Serial Interface; Serial Interface Frame Protocol Modes - 3Com SuperStack II PathBuilder S330 Reference Manual

240 A B: P B
PPENDIX ATH UILDER

Serial Interface

Serial Interface Frame
Protocol Modes
S330/S310 M A
ODULE AND PPLICATION
The E3 UNI module performs the following key functions:
Performs ATM to physical layer mapping and adds PLCP according to UNI 3.0
Performs peak traffic shaping on the transmit (14 bulk shapers)
The serial interface is designed to interconnect frame-based devices/networks and
cell-based ATM devices/networks. The PathBuilder S330/S310 switch provides a
single serial interface that can be configured as DTE or DCE and, with different
cable adapters, can support V.35/RS-449/RS-530/X.21 interface to routers.
The PathBuilder S330/S310 switch can perform cell-to-frame as well as
frame-to-cell conversion. On the serial interface receive side, frames received from
the HDLC serial interfaces are segmented to cells by the SAR and passed to the
CTX chip where they can be switched. On the serial interface transmit side, cells
received from the ATM interfaces are reassembled into frames and passed to the
HDLC serial interfaces.
The PathBuilder S330/S310 switch uses a RISC processor to perform the lookup
and interworking functions between frame and ATM services. It also performs the
LMI functions and collects alarms and statistics.
The PathBuilder S330/S310 switch provides for frame relay service and network
interworking (FRF 5 and 8), as well as ATM DXI and transparent HDLC operation.
You can use it for interworking between the ATM network and a variety of
different frame-based networks or devices such as Frame Relay and ATM DXI.
The interface can be clocked up to 6.2Mbps, and it supports the following modes
of operation:
Internal timing — DCE provides the clock for a router.
External timing — DTE receives a clock from a DCE device such as a DSU (digital
service unit).
The mode of operation is selected automatically (by autosensing), based on the
type of cable connected to the unit—DCE or DTE.
The PathBuilder S330/S310 switch supports three modes of Frame-to-Cell transit
services:
ATM DXI Mode 1A — Supported by certain routers.
HDLC/SDLC — Used mainly for transparent point-to-point operation.
Frame Relay Forum Specification 5 and 8; modes 1 and 2 — Used to
terminate a frame relay router.
Each service is designed to support a different type of user application; however,
all the services share the same ATM backbone characteristics. The serial port
modules are mapped over ATM Permanent Virtual Circuits (PVCs).
When connecting the PathBuilder S330/S310 switch to an ATM network, verify
that the PVC mapping for in and out ports is defined for proper operation. (See
Figure 169.)
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VERVIEW