuit switched.

You can even test it yourself.  Go to your voice gateway (assuming it a cisco router) and do "

sh voice call sum" and watch your channels.  Make a call to a number.  Watch it use a channel.  Then make another external call to the same number and pick up or simply watch again from the command.  You will see it use another channel.

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Correct Answer
babatunde_sanda Wed, 02/15/2012 - 19:37

From PRI experience, I can tell you this channels are allocated dynamically.  And I want to say the same will likely apply for an E1.

If you were to think about it really.  The number of available channels will not necessarily equate the available phone numbers.  Say for instance your carrier allocates 100 TNs or even maybe just 20 TNs to you.  Either ways all the available chanels on your media (E1/T1) will be availble to you except you get something like a fractional T1/E1 but still you will be able to get calls for any of the numbers since the provider will send it to your available connection.  The channels are just transport mediums for your 64k calls.  You wouldn't buy/get 4 E1 connections to get your 100 numbers routed to you.

Moreover that is why it is digital connection.  It is not circuit switched.

You can even test it yourself.  Go to your voice gateway (assuming it a cisco router) and do "

sh voice call sum" and watch your channels.  Make a call to a number.  Watch it use a channel.  Then make another external call to the same number and pick up or simply watch again from the command.  You will see it use another channel.

jcoralo1987 Thu, 02/16/2012 - 12:57

hi

i configured the E1 with only the 8 channels and it works fine for the nine numbers, so the assignment is made dinamically.

Thank you babatunde, your help was very useful.

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Posted February 15, 2012 at 6:08 PM
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Tags: pstn, pri, dsp, voice, t1, cme, e1, ds0
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