John Linton A few hours more than seven days ago we made a change to our various broadband offerings to move the start of the 'off peak free' download period from 12 midnight to 2 am thereby reducing the time available for Exetel customers to use their 54gb/60 gb (depending on their plan) 'free download allowance'. This decision was made to address a problem that we had struggled with for over five years to resolve - the problem of too many people starting downloads at exactly midnight and making it very slow for people who were playing games or browsing or streaming video or audio for around 30 minutes. The results of doing this are very clear cut - the problem is completely resolved. If you're an Exetel customer you can see the dramatic changes by going here:
http://public.mrtg.exetel.com.au/bwsummary/total-supplier-bandwidth.html
and for those of you who don't have access to Exetel's bandwidth graphs (a surprisingy hig percentage) the daily graph shows that usage at midnight is around 75% of total capacity (compared to 100% the on Thursday of the previous week) and at 1 second past 2 am it moves to 90% of capacity before dropping back rapidly over the next hour to 75% capacity before gradually increasing to around high 80s before falling to around 50% at 1 second past midday.
If you scroll down that page to the yearly graph you will see what Exetel has added in terms of bandwidth capacity over the previous 12 months where daily usage has increased from around 2 gbps in July 2008 to more than 3 gbps in July 2009 and current peaks at around 4 gbps for some 60 minutes of each day in August. You will also notice on the daily graph that for much of the day the usage is relatively low barely exceeding 60% for most of the peak usage period.
Since we made this change many people have asked me why, if our "network is so congested", we simply don't buy more bandwidth? It seems to be a reasonable question, for the people asking it, and it seems to be a reasonable question to me. The answer is that Exetel almost certainly provisions more bandwidth than is necessary and almost always has and if you look at the MRTG yearly graph you will see that the average usage has increased by over 70% in the past year and I can assure you that we haven't increased our customer base by 70% - actually around 30%. However we still have less than 5 gbps of IP ingress/egress and customer connectivity bandwidth - and we have many, many tens of thousands of users. As you can see that bandwidth is enough (now) for there to be zero congestion at any time of day but 7 days ago between midnight and 12.20 am it wasn't enough. How can that be the case?
The answer is that, in theory, at 5 gbps it could only take around 500 users using some sort of multiple sourced download program that achieves 10 mbps (easily done on an efficient ADSL2 service) to take the WHOLE of the bandwidth that is usually enough to give zero contention access to around 100,000 users. Following the reasonable question logic of the enquirer that would mean that Exetel (or any other ISP) would need to increase both its IP ingress/egress bandwidth and its customer connectivity bandwidth by a factor of 20 to ensure zero contention if that arithmetic was correct.....which it isn't (use the download speed achieved by P2P of your choice for your own calculations) but it demonstrates the 'scope' of the issue for Exetel which provides very large 'free' downloads and can support that amount of download if the actual downloading is spread over one or two hours but can't deliver it if it's spread over one or two minutes.
The whole purpose of offering the free download period in the first place was to use the $A150,000 per month of 'wasted/idle' bandwidth as a bonus for Exetel's users - not to create an added cost to fulfil the requirements of a relatively few customers - so now the balance has been restored after such a miserably long time of failure.
Irrespective of what arithmetic you choose to use (and the constant comments on the forum and in emails that "moving the start of free time back will only move the problem to another time period - (the MRTG reports show that is nonsense better than I can explain it) moving the start of 'free time' back 2 hours solved the issue and allowed various people within Exetel to use the 'thinking time' this freed up to deal with other important issues that have been relatively neglected.