Usability - Productivity - Business - The web - Singapore & Twins

How much bandwidth does Sametime need?

A question that pops up quite regularly is how much bandwidth does Sametime need. As a rule of thumb you can use this values:
  • A one to one text chat need about 0.2kBit/sec, yes that would be 200 baud. What worked in the 300Baud modem days with your favorite BBS hasn't changed: chat is cheap. Presence transfer consumes about the same (Your Netbios broadcasts probably slanders 10 times the bandwidth. If you transfer files or images (pasted into the chat) bandwidth consumption will peak as: get what you can get and finish the transfer
  • Voice chat requires around 10kBit/sec per connection. A two way chat has one connection, a three way chat two (n-1 actually, you don't need network bandwidth talking to yourself)
  • Video chat consumes 256kBit/sec per connection. The same rule as for voice chat applies. A threesome thus requires 512kBit/sec.
The Sametime codecs have adaptive features and you can tweak the video quality, so YMMV.
Thanks David

Posted by on 25 August 2008 | Comments (3) | categories: Show-N-Tell Thursday


  1. posted by Carl Tyler on Monday 25 August 2008 AD:
    Stephan are you sure about your 0.2kbit number? That was true in the pre 7.5.0 days, but I'm not sure it's still true.

    Sametime 7.5.1 has added a lot of extra overhead for rich text, then also don't forget Sametime now sends around emoticons, screenshots etc.

    Would be great if IBM would update this spreadsheet that came with this 2.0 deployment guide

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  2. posted by Chris Miller on Monday 25 August 2008 AD:
    I have to agree with Carl. I do a bid section on this in my Sametime sessions. The bandwidth is far beyond the 2kb you used to have in 7.0 and previous
  3. posted by Stephan H. Wissel on Tuesday 26 August 2008 AD:
    Well, the figures are David's. The HTML in 7.5 was quite ugly, but AFAIK has been fixed in 8.0.
    Looking forward to one of Chris' sessions.
    Emoticon smile.gif stw