Token-Ring and Ethernet Integration

In recent years prices have dropped on Ethernet adapters, hubs, and switches. At the same time Ethernet speeds have increased from 10 Mbps to 100 Mbps to 1 Gbps. These developments, despite the numerous performance and technical advantages of Token-Ring technology, have led some Token-Ring Network Managers to begin looking at Ethernet as a possible solution when upgrading their Token-Ring networks to higher speeds. Some Network Managers are also convinced they will save money by doing so.

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Cost of Ownership

Our “Cost of Ownership” analysis, which includes tangible costs such as new equipment, installation-related costs such as cabling changes and intangible costs such as network planning and staff retraining, shows that installing dedicated 16 Mbps switch connections to every desktop and 100 Mbps full-duplex Token-Ring in the backbone in an existing Token-Ring network is much less expensive than migrating that same network to Ethernet with dedicated 100 Mbps switch connections to every desktop in a 500 node network. Considering equipment costs alone, our calculations show that price-per-megabit-per-workstation is less expensive for migrating to 16 Mbps full-duplex switched Token-Ring to the desktop than migrating to Ethernet.

Performance

The higher speed and inherently more efficient operation of Token-Ring means that, in some configurations, the 16 Mbps full-duplex switched desktops will run as fast as 100 Mbps Ethernet connections. A switch from Token-Ring to 100 Mbps Ethernet at the desktop might not result in the expected improvement in overall network performance. The maximum per-link bandwidth efficiency of a Token-Ring link is 98%; this means a 100 Mbps full-duplex Token-Ring link provides you with up to 196 Mbps of throughput. An Ethernet network will start experiencing performance problems, application time-outs and intermittent lost connections at much lower levels of network utilization. Token-Ring on the other hand runs better under load; this means that a Token-Ring network will not experience these performance problems, even if the network utilization reaches 98%.

Capabilities inherent in Token-Ring make it a more robust solution for the future because of capabilities already present in Token-Ring (file transfer efficiency because of Token-Ring’s large frame sizes and Class-of-Service, or priority mechanism).

Implementation

An incremental Token-Ring upgrade can be implemented quickly and easily. A “one-time” move to Ethernet is far riskier, more complex and could involve a higher degree of service interruption. Where coexistence of Token-Ring and Ethernet networks is required, translational-bridging products can be used to effect a seamless integration between the two technologies.

Therefore, not only does it make economic sense for a Token-Ring customer to stay Token-Ring, but it is technically advantageous as well.