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Chapter 1
Product Overview
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The Cisco CVA122/CVA122E Cable Voice Adapter downloads the DOCSIS configuration
Note
file each time it is powered on, but it downloads the Cisco IOS image and Cisco IOS
configuration file only when needed. A new configuration file or image can be
downloaded whenever necessary, such as when the cable service offers new services or
subscribers upgrade their services.
To ensure that subscribers obtain the exact services they have ordered, the Cisco CVA122/CVA122E
Cable Voice Adapter arrives from the Cisco factory with a unique identifier (UID) that consists of a
serial number and MAC address. These factory-assigned values are on a label at the bottom of the cable
voice adapter; for convenience, these values are also in a barcode label that can be easily scanned for
easy entry into the service provider's provisioning and billing system.
Using the MAC address of the cable voice adapter as the key, the CMTS downloads the DOCSIS
configuration file and Cisco IOS image that will provide the services that this particular subscriber has
purchased. Service technicians at the headend typically create a number of standard configuration files
to match the range of services offered by the provider; these configuration files can be created manually
or with tools provided by Cisco Systems for this purpose.
The following sections describe the initial power-on and provisioning sequence in more detail, as well
as the requirements that must be met by both the cable voice adapter and the CMTS before provisioning
can succeed.
Initial Power-On Sequence
When connected and first powered on, the Cisco CVA122/CVA122E Cable Voice Adapter performs the
following DOCSIS-mandated procedure for automatic installation and configuration:
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6.
OL-0799-02 (05/2001)
To customize the cable voice adapter's configuration further, the DOCSIS configuration file can
also specify a Cisco IOS configuration file that the CMTS should download to the cable voice
adapter. This second configuration file is an ASCII text file that contains the Cisco IOS commands
needed to configure the cable voice adapter for advanced features, such as VoIP.
The cable voice adapter boots the Read Only Memory (ROM) from the ROMMON partition of its
Flash memory.
The cable voice adapter performs a self-test, initializes processor hardware, and boots the main
operating system software—the Cisco IOS release image stored in Flash memory.
The cable voice adapter acquires a temporary downstream channel by matching the clock sync
signal that is regularly sent out by the CMTS in the downstream frequency range.
The cable voice adapter then waits for an Upstream Channel Descriptor (UCD) message from the
CMTS and configures itself for the upstream frequency specified in that message.
The cable voice adapter waits for the next upstream bandwidth allocation map message (MAP).
These messages are regularly sent from the CMTS to find the next available shared request timeslot.
The cable voice adapter then uses this timeslot to send a ranging request message to the CMTS,
communicating the cable voice adapter's user ID (UID, which includes its unique MAC address),
using a temporary service identifier (SID) of 0 (zero) to indicate it has not yet been allocated an
upstream channel.
In reply to the cable voice adapter's ranging request, the CMTS sends a ranging response containing
a temporary SID to be used for the initial cable voice adapter configuration and bandwidth
allocation. As needed, the cable voice adapter adjusts its transmit power levels using the power
increment value given by the CMTS in its ranging response message.
Cisco CVA122/CVA122E Cable Voice Adapter Description
Cisco CVA122/CVA122E Hardware Installation Guide
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Table of Contents
Troubleshooting
