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Table 6-13 show controller cable-modem mac state Field Descriptions (continued)
Field
Change Count
Preamble Pattern
Burst Descriptor:
Interval Usage Code
Modulation Type
Differential Encoding
Preamble Length
FEC Error Correction
FEC Codeword Info
Scrambler Seed
Maximum Burst Size
Guard Time Size
Last Codeword Length
Scrambler on/off
Network Access
Cisco Broadband Cable Command Reference Guide
6-110
Description
Incremented by 1 by the CMTS whenever any of the values of this channel
descriptor change. If the value of this count in a subsequent upstream
channel descriptor (UCD) remains the same, the router can quickly decide
that the remaining fields have not changed, and may be able to disregard
the remainder of the message.
Byte pattern used for the preamble.
A compound type/length/value (TLV) encoding that defines, for each type
of upstream usage interval, the physical-layer characteristics that are to be
used during that interval. Each burst descriptor is given an identifying
number.
Each upstream transmit burst belongs to a class which is given a number
called the interval usage code (IUC). Bandwidth MAP messages are used
by IUC codes to allocate upstream time slots. The following types are
currently defined:
1. Request: bandwidth request slot
2. Request/Data: bandwidth request or data slot
3. Initial Maintenance: initial link registration contention slot
4. Station Maintenance: link keep-alive slot
5. Short Data Grant: short data burst slot
6. Long Data Grant: long data burst slot
Upstream modulation format. (1 = QPSK; 2 = 16-QAM)
Indicates whether or not differential encoding is used. (1 = yes; 2 = no)
Length of the preamble in bits. This value must be an integral number of
symbols—a multiple of 2 for QPSK; a multiple of 4 for 16-QAM.
Length of the forward error correction in bytes. The range is 0 to 10 bytes;
a value of 0 implies no forward error correction.
Number of information bytes in the FEC codeword.
Bytes
15-bit seed value loaded at the beginning of each burst after the register
has been cleared. Not used if scrambler is off.
Maximum number of mini-slots that can be transmitted during this burst
type. When the interval type is Short Data Grant, this value must be
greater than 0. If this value is 0, the burst size is limited elsewhere.
Amount of time in symbols between the center of the last symbol of a
burst and the center of the first symbol of the preamble of an immediately
following burst in an upstream transmission from the router to the CMTS.
Indicates whether or not the length of the last codeword is fixed or
shortened. (1 = fixed; 2 = shortened)
Indicates whether or not a scrambler is enabled in the upstream modulator.
(1 = on; 2 = off)
Indicates whether or not the router has access to the HFC network.
Chapter 6
Cable CPE Commands
OL-1581-07
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