Troubleshooting guide

Cable Modem Registration Process
A-139
• Cable modem Subnet Mask.
• TFTP server IP address used to connect to the TFTP server.
• Download Configuration file name is the name of the cable modem
configuration file to be read from the TFTP server by the cable modem.
• Cable Modem Lease Time used for keeping the correct time on error logs.
Establishing Time of Day
For security purposes, the cable modem obtains its IP parameters from the DHCP
server and it establishes the Time of Day (TOD).
TFTP Connectivity
The cable modem communicates with the TFTP server on the network to obtain its
configuration file. The configuration file contains bandwidth specifications, class of
service parameters, network access authorization, and upstream and downstream
operating frequencies. The cable modem requests the TFTP server configuration file.
The TFTP server sends the configuration file.
Registration
The registration process authorizes the cable modem to forward traffic on the
network. The cable modem must send a TFTP response containing its configured
class of service, SID, Service Flow Identifier (SFID), and any other operational
parameters in its configuration file to the CMTS.
The CMTS uses a Message Integrity Check (MIC) to verify the contents of the
configuration file and checks that the configuration file was created by a valid TFTP
provisioning server. The CMTS ascertains that if the configuration file was created by
a valid TFTP provisioning server using a secret key shared with the TFTP server. The
network administrator enters the secret key at both the TFTP provisioning server and
the CMTS. Once the CMTS receives verification from the cable modem after
computing the secret key, the CMTS sends a registration response telling the cable
modem that it is authorized to forward data on the CM network.