3Com 3C63311 Reference Guide - Page 247

CBR Module 235 These frames are then followed by the ABCD bits of each active DS0. Two DS0's ABCD bits are provided in each byte after the last DS0 group. Figure 174 shows an example of three DS0s and their ABCD bits sent in a structured encapsulation. Figure 174 Multiframe Structure for 3x64kbit/s DS1 with CAS AAL1 Pointer First Transported Octet of Multiframe Second Transported Octet of Multiframe First 125 µsec Frame of Multiframe for DS1 . . . Second 125 µsec Frame of Multiframe for DS1 ABCD for First Transported Timeslot ABCD for Third Transported Timeslot Last 125 µsec Frame of Multiframe for DS1 Signaling Substructure ABCD for Second Transported Timeslot Figure 175 illustrates AAL1 structured DS1. Figure 175 AAL1 Structured DS1 FEC for SN/CSI Lost Cell Detection Clock Recovery CSI SN SNP 1 Bit 3 Bits 4 Bits SAR-SDU 47 Bytes AAL 1 VCC ATM Header 5 Bytes AAL 1 Data 48 Bytes CSI - Convergence Sublayer Indicator FEC - Forward Error Correction SNP - Sequence Number Protection SN - Sequence Number SAR - SDU - Segmentation and Reassembly Service Data Unit VCC - V irtual Channel Connection AAL Layer SAR ATM Layer