Carousel players pull and cache their playlists and content from the server. Carousel DOES NOT stream or push content from the server. We do this because it is a more reliable way of running the players. If the network or servers go down, the player keeps showing it’s content.

There are two things that players pull form the server. The graphics content and the playlist. The graphics content is downloaded over TCP port 80, and the playlists over port 56901.

The graphics are only updated when they change. So regular bulletins are possibly only pulled once. If you have a dynamic bulletin like RSS or EDS, then it would be pulled every time the data changes.
Playlists are pulled every 15 seconds. The size of each bulletin is approximately 1mb. This of course depends, because if you upload a 200mb video, it will sync 200mb to the player! But, in general static text bulletins take 1mb. Each playlist sync takes about 15k of data. This also depends on the size of the playlist. Each bulletin takes about 512 bytes. So 15k is about a 30 bulletin playlist. If you had 200 bulletins, this load would be about 100k.

The pulse of the playlist is what uses a more sustained amount of bandwidth. This pulse makes sure the players are in sync, that alert messages have been dispatched, impressions tracked, and channel layouts are correct. It is a critical part of the Carousel design.

Now we have an idea of how much bandwidth one channel will take. If we add more players, they will each take up the same amount of bandwidth back to the server. So, a 10 player network may take about 150k every 15 seconds. That is a 10k per second average to the server.

Sometimes, we have a lot of players and a slow or limited connection back to the server. This could be a t1 or legacy networking equipment. In this case there are three things you can do:

• Use Offline Hours in the players
• Turn on bandwidth throttling for port 80
• Use QOS on your routers to manage the bandwidth of port 80 and 56901.

Offline hours is documented in the Carousel manual. Bandwidth throttling is a blog post. QOS may be implemented by your IT staff.

I hope that this clears up how much bandwidth Carousel uses. It is still a slightly elusive number, but for reference, a standard 100Mb LAN connection could support about 5,000 Carousel players. We have signage networks with hundreds of players and there is minimal affect on the network. Bandwidth mainly becomes a concern on limited connections.