3Com S330 Press any key to return to the Virtual Circuit menu, Configuring CBR Circuits for DBA

Configuring Virtual Circuits 139

Figure 109 Completed Data Port VCC Virtual Circuit

9Press any key to return to the Virtual Circuit menu.

Configuring CBR Circuits for DBA

This section provides guidelines for configuring CBR circuits for various types of dynamic bandwidth allocation (DBA)—both for CAS (channel associated signaling) and CCS (common channel signaling applications). Table 25 summarizes the key CBR port and virtual circuit parameters for these types of applications. For details about how DBA works, see “DS0 Signaling and Dynamic Bandwidth Allocation” in Appendix B.

Table 25 CBR Port and Circuit Settings for CAS versus CCS

Parameter	Setting for CAS	Setting for CCS
Port Mode	Structured Voice	Structured Data
Port Data Bits Mask	N/A	Leave at default setting (127) in
		most cases; for details see
		“Checking the Data Bytes to
		Determine a DBA Bits Mask
		Setting” after this table
VC Payload Size/Type	Voice	Set automatically when VC
		Mode set to DBA
VC Onhook Detection	Enabled	Set automatically when VC
		Mode set to DBA
VC Mode	N/A	DBA for channels 1-23 (DSX-1)
		or 1-15 and 17-31 (E1)
		Normal for channel 24 (DSX-1)
		or 16 (E1)

Checking the Data Bytes to Determine a DBA Bits Mask Setting CCS monitors for voice activity. In most cases the default DBA Bits Mask (127) works, but if you are having a problem with a CCS circuit, you can set the DBA Bits Mask to monitor any bits. The unit will monitor the virtual circuit, and you can use the activity reported on the channel (reported under CBR ATM statistics as Data Bytes To) to determine the proper DBA Bits Mask. For details about checking the data bytes, see “CBR ATM Statistics” in Chapter 5.