The All-New Switch Book: The Complete Guide to LAN Switching Technology, Second Edition

7.4. Dedicated Token Ring

Token Ring networks were not immune to the advancements being made in switching technology. The architecture depicted in Figure 7-3 applies independent of the MAC employed in the stations and switch. A Token Ring network can be microsegmented just as easily as an Ethernet LAN — it just costs more. During the mid-1990s, manufacturers began to provide Token Ring switch products, bringing the advantages of switching to the Token Ring community.

Similar to the evolution of Ethernet switches, there were two steps taken in the migration path:

1. Implementation of microsegmentation through the use of switching hubs: Just as in Ethernet, changing from a shared-LAN hub to a switch effectively converts each port on the hub device to a two-station LAN. However, this LAN still operates in a shared-access mode. In the case of a Token Ring switch, there is still a token rotating between the two devices on each LAN (the end station and the switch). The two devices share the available capacity by passing the token back-and-forth between themselves, as depicted in Figure 7-6. Because each switch port is dedicated to serving a single end station, this configuration is called Dedicated Token Ring (DTR).

   The main advantage of using DTR in half duplex mode is that it is fully compatible with existing Token Ring NICs and end stations. By changing just the hubs, we get a migration ...