When to Use VCMs

[TheMitelGuy]

Does this remain true?

VoIP/VCM Channels
Though linked to the IP Office via a LAN connection, voicemail does not use VoIP VCM channels. The Voicemail Server is seen as a device on the IP Office's TDM telephony interface.
• Calls to/from voicemail involving non-IP trunks and extensions do not use VCM channels.
• Calls to/from voicemail from IP trunks and extensions do use a VCM channel.

It's been years (2000) when I was last trained on this product - when is it again that we need to use VCMs? I know it used for TDM to IP. I'm thinking if I'm using all digital sets and no IP sets, and I wanted to use VM Pro, I would not need any VCMs (based on the information that Avaya has provided above).

Thanks.

 

[kwing112000]

You are correct. No VCM for voicemail. You need VCM when you have any IP endpoints or trunks. Including IP softphone or multisite connections over IP.

 

[TheMitelGuy]

So here's a weird (extremely rare) configuration, but it will help me fully remember.

If I have a IP 500, 5x IP Phones and no TDM components (i.e. no analog/digital phones, or trunks) would I still need a VCM? In other words, I'm using using IP Phones for calling between each other? I'm thinking yes, I would still require a VCM.

 

[kwing112000]

I am not 100% sure but i would say yes. because if you need to do any kind of codec conversion you would need it. If your trunk was 729 and your phones 711 then i think you would need it. I am not 100% sure about this. I have not tried it or heard of it.

 

[robboardman]

on an all ip network

ie ip phones and trunks, alothough you would think you wouldn't need VCMs they are still used for call setup

so you would need the total amount of VCMs required for concurrent call setup

and for speaking the the voicemail system

Robb

 

[IPOfficeIreland]

you always need a vcm resource. if calling from ip to ip (e.g. sip to ipphone or ipphone to ipphone) then the device uses the vcm to establish the call but releases it immediately. So with 5 ip phones then only minimum vcm resources required.

incoming calls over sip also use vcm during ringing but are released when answered by ip device. remain used with tdm device.

1 last thing, all said and done vcms may still remain in use even with ip to ip if you are using different codecs on both devices.

The best thing to check vcm usage is open Monitor, System, enable Development tracing, now you can select from Tab up top-Tracing options, VCM Rescoures. This will give you live monitoring of usage and codecs, etc.

cheers

 

[sizbut]

you quoted the answer yourself. The voicemail server is treated as a TDM side device. IP phones need a VCM when talking to an TDM side device. Join the dots.

And as the others have said even in an IP device only system VCMs are still needed for actions such as call setup.

Fundamentally the IP Office dates from a time when IP phones were rare and TDM rules the telephony side, hence the VCM being an add-on rather than standard (except the SOE). The IP in its name was more to do with data routing for PC's.

 

[AndrePa]

TheMitelGuy

You need VCMs for IP trunks/phones period!
If using 44xx/64xx phone it will use 1 VCM per line.
If using 46xx phone, at startup 1 VCM will be used, then released, using no VCMS! If You put the call on Hold, then it will use a VCM again.
If Your using 5 IP phones only, You can get away with as few as 4 VCMS, otherwise You would want 8-16+ vcms for 5 tdm/analog phones on system.

Andre