Troubleshooting guide

Cable Modem Registration Process
A-137
Introduction
This appendix describes the cable modem registration process. A cable modem goes
through a standard registration process as defined by the Data Over Cable Service
Interface Specification (DOCSIS) to successfully connect to the BSR 1000 CMTS
and the BSR 64000 DOCSIS 1:4 and DOCSIS 2:8 CMTS modules on the CM
network.
Scanning
When attached to the network and powered on, the cable modem scans the
downstream channel frequency for a valid 8 MHz channel frequency (European
DOCSIS - Annex A) or 6 MHz channel frequency (North American DOCSIS - Annex
B), or it uses its last known downstream frequency that is stored in its NVRAM.
The cable modem establishes a 64 or 256 Quadrature Amplitude Modulation (QAM)
downstream connection. The cable modem listens on the downstream frequency for
the following upstream interface management information:
• Upstream Channel Descriptor (UCD) - The UCD describes the characteristics
of an upstream channel for the cable modem. The UCD contains information on
the mini-time slot size, upstream channel ID, and downstream channel ID. It also
contains information on how to transmit the symbol rate, frequency, and preamble
length. The UCD also has a burst descriptor that identifies the maximum burst
size, guard time size, and amount of Forward Error Control (FEC) for all six
Interval Usage Codes (IUCs).
• Upstream Bandwidth Allocation Maps (MAPs) - MAPs tell the cable modem
where and when there is an opportunity to transmit bursts of data in time slots that
are in contention by using six types of IUCs:
• Request uses discover time-slot contention areas on the upstream frequency
in which a cable modem may request a future time when the cable modem
could transmit.
• Request Data discovers descriptions of time-slot contention areas in which it
can transmit either small data packets or requests for future grants.
• Initial Maintenance ranging uses time intervals to find a time slot
opportunity on the upstream frequency and initializes and transmits a
temporary Service Indentifier (SID) for a new cable modem to connect to the
CM network.