Comcast Corp. said Wednesday it will collaborate with Vonage Holdings Corp., the leading independent Internet phone service, to make sure that Internet calling will work well for its subscribers.

Comcast, the country’s largest cable company, is being investigated by the Federal Communications Commission for what critics say is a heavy-handed approach to management of its subscribers’ Internet traffic. It has been hampering or blocking certain types of file-sharing.

The company has held that this practice is necessary to keep a few high-traffic subscribers from overwhelming and slowing down a neighborhood network. But it has said that it will, by the end of the year, introduce a new traffic management system that treats different types of traffic equally.

Comcast has also reached out to file-sharing companies to try to develop mutually acceptable techniques. The accord with Vonage follows the same pattern.

Comcast said it will work with Vonage to ensure that its new network management techniques balance congestion-fighting with the need to ensure that Internet calling services like Vonage function.

Internet telephone traffic is particularly sensitive to delays, making it vulnerable to both congestion and traffic management.

Comcast and Vonage compete in the phone business. Comcast has 5.2 million phone customers, while Vonage has half that number.