While Comcast has started deploying 2Gbps fiber-to-the-home service to certain parts of its territory, much of its network is going to be stuck on cable for years to come.

But customers outside the fiber footprint will still be able to buy gigabit Internet service after Comcast upgrades to DOCSIS 3.1, a faster version of the Data Over Cable Service Interface Specification. Comcast said in April that DOCSIS 3.1 will be available to some of its customers in early 2016 and eventually across its whole US footprint. Last week, Comcast said it wants to complete the whole upgrade within two years.

"Our intent is to scale it through our footprint through 2016," Comcast VP of network architecture Robert Howald said in an interview with FierceCable. "We want to get it across the footprint very quickly... We're shooting for two years." It could take up to three years, the story said.

Comcast, the nation's largest Internet provider, with 22.5 million subscribers, operates in 39 states and Washington, DC.

The DOCSIS upgrades will require new modems in customer homes and back-end upgrades in cable plants. Unlike Comcast's symmetrical fiber service, upload speeds would be slower than download speeds. But 1Gbps downloads aren't the limit with DOCSIS 3.1, which can support up to 10Gbps downstream and 1Gbps upstream.

While Comcast's initial DOCSIS 3.1 rollout is expected to offer up to 1Gbps download speeds, Howald said the new standard "allows us to do that and higher."

The price will be high, of course. Comcast's 2Gbps fiber service costs $300 a month plus one-time installation and activation fees of up to $1,000. Comcast says it will build fiber to any home that's already within a third of a mile of its fiber network, but reports a few weeks ago from Stop the Cap and DSLReports suggest that some potential customers are having trouble signing up for the service.