DOCSIS 10 Configuration File
The DOCSIS 1.0 configuration file specifies the operational parameters for a DOCSIS 1.0 cable modem in the following list. Because of the limit of a single SID per cable modem, the operational parameters included define a set of parameters that are applied to all traffic traversing the cable modem.
The list of available parameters configured in a DOCSIS 1.0 configuration file includes the following:
• Radio frequency—Defines downstream frequency and upstream channel ID. In the case of the cable modem initializing on the wrong downstream or upstream channel, the configuration file forces the re-registration of the cable modem on the specified channels.
• Network access—Cable modems might need to be managed remotely while disallowing subscriber access to network services. The network access flag can allow a modem to register and block the transmission of subscriber traffic, and it allows a network administrator to connect to and configure the modem as necessary. Using this portion of the configuration file is the only recommended method of controlling network access and is the most efficient method to disable a non-paying subscriber.
• CoS — Specifies a CoS ID for the cable modem's associated SID. Specifies maximum downstream rate, maximum upstream rate, upstream channel priority, guaranteed minimum upstream rate, and maximum upstream transmit burst for that cable modem. Some primitive DOCSIS 1.0 CMTS units do not support these parameters and only provide best-effort service for all modems. The best DOCSIS CMTS units can enforce these parameters even if the cable modem does not cooperate (or self-police) its upstream bandwidth requests.
• Baseline privacy—Defines the baseline privacy (security) settings for the SID associated with the cable modem. Enables baseline privacy. Configures authorize wait timeout, reauthorize wait timeout, authorization grace timeout, operational wait timeout, rekey wait timeout, TEK grace time, and authorize reject wait timeout. Frequent key exchanges can improve overall data security but also increase resource use (CPU load) on both the cable modem and the CMTS. Information on baseline privacy is detailed in the "Security and Baseline Privacy" section later in this chapter.
SNMP—Sets the SNMP manager IP address and SNMP write-access. Because cable modems can be closely managed through SNMP these settings are vital. The configuration file also allows for the setting of any SNMP MIB object through configuration file options. DOCSIS contains a large body of SNMP MIBs that are standardized for both the cable modem and the CMTS. Often vendors provide additional SNMP MIBs to enable the management of advanced features.
CPE—Cable operators can define the number of allowed devices at the customer premises by using this command. Depending on the modem vendor, a single cable modem can be defined to support from 0 to 255 computers or other devices at the customer premises. The configuration file can also define the MAC address or addresses of allowed hosts. Some DOCSIS equipment uses the value 0 or 255 to indicate unlimited CPEs, and others use these values to indicate that no CPEs are allowed.
Software upgrade—Cable modems might need software upgrades after deployment. This configuration file option includes a TFTP server IP address and the filename for an upgraded software image. When modems reinitialize they automatically upgrade, reload, and reregister if the specified filename doesn't match their current filename. Software upgrades are obviously specific to the modem make and model, although this field can be used for all cable modems. Use of this field typically requires a unique configuration file for each type of modem on the cable network to avoid modems uploading invalid or unmatched software versions.
Telephone return—For modems without a cable-based return path, the configuration file can contain a set of telephone modem parameters for upstream connection.
Vendor—Vendor ID, vendor-specific information. Used for modem vendor-specific features such as Cisco DOCSIS 1.0+ features, including VoIP support, a Cisco IOS filename, the number of phone lines, IP Precedence masks, and so on.
Miscellaneous—Other parameters include vendor-specific options, security transform sets, modem authentication parameters, and IP Precedence for the corresponding SID.
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