Cisco CVA122 Hardware Installation Manual page 20

Cisco CVA122/CVA122E Cable Voice Adapter Description
Note
After the next MAP message broadcast, the cable voice adapter uses a shared request timeslot to
7.
invoke the Dynamic Host Configuration Protocol (DHCP) to establish IP connectivity with the
TCP/IP network at the headend.
8. The DHCP server—typically a dedicated server at the headend, but it could also be a CMTS such
as a Cisco uBR7200 series universal broadband cable voice adapter—sends a response containing
the cable voice adapter's IP address, as well as the IP addresses for the default gateway and time of
day (ToD) server. It also sends the IP address for the authorized Trivial File Transfer Protocol
(TFTP) server from which the cable voice adapter should download its DOCSIS configuration file.
Depending on the particular network configuration, other information could be provided, such as
the IP addresses for a syslog server or security server.
The cable voice adapter configures itself for the specified IP address and gets the current date and
9.
time from the specified ToD server.
Using the TFTP protocol, the cable voice adapter downloads the specified DOCSIS configuration
10.
file and configures itself for the appropriate parameters. The DOCSIS configuration file defines the
cable voice adapter'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 CVA122/CVA122E Cable Voice Adapter 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 cable voice adapter sends another registration request to the CMTS containing the CoS
parameters given in the DOCSIS configuration file.
The CMTS verifies that the cable voice adapter is using the appropriate CoS profile and converts
12.
the temporary SID into a data SID with a service class index that points to the applicable CoS
profile.
Note
The cable voice adapter completes its secondary ranging and is then online, passing data between
13.
the cable network and the PCs and other CPE devices connected to the cable voice adapter.
Cisco CVA122/CVA122E Hardware Installation Guide
1-6
At this point, the cable voice adapter has established connectivity with the CMTS
but is not yet online. The next steps allocate permanent upstream and downstream
frequencies, as well the configuration required for IP network connectivity.
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.
Chapter 1 Product Overview
OL-0799-02 (05/2001)