3Com 2000 TR TR-in-FE Compared to Traditional Methods, 3Com Token Ring-in-Fast Ethernet System

2-2CHAPTER 2: TR-IN-FE CONCEPTS

TR-in-FE Compared to Traditional Methods

Traditional means of combining Token Ring, Ethernet, and Fast Ethernet include bridging and routing. With routing, frame forwarding decisions are made in soft- ware by looking into the network layer of each frame and modifying the frame to reflect the standard format of the media for which it is destined.

Similarly, bridging between these media may be accomplished using Translational Bridging, sometimes referred to as SRTB or SRTG. This is necessary with non-routable protocols like SNA and Netbios. This type of bridging deals with all the differences between Token Ring and Ethernet frame formats such as:

■Address fields

■Variable length source-route fields

■Functional address to multicast address mapping

NetBuilder provides both routing and SRTG function- ality. The decisions are, again, made in software and the result is conversion of the source frame to a stan- dard destination frame format. The benefit of the tra- ditional means listed above is that all frames are converted from media to media using standard frame formats, which allows for simple mixing and match- ing of products from multiple vendors. The downside is that these bridges and routers are typically slow, expensive, and more difficult to manage than switch products.

TR-in-FE technology works, not by providing frame conversion, but by using the Fast Ethernet as a trans- port for the Token Ring frames. This means that every frame does not need to be parsed deeply, nor does source route to transparent frame mapping need to happen.

Presently, TR-in-FE is based on developing standards and requires that FE server connections and Switch 2000 TR Downlink Modules are 3Com products.

Once approved, TR-in-FE will be able to be integrated with other vendors. FE switching infrastructure may be from any vendor.

3Com Token Ring-in-Fast Ethernet System

The 3Com Token Ring-in-Fast Ethernet includes:

■SuperStack II Switch 2000 TR

■SuperStack II Switch 2000 TR Token Ring-in-Fast Ethernet Module

■Fast Ethernet Switch (SuperStack II Switch 3000)

■3Com Fast Ethernet network interface cards (NIC)

Token Ring-in-Fast Ethernet Module

This slide-in module provides a 200 Mbps Full-duplex Fast Ethernet interface, which enables the Switch 2000 TR to become part of a Fast Ethernet switched infrastructure. This module allows wire-speed trans- mission of Token Ring-in-Fast Ethernet frames. Fast Ethernet can be used to connect Token Ring clients to Fast Ethernet servers or as an aggregation point for multiple Token Ring switched connections.