Linksys WCM300 Cisco Cable Wideband Solution Design and Implementation Guide, - Page 57

Chapter 4 Implementing and Configuring the Solution Wideband Cable Modem Behavior The configuration file used for the Scientific Atlanta DPC2505/EPC2505 wideband cable modem is identical to a DOCSIS 2.0 configuration file. DOCSIS 2.0 configuration file tools like the Cisco Broadband Configurator can be used to create configuration files for this modem. Automatic Adjustments During Scientific Atlanta DPC2505 and EPC 2505 Registration During modem registration, upon reception of the REG-RSP from the CMTS, the Scientific Atlanta DPC2505/EPC2505 modem first checks for presence and correctness of the various encodings. • If any encodings are incorrectly formatted or exceed the modem's capabilities, the wideband cable modem may detect this and immediately send a REG-ACK message with a confirmation code indicating failure. The confirmation code will be reject-bad-rcc(208) if the RCC encoding is bad, or reject-other(1) if some other problem is found. • If encodings appear to be valid, the wideband cable modem attempts to tune its non-primary receivers to the non-primary downstream channels specified in the RCC. The RCC may specify zero, one, or two non-primary downstream channels. If the cable modem fails to tune to the designated non-primary downstream channels, it will send a REG-ACK with confirmation code reject-bad-rcc(208). In the case of wideband channels overlapping on some sets of QAMs, if the DPC2505 modem rejects the registration with confirmation code of reject-bad-rcc(208), something is wrong- either an incorrect plant topology configuration or a bad tuner in the cable modem. The CMTS records this occurrence. When the same cable modem tries to register again, the CMTS chooses different wideband channels preferably residing on a different sets of QAMs. The process continues until the wideband cable modem successfully registers on a wideband channel or all choices of wideband channels are exhausted. If all choices are exhausted, the CMTS put the Scientific Atlanta DPC2505 modem in DOCSIS 2.0 mode on its next attempt to register. A timeout value of 24 hours is defined for the CMTS to clear the bad QAM status recorded for each CM. Therefore, the wideband cable modem is allowed to retry the bad set of QAMs in the future. CMTS Interactions with Wideband Cable Modems This section provides information CMTS interactions with wideband cable modems: • Registration for Wideband Cable Modems, page 4-9 • Load Balancing for Wideband Cable Modems, page 4-10 In these sections, all statements are generic and apply to the following modems: • Linksys WCM300-NA • Linksys WCM300-EURO • Linksys WCM300-JP • Scientific Atlanta DPC2505 • Scientific Atlanta EPC2505 Registration for Wideband Cable Modems After the wideband cable modem completes the initialization process on the primary downstream channel, the CMTS uses the REG-RSP message to enable multiple downstream RF channel operation (wideband channel operation) and to assign channels to the cable modem. OL-10705-02 Cisco Cable Wideband Solution Design and Implementation Guide, Release 1.0 4-9