3Com S330 manual Illustrates the Srts and Adaptive timing options

Configuring the CBR Module 125

Figure 96 illustrates the SRTS and Adaptive timing options.

Figure 96 CBR T1-DSX Timing Options

Send Difference (-5 Hz)

DS1 AAL Header

-5 Hz

Reference Check

Reference - 5 Hz

Synchronous Residual Time Stamp (SRTS)

DS1

AAL 1

Buffer

Adaptive

Clock

><

Depends on Buffer

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.

The DBA Bits Mask parameter is designed to accommodate situations in which the PathBuilder S330/S310 must communicate with equipment that uses non-standard signaling patterns. In most cases you should leave this parameter set to its default value. If you are experiencing problems with a CCS circuit, however, you may need to set the DBA Bits Mask to a different value. The PathBuilder S330/S310 performance monitoring feature reports the data bytes to the cell bus on the CBR port. You can check this statistic to determine if you need to set a non-default DBA Bits Mask. For details, see “CBR ATM Statistics” in Chapter 5.