Software developer Autodesk has said it will fix the file format that's caused trouble for AutoCAD users who also use Riverbed's Steelhead WAN accelerators.

In an exclusive interview with Techworld, the company said it will debut a new version of its DWG drawing file format in its next major release that should level the playing field - both for WAN accelerators and for other gear that uses caching and data de-duplication, such as archiving and replication appliances.

"We are actively learning about those technologies - we are learning a lot about those vendors and what they're doing with our files. What we don't know is which vendors are affected," said AutoCAD product line manager Eric Stover.

He added that it took Autodesk by surprise when the problem first reared its head a year or so back.

"In our 2007 release, we stripped out the old AutoCAD 3D capability and replaced it with the much more modern modelling kernel from Autodesk Inventor, but that made the files extremely large, so we added compression," he said.

It was that compression which caused problems for Riverbed, he claimed. By making each saved file look like a wholly new file, it prevented the Steelhead from saving time and bandwidth by sending only the changes over the WAN.

The problematic file format first appeared in 2006, when Autodesk released the somewhat confusingly-titled AutoCAD 2007. However, users did not migrate from older versions straight away, so it took time for the implications to sink in.

To complicate matters, different WAN accelerators use different caching and de-duplication techniques, and not all were affected by the change, according to Stover.

"Silver Peak and Cisco told us they don't have any problems," he said. He added that users of some AutoCAD versions - Civil 3D and Architecture, in particular - were worse hit than others, while those who didn't need the 3D capability were able to sidestep the issue by sticking with the previous file format.

Stover said the problem demonstrates that software designers across the industry must in future consider how their choices affect the rest of the IT ecosystem.

"We now have an Autodesk software architecture team working with the other vendors on where this technology is going - I see a lot of openness from the other vendors on the topic of file formats," he said.

He added that the new DWG format is due in 2009 with the planned release of AutoCAD 2010. Interested hardware vendors will be invited to take part in the alpha and beta programmes for this, which will kick off this summer, he said.