Specifications

MBG Engineering Guidelines, Release 8.0
MCA voice and video conferencing between MCA clients via the MCA server is also supported through MBG.
The bandwidth usage per video stream is configurable on the MCA client. An additional consideration is that an
MCA client can receive multiple video streams, one for each video participant in the conference. That number
can be reduced at the MCA client by minimizing or closing video windows.
For details and current values, please see the engineering guidelines for the devices/applications referenced as
examples here (available from http://edocs.mitel.com/).
Fax Calculation
A fax call made over a SIP trunk or to a SIP device supporting fax will be either a G.711 voice stream or a T.38
fax session. For the purposes of bandwidth calculations, consider both cases to be an 80 kbps G.711 stream.
Call Recording Calculation
When using MBG's Secure Call Recording service, a third-party Call Recording Equipment (CRE) device
registers to MBG and requests “taps” of calls in progress. The control connection is an SSL-encrypted TCP
stream authenticated by an X.509 client certificate provided by the CRE. (Refer to the MBG Installation and
Maintenance Guide for information on the process used to obtain and install the CRE certificate.)
A small amount of bandwidth is used for the CRE control connection. However, it is usually insignificant when
compared to the volume of voice traffic, and can be safely ignored. A small amount of CPU load is also incurred
for the control connection. Again, it is usually insignificant compared to the load of processing voice signaling
and RTP.
MBG makes a copy of the RTP streams for each call that is being recorded, and forwards them to the CRE.
Therefore, each tapped call requires 50% more bandwidth than an untapped call. Only audio is recorded; any
video or T.38 streams should be ignored when calculating call recording bandwidth requirements. Simply
estimate the number of calls that will be recorded simultaneously, and multiply by the codec in use. When in
doubt, it is safest to assume G.711 for all calls.
For example, assume that 10 calls will be recorded at a time. All calls are G.711.
Bandwidth = 10 calls * 80 kbps
= 800 kbps
The site requires 800 kbps on top of the bandwidth used by the calls themselves.
Note: When transcoding, the bandwidth requirements are different on the two “sides” of the MBG.
Example Bandwidth Calculation
A site has 48 SIP trunks shared by remote and in-office users. Most users are in the office, but 100 work in
various remote branch offices with Teleworker phones hosted on an MCD at the main office. Remote phones are
configured for G.729 to save bandwidth, and all SIP trunk calls are G.711. (MCD handles any transcoding.) In
addition, the site records up to 10 remote office calls at any given time.
At peak, the site uses 40 trunk channels and 75 of the remote users are in a call. Ten percent of the remote
users are in UCA video calls configured to match the lowest bandwidth setting of a UC360 device.
The system is deployed in gateway mode, in parallel with the company firewall.
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