Cisco Systems Inc. (Nasdaq: CSCO) has warned its customers that bandwidth management software deployed in its IOS software is defective and could be generating inaccurate data, Light Reading has learned.

The software module comes from Cisco partner Corvil Ltd., which announced its technology relationship with the router giant earlier this year (see Cisco Gets Closer to Corvil and Corvil Now Inside Cisco Routers).

Sources say the problem has sent shockwaves through Corvil and resulted in layoffs. Indeed, the software bug presents a major speedbump for Corvil, as Cisco has stopped selling Corvil software licenses, shutting off the startup's major revenue channel.

The Corvil software was incorporated into IOS so that Cisco could deliver enhanced, integrated quality of service (QOS) capabilities with its routers. When activated, Corvil's software generates data that determines the minimum bandwidth required by individual applications, and manages the bandwidth so that specified levels of packet loss and delay are not breached.

Users benefit from this as it allows them to manage application-specific QOS levels and avoid the costly strategy of over-provisioning network bandwidth.

Corvil's technology has been added to IOS versions 12.3(14)T, 12.4, and 12.4T (the latest releases) for a range of Cisco routers, from the 800 series to the 7200 series.

Now Cisco has been forced to issue a field notice, warning its customers that the software can overestimate the bandwidth requirements of network applications. Cisco warns that in instances where packet loss, rather than delay, is the dominant concern, results generated by the Corvil technology can overstate bandwidth "by more than the 20% tolerance agreed upon."

So does Cisco, which is also one of Corvil's backers, view this as a major embarrassment? (See Corvil Secures €15M). What impact will this have on its relationship with Corvil?

Cisco declined to comment directly. Its sole response was an emailed statement: "We are aware that Corvil's recent announcement about issues with its CorvilNet product does impact a certain IOS feature used for bandwidth estimation. As a result, Cisco will not be issuing any new licenses related to this feature. We will work with Corvil to resolve this issue as quickly as possible."

And what is that timescale? Cisco is telling customers it doesn't know when the problem will be fixed and is asking them for feedback on "the impact of this defect."

Corvil, meanwhile, says the issue is almost resolved. CEO Donal Byrne says the bug has been identified and fixed. But that fix is still undergoing internal testing, and he can't estimate when a patch will be delivered to Cisco, though he claims it's "a case of weeks, not months."

Byrne says the problem arose following the deployment of Cisco routers in Europe for a customer with about 800 branch offices.

"That's the most stressful environment our technology's been deployed in. Our sales engineer noticed that some of the results didn't seem right, and so informed the customer and reported back to us. We told Cisco and then launched an investigation, which uncovered a coding bug." Adds Byrne: "It's not our first bug, and I'm sure it won't be our last." [Ed. note: Whew! That puts the mind at ease!]

But while Byrne admits to the technical hiccup, he rejects suggestions that Corvil has been forced to lay off sales staff to cut costs while it deals with the issue. He does admit that 15 of the firm's 26-strong sales and marketing team have gone, but claims this isn't related to the technical hitch.

"Sales weren't happening as fast as we'd been hoping, and as a startup you're always looking to conserve your cash. Now we have this sales channel with one of the world's biggest companies and we didn't need as many direct sales people. Some of them have actually moved across to Cisco."

Except, of course, Cisco isn't selling any more Corvil licenses at the moment. So will Byrne be looking for other indirect channels? "We've got our hands full with this one. We're flat out, and we need to make sure we're delivering as promised to Cisco before we look at any other relationships," says the CEO.

— Ray Le Maistre, International News Editor, Light Reading