Configuring Virtual Circuits 139Figure 109 Completed Data Port VCC Virtual Circuit9 Press any key to return to the Virtual Circuit menu.Configuring CBR Circuits for DBAThis section provides guidelines for configuring CBR circuits for various types ofdynamic bandwidth allocation (DBA)—both for CAS (channel associated signaling)and CCS (common channel signaling applications). Table 25 summarizes the keyCBR port and virtual circuit parameters for these types of applications. For detailsabout how DBA works, see “DS0 Signaling and Dynamic Bandwidth Allocation” inAppendix B.Checking the Data Bytes to Determine a DBA Bits Mask Setting CCSmonitors 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 Maskto monitor any bits. The unit will monitor the virtual circuit, and you can use theactivity reported on the channel (reported under CBR ATM statistics as Data BytesTo) to determine the proper DBA Bits Mask. For details about checking the databytes, see “CBR ATM Statistics” in Chapter 5.Table 25 CBR Port and Circuit Settings for CAS versus CCSParameter Setting for CAS Setting for CCSPort Mode Structured Voice Structured DataPort Data Bits Mask N/A Leave at default setting (127) inmost cases; for details see“Checking the Data Bytes toDetermine a DBA Bits MaskSetting” after this tableVC Payload Size/Type Voice Set automatically when VCMode set to DBAVC Onhook Detection Enabled Set automatically when VCMode set to DBAVC 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)
