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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
OL-2239-05
Chapter 1 Overview of Cisco uBR7200 Series Software
Supported Software Features for the Cisco uBR7200 Series
implemented on the cable modem. The CMTS provisions a registering cable modem with a default
Data-over-Cable Service Interface Specifications (DOCSIS) 1.0 service class that is assigned by the
operator. This service class has no upstream or downstream rate limits.
When the modem sends data upstream, it makes bandwidth requests without throttling or dropping
packets because of its own rate-policing algorithm. The CMTS does traffic shaping based on the QoS
profile enforced by the operator.
For configuration information, refer to the document titled QoS Profile Enforcement for the Cisco
uBR7200 Series Router on Cisco.com:
http://www.cisco.com/en/US/docs/ios/12_0t/12_0t4/feature/guide/qospr124.html
Time-of-Day Server
The Time-of-Day (ToD) server enables the Cisco Cable Modem Termination System (CMTS) to provide
a ToD server to the CMs and other customer premises equipment (CPE) devices connected to its cable
interfaces. The cable modem uses the ToD server to get the current date and time to accurately
time-stamp its Simple Network Management Protocol (SNMP) messages and error log entries.
The Data-over-Cable System Interface Specifications (DOCSIS) 1.0 and 1.1 specifications require that
a DOCSIS cable modem or other CPE device must specify the following time-related fields in the
Dynamic Host Configuration Protocol (DHCP) request it sends during its initial power-on provisioning:
• Time Offset (option 2)—Specifies the time zone for the cable modem or CPE device, as the number
of seconds that the device's time stamp is offset from Greenwich Mean Time (GMT)
• Time Server Option (option 4)—Specifies one or more IP addresses for a ToD server.
• During initial provisioning, a DOCSIS cable modem or CPE device attempts to contact the ToD
server. If successful, the cable device updates its onboard clock with the time offset and timestamp
received from the ToD server. If a ToD server cannot be reached or if it does not respond, the cable
device eventually times out and continues on with the initialization process.
For configuration information, refer to the chapter titled Time of Day Server” in the Cisco Cable Modem
Termination System Feature Guide on Cisco.com.
Trivial File Transfer Protocol Server
A DOCSIS-compliant cable modem requires access to three types of servers in order to successfully
come online:
• A DHCP, Time of Day (ToD) and TFTP Servers provides the cable modem with an IP address, a
subnet mask and other IP related parameters.
• A Time-of-Day Server which lets the modem know what the current time is. A cable modem needs
to know the time in order to be able to properly add accurate timestamps to its event log.
• A Trivial File Transfer Protocol (TFTP) server from which a cable modem is able to download a
DOCSIS configuration file containing cable modem specific operational parameters. After a cable
modem has attempted to contact a ToD server, it contacts a TFTP server to download a DOCSIS
configuration file. If a binary DOCSIS configuration file can be copied to a Flash device on a Cisco
CMTS, then the router can act as a TFTP server for that file.
Type/Length/Value Parser and Encoder
The Type/Length/Value (TLV) parser and encoder is a new module that handles parsing and encoding
TLVs on the CMTS. All old DOCSIS1.0/1.0+ TLVs are supported. In addition, many new TLVs have
been added in DOCSIS1.1, such as service flow encodings, classifier encodings, and support for PHS
rules. The new TLV parser features are used by different MAC message modules.
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