What is early token release and delayed token release?

Token ring is a physical unidirectional ring topology where systems are connected through dedicated interfaces. In this network architecture, data transmission is controlled by a special frame called a token that continuously circulates around the ring.

Only the station possessing the token can transmit data, ensuring collision-free communication. After transmission, the source station is responsible for removing its data frame from the ring and regenerating the token for other stations to use.

Types of Token Release

Token ring networks implement two different strategies for token regeneration, each affecting network efficiency and performance characteristics.

Early Token Release

In early token release, the transmitting station immediately regenerates and releases the token after completing frame transmission, without waiting for the transmitted frame to return. This allows the next station to begin transmission while the previous frame is still circulating.

Ring latency (R) represents the time required for a single bit to complete one full revolution around the ring. For N equidistant stations, the propagation delay between adjacent stations equals R/N.

Efficiency Analysis

Single transmitter scenario:

? = t_x / (t_x + t_xt + t_p)

Multiple transmitters scenario:

? = t_x / (t_x + t_xt + t_p/N)

Where t_x = frame transmission time, t_xt = token transmission time, and t_p = propagation delay.

Delayed Token Release

In delayed token release, the transmitting station retains the token until its transmitted data frame completes a full ring traversal and returns to the source. Only after removing its own frame does the station release the token.

Operation Steps

• Station acquires token and transmits data packet

• Token remains with transmitting station

• Data packet traverses the entire ring

• Source station removes returning packet and releases token

Efficiency Analysis

Single transmitter scenario:

Total time = t_x + t_p + t_xt + t_p

Multiple transmitters scenario:

? = t_x / (t_x + t_p + t_xt + t_p/N)

Comparison

Conclusion

Early token release provides better network utilization by allowing multiple frames to circulate simultaneously, while delayed token release ensures simpler frame management but with reduced efficiency. The choice between these approaches depends on network size and traffic patterns.