The Converged Regional Area Network, or CRAN allows all voice, video, and Internet traffic to go over a single network with redundant 10 GigE networks. The speed of the connections are very fast. All devices on the Comcast network, regardless if it is a cable modem, digital cable box, VoIP modem, or whatever are connected to each other (from demarc of the home and outward) on a redundant 10 GigE optical network. Such a network can provide network speeds far in excess of what Verizon's Fios offers with little upgrade by Comcast should they want to offer equivalent speeds.
All areas are being converted to the CRAN. The most apparent thing you will notice when you are switched, is the additional hops. These hops have little to no effect on speeds or latency. The good news is; by keeping the traffic more internal, it reduces cost to Comcast and allows the subscriber to put a less detrimental affect on the network.
Two threads for review on CRAN:
How can I check if I am on Comcast CRAN or not?
How can I tell if I am on the CRAN?
*This FAQ is based on user knowledge from a volunteer core of BroadbandReports' members. This FAQ in no way constitutes official information from Comcast or any of its affiliates.