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3 Initial Ranging (Also called Initial Maintenance). This IE allows cable modems a method to adjust their timing, frequency, and
transmit power so that they can reliably communicate with the C4 CMTS. The timing adjustments allow for the round trip delay of
the fiber optic/coax plant plus the time to transmit the range request message. A DOCSIS 1.X cable modem can send a range request
message only during this IE. A DOCSIS 2.0 cable modem can send a range request message or an initial range request message
depending upon the type of the upstream channel. Normally, range request messages are sent in this IE when it contains a
broadcast SID, meaning cable modems must contend with each other when transmitting. An initial range request message can be
sent either with a broadcast SID or with a unicast SID depending upon the situation.
4 Periodic Ranging (Also called Station Maintenance. This IE is used so that cable modems can perform station maintenance. This IE
is unicast. Only the range request message — no other data — can be sent in this IE.
5 Short Data Grants This unicast IE gives permission to a specific cable modem to transmit one or more Protocol Data Units (PDUs).
The cable modem uses this region in the upstream map interval if the number of minislots required to send the message is less than
or equal to the maximum burst interval specified for a short data grant in the Upstream Channel Descriptor (UCD) message. The
reason that grants can be split into short and long data grants is for the sake of FEC encoding. Short data grants are used only when
a cable modem is transmitting via an upstream channel that is compatible with DOCSIS 1.X.
6 Long Data Grants This unicast IE gives permission to a specific cable modem to transmit one or more PDUs. The cable modem
uses this region in the upstream map interval if the number of minislots required to send the message is greater than the maximum
burst interval for a short data grant in the Upstream Channel Descriptor (UCD) message. The reason that grants can be split into
short and long data grants is for the sake of FEC encoding. Long data grants are used only when a cable modem is transmitting via an
upstream channel that is compatible with DOCSIS 1.X.
NOTE: The following Advanced PHY types are provided for channels carrying combined DOCSIS 1.x and DOCSIS 2.0 bursts and also
for channels carrying DOCSIS 2.0 bursts only.
9 Advanced PHY Short This IE is the same as a short data grant except that it is used when the cable modem is communicating via
an upstream channel that is only DOCSIS 2.0 compatible.
10 Advanced PHY Long This IE is the same as a long data grant except that it is used when the cable modem is communicating via
an upstream channel that is only DOCSIS 2.0 compatible.
11 Advanced PHY UGS This IE is new with DOCSIS 2.0. It allows parameters to be optimized for UGS flows, which normally carry
VoIP.
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