Rescheduling A Cable-Modem Upstream Channel After Changing One Or More Of Its Properties
20 June 2004
In a cable-modem network, a cable modem (CM) talks to a cable- modem termination system (CMTS) over a traditional cable-television network. The cable-industry-backed standard that specifies how a CM and CMTS talk to each other is called DOCSIS. In DOCSIS the CMTS schedules the upstream (CM-to-CMTS) channels, each of which is time-division multiplexed into a sequence of minislots. DOCSIS provides a simple mechanism that lets the CMTS change an upstream channel's properties at any time. Although the DOCSIS protocol for changing upstream properties is simple, the internal CMTS ramifications are not. Often, a property change renders the current upstream schedule illegal, in which case the CMTS must reschedule. DOCSIS, however, says nothing about how a CMTS might reschedule. This paper describes a novel algorithm for rescheduling a DOCSIS upstream channel in response to an upstream-property change.
