Capacity Calculation
- PeterF (Deactivated)
Or what speed link do you need to make voice calls?
Rule of thumb
So you don't have to read all of the following technical gobbledygook you can use the following rule of thumb:
100Kbps for each voice call, for both upload and download.
If you are using Noojee Campaigner add another 100Kbps.
So for each agent you need 200 Kbps.
If you have a really good ADSL + link (and most people don't) you might get speed of 16Mb/1Mb.
This means you can run 1Mb/200Kbps = 5 Agents on the link.
If you use compresson on the the voice component see below.
Compressed
If you don't know what compression is then use the above number ;)
If you are running compression such as g.729 then 50Kbps in both directions.
If you are using Noojee Campaigner add another 100Kbps.
So for each agent you need 150 Kbps.
If you have a really good ADSL + link (and most people don't) you might get speed of 16Mb/1Mb.
This means you can run 1Mb/150Kbps = 6 Agents on the link.
Monthly Data usage
So now you know the bandwidth how much data will you use in a month.
Uncompressed voice
9 GB per month per agent
Compressed
7GB per month per agent
What speed connection do I have?
Run this speed test to find out.
A typical result for an ADSL connection might be:
6Mb download
600Kpbs upload
To work out how many phone calls you can make (assuming you don't use the Internet whilst make calls) take the smaller of the above two numbers (600Kpbs in this case) and divide by one of the two rule of thumb numbers above.
In this case
600Kbps / 100 Kbps = 6.
So you can make 6 concurrent calls across this link.
Technical details
The following constants are used in calculations of required capacity for systems.
The values are (conservative) approximations based on measured averages.
Voice Bandwidth
Overhead
For VOIP codecs, by a general rule of thumb, it can be assumed that header information will add 16kbps to the bandwidth requirement for voice over IP[1].
ULaw
u-law and a-law (G.711) are uncompressed codecs, and therefore require 64 kilobits/second of underlying bandwidth, hence 80 kilobits/second of IP bandwidth per call in each direction.
Bandwidth: 80 Kbps (both directions)
G729
G.729 is compressed and has an underlying bandwidth requirement of 8 kilobits/second, hence 24 kilobits/second of IP bandwidth per call in each direction.
Bandwidth: 24 Kbps (both directions)
Recordings
Storage
Short term Storage
Noojee Recorder records live calls to Short Term storage as an uncompress wav file.
Uncompressed recording (wav file): 1 megabyte/minute on disk
Mid term Storage
Each night Noojee Recorder migrates all recordings in the Short Term storage area to the Mid Term storage area. During the migration the recordings are compressed using the Ogg Vorbis codec. When recordings are accessed by an end user they are converted back to a wav file for ease of playback.
Compressed recording (Ogg Vorbis): 200 kilobytes/minute on disk
Disk IO
Hence the disk system must be able to write 125 kilobytes/second for each simultaneous recording.