How fast is fast enough?
But DSL service, which is delivered over traditional copper phone lines, does not measure up to the speeds of cable Internet service. The most recent F.C.C. figures available, from mid-2012, show that only 8 percent of DSL connections in the United States transmit at a speed of at least 10 megabits per second. Seventy percent of cable modem service travels that fast.
All of that brings into focus another debate that is expected during consideration of the merger: Just what qualifies as high-speed Internet, or broadband, service?
The F.C.C. has a formal definition: broadband that moves at 3 megabits per second or faster. But that speed is woefully inadequate for many sites that stream video. Many of the newest generation of mobile broadband services can transmit data at up to 8 megabits per second, but that is still below the average cable modem speed.
In that respect, Comcast says it is a victim of its success. It has spent heavily to build its capacity and offer customers better Internet service. “People who are critics of us,” Ms. Fitzmaurice said, “can’t decide that now that we’re offering higher speeds, competition from DSL doesn’t exist.”