3Com SuperStack II PathBuilder S330 Reference Manual page 228

216 A B: P B
PPENDIX ATH UILDER
S330/S310 M A
ODULE AND PPLICATION
DXI protocol defines an open interface between the router and the Data Service
Unit. The Data Service Unit off-loads cell encapsulation services from the Brouter.
This will allow 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 the mapping within the
HDLC frame to place the router data on an appropriate VC. (See Figure 156.)
Figure 156 DXI Protocol Enabling Transmission Between ATM Network and DXI Device
IP
Internet Router
DXI
DXI Link
Transport
Router/DXI
The ATM DXI Specification defines 3 different modes (1a, 1b, and 2) of
connections. This software release supports Mode 1a, which includes the
following features:
Up to 1023 virtual connections
n
Uses AAL5
n
Maximum DTE SDU size: 9232 bytes
n
Uses 16-bit FCS
n
O
VERVIEW
Synchronous
V.35
RS 449/422, X.21, RS-530
DXI
Protocol
DXI Link
DS1
AAL 5
ATM Cell
Path Layer
Line Layer
Section Layer
Photonic Layer
ATM/DSU/SONET
DXI
Transport
A TM
SONET