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If frame lengths are exponentially distributed, then:
Performance of Token Rings
Comparing Token Management Techniques with Exponentially Distributed Frame Lengths
For exponentially distributed frame lengths and a fixed normalized ring latency of a', we can compare the performance of single token, multiple token, and single frame token ring operations.
The graph above indicates that multiple token operation yields the best performance, followed by single token, and single frame operation with the worst performance. The best performance was achieved by minimizing the normalized ring latency, a', where performance is approximately the same for all three operating modes. It can also be observed that for a fixed normalized throughput, S, the number of hosts, M, impacts performance primarily through its effect on a'. Instability occurs for some values of S less than 1 if operating in single token or single frame mode.
Comparing Token Management Techniques with Fixed Frame Lengths
For fixed frame lengths and a fixed normalized ring latency a', it can be observed that the best performance is achieved with multiple token operation. On the other hand, the poorest performance is achieved with single frame operation. The performance for single token and multiple token are the same for a' <= 1, and the performance of single frame and single token are approximately the same for very large a' (which was previously shown for exponentially distributed frame lengths). There is however a lower delay for fixed length frames than exponentially distributed frame lengths.
Single Token Operation with Different Network Loads and Exponentially Distributed Frame Lengths
When single token operation is used with exponentially distributed frame lengths, it can be observed that the transfer delay is approximately independent of a' for small values of a'. Higher throughput, S, places more sever constraints on ring latency, and high ring latency severely restricts the allowable throughput.
