Re: Is raw speed everything?
One of the things I used to see is the "contention ratio".
It's not mentioned any more.
That's because it's no-longer useful. Rate adaptive services weakened the concept and I think the wide range of bandwidth usage across users and exchanges makes it unhelpful.
Instead what CPs do is rely on triggers. They upgrade network links as/if/when they get close to capacity. It's still possible to calculate contention ratios but you have to specify a context. And the wider the context the less useful it is. The contention at an exchange might be interesting to know. But the national average contention ratio only has curiosity value. It's of no use in planning. It would be like Tesco trying to use a national contention ratio to decide how much milk each store should get delivered to it (0.35 litres per person for instance).
But network capacity planning is a funny thing. Very complex. It's amazing how high a contention ratio can go before anyone starts complaining. VM are probably experts at doing that in the UK. Usage patterns are a huge factor. Providing 1Gb/s to a thousand users who want to watch IPTV is easier than providing 100Mb/s to a thousand users who want to download stuff all day. It's all about the traffic - is it bursty or constant. Constant traffic is the difficult thing to handle. But interestingly something that's constant can become bursty if you raise the speed. IPTV is the best example of that. For a 5Mb/s connection IPTV is constant and a pain to deal with. But on a 50Mb/s connection it's bursty and far easier to cater for.
Biting the hand that feeds IT
