Friday, March 16, 2007


FUP - Why all the fuss ?

Lots of hot air is currently in circulation on the subject of Fair Usage Policies (FUP) on some UK broadband services. Typically services using an FUP are advertised as "unlimited" as they do not have an explicit rigid data quantity limit such as 20 GB. An ISP like Demon with an FUP may take action against subscribers that transfer more than 50 or 60 GB per month.

ISPs use an FUP as one method to limit peak demand on their services. Demon's ADSL was becoming near-useless at peak times (09:00 through 23:30) until they invoked the FUP and restricted some high users to 128k in peak times, thereby reducing the load and improving speeds seen by the vast majority of customers.

Other methods are in use, such as traffic shaping or throttling certain protocols (FTP, NNTP and P2P are common targets), capped accounts which stop working at a pre-defined GB limit, metered accounts charged per GB and so on. With over 100 ISPs to choose from there is plenty of variety and nobody need have a service that works in a way they don't like, if they bother to do some research first.

Why are these methods necessary ? in essence they are there to protect the interests of the majority from the excesses of the few. Residential broadband is a contended or shared service which means the total end user link capacity is way in excess of the capacity further down the line. If a few people set out to use their line flat out, as opposed to the bursty use the system is designed and sized for, then congestion occurs and everyone gets stressed.

As an example, a 622M connection to an ISP can carry at least 30,000 connections however it only needs 100 of them to be 6M connections running full blast and everyone will see a slow down.

Some idealists argue that the ISP should just provide more bandwidth. The problem here is economic, the 622M connection costs £120,000 per month and our end user subscription of £20 contributes less than £10 per month towards it. So logically we are buying about 52 kbits/s on average or if you prefer 6 kbytes/s or about 15 GB per month if used consistently 24/7.

If we want accounts where everyone can pull 50 GB per month then we need to be paying £20/month more under current pricing regimes. Nobody wants to do that, of course, they just want to have their cake and eat it.

So ISPs have to hold the peak time demand at a workable level, and the average demand at something around 15 GB/month or less. Plusnet choose to use heavy traffic management and shaping, some ISPs have GB limits as low as 2 or 5 GB/month, others have FUPs. Plenty of choice is out there in the market.

The advantage of an FUP is that it allows an intelligent being to take a view on the use of a connection. It will be obvious to them that a 24/7 BitTorrent addict trying to download the internet is different to a typical user with variable usage. The baying mob however demand "clarity" of the FUP limits so they can operate at 99.9% of the limit thereby missing the point entirely - to manage the average does not require that you limit everyone to the average, merely that you lop off the top end demand to hold the average at the right level.

Some seeking clarity of a contract term that incorporates leeway for reasonable behaviour is more than likely setting out to be less than reasonable. Nobody worries about the exact trip point of a speed camera unless they are bent on breaking the speed limit and trying to get away with it.

So for the majority of users an FUP is a perfectly reasonable way for an ISP to manage demand. The action level isn't fixed as it depends on the usage patterns of the user population. I believe it is better for most users to have an FUP kicking in at 40, 50 or 60 GB than a rigid cap at 20 GB.

The only people it doesn't suit are the roaming band of heavy users who aren't prepared to pay the economic cost of their habits and move from ISP to ISP as their presence either results in an FUP, traffic management, unusable service or the ISP goes bust. One day they'll figure it out and start paying their way.

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