Required help regarding videoconf bandwidth use!!!

[morpheus]

Hi!
I am new to video conferencing.
My company is about to buy a video conferencing device and I am asked to find about the network structure.

Let me tell you what we have.
1. We have a broad band connection of 512 kbps.
2. Download limit is 8 GB.

I guess 512 kbps connection is okay for normal video conferencing, however, my boss like to know how much downloads and uploads happen if we use video conferencing for an hour. I don't know about the answer but bluntly if i calculate it comes up to 1800 mb if entire bandwidth is used for upload and download.

When we say 512 kbps is needed then does this mean that we have 512 upload speed and 512 download speed if we are using broadband connection?

Please suggest.

[david.sharp]

Hi Morpheus

I would be asking the question as to whether or not you are using ADSL or SDSL.

If you are using ADSL then the upload speed on your line is likely to be less than 512Kbps and if it follows the common trend could be 256Kbps.

This would mean that the only effective bandwidth you would be able to use to place a video call through this line would be 192Kbps because of the extra data that is added to the packet during encapsulation of the data.

However on certain endpoint you can set the system to send the video and audio RTP traffic at a lower bandwidth than the codec can recieved so you could effectively have a call running at 384Kbps download and 192Kbps upload, dependant on the far sides capability.

If the codec is to be used on a standard broadband connection then there is a good chance that you will be NATing traffic between your LAN and the Internet, NAT whilst all well and good for standard data transfer does cause issues with video conferencing where the number that the far side is trying to connect to simply does not exist.

For instance, if you have the codec on 192.168.1.x and you have an external IP address of 212.212.212.x then you would need to setup a static NAT translation between the external IP address and an the internal IP address.

H.323 network infrastructure equipment is available to help with the issues of NAT and Firewall traversal.

Also you need to bear in mind that when using the Internet for RTP there is no gauranteed quality of service so you may suffer poor video due to packet loss and jitter.

How much bandwidth would 192Kbps use for an hour.

192Kbps/8 * 120 = 86400KBps * 8 = 691,200Kbps

Hope this information helps.