CPMG vs CPMGS

The CPMGS has secure, or encrypted DSP's. Typically seen in government applications.

KCFLHRC,

Thanks for the info. I actually have a different question if you don't mind. We have installed 2 new 1000E's recently and I have noticed that our external US Robotic modems don't work. The lines for the modems come off the 1000E's. At first I thought that maybe the modems were bad but the modems work fine with a flat business line. They also work fine off our 1000M. The 1000m is connected to our 1000E via SIP Trunks. My suspicion is I'm having problems coming across the SIP trunks to the 1000E. Have you heard of modems not working with SIP trunks?

Any Insight is Appreciated.

I have not heard of that issue. I will tell you that I have found MGC cards support a maximum speed of data transmission of 14,400. I have seen this issue with fax machines. It could also be a codec issue if you are using anything other than G729 which I believe is uncompressed. The compressed codecs seem to cause issues with faxing etc., but the fact remains, the MGC portion of your CPMG will only support a max speed of 14,400.

The modems that I programmed were set for 9600. The other odd ball thing about this is that if I hook up an analog line from the 1000E to my PC modem and dial up to the PBX modem it will work ONLY if its on the same card. If the TN's are in seperate loops(Chassi's) then they won't talk.

What you describe is the exact problem I encountered. When crossing MGC's your maximum rate is 14,400. I would check your codec settings in your MGC configuration and also make sure MSEC is turned off, that is media security.

I'll check those setting shortly. I did an enhanced trac last night and we are using G.711 Codec.

After a simple google search I believe G711 is what you want, however a lot of machines will try and auto baud at a higher rate that 14,400 and this will inevitably cause you issues. You need to lock the machine down to 14,400 if possible. If not put that analog device in the same media gateway as your trunking, that way it will not use a DSP

G711 supports up to 64k, which is definitely what you need for your modems or faxes. I had an issue with a security system and fire alarm system. I ended up moving an analog card into the media gateway where my PRI was and it solved the problem. Good luck

It's funny you mentioned this. I had another site act like this and I had to install another analog card in the main cabinet where the T-1's were. The modem worked fine after that. Bad thing about the current site is that I'm using SIP trunks to our CS1000M's. I guess I will be installing PRI's. I really appreciate your help!

Yep, unfortunately using the SIP trunks to an analog device you will always be using a DSP resource.

I found this document, maybe it will help you.

FAX Configuration Recommendations in the Call Server 1000
Fax settings and performance over VoIP solutions vary depending on the network configuration. In order to achieve a successful faxing environment the VoIP solution has to be engineered properly. Following are configuration and network design aspects that need to be taken into consideration when implementing faxing in VoIP solutions:

CODECs:

T.38:
• Older fax machines use V.21
• For lower speeds (V.21) protocol T.38 should be used in the VoIP segments of the call.
Modem Pass Through (G.711):
• Newer fax machines use Modem Protocols to achieve higher speeds (V.34)
• The Modem pass through feature is intended for modems and high speed faxes employing V.34, it uses clear channel G.711 over the VoIP segments of the call.
• The Modem Pass Through will detect the phase reversal tone negotiation used for higher speeds and will tell the DSPs involved in the call to disable echo cancellation and all other non linear components.
• MPTD class of service for analog fax lines allows the change of the DSPs between T.38 for lower speeds and G711 for higher speeds.
• MPTD must be used on ALC (Analog Line Cards) units connected to Fax machines when there are trunk cards present in same and other IPMGs that connect to PSTN. This is required to support T.38 and V.34 faxes that could originate or terminate from/to the PSTN.
• In order for MPTD to work a system bandwidth strategy of BQ (Best Quality) must be used.
• The MPTA class of service should be used only for Modems, it will force all calls to use G711.
• When going to the PSTN we have no control over the far end, however if the far end supports T.38 and Modem Pass Through speeds of 33.6 should be achievable.

ATTENTION
Fax performance at higher speeds (33.6) requires that all network elements are properly engineered to support it. When high speed faxes can not be achieved with a consistent success rate it is recommended to set the fax units at a lower speed (14.4).

Scenarios:
Typical scenarios for Faxing in a CS1KE solution:
a) Two faxes connected to analog lines in the same MGC
b) Two faxes connected to analog lines in different MGCs of the same CS1KE
c) One fax connected to analog line in an MGC to IP Trunk to a remote system with a fax
d) One fax connected to analog line in an MGC to Analog trunk in same MGC to PSTN (Local or LD) fax
e) One fax connected to analog line in an MGC to Digital trunk in same MGC to PSTN (Local or LD) fax
f) One fax connected to analog line in an MGC to Digital trunk in different MGC of the same CS1KE to PSTN (Local and LD) fax
Please note that the following scenario is not supported for faxing:
- One fax connected to analog line in an MGC to Analog trunk in different MGC of the same CS1KE to PSTN (Local or LD) fax
Data Network:
Depending on the fax scenarios fax calls can traverse the IP network, either internally (ex: MGC to MGC) or externally (ex: IP Trunks). It is important to engineer the data network to support the following:
• Media card configuration:
— G.711/T.38 codecs
— 20 ms packet size
• Round trip delay must be less than 50 ms
• packet loss must be less than 0.5%
• V.34 rate (33.6 kbit/s) as long as far end supports Modem Pass Through feature
• Mean Jitter is less than 5 ms

ATTENTION
Performance degrades significantly with packet loss (must be less than 0.5%) and when the delay (round trip) is greater than 50 msec and mean jitter is greater than 5msec.

ATTENTION
Avaya has conducted extensive but not exhaustive tests of fax calls in different scenarios. While all tests have been successful, Avaya cannot guarantee that all fax brands will operate properly over all G.711 Voice over IP (VoIP) networks. Before you deploy faxes, test the fax within the network to verify reliable operation. Contact your system supplier or your Avaya representative for more information.

Call Server
Typical recommended configuration for analog lines cards connected to faxes:
MGCs:
• Enable modem/fax pass through mode: Should be enabled in element manager
• Enable V.21 FAX tone detection: Should be enabled in element manager
• VGW trunks should be in a zone with Best Quality (BQ) setting.
Analog Lines:
• Class of service: FAXA, this will set the proper trunk capability for fax calls.
• Class of service: MPTD, this setting will allow lower speed faxes (up to 14.4) to use T.38 and higher speed faxes to use G711 clear channel (no echo cancelation, no nonlinear DSP features).

I was told that CPMGS is Core, MGC, and SigServer all combined. MC32S is for secure/encrypted DSPs and I thought you could already turn on security on regular MGCs ...
We have a CPMGS at one of our survivable sites and IP phones can register to it like a SigServer. I was questioning what it was as well because I was not familiar with that type of card.

The CPMG and CPMGS are really the same card. Only difference is the "S" for secure DSP's. They both are CPU, SS and MGC all in one. Or CoRes is a better term.