VeEX CX380C, Руководство пользователя

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Pass Through: emulating a stand-alone Cable Modem. Once the Cable Modem goes online, connect a PC to the
10/100/1000 Ethernet test port at the top of the unit. The meter will automatically assign a Client IP address to the PC. Then
with the PC, access the internet. This mode helps sectionalize and troubleshoot issues in the customer premises (e.g.
replace the actual cable modem).
Always On: terminate mode and also enables the Cable Modem to remain online when exiting from the Cable Modem. This
allows online connectivity while using other features, such as Remote View and V300 R-Server access.
Once these settings are completed, press Connect . The test set will go directly to the Results page. Each step of the connection
process is listed. As a step is performed, an "in progress" indicator displays the current status.
After a step is completed, a
Pass
or
Fail
status is provided. If any one of the steps fails during the connection process, the cable
modem will stop and declare a failed connection. At this point, reset the test and try again, or go back to setup and verify the
settings.
DOCSIS Cable Modem (CM) Initialization Sequence
Cable Modem (CM) Connection Procedure and Training Sequence
1. CM scans the Downstream (DS) spectrum for a valid DOCSIS signal (either 64QAM or 256QAM). This can be a time
consuming step if the CM is not on a channel.
2. CM demodulates the DOCSIS signal and looks for a SYNC message.
3. CMTS periodically broadcasts Upstream (US) Channel Descriptors (UCD) over the DS channel, from which a CM learns its
assigned upstream operational frequency.
The CM in turn scans for these UCD messages, which instructs the CM how to configure a burst profile (frequency,
modulation, and burst parameters).
The CM has now established both a US and a DS frequency.
4. CMTS periodically transmits US bandwidth allocation maps (MAP) in shared time slots in the DS direction. The CM looks for
these MAP messages, which list the granted and contended Time Slots (TSs) for US communication.
5. CMTS assigns a temporary Service Identifier (SID) to the CM, which initiates a coarse power ranging and time
synchronization process.
The first Upstream burst that the CM sends is the initial maintenance - the CMTS responds with the Range-Response (RGN-
RSP) message for frequency, power, and timing settings.
6. CMTS periodically sends keep-alive messages to verify link continuity between itself and all CM units in the same domain.
When a CM receives its first keep-alive message, it reverts to a fine power ranging.
7. CM now forwards a bandwidth request to the CMTS, which in turn forwards a grant to the CM, permitting it to forward
upstream information in allocated time slots.
8. CM now makes a DHCP discovery followed by a DHCP request. The CMTS forwards a DHCP acknowledgment from the
CX380C User Manual RevA00 Page 41 of 105