Troubleshooting guide

Cable Modem Registration Process
A-141
Data Exchange
Cable modems use the dedicated data intervals in the current upstream MAPs to
transmit data to the CMTS. When no dedicated data interval in the current upstream
bandwidth allocation map exists and the Protocol Data Unit (PDU) data frame is
within the appropriate size range, cable modems compete for request and data
contention intervals to transmit data to the CMTS. If a dedicated data interval
becomes available while the cable modem is competing for a contention interval, the
cable modem drops its bid for the contention slot and uses the dedicated data interval
instead of the contention interval.
The cable modem sends data with bandwidth allocation requests whenever possible.
The cable modem continuously monitors allocation MAP messages for short and long
grants and for pending indications given by the CMTS. The cable modem also
monitors its transmission rate to keep it within the maximum upstream data rate for its
class of service.
The CMTS supports the concatenation of MAC level frames. Cable modems that
support concatenation combine multiple MAC level frames into one larger frame for
an efficient and smooth traffic flow over the upstream channel path. The CMTS
processes these concatenated frames and sends the data to its destination.