As more and more organisations look to consolidate their applications, servers and storage, it's not just RoBo's - remote offices and branch offices - that are affected. At the same time as you centralise your key resources, your users are doing the opposite.

They are spreading out, whether it's through teleworking and homeworking, or because the organisation wants more but smaller offices, or simply because they are picking up their laptops and going mobile.

At first, some WAN acceleration vendors tried to deal with this shift by downsizing their appliances and producing an entry-level box for £1000 to £2000. That's cheap by comparison with their high-end appliances, but still expensive if it's for a single PC - and of course no laptop user is going to want to carry a second box around!

The dam was broken last year when newcomer Orbital Data announced a software-only WAN accelerator for Windows PCs. It still needed an appliance in the data centre, but one appliance could support many PCs.

Orbital Data said it planned to do versions for other operating systems, but before it could announce any of those it was bought by Citrix. Its PC software is now sold as the WANscaler Client.

Others have joined in as well. For example, AcceleNet from Intelligent Compression Technologies supports MAPI and CIFS, plus HTTP, and is also available in a version optimised for wireless connections, so it disables itself when it detects a low latency link such as a LAN.

Another smaller vendor is Stampede Technologies, which aims primarily at web, J2EE and Ajax apps, including Lotus Notes/Domino. The company also has a version that needs no client installation – Stampede says it injects acceleration technology into the response delivered to the client browser.

Perhaps more surprisingly, Packeteer was a relatively early entrant too, having bought Tacit which had in turn acquired software developer Mobiliti. Its software client initially offered only file synchronisation and remote backup – in effect it was a software-only version of Tacit's iShared WAFS technology - but the upcoming version 7.0 of Mobiliti will add in TCP latency and data reduction technologies derived from Packeteer's SkyX WAN accelerators.

"It's similar to something like Lotus Notes replication, but it's file shares and documents," says Packeteer's product marketing director Mark Urban. For example, it can cache shared files to your PC hard disk and make them available off-line. Urban adds that the acceleration features need a SkyX appliance in the data centre – in fact, all these acceleration schemes involve a server in the data centre talking to client software on PCs.

2007 will see more suppliers join the fray, offering relatively inexpensive PC-based versions of the software that they currently run on appliances costing £1000-plus.

"We will have software for the PC later this year," says John Martin, Riverbed's VP of product management.

Efi Gatmor, CTO of Expand Networks, says Expand is developing a PC client where you can activate only those acceleration features you need. "It will be self-adapting and also centrally managed, for example you could configure it so only the active application gets QoS. It can talk QoS per application too, because it is application-aware," he adds.

Others who may well join in with soft clients this year or next include Blue Coat, through its acquisition last year of PC remote access developer Permeo, F5 Networks and Juniper, the latter two by adding acceleration capabilities to their current SSL VPN clients.

Like Orbital Data's, most of the other WAN acceleration clients currently available or planned are Windows-only – and for the moment, that means Windows on a desktop or laptop PC, although Gatmor notes that he's looking at versions for Windows Mobile and perhaps for other mobile devices too.

All of them are likely to require a fairly hefty PC as well, in terms of processing power. But for modern systems, with their dual-core, multi-GHz processors, it should be a small price to pay if it does indeed yield LAN-like performance over a narrowband connection.