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.