Looking for STCAPP documentation

[Hunor Szombatfalvi]

Hello Everyone,

I recently had to troubleshoot a digit manipulation issue on some FXS ports for a gateway controlled by SCCP (STCAPP) and while I figured out that the manipulation should be done on the call manager I was left with some questions about STCAPP that I can't really find any answers for in any documentation.

As I found out with digit manipulation, it seems that any method defined on the gateway is completely ignored, whether if this is set on voice-port, dial-peer or globally on the gateway, yet I can't find a cisco document actually saying this would be the case.

This raises the question, what else is impacted and how?

There's also the fact that if you ever do debugs that show which dial-peers are used, if using STCAPP the inbound dial-peer will always be shown as dial-peer 0 (I have found some references to this, but it was decently well buried)

There seems to be plenty of docs out there saying how to set it up, but I would really like something that goes a bit in-depth in STCAPP covering it's entire behaviour, and I can't seem to find this.

[Nithin Eluvathingal]

For sccp and mgcp configuration digit manipulation will be from CUCM. 

you can configure VG using h323/sip and u can use dial-peers.

what kind of digit manipulation are you looking with this gateway?

[Hunor Szombatfalvi]

I've already solved the issue and I figured out that digit manipulation should be done on the CUCM with SCCP, and yes, I know that H.323/SIP would allow me to do it on the gateway. There is no actual issue to troubleshoot.

What I would be looking for is any documentation that actually says this, that no digit manipulation is possible when using SCCP on the gateway, since most of the commands can still be applied in IOS, they just have no effect.

I'm interested to see if there is any other limitation that I should be aware of, or alternatively, if someone knows any other caveats to look out for?

[Maren Mahoney]

Is this the kind of thing you are looking for?

In Depth Explanation of Cisco IOS and IOS-XE Call Routing - MGCP and SCCP with Dial-Peers 

"MGCP and SCCP follow their own rules for dial-peers. The only concept they utilize is that they must be configured with the desired voice-port for the call. The rest is handled by the STCAPP and MGCPAPP process"

Maren

[Hunor Szombatfalvi]

That piece of text is the most information I've found on STCAPP, that's also where debugs showing dial-peer 0 is mentioned, but, is that really all there is?

"The only concept they utilize is that they must be configured with the desired voice-port for the call" Is a bit misleading, I mean, a number of settings still can be changed on a voice-port configured to be controlled by STCAPP, caller-id can be enabled or disabled, VAD too, cptone can be changed, etc. however defining a translation-profile while possible is completely ignored.

At this point my working assumption is that any setting that you can modify on CUCM can only be changed there, like for example Fax Relay, but it would be nice to have a list of what gets disabled on the gateway level.

[Adam Pawlowski]

I couldn't find anything either when we were debugging it, we discovered an issue where it exhausted sockets and basically became unusable after some period of time. It wasn't clear to me how it worked, but, my best guess is that since it applies with the "service" command, the configuration is largely not relevant.

It's not TCL I don't believe itself, but it most likely hooks state of the voice port and shunts actions, media, etc to the SCCP application. That being said, there are few configuration options that apply, largely the ones you note for barge, vad, etc and things that apply to the voice-port itself and not how it behaves in relation to call control. My rule of thumb with these is that the port is the device, and following along with other SCCP devices, the buck stops with the call control agent for configuration. If you're configuring a VG, they are rather limited in capability anyway compared to a full voice router which can be frustrating.

I hope you do find something more solid.