Cisco uBR905 Installation Manual page 28

Functional Overview
The router configures itself for the specified IP address and gets the current date and time from the
9.
specified ToD server.
Using the TFTP protocol, the router downloads the specified DOCSIS configuration file and
10.
configures itself for the appropriate parameters. The DOCSIS configuration file defines the router's
operating mode such as the provisioned downstream and upstream service assignments, assigned
frequencies, data rates, modulation schemes, Class of Service (CoS), type of services to support,
and other parameters. Cisco provides tools to help automate the creation of configuration files.
The DOCSIS configuration file must be in the exact format given by the DOCSIS
Caution
specification. An incorrect DOCSIS configuration file can cause the Cisco uBR905 router
to constantly cycle offline. Such errors include wrong downstream frequency, wrong
UCD, wrong downstream Channel ID, invalid CoS, incorrect BPI privacy configurations,
or shared secret strings.
11. The router sends another registration request to the CMTS containing the CoS parameters given in
the DOCSIS configuration file.
The CMTS verifies that the router is using the appropriate CoS profile and converts the temporary
12.
SID into a data SID with a service class index that points to the applicable CoS profile.
Note
13. The router completes its secondary ranging and is then online, passing data between the cable
network and the PCs and other customer premises equipment connected to the router.
Note
If the DOCSIS configuration file specifies that the router must download a secondary Cisco IOS
14.
image and a Cisco IOS configuration file, the router uses TFTP to download the image and
configuration files into its local memory. It then installs the new Cisco IOS image and runs the
configuration file.
Alternatively, a system administrator can manually configure the Cisco uBR905 router by giving
commands at the router's CLI interface or by using an SNMP manager.
15. If Baseline Privacy Interface (BPI) encryption is configured and enabled on both the router and
CMTS, the router and CMTS negotiate the appropriate encryption parameters. After encryption is
enabled, all information within Ethernet packets that is sent between the router and CMTS is
encrypted to prevent interception or modification by an unauthorized party.
Figure 1-6 illustrates the traffic flow during this process.
Cisco uBR905 Router Hardware Installation Guide
1-12
Depending on the software image being run and the capabilities of the CMTS, the
DOCSIS configuration file can also specify multiple CoS profiles. Each CoS
profile is assigned its own SID, either dynamically or statically, depending on the
capabilities of the CMTS and software image being used.
At this point the router is online and operational in the basic DOCSIS bridging
mode ("plug and play" mode). The next step is done only if the DOCSIS
configuration file specifies that the router must also download a Cisco IOS
configuration file and new Cisco IOS image.
Chapter 1 Product Overview
OL-0598-01 (9/2000)