3Com SuperStack II PathBuilder S330 Reference Manual page 133

signal. SRTS measures input frequency against the master network clock source
and adjusts the line rate by sending residual time stamps in the AAL1 header to
the remote end.
Adaptive (unstructured ports only) — A non-required network-wide
synchronization technique used to regenerate the input service clock. Adaptive
timing uses a buffer depth indicator at the receiver to adjust the line rate: the
fuller the buffer, the faster the line rate; the emptier the buffer, the slower the
line rate.
Figure 112 illustrates the SRTS and Adaptive timing options.
Figure 112 CBR T1-DSX Timing Options
Send Difference (-5 Hz)
DS1
-5 Hz
Reference Check
Synchronous Residual Time Stamp (SRTS)
DS1
Adaptive
Idle Timer — This parameter applies to the video dial feature. Use it to set the
length of time, in seconds (6-60) after which the CBR software shuts off cell
transmission and puts the virtual circuit into a listening mode if no cells have been
received on a T1-DSX/E1 port connected to an MCU device. If a T1-DSX/E1 port is
connected to an MCU device, the bandwidth allocated to the virtual circuits must
be saved when a video conference is not in progress. To accomplish this, the CBR
software starts an internal timer when no cell is being received. If the amount of
time you specify as the Idle Timer expires before another cell is received, the
software shuts off cell transmission and puts the virtual circuit into a listening
mode.
DBA Bits Mask (Structured Data ports only) — Dynamic bandwidth allocation bits
mask; a numeric code, in the range 1-255, representing a mask that masks off bits
that are not a portion of the idle code. When a DSX-1/E-1 CBR port is configured
as structured data, all virtual circuits in the port use a preselected DBA Bits Mask.
The decimal number that represents the DBA Bits Mask corresponds to an internal
8-bit value. The default DBA Bits Mask is 127.
AAL Header
AAL 1
Buffer
Configuring the CBR Module
Reference - 5 Hz
Clock
> <
Depends
on Buffer
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