Multiservice switch vendor Tenor Networks Wednesday shut down, the latest casualty in a brutal market for carrier equipment sales.The company, which was founded in 1998 and raised more than $120 million in funding, managed to sell some of its gear for use in carrier service trials but was never able to land its offerings in production networks. Tenor's IP\/MPLS-based packet infrastructure products were designed to support Ethernet, frame relay and ATM services - with metro Ethernet increasingly becoming the company's focus."I don't see any MPLS core switch market," Tenor President and CEO Dave Tolwinski told Network World\u00a0last summer, when the company cut its staff from 120 to 70 employees in an effort to conserve cash and survive the severe downtown in carrier spending. "The biggest risk now is to understand when the market's going to recover, how it will restructure, how it will re-emerge. I don't think the worst is over yet."The worst came last week when Tenor said it was cutting its 63-person workforce down to about a dozen employees, mainly engineers, who will maintain the company's technology in hopes of selling it off. Tenor's workforce peaked at just over 150 employees a couple of years back, according to a company spokesman.Tenor is the latest among a host of carrier equipment companies forced to close shop over the past year. Others have included\u00a0Crescent Networks\u00a0and\u00a0Gotham Networks.