3Com 3C63400-3AC-C - PathBuilder S700 Switch Reference Manual page 115

Figure 67 DCE Allows DTE to Participate in ATM Network through ATM DXI
DTE SDU
DXI Data Link
DXI Physical
DTE
DXI protocol defines an open interface between brouter and Data Service Unit.
The Data Service Unit off-loads cell encapsulation services from the brouter. This
allows your current brouter to support ATM simply by supporting V.35 and
High-level Data Link Control (HDLC). The DXI protocol itself is based on HDLC and
provides simple and efficient encapsulation of the Data Service Unit and the
mapping within the HDLC frame to place the brouter data on an appropriate VC.
See Figure 68.
Figure 68 DXI Format Mode 1A Encapsulation
DTE
SDU
Error Check
DTE to DSU
Flag FCS
DXI Frame
Octet 1 2
DSU to ATM
Network
Translation
SAR-PDU
AAL 5
SAR-PDU
SAR
DXI Protocol Mode 1A
DTE SDU
DXI Data Link
DXI Physical
DXI
DTE Service Data Unit
Data DXI Information Flag
0-9232 2
AAL 5 CPCS-PDU
SAR-PDU
SAR-PDU
ATM Cell
Supported Applications
AAL 5 CPCS
AAL 5 SAR
ATM
UNI Physical
DCE
1
DSU
01111110
Address Maps
to/from VPI/VCI
101
UNI