Investors have yet to be convinced the deal makes sense

Cisco chief John Chambers said the deal would help it deliver entertainment, communication, and online services.

"Video is emerging as the key strategic application in the service provider triple-play bundle," he said.

Analysts said the deal should bring closer the time when any network can deliver to any screen.

"As consumers demand more sophisticated information and entertainment services in their home, tightly coupled applications, devices and networks will be essential," said Mr Chambers.

Said Scientific-Atlanta chief executive Jim McDonald: "The combined strengths and resources of our two companies will position us to address more quickly the growing number of opportunities in the markets we serve and enable us to create new products and services that might not have existed otherwise."