Dedicate Channels

[pcromwell]

I have a 2911 Gateway using Isdn PRI E1 connection.

I want to be able to dedicate one of the channels for 1 incoming/outgoing number only.  (This will be a fax line) The other channels can be first come first served

I am thinking this can be done, but I cannot find any examples in docs to show the config.

I guess I need to divide the timelots into groups and have seperate dial peers etc?

[paolo bevilacqua]

Do you actually anticipate that alls 30 channels can go busy ? How many users do you have ? How long you had this in service to make sch an assumption ?

[dksingh · Accepted solution]

Not sure why you want to do this but yes, you should be able to split

the PRI for such purposes but there are few caveats:

- For Chan1 that u want to dedicate for fax, you'll have to ask

  your telco(ISDN provider) to assign it a dedicated DID for inward

  calls.

- Telco should not be routing that DID on any other channel except 1.

- You may need some translations/digit manipulation and/or prefix

   dialing to differentiate the two type of calls which users may find

   inconvenient.

Here's an example on how to split a PRI...use it as a guideline and

modify things as per your requirments and dial plan...

controller E1 1/0

pri-group timeslots 1-31

trunk-group FAX timeslots 1

trunk-group VOICE timeslots 2-30

dial-peer voice 1 pots

incoming called-number .  <--hardcode fax DID being rec. from telco

direct-inward-dial

trunkgroup FAX

description - FAX : access code 77

destination-pattern 77T

dial-peer voice 2 pots

incoming called-number .

direct-inward-dial

trunkgroup VOICE

description - VOICE : access code 78

destination-pattern 78T

In this case, FAX user would dial 77 as an access code and VOICE users would dial 78.

These access codes would 'steer' the call to the appropriate timeslots on the PRI.

Since your case is simpler, u can use another prefix like a 7 or 8 when u dialing from

the fax and let all others dial 9 for outside as usual.

This could be enhanced using Class Of Restrictions (COR) to prevent users dialing out each

other's channels on the PRI.

HTH,

DK

[pcromwell]

Thanks Dilip that's exactly what I need.

[paolo bevilacqua]

Please note that the above sugestion will only work for outgoing calls from router to PSTN.

You cannot control the channel for incoming calls, as it will be always dictated by the switch.

That leads to the following scenario;

1. your users orignate 29 calls as allowed by trunk-group definition

2. A 30th call comes in, it voice not fax and must be accepted.

3. 31th call comes in, fax call, but all channels are now busy.

Also note from above suggstion:

- Telco should not be routing that DID on any other channel except 1.

No telco in the world will even consider such a request !

What you want to do, is not easily doable !

[dksingh]

Yes, GW/IOS side has no control over which channel the

incoming call comes in on and hence those caveats.

It can be done as long as the PRI is ordered properly.

Switches are programmable and do let u split the PRI

in group(s) of DS0s and assign a DID or a range of DID.

As long as telco can fulfil that, the config will work fine.

[paolo bevilacqua]

I stand my statement by experience:

No telco in the world will make any special channel arrangement on PRIs.

If you have a real expereince otherwise, post it here.

[dksingh]

Yes, I can say that I have helped both telco and customers

configure such feature in the past. Not common at all but

doesn't mean that if we have not seen something its not

happening.

[paolo bevilacqua]

Let's await for the OP to report on his experience asking a special channel arrangment in his country.

[muranskycotech]

I agree... most telcos aren't very accommodating unless you just happen to get someone in a higher level support position that's knowledgeable and willing to help you. I wouldn't say impossible, but certainly uncommon.

Honestly, if the OP has that high of a need for a dedicated fax line, wouldn't they be better off having a simple copper line attached to an FXO port and go from there?