Thursday, January 21, 2010

Estimating future bandwidth requirements


The Broadband Stakeholder Group's Predicting UK Future Residential Bandwidth Requrements study from May 2006 reported that:
"By 2008, the bandwidth demand for the most bandwidth intensive households could reach 18Mbps downstream and 3Mbps upstream. By 2012, the bandwidth demand for the most bandwidth intensive households could reach 23Mbps downstream and 14Mbps upstream."
The two most bandwidth intensive household types from the eleven identified were "two adults, young couple" and "two adults, with children". A key point made later in the study is that "a significant percentage of UK homes may not be able to receive such downstream speeds using current technology/networks." Bandwidth requirements were estimated from first principles and industry data, shown on the following chart:



Ante meridiem usage by the two adults, two children household is shown below:



While post meridiem usage is shown here:



Interesting to see educational use getting a mention. Perhaps a similar exercise could be undertaken to identify school broadband usage and consequential future bandwidth requirements? However, in comparison, CED Magazine (Communications, Engineering & Design) had this to say in January 2008:
"...analysis shows that by 2012 the power user will require over 100 Mbps of downstream bandwidth and the average user will require over 40 Mbps of downstream bandwidth. (A power user is defined as a first adopter of new technologies and would expect the best bandwidth. The average user is defined as a late adopter of new technologies and would be satisfied with standard bandwidth.)"
Their calculation, based on bandwidth per application and number of digital streams, including the number of connected devices (TVs, phones, computers, digital video recorders) per household, produced the following graph:



...showing usage significantly higher than the BSG's estimates. A 2006 study (Quantifying the Broadband Access Bandwidth Demands of Typical Home Users) by the Australian Centre for Advanced Internet Architectures concurs with these higher estimates, but also flags that requirements could be higher still, depending on the approach taken by ISPs:
"We take a closer look at the probable demand for bandwidth, presumed to motivate the deployment of new broadband access technologies. We construct plausible estimates of what a ‘typical home’ might need, given two different service provision scenarios - managed bandwidth and best-effort statistical multiplexing. We estimate a household of five people requires between 58 and 113Mbit/sec if bandwidth is managed on a per-application basis. If statistical multiplexing is used, the same family’s bandwidth requirements jump to between low hundreds of Mbit/sec to almost a Gbit/sec."
To explain managed bandwidth versus statistical multiplexing:
"Our estimates in the previous section make a key simplifying assumption - the home broadband service provides ideal isolation between traffic belonging to different classes of application. In other words, we have assumed that some form of quality of service mechanisms are deployed to ensure bursts of packets from one application do not temporarily ‘starve’ other applications (such as HD channels being rendered in real-time). This can only really be achieved if the ISP deploys and manages, moderately sophisticated queuing and traffic classification in their routers.
A more likely situation is that an ISP will utilise statistical multiplexing to ‘manage’ the interactions between packets belonging to different application flows. Statistical multiplexing manages through benign neglect and over-provisioning. Enterprise IP network operators often use a rule-of-thumb that the link speed should be 2 to 5 times the average capacity. In this case our pessimistic estimate would require something in the order of one Gbit/sec at the link layer to support the proposed mix of application traffic."
I would imagine that this second scenario remains the most likely, though I guess it must all come down to cost - is it still cheaper and easier to over-provision than to manage your network?

Finally, Connected Planet offer this in relation to the "how much bandwidth?" question:
"Bandwidth planning is nothing more than ensuring that your network can adequately support the dynamic service requirements of your customers...How can I build a network without a definitive amount of bandwidth? Well, the answer is – do the best that you can...So, how much bandwidth is enough? Rather than a definitive number, the real answer is more along the lines of “as much as you can deliver” given the circumstances in front of you. At a minimum, this means meeting and anticipating the demands of your customers better than your competition does. Ultimately, the broadband service provider of choice will be the one who delivers the most salient and valued services from the consumers’ perspective, over the most efficient network that can best throttle to meet customers’ varying demands. So enough about how much is enough. Build what you can – but keep in mind that there will be a direct correlation between the network speed you can deliver and the capacity you have to dynamically deliver what the customer needs."
Wise words I think.

1 comment:

  1. Interesting, but exponential growth predictions from a few years ago don't really match up with the current situation, do they ?

    As we haven't provided the above forecast capacity, and still seem to be here, is it time for a reforecast ? Talk Talk and BTw in recent public domain documents are both seeing demand on average around the 60 kbits/s level for example.

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