ISDN GW and Telephony

[Martin Koch]

Hi Cristian and all others,

I just wonder about the ISDN GW (Codian and Tandberg MPS) and dial in from ISDN to an alias on h.323

How about the telephony gateway functionality on a number which is defined as a

384kbit video dial in. In most cases I can see that it works out fine, but I also remember

having seen some failed calls before.

So, is it ok to define a 384kbit/s dial in and use it for telephony-only dial in as well or can there be issues

and its better to define a second number with just telephony capabilities?

[sagsheth]

Hi Martin,

i assume you are referring to audio only call through ISDN GW/MPS to a h323 alias.

There should not be any issue to define 384 kbps bandwidth for dial in.

Let consider incoming audio only call that requires 64 kbps. It is matched against ISDN to IP rule having 384 kpbs configured. In that case, it will only use 1 channel from the PRI line.

It should not result into any call failures because of this generic rule.

Hope this helps

-Sagar

[Martin Koch]

Hi Sagar!

Thx for the quick response! I wondered about the signalled ISDN capabilities.

If I see it right they are different if its an ISDN phone, an analog line, a mobile line or whatever source.

So at least I could see doubts to just use a 384kbit/s ISDN Video setting for audio.

[sagsheth · Accepted solution]

Hi Martin,

Yes Signalling & Capabilities differs.

But you don't have to worry about that. The originating call-leg (be it mobile or ISDN or landline) is handled by Telco.

It's their job to transcode and get it to supported format. It will advertise the capsets which are ISDN supported.

The terminating call-leg generated by Telco will land at ISDN gateway, so siganlling and media negotiation will not differ.

-Sagar

[Martin Koch]

I do not really agree with that, a telco will most likely only transport what they are asekd to do

and not really do transcoding (maybe some g711u/a if the call originated in the us and hits europe), rather then

to transport what the originating site is delivering.

So if there is any signalling the isdn gw does not like I still see possible reasons for issues.

So I also assume that it shall work, but I need to exactly know if there is anything which might cause

a failure and if what.

If you say it an official cisco statemant: 368kbit/s video dial ins can also be used without ANY trouble for

pure voice calls on codican and tandberg isdn gw´s then its also fine for me. :-)

Martin

[crisalex · Accepted solution]

Hi Martn,

I can confirm Sagar point of view

A ISDN to IP 384k video dial plan, it's basically setting a maximum limint on the ISDN GW in terms of what is the maximum call rate it will acept.

384kbps video dial plan = I can accept maximum a call at 384kbps, an a call with up to video capabilities. This means that this dial plan will accept without any problem a telephone call, no matter wher it's originated from ( mobile phone, landline, etc...)

The opposite will not work. So if you craete a "telephone" dial plan and you try to call from a video system to it, the GW will reject the call, will not downspead it to a telephone call.

When it comes to signaling this is as follows :

Telephone call - this will be signaled in the ISDN Q.931 Setup message as  "ITU-T Speech 64k for Bearer Capabilities"

Video call - this will be signaled in the ISDN Q.931 Setup message as " Unrestricted digital Data 64k"

Both ISDN Q.931 setup messages will be acepted by the 384 kbps video ISDN to IP dial plan.

We are currently not matching on the call type when it comes to ISDN to IP dial plan. We are looking at improving this and adding this functionality in the next major relase but I can not make any commitments when it comes to an eta for having this available.

Kindly asked to let me know if this helps

Regards