Jitsi Bandwidth Calculation requirement

If we are running 3 simultanious meetings with lastN = 25. There are 75 people in one meeting. How much bandwidth required at jitsi (self deployed) infra side.

My calculation is as below for one meeting:

25 camera max (beause of last N)
150kb BW (low bandwidth mode)
75 people will receive stream of all 25 users

So 25150/1024 (to calcuate in MB) = 3.66 MB total required by each user.
There are 75 users so 75
3.66 = 274.66 MB required

Please confirm, if my understanding is correct.

So you want to say there will be 75 people receiving video … that’s true. And if all are sending just 180p (as you wrote 150kb BW (low bandwidth mode)) This is ~10MBs just upload for the server, the download depends on the number of participants and whether layer suspension is enabled.

The rest of your description I don’t get it …

So you have 3 meetings with X number of people and one meeting with 75 …

Thanks for your reply.

Allow me to be more clear…

Total 3 Meetings
Resolution 180 for everyone (150kb bw required for each video)
Last4 = 25
Each room has 75 participants with video on
Layer suspension is enabled.

How much bandwidth required at server side.

At server side

upload: 3*25*150 / 1024 ~11MBs 
download: 3*75*150 / 1024 ~33MBs

Is it per room for total all 3 meetings ?

please explain your calculaion that will be helpful.

I just edit the post, it is obvious now.
It is for all the conferences total.

Looks upload is correct… but still download is not clear… as server received 11 MB data from 75 people video, but video will be distributed to all 75*3 users. So bandwidth requirement for download should be more. Please clerify.

Its the other way around, this is from the point of view of the server. And these are 11MB per second.
So server receives video from 75 people per conference which is around 33MB per second. But if you have lastN 25 this means videos will be send only to 25 per conference, that’s why upload is less(sever is sending less than receiving)

Divide the result by 8 to convert bits to bytes

Hello Damencho,

I said, three rooms with 75 each, which means each room will have 25 videos broadcast, which means total 75 streams… so… download should be more… 3 times than receiving, assuming only 25 videos are on in each room.

I think you’re confusing server download with client download. Think about it carefully:

  • There are 3 conferences running concurrently, each having 75 participants (clients)
  • In each conference, only 25 of the 75 participants (clients) stream (upload) video [to the server]
  • In each conference all 75 participants (clients) receive (download) video [from the server]

CALCULATIONS

Upload

  • At 150kbps each, total bandwidth sent from clients to the server per conference is 150 x 25 (only 25 clients are sending video) = 3.75Mbps
  • 3 of those conferences will send a total of 3 x 3.75 of data to the server = 11.25Mbps
  • So, the UPLOAD to the SERVER is 11.25Mbps

Download

  • At 150kbps each, total bandwidth sent from server to clients per conference is 150 x 75 (assuming all clients will be receiving video) = 11.25Mbps
  • For 3 conferences like that running concurrently, the server will send a total of 3 x 11.25 out = 33.75Mbps
  • So, the DOWNLOAD from the server is 33.75Mbps

So, in terms of upload and download, your focus should be on the server.
Server upload = Total of data server receives from clients
Server download = Total of data server sends out to clients

Hope this clarifies it for you.

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Your download comment - * At 150kbps each, total bandwidth sent from server to clients per conference is 150 x 75 (assuming all clients will be receiving video) = 11.25Mbps

Dont you think it should multiply with 3.75 rather than 150 KB .

Why would you think that?
75 clients receiving 150kbps each comes to a total of 75 x 150. All the clients are receiving video. Each video stream is 150kbps. So collectively, they’re getting a total of 11.25Mbps of data from the server, per meeting.

No , each client is receiving 25 stream of video, so naturally it should multiply with 3.75 rather than 150.

Again, you’re confusing client bandwidth with server bandwidth. Read over the breakdown one more time - carefully.

Sorry Freddie… I am talking about server only. What I understand is that server will send 25 streams of video to each client. So server will need that much bandwidth for each client to send these many video. I am not talking about client bandwidth at all.

But you are. Think through it again carefully - focus on just the server.

25 clients send video to the bridge (upload to the server)
75 clients request video from the bridge (download from the server)

So data transmission through the bridge is 25 in, 75 out. Multiply that by 150kbps for each conference. Then multiply the total by 3 (for 3 conferences). This is the traffic through the bridge. That’s it.

My view.
25 clients send video to the bridge (upload to the server)
75 clients request video from the bridge (download from the server)

So data transmission through the bridge is 25 in, 75 out. Since each client has to be sent 25 video stream by server. so server will need 3.75 MB for each client to and 75x3.75 = 281.25 MBPS bandwidth is required at sever to send 25 video streams to each client.

Ok, one last try.

I just ran a quick test with 4 participants in a conference, all sending video, all receiving video. Video constrained to SD quality (360p) at that height and simulcast is enabled. There are several constraints to peg the bitrate in my environment. Here’s what my network monitor reports:

Screen Shot 2021-07-02 at 2.50.00 AM

Screen Shot 2021-07-02 at 2.50.35 AM

This should give you an idea. Per your thinking, the server download should be around 20Mbps (5Mbps x 4), but clearly this is not so. The server download here is only 7Mbps (and it’s this high because the streams are constrained to send about 600kbps each at this resolution and height ,and 3 streams are being sent per client because of simulcast).

For reference, here’s the network traffic when there’s no conference running:

Screen Shot 2021-07-02 at 3.11.03 AM

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