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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
OL-2239-03
Chapter 3 Configuring Cable Modem Interface Features
Configuring Payload Header Suppression and Restoration
Configuring Payload Header Suppression and Restoration
Payload Header Suppression (PHS) is a new feature in the DOCSIS1.1 MAC driver. The PHS feature is
used to suppress repetitive or redundant portions in packet headers before transmission on the DOCSIS
link. The upstream receive driver is now capable of restoring headers suppressed by CMs, and the
downstream driver is capable of suppressing specific fields in the packet header before forwarding the
frame to the CM.
Setting Optional IP Parameters (Broadcast and Multicast Echo)
You can set additional IP parameters to enable downstream echoing of upstream data. This section
contains two procedures to configure these optional IP parameters:
• “Activating IP Multicast Echo” section on page 3-33
• “Activating IP Broadcast Echo” section on page 3-34
Note The default values for the commands used in these configuration steps are adequate in most cases to
configure the Cisco uBR7200 series CMTS.
Activating IP Multicast Echo
The Cisco uBR7200 series CMTS echos IP multicast packets by default. To activate IP multicast echo if
it has been previously disabled, use the following command in cable interface configuration mode.
To disable IP multicast echo, enter the no cable ip-multicast-echo command in cable interface
configuration mode.
Command Purpose
show interface cable x/0 service-flow
[sfid] phs
Displays cable interface information.
debug cable error
Displays errors that occur in the cable MAC protocols.
To disable debugging output, use the no form of the
command.
debug cable phs
Displays the activities of the PHS and restoration driver.
The no form of this command disables debugging output.
Command Purpose
Router(config-if)# cable ip-multicast-echo
Enables IP multicast echo. This is the default.
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