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Performance Analysis of Token Ring Networks
Assumptions and Notation
For the following analysis of token ring networks, we will assume:
- Poisson arrivals at each host
- equally likely destinations from each source (i.e. the average distance between the source and destination is 1/2 the ring length)
- equally spaced host around the ring (i.e. propagation delay between consecutive hosts is the the propagation delay around the ring / the number of hosts)
- same distribution of frame lengths at each host
- exhaustive cyclic service
The notation we will use is summarized in the following table:
| Variable | Description |
|---|---|
| X | RV denoting length of an arbitrary frame |
| R | link speed in bits/second |
| B | bits of latency per host |
| τ | propagation delay around entire ring |
| τ' | ring latency |
| a' | normalized ring latency |
| w | walk time |
| T | average transfer delay |
| W | average access delay |
| S | normalized throughput |
| S' | effective throughput |
| E | effective service time of a frame |
| M | number of hosts in the ring |
Latencies in Token Rings
There are a couple different latencies or delays that must be considered when analyzing a token ring network.
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