[cisco-voip] No More MTP Resources Available

[Ryan Ratliff]

What you describe regarding the supplementary services failing is a  
symptom of "MTP required" set on the gateway and you being out of MTP  
resources.   The only time that setting is required is when you are  
going to some 3rd party H.323 gateways and when you want to use  
outbound FastStart.  If you are going to a Cisco gateway and don't  
care about outbound FastStart then by all means don't require MTP and  
your calls will work fine.

Supplementary services do not require an MTP.

-Ryan

On Jun 6, 2006, at 8:00 AM, Andre Beck wrote:

Hi,

I just hit that issue last week ;)

On Mon, Jun 05, 2006 at 03:17:07PM -0400, Todd Franklin wrote:
>
> We recently converted one of our gateways to H323 because we needed  
> a lot of
> POTS lines and Caller ID, and this appeared to be the only way to  
> do it.

If only Cisco would not go the way of supporting non-overlapping feature
sets on H.323 vs. MGCP. Either you chose MGCP and lack features that are
present with H.323 only or you chose H.323 lacking features that are  
there
with MGCP only...

> Ever since, my CCM in the Windows Event Viewer, shows lots of  
> occurences of
> this message: "No More MTP Resources Available."  Occasionally,  
> after this
> message, we will drop a call, or a phone (oddly enough, in another  
> location
> not attaced to the H323 gateway) will unregister without warning.

This is the worst case. Way before that, you will notice invocations
of Hold or Transfer (and maybe Park and related features) will fail,
the phone's soft buttons just will not do what is expected.

> Is the MTP resource issue related to the H323 thing?

Yep. MTPs are required to provide features like Hold and Transfer on
calls coming into CCM via H.323, as H.323 itself doesn't provide them.
You have to enable it in the gateway/gatekeeper profile, though.

> A friend told me I can add more MTPs by simply installing the software
> on another NT/Win2x server.

First of all you should check how much MTPs are configured on the CCM
itself (Voice Streaming App Service Parameters). It defaults to 48,
while claiming the maximum is 512. Be careful with specifying the max,
my voice streaming service failed to start correctly when I just set
this to 512, it seems to overrun some other internal limits for MOH
ressources if done so. When configuring the number of MTP ressources,
keep in mind that the number you configure is essentially devided by
two, as one MTP is required for each stream direction of a call. So
the default of 48 actually allows you to terminate 24 H.323 calls only.

If you cannot provide enough MTP ressources on the CCM alone (by either
running in the total limit of 512 or even one of the interdependencies
mentioned above) you will have to add external ones. I've not done so
yet, as increasing to 128 was sufficient to terminate my max 60 B- 
channels,
but your installation might require more.

BTW, in Real Time Monitoring Tool/Performance you can nicely monitor
the MTP usage on your CCM up and down.

-- 
                   The _S_anta _C_laus _O_peration
   or "how to turn a complete illusion into a neverending money source"

-> Andre Beck    +++ ABP-RIPE +++    IBH Prof. Dr. Horn GmbH, Dresden <-
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