METHOD AND APPARATUS FOR PREVENTING RE-RANGING AND RE-REGISTRATION OF CABLE MODEMS DURING PROTECTION SWITCHING BETWEEN ACTIVE AND SPARE CABLE INTERFACE CARDS IN A CABLE MODEM TERMINATION SYSTEM

摘要

In a cable data system that includes a cable modem termination system or CMTS (Fig. 2), high-reliability is accomplished by reducing the time required to switch over traffic from a failed circuit (312) to a back up circuit (311). Fault recovery time to switch over to a spare circuit (311) is reduced by copying the operational parameters used in each of the active circuits into a spare circuit such that upon the failure of an active circuit, the spare circuit needs only to be instructed which set of operational parameters for a particular failed circuit to use. Clock counters that are continuously incremented in active circuits can be copied into a newly installed circuit by copying into a local register for the newly installed circuit, a future value of a clock counter. At a predetermined instant, preferably just before the clock counter value equals to the future value, the future value is clocked into the newly installed circuit so as to synchronize the clock counter value in the new circuit to the clock counter values in the previously activated circuits.