Estimating Bandwidth Requirement

Unanswered Question
Apr 6th, 2009
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What is a good method to estimate bandwidth required to support a particular office?


I know the concerns and questions to consider: where the the Apps located; how do they get Internet access; etc; but what I need is a specific way to calculate the actual estimated bandwidth.


Thanks

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lamav Mon, 04/06/2009 - 05:54
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Interesting question for me since I posted a similar concern on Friday.


Copying from my thread, this is my thought process:


"With 500 users, thats 100 users per 2Megs. Thats 50 per 1 Meg. Thats 75 per 1.5 Megs (T1). So, given that a T1 is 24 DS0s, and ideally it would be great to give everyone 64Kbps of dedicated bandwidth (that isnt possible, too expensive and overkill), then 75 users per T1 is about a 3:1 oversubscription rate."


Im not too sure of the sanity of my method and I dont know if this helps you or not...


Victor


Edison Ortiz Mon, 04/06/2009 - 06:22
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Hi Joe,


Very hard to estimate application and user behavior.


If you were to perform a bandwidth analysis on location A, you will find the result will be a lot different if it was to be performed another day when lots of emails were flowing around with huge attachment - and that's just one example.


I suggest getting the most bandwidth the budget allows you to buy and then apply QoS in your network in order to maintain some balance and guarantee on the traffic flow in|out of the network.


HTH,


__


Edison.

ex-engineer Mon, 04/06/2009 - 06:29
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Hi, Edison:


I understand what you mean. It will vary from day to day.


What I was wondering though is whether there exists a loosely-constructed formula, such as alloting at least 32Kbps per user in the event that everyone is on the network at once. Or perhaps what Victor states above regarding an oversubscription of 3:1. To narrow it down a bit, lets say that the Applications are basically email, Internet, maybe some Intrannet application stuff, but nothing too "special."


Thanks



Edison Ortiz Mon, 04/06/2009 - 06:45
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Hi Joe,


In today's network, you can't count just on users. There are many 'network ready' devices that consume bandwidth in a network.


If you want to have a guideline as to how much bandwidth each user will consume based on the application they use - most applications will have a bandwidth requirement listed in their reading material. As for internet, is just best effort. If you decide to purchase a 56kbps line, they will browse the internet but they will complain is too slow - IOW, internet won't break but it won't be a pleasant user experience.


If you have outlook at that connection speed, most likely it will time out or the computer will just freeze.


If the location is already opened, you can invest a couple of days with a bandwidth analyzer and profile the traffic flows.


__


Edison.


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