[Sugar-devel] [Server-devel] Reasonable number of users sharing an activity instance?

James Cameron quozl at laptop.org
Wed Apr 6 02:46:07 EDT 2011

When laptops are connected without a school server, the data is
exchanged using multicast packets, which on most routers means the
lowest data rate.  The data is also subject to loss, the retransmission
algorithms are time based, and excessive retransmissions can consume
airtime to the point that nothing can be transmitted.

When laptops are connected via a school server, the data is exchanged
using TCP packets, which on most routers means the highest data rate.
The data is also less subject to loss, since TCP retransmits based on
exchange of sequence numbers in the stream.

The maximum user density will therefore depend on:

1.  whether you are using a school server or not,

2.  if not, what data rate your wireless routers use for multicast,

3.  how many wireless router channels are allocated,

4.  any other wireless network traffic, such as use of other activities,
use of web browsers, remote access or administration, software updates,
or improperly configured LAN bridging,

5.  the amount of data that the activity transmits or receives,

6.  the radiofrequency noise in the environment,

7.  the distance between the laptops and the wireless router,

8.  the distance between the furthest client of the router and the
router (since this may be using a lower data rate, thus consuming more
air time).

But no, I don't have any estimate handy.  I recall others mentioning
estimates and test results from earlier versions.

James Cameron

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