Troubleshooting guide

BSR Troubleshooting Guide
A-138
• Station Maintenance ranging uses periodic time intervals to send a unicast
message containing a registered SID between the cable modem and the
CMTS.
• Short Data Grants and Long Data Grants are grants of time that a cable
modem with a particular SID has to transmit upstream.
The cable modem establishes downstream synchronization with the CMTS.
Initial Ranging
The cable modem sends an Initial Ranging request to establish its time reference and
transmit power settings from the UCD. The CMTS responds to the Initial Ranging
request with a temporary SID equal to zero, and the downstream channel ID.
The cable modem receives the upstream interface information and transmits a
Ranging Request to the CMTS that is consistent with the UCD and MAP information.
The CMTS replies to the cable modem Ranging Request with a Ranging Response
that contains the appropriate SID or SIDs, upstream channel ID on which the CMTS
heard the Ranging Request, and specific adjustments to its MAP for the cable modem
transmitter so that the cable modem can effectively transmit to the CMTS.
Establishing IP Connectivity
The cable modem obtains an IP address from the Dynamic Host Configuration
Protocol (DHCP) server on the network to establish IP connectivity, and it exchanges
configuration parameters automatically without manual intervention over the CM
network.
1. The cable modem broadcasts a DHCP discovery packet containing its MAC
address.
2. The DHCP server checks the validity of the cable modem MAC address and
sends a response offer if the MAC address is valid.
3. The cable modem selects the response offer and sends a DHCP request for its IP
parameters to the DHCP server. The DHCP server sends a response to the cable
modem containing the following parameters:
• Cable modem IP address.
• Gateway Router IP address if the DHCP server is on a different network.