On Tue, 27 Jun 2006, Travis Johnson wrote:

5GB per month is about a 28.8 dial-up connection running all month long. That equates to about 24kbps per user.

1,000 users * 24kbps = 24,000kbps / 1024 = 23Mbps (or about 1/2 of a T3) for 1,000 users. 2,000 users would be about 45Mbps.

Does my math work? I guess when you are talking about running 24 hours per day, it adds up fast.

This would be something to worry about, but bandwidth usage doesn't work like this. You'd have to figure that at least 30% of the time, there is very little bandwidth usage, so that would leave about 16 hours/day. Also, comparing a high speed (figure an average of 512k) to a 28.8 dialup is not really fair, either. For the about 70% of the time that people use bandwidth, you'd be able to safely assume that some of these users are daytime and some are nighttime users. I'd assume that they are about 75% nightime. So...75% usage would be running 5GB during about 5-6 hours/day over a 30 day period.

That is:
(5GB/30)/5 = 33meg/hour = or about 10k/sec average. multiply that by the 1000 users, and you only use about 10M during the peak time. Ok..so all of you with 1000 users, stand up! :-)

Really, there is not a good way to do this mathematically without a solid profile of your peak periods. This requires good graphing of your utilization. I'd wager that running 1000 users on a 10M pipe would get some complaints. Running 1000 users on a DS3 would probably be pretty close to full during peak usage times. Dual DS3 could run reasonably well, but that all depends on how much you allow each customer.

Butch Evans
Network Engineering and Security Consulting
Mikrotik Certified Consultant
WISPA Wireless List: wireless@wispa.org


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