Explain the timers and time registers in FDDI?

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13.Explain the timers and time registers in FDDI?

FDDI (Fiber Distributed Data Interface) is a high-speed LAN (Local Area Network) technology that uses optical fiber as its transmission medium. FDDI defines a set of protocols and specifications for data transmission over the network. In FDDI, timers and time registers play an essential role in managing various aspects of network operation, including frame transmission, fault detection, and network recovery. Let's take a closer look at timers and time registers in FDDI:

timers and time registers in FDDI
timers and time registers in FDDI

1. Timers in FDDI:

    Timers in FDDI are used to manage specific time-related operations and events. They are implemented in both the FDDI stations and the FDDI concentrator (also known as the dual-attached concentrator or DAC). Some of the critical timers in FDDI include:

a. T-Max: This timer determines the maximum time a station or concentrator can hold a token before forwarding it. It ensures that the token circulates efficiently and prevents a station from monopolizing the network.

b. T-Req: When a station or concentrator wants to transmit data, it sends a request to the network for the token. The T-Req timer is used to measure the duration the station or concentrator waits for the token before timing out and resending the request.

c. T-Response: After receiving a token request, the active monitor (a special station responsible for network management) allocates the token to a station or concentrator. The T-Response timer is used to measure the time the active monitor takes to respond to the token request.

d. T-Monitor: This timer is used to detect the absence of a token or a malfunctioning active monitor. If a station or concentrator doesn't receive a token within the T-Monitor duration, it may initiate the recovery process to restore the network's normal operation.

e. T-TRT (Token Rotation Time): This timer determines the maximum time a token can remain in the network. It helps ensure a timely token rotation, preventing excessive delays and improving network performance.

2. Time Registers in FDDI:

    Time registers are used to store and manage timing information within the FDDI stations and concentrator. Some of the key time registers include:

a. Token Hold Time Register: This register stores the value of the T-Max timer. It is used to determine the maximum time a station or concentrator can hold the token.

b. Token Rotation Time Register: This register stores the value of the T-TRT timer, representing the maximum time allowed for a token to circulate the network.

c. Timer Registers for T-Req, T-Response, and T-Monitor: These registers store the values of their respective timers, determining the durations for token request, response, and monitoring.

The timers and time registers in FDDI play a crucial role in maintaining network efficiency, handling token passing, detecting faults, and ensuring timely responses to network events. By carefully configuring these timers and monitoring their values, FDDI networks can operate reliably and provide high-speed data transmission capabilities.

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