3Com S330 manual Aal

216APPENDIX B: PATHBUILDER S330/S310 MODULE AND APPLICATION OVERVIEW

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

				Synchronous
				V.35
IP				RS 449/422, X.21, RS-530
		Internet Router
			DXI
DXI			Protocol			DXI
		DXI Link		DXI Link
Transport			DS1		Transport
	Router/DXI			AAL 5
						ATM
				ATM Cell
				Path Layer
				Line Layer
				Section Layer		SONET
				Photonic Layer
				ATM/DSU/SONET

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

■Uses AAL5

■Maximum DTE SDU size: 9232 bytes

■Uses 16-bit FCS