Cisco Broadband Cable Command Reference Guide

Chapter 2 Cisco Cable Modem Termination System Commands
cable map-advance
Syntax Description
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Cisco Broadband Cable Command Reference Guide
cable map-advance
To configure the dynamic map advance algorithm, use the cable map-advance command in cable
interface configuration mode. Use the no form of this command to disable this function.
cable map-advance [dynamic [safety] | static] [max-delay]
no cable map-advance
Defaults Dynamic map advance with a safety factor of 1000 microseconds and a max-delay of 1800 microseconds
Command Modes Interface configuration (cable interface only)
Command History
dynamic safety Enables the dynamic MAP advance algorithm that automatically tunes
lookahead time in MAPs based on the current farthest CM on a
particular upstream port. The safety argument specifies a safety factor
for the dynamic map advance algorithm in microseconds. This value
controls the amount of extra lookahead time in MAPs to account for
inaccuracies of the measurement system and internal software
latencies. The valid range is 300 to 1500 microseconds, with a default
of 1000.
Note Using larger safety factors increases the run time lookahead in
MAPs, but reduces the upstream performance.
static Enables the static map advance algorithm that uses a fixed lookahead
time value in MAPs based on the worst-case propagation delay of 100
mile HFC cable network.
max-delay Specifies the maximum round trip delay between the cable plant and
furthest CM in microseconds. The valid range is 100 to 2000
microseconds, with a default of 1800. The typical delay for a mile of
coaxial cable is approximately 7 microseconds. The typical delay for a
mile of fiber cable is approximately 8 microseconds.
Release Modification
12.1T This command was introduced.
12.0 (9)SC, 12.1(2)EC1 The dynamic option was added.
12.1(10)EC The max-delay option was added. The dynamic MAP algorithm was also
enhanced so that it can quickly determine whether the furthest CM is now
offline, so that the MAP advance algorithm can be updated accordingly.
12.2(8)BC1 The range for the max-delay option was changed to the current values of
between 100 and 2000 microseconds.
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