3Com S330 manual

236APPENDIX B: PATHBUILDER S330/S310 MODULE AND APPLICATION OVERVIEW

Structured data DS0s allow for clear channel signaling (CCS). As opposed to CAS, in which signaling is done on all channels, in clear channel signaling (CCS) one channel is used to signal for the other channels.

The PathBuilder S330/S310 software can also monitor a full 8-bit pattern on a DS0 to determine circuit activity. This is the basis for the two supported types of dynamic bandwidth allocation (DBA):

■Structured voice DBA

■Structured data DBA

Structured Voice DBA When a CBR port is configured as structured voice, signaling bits of voice channels are carried along with their payload in AAL1 cells. These signaling bits, which are received from T1/E1 framers, are stored in buffers provided in the SAR processor. The CBR software periodically reads the stored signaling bits and checks for an idle condition of voice channels with on-hook detection enabled.

■When an on-hook (idle) signal is detected, the CBR virtual circuit is deactivated, and the bandwidth reserved for that channel is released for other uses (such as VBR traffic).

■When an off-hook signal is detected, the CBR virtual circuit is activated.

Use structured voice circuits with DBA for CAS (channel associated signaling) applications.

Structured Data DBA When a CBR port is configured as structured data, only DSO payload bytes are carried in AAL1 cells. These data cells are stored in buffers provided in the SAR processor. The CBR software periodically reads the stored data bits and checks for an idle code in the stored data bits of each DS0 channel. All virtual circuits in the port use a user-selected DBA bit mask to mask off bits that are not a portion of the idle code.

■When an on-hook condition (idle code) is detected, the CBR virtual circuit is deactivated, and the bandwidth reserved for that channel is released for other uses.

■When an off-hook condition (no idle code) is detected, the CBR virtual circuit is activated.

Use structured data circuits with DBA for CCS (clear channel signaling) applications.

A structured DS1 channel will not pass the original DS1 frame to the remote end. For instance, ESF network management will terminate at the PathBuilder S330/S310 on a structured DS1, so CSU-to-CSU Facility Data Link (FDL) communication will not be possible. FDL communication is possible with unstructured DS1.