Bandwith capacity planning

[muca]

I know there are a lot of considerations when choosing the adequate bandwidth for a network, like type of traffic etc..

But suppose you have 10 users for moderate web surfing and downloads.

A 256 kbps adsl link would be sufficient? The calcule is simple as dividing 256/8= 32/10 = 3,2 KB/s.

Any documentation would be very appreciated.

Thanks

[muca]

Hi all. Is there anything wrong with my question?

Any help or document would be very appreciated.

Thanks

[Marvin Rhoads]

There are many many variables that go into answering such a question with other than generalities. Dividing bandwidth by users is misleading, since all users will typically not be actively transferring bits simultaneously, especially with a relatively small set of users such as your describe. If indeed all they are doing is surfing and some e-mail, I'd say the 256 kbps line is marginal. However, today's typical users (in the US) are more and more looking to avail themselves of broadband services (streaming video clips and other rich contect types of media). 256 kbps is the low end for a single user actively accessing that sort of content. If two or three of your 10 users are accessign such content simultaneously, they will be hitting a network bottleneck. I'd recommend going with a 768 kbps DSL line minimum, if available.

Your options depend on part on your provider's offerings as well. For instance, if you buy into 256 kbps DSL, do you have the option to bump up your rate to 728 kbps (or higher) if you find that inadequate?

[muca]

Thanks Mklemovitch. This small set of users is just an example (not a good one) :)

Actually I am looking for some documentation, book or some kind of rule to determine the adequate bandwidth for, let's say, 200 users accessing varied sort of contents.

Suppose 200 users for just e-mail and surfing?

20 users for streaming video?

Sorry, for my poor knowledge but how do you conclude that 2 users (streaming and other rich content) with a 256 kbps will be hitting a botleneck.

Sometimes the only way is to buy bandwidth and if not adequate bump up the rate?

I know it's a complicated question....

[Marvin Rhoads]

You're welcome - Marvin is the name.

Streaming video worth watching (in my opinion) generally runs on the order of 256-768 kbps per stream. 256 kbps ADSL + more than one user watching streaming video = network bottleneck.

Is your application a greenfield (all new office)? If not, then one approach is to measure current network usage and use that as a basis for whatever your are doing new.

In any case, you should array your providers' offerings along with costs agaisnt possible location scenarios (m to n users, usage profiles x, y, z etc.) and create a decision matrix to guide your decision making process.

I'm not aware of any reference per se although folks have surely wirtten on this topic. Rather, I'd advocate a basic systems engineering approach such as I sketched above. The methodology is known as multi attribute utliity assessment; whereby one evaluates choices based on multiple attributes to which one has assigned values and/or weights. Taking such an approach allows you to both explain your methodology and rationale for decision making as well as revisit your choices down the road if and when new information becomes available or conditions change.