Riverbed Technology has upgraded the software on its WAN acceleration appliances to help customers keep corporate files available to remote workers if WAN connections fail.

Placed at either end of a wide-area connection, Riverbed's Steelhead appliances already use a variety of means to speed up performance on those links, and they can now serve files locally even if the connection between branch sites and central servers is broken.

Similar to capabilities announced recently by Tacit Networks, Riverbed's new Proxy File Services feature in Steelhead 2.0 software lets customers designate which files should remain accessible during outages and how extensive the access should be.

For example, a file can be designated for read-only access, read/write access or no access in the event of a WAN failure. This capability defaults to a global-access setting, which means files can be directly accessed only from the server storing them. Local storage mode places a copy of a file on a local Steelhead device where it can be accessed and altered. Broadcast mode places a file on multiple Steelheads but allows users to only read them, the company said.

"It's not an all-or-nothing proposition," said Steve Duplessie, an analyst with Enterprise Strategy Group. If all files were stored at the local server and had to be updated periodically, that could clog the WAN links that the Riverbed boxes were installed to keep free, he said. "It's going to take up some space. This helps to fine-tune the wire."

Jon Arnold, Riverbed's Northern Europe regional director, acknowledged that the company is playing catch-up in this one area - which it prefers to call Wide-area Data Services, or WDS - but insisted that in overall terms it is months ahead of the competition.

"It is an area where the WAFS people see strength," he said. "Now we have exactly the same capabilities as them, but with the addition of all the other things we do."

For Nevada architectural/engineering firm Blakely, Johnson & Ghusn, the local file serving not only protects against WAN outages but speeds general file access, says Ron Maxwell, IT manager for the firm, which has removed file servers from its Las Vegas branch office in an effort to reduce confusion among different versions of files. "Instead of going across the WAN to the main office and grab files and bring them back, they'll go to a local file server," he says.

Steelhead already featured TCP acceleration, improving performance across IP networks by making less-pronounced reductions in sending speed when lines become congested and by returning to full speed more quickly when congestion clears, making effective throughput subject to less dramatic and prolonged swings. Duplessie says TCP acceleration is also implemented by competing vendors such as Tacit, Swan Labs and Juniper.

Riverbed is now expanding its support for specific applications, said Arnold: with Steelhead version 2.0, it has re-worked its MAPI module to optimise it for Exchange 2003, and added a new module that supports SQL Server. He claimed that by optimising on top of its generic support for TCP applications, performance could improve by five to 10 times.

This acceleration works because many protocols require many back-and-forth transactions that can result in delay. By having local Steelhead machines respond as if they were the remote database, some of these transactions don't have to cross the WAN, thus improving response time.

"This market is becoming very significant now," said Arnold. "In the last year there have been acquisitions in this space of around three-quarters of a billion dollars." He added that Riverbed has had approaches from would-be buyers but turned them down, as its board believes it will earn more from an eventual IPO.

He admitted that the various wide-area optimisation technologies are converging, but claimed that where his competitors come from either the bandwidth-centric WAN optimisation side, or the storage-centric WAFS direction, only Riverbed takes an application-centric approach.

Riverbed also is introducing the Steelhead 2510 and 3510 appliances. Both are based on existing Steelhead hardware but have software that supports larger WAN links and more simultaneous TCP sessions than current models.