Media Resources and how detailed they really are

So, I still haven't retaken the CIPT1 exam yet.  I am still retraining to pass that exam with flying colors and since it was so heavy on media resources.  I figured I would put some of my thoughts here for those that may need to take it or simply want to know a bit more about media resources.

Basically, media resources are resources on your call manager that are used for certain aspects of a call.  Things like conferences, media termination points, annunciators, transcoders, and hardware resources of the like as well.  When you first fire up call manager, certain software media resources are already available.  These are inherently unregistered and not available until you turn on the Cisco IP Voice Media Streaming Application service.  Once this gets turned on, the software conference bridge, annunciator, an software MTP becomes available.

Software conferencing resources are very limited to certain codecs.  A person calling in from the outside or even in a different region that specifies a different codec will not be able to participate unless they can use G.711 or wideband.  Someone on G.729 or GSM for instance calling into the conference won't be able to join since CUCM cannot convert that stream.  With that being said, this leads me to my next topic, transcoders.

Transcoders are hardware only resources on your IOS gateway.  These resources convert digital to analog, change over codecs, and can alter packetization ms samples. Essentially, anyone calling into your VoIP network will need a transcoder unless that is provided somewhere else, maybe on their network prior to hitting yours.

These transcoder resources are provided by something called a DSP or PVDM module.  PVDM modules come in three different flavors, one of which is obsolete, the PVDM-1 or just PVDM.  PVDM-2 and PVDM-3s are the currently used hardware resources for transcoding.  These also supply T1/E1 channels as well as CME resources and media termination points (MTPs).

I feel the need to write this stuff since it helps me remember these things even though they are second nature to me by now.  Additionally, I hope to help y'all out as well with this information if you didn't already know or simply want a different way of reading something and seeing something.

Another media resource we spoke briefly about is the annunciator.  The annunciator on CUCM is responsible for playing tones, recordings when you screw up a number, and the barge-in beep when people join Meet-Me conferences.  The annunciator is the ONLY resource capable of transcoding on it's own between G.711a/u, G.729a, and wideband.  This is key to part of the test, as for some reason I was thinking that it could not transcode but it can.  Keep in mind, this is only for it's use and cannot be supplemented as a hardware transcoder for calls.

Conferencing is the second to last topic I am going to cover (there is so much more.....) and is actually quite long so I am going to throw all of this into a nutshell and you can leave comments asking for more info.  On a brief note, there are two different types of media resources for conferences, hardware and software.  Software comes with CUCM and registers the minute you enable the IP Voice Media Streaming Application.  Hardware conference resources are provided by the PVDM modules and can allow callers from different codecs like G.729 to call into a Meet-Me and have a conference with others on a codec like G.711 or wideband.  Software conferencing I have already covered in the above.

Finally, media termination points.  Believe it or not, there are two types but three reside on a CUCM deployment if you use PVDMs, which almost everyone does, not sure why you wouldn't...  First, the software CUCM MTP, second the hardware MTP on the IOS with PVDMs, and third, the software IOS MTP on the gateway.  The software IOS MTP is only used for features like hold/resume and transfer.  It is not capable of handling differentiating codecs and the like while the hardware MTP with PVDMs can handle other features.  CUCM software MTP fulfills the same role local on the server with hold/resume, transfer, barge, etc.  There is a lot more to discuss but I think that will be another blog post as it is getting late and my fingers are getting tired and sore.  To much War Thunder me thinks...