Cisco SR2016T-NA Reference Manual page 342

cable upstream minislot-size
Release
12.2(15)BC1
12.2(15)BC2
Usage Guidelines
The minislot size determines the minimum amount of information that can be transmitted on the
upstream. How much a particular minislot size can contain depends on the modulation profile and
channel width being used, with higher-bandwidth settings allowing larger amounts of data.
Because DOCSIS specifications require that the minislot size contain at least 32 symbols, you might
need to change the minislot size whenever you change the channel width or modulation of an upstream,
to meet the DOCSIS requirements.
In Cisco IOS Release 12.2(15)CX, Cisco IOS Release 12.2(15)BC2, and later releases, manually
Note
changing the minislot size is not needed on the Cisco uBR-MC16U/X, Cisco uBR-MC28C, and
Cisco uBR-MC28U/X cards, because these cards automatically change the minislot size when the
channel width is changed, to produce 32 symbols per minislot, as required by the DOCSIS
specifications.
Table 2-12
Cisco IOS Release 12.2(15)BC1.
Table 2-12 Default Minislot Sizes
Releases Earlier than Cisco IOS Release
12.2(15)BC1 (creates 64 symbols and 16 bytes
per minislot)
Channel Width
0.2 MHz
0.4 MHz
0.8 MHz
1.6 MHz
3.2 MHz
1. You must be using a 6.4 MHz channel width if using a minislot size of 1 tick. Otherwise, you will violate the DOCSIS
Cisco Broadband Cable Command Reference Guide
2-330
Modification
The default minislot size was reduced to optimize the upstream for data and
Voice-over-IP (VoIP) traffic. The previous defaults produced 16 bytes per
minislot when using QPSK modulation and a 1.6 MHz channel width, and
the new defaults produce 8 bytes per minislot with the same configuration.
Support was added for the minislot size of 1 to support DOCSIS 2.0
A-TDMA and mixed modulation profiles on the Cisco uBR-MC5X20S/U
cable interface line cards.
lists the default minislot sizes for each channel width for Cisco IOS releases before and after
Default Minislot Size (in
Ticks)
64
32
16
8
4
requirements that each minislot should contain 32 symbols.
Chapter 2 Cisco CMTS Configuration Commands
Cisco IOS Release 12.2(15)BC1 and Later
Releases (creates 32 symbols and 8 bytes per
minislot)
Default Minislot Size (in
Channel Width Ticks)
0.2 MHz 32
0.4 MHz 16
0.8 MHz 8
1.6 MHz 4
3.2 MHz 2
1
6.4 MHz 1
(DOCSIS 2.0 only)
OL-1581-08