Dear Dr. Jorgenson,
My

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company - an Internet service provider headquartered in Nigeria is having problems managing our network. We deploy services using radio and VSAT technology. Initially, when we started out - without clients - our download speed was great. Now that we have a client base of over 15 companies we seem not to have a clue as to why the download speed has depreciated. When I joined the company, I was made to understand that our technology can provide service to at least 64 companies and not have any problems at all, but this is not turning out to be so. I ask for your expert advice and opinion as to what to do and how to best manage the situation. Many thanks
There are many possible answers to your problem, ranging from low level packet loss degrading performance over the long satellite propagation times (congestion avoidance behavior) to poor drivers in some of your critical interfaces not delivering to their specified capacities. Or maybe the manufacturer is over-simplifying their capacity estimates. Alternately, some of your customers may actually be over-burdening the system - VSAT is typically intended for lower traffic densities.

Resolving the problem may be exceptionally difficult since the end-to-end path has so many different components, most of which you probably can't inspect directly. If all your clients are experiencing the same problem, it is probably a common component such as the central hub.

I would recommend you take an end-to-end perspective and use whatever means that you have to characterize each segment and what it contributes to the overall network path. Preferably do that with a customer that will work closely with you, or even better, with a sample path that you have full control of from end-to-end.

If you provide me with an IP address of a customer end-host, I can provide a remote analysis of the end-to-end behavior that may help you solve your problem.

This was first published in January 2003

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