This soft copy for use by IBM employees only.
4.7 ATM 4-Port TR/Ethernet Bridge Module
The ATM TR/Ethernet Bridge Module is a two-slot module that functions as a
multiport bridge providing a simple way to connect shared media LAN segments
to a high-speed ATM backbone. This is an ideal way to begin a migration to an
ATM backbone, especially for those customers running flat or bridged networks
today, since it is completely transparent to your shared media users.
The main features of this module are:
•Provides four external ports for interconnection to either Ethernet (IEEE 802.3
and DIX V2) or token-ring (IEEE 802.5) LANs. This module does not allow the
mixing of various LAN types.
•Provides media-speed bridging between all four LAN ports even
when configured for full-duplex token-ring.
•Provides a single UNI 3.0-compatible ATM interface to the ATM backplane of
the 8285 Expansion Chassis.
•The ATM port supports clients for either Forum-compliant LAN Emulation
(LANE) or IBM LAN Emulation (IBMLE). This enables traditional LAN users
connected to one of the external ports to access transparently devices (for
instance, servers) on a high-speed ATM ELAN, either LANE or IBMLE.
Note
The emulated LAN must be the same type of LAN as the one used on the
four LAN ports. This means that the ATM 4-Port TR/Ethernet Bridge
Module cannot be used to connect Ethernet devices to token-ring devices
across an ATM network. However, such connectivity can be provided
when the ATM TR/Ethernet Bridge Module is used in conjunction with an
ATM router such as the IBM Multiprotocol Switched Services Server
•Supports standard source route bridging (SRB) when the ports are
configured to use token-ring. This enables easy migration from existing
token-ring backbones to high-speed ATM backbones.
•Supports transparent bridging when the ports are configured to use Ethernet.
•Supports 256 virtual circuits (VCs) over the ATM connection.
•Supports both Generic Flow Control (GFC) and Operation and
Maintenance/Flow 5 (OAM-5) to throttle traffic in a congestion situation.
•Supports powerful, flexible filtering of inbound LAN traffic:
−In the token-ring environment, filters can be based on:
- Hop count
- MAC address
- Ring number
- Source service access point (SAP)
- Subnetwork access protocol (SNAP)
−In an Ethernet environment, filters can be based on:
- MAC address
- Source service access point (SAP)
- Ethertype
Chapter 4. IBM 8285 ATM Modules 57