"I don't think there's any way Nortel can make it without splitting up," said Yankee Group analyst Zeus Kerravala. And the wireless and enterprise units are the most promising candidates. "There are only so many parts of the business that have value," he said.

The main draw for Nortel's enterprise business might be its roster of customers, according to Kerravala. Avaya, the main rival to Cisco Systems in IP (Internet Protocol) telephony, has a hard time attracting new customers because it's perceived as a legacy equipment company, he said. (Avaya traces its roots to the old U.S. Bell System.) Buying Nortel would give them easy access to companies that use that company's gear today.

Cisco itself might be a plausible buyer for Nortel's wireless business, said IDC analyst Godfrey Chua. Nortel has a well-respected product portfolio in both CDMA (Code-Division Multiple Access) and GSM (Global System for Mobile Communications) and related 3G (third-generation) systems, he said. Cisco sells mobile operators gear for the core of their networks, such as routers, but not the actual wireless base stations at the edge that communicate with subscribers' devices. The edge is where cellular companies make roughly 60 percent to 70 percent of their network investment, so it could be a lucrative piece of the pie for Cisco as operators migrate to 4G, he said.

"Carriers just don't think of Cisco when they think of 4G," Chua said. With both the core and the edge, "they could potentially have a huge business on their hands."

For Cisco, Nortel would not be a very expensive company to buy, even outright, Chua said. When its shares on the New York Stock Exchange stopped trading the day before the bankruptcy filing, they were worth only $0.32 each. But the real cost lies in the pension obligations built up by the company over a history of more than a century.