The core of the net is outstripping the speed at which people connect to it.
By Mark Ward
BBC News Online technology correspondent
The cables at the core of the net can already handle terabits of data every second and look to get even faster.
The core of the net is getting faster all the time
By contrast the cables that link consumers to the net look set to stumble along at mere megabit speeds for a long time to come.
This could mean download delays for domestic broadband users.
The core of the net is speeding up thanks to several technology developments.
The main help is coming from work on Dense Wave Division Multiplexing. This allows different frequencies, or colours, of light to travel along the same optic cable without interfering with each other.
This, plus better control of the way that light pulses travel through fibre cables, mean that the top speed of the net's core has increased a thousand-fold in less than a decade.
The core networks routinely run at 10gigabits per second (gbps) and can easily step up to hundreds of gbps.
A speed of 10gbps means a DVD quality film can be transferred approximately every four seconds.
Relatively slow home broadband could dampen downloads
Home networks are speeding up too.
The basic ethernet technology used by many consumers works at 10mbps, has been upgraded to 100mbps and forthcoming wireless networking technologies work at speeds up to 54mbps.
But the technologies used to link homes with the net look like they will be lagging behind these very high speeds for some time. This could mean that downloads of large files, such as films, will always take time.
"There is always going to be a disparity between storage and bandwidth," said Paddy Falls, chief technology officer of technology firm iOra that helps mobile workers cope with this shortfall.
He said the situation was getting worse because cheap storage was making people lazy and generate huge numbers of large files.
"Storage is exploding but if you look at the trends in bandwidth they have not been growing exponentially," he said.
Most British people get high-speed net access to their homes via ADSL, or Asymmetric Digital Subscriber Line, technology that works at 512kbps.
This speed is a third of the 1.5mbps laid down in the specifications for the flavour of ADSL offered by UK net service firms.
New versions of ADSL, called ADSL2 and ADSL2+, boost these speeds to 12 and 25mbps respectively but work over much shorter cables than the existing technology. This could limit the numbers of homes that could possibly use them.
Both ADSL2 and 2+ have only just been standardised and could take a long time to find their way into products and services.
Broadband delivered via cable can offer similar theoretical speeds but can suffer because many people share the same link to the net.
Fixed wireless services offer higher speeds but currently are not widely available.
It is likely that the only way that domestic home net access speeds will increase is if net firms start installing fibre to homes. However, few are likely to be able to raise the cash to build a new network.
There could be other problems that dent the chance of getting fast, reliable access to the net.
Matthew Finnie, chief technology officer at European high-speed network Interoute, said the growing use of broadband and peer-to-peer networks gave people a hunger for speed that was going to be hard for many net firms to meet.
Mr Finney said customers with a dial-up account tended to only use the net when it was cheap to do so which made it easy to plan for demand.
By contrast, he said, broadband users can be online anytime and typically pass back and forth large amounts of data.
Fast networks can transfer movies in a moment
Particularly problematic, he said, was the growing use of peer-to-peer networks that consume as much bandwidth as they are given to spread out the load of their users.
"Peer-to-peer trashes the performance at the edge of the network," said Mr Finnie, "it does not matter how much you put in there."
In early July Tom Leighton, the chief scientist of net firm Akamai, said that simply installing more and faster wires would not solve the net traffic jams.
In a speech to the Fifth International Congress on Industrial and Applied Mathematics Mr Leighton said firms had to do a better job of putting what consumers want at the edges of the net to make it easier to get at.
Mr Leighton said it would be best to redesign the internet.
"It simply wasn't designed to do the things we ask of it now," he said, "The best we can hope for is an overlay to hide its worst deficiencies".