Bristol Water has become another high profile user to replace ATM network with Gigabit Ethernet.

The utility operator uses its graphic information system (GIS) to store detailed maps, which have the position of every water main marked on them.

Accessing these large files was causing the network to slow down.

The company follows British Airways, who also shifted to Gigabit Ethernet because it was cheaper than ATM.

Head of the outsourced IT team, Ian Featherstone, said: "It is easy to understand why Bristol Water continuously require more IT capacity just to keep the water flowing. The maintenance, administration and audit departments also need more capacity. We knew that networking problems were beginning to occur and we decided to bite the bullet."

A network traffic analysis report was carried out by integrator ONI and the cause of the problem was found to be the 100Mbps link between the core Centillion ATM switch and the Bay 350T workgroup switches.

Bristol Water had two options: upgrade from half to full-duplex, providing a 200Mbps connection; or provide routing at the core by replacing the ATM switch with a Layer Three switch - connected to the workgroup switches via Gigabit Ethernet.

The company opted for the latter and upgraded its network to a Nortel Accelar 1200 Layer Three switch, with Gigabit Ethernet over duplex fibre running to 12 Nortel BayStack 450T workgroups switches.

Featherstone said the more expensive option was chosen to allow for future growth. "With utilisation on the Gigabit pipes now below 10 per cent, there is huge capacity available for future growth. This future proofing gives us the capacity to accommodate more users with ease and run bandwidth-hungry applications such as Windows 2000," he said.