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Configuring LAN Interfaces

Configuring a Fiber Distributed Data Interface

IC-41

Cisco IOS Interface Configuration Guide

Setting the Token Rotation Time

You can set the FDDI token rotation time to control ring scheduling during normal operation and to

detect and recover from serious ring error situations. To do so, use the following command in interface

configuration mode:

The FDDI standard restricts the allowed time to be greater than 4000 microseconds and less than

165,000 microseconds. As defined in the X3T9.5 specification, the value remaining in the token rotation

timer (TRT) is loaded into the token holding timer (THT). Combining the values of these two timers

provides the means to determine the amount of bandwidth available for subsequent transmissions.

Setting the Transmission Valid Timer

You can set the transmission timer to recover from a transient ring error by using the following command

in interface configuration mode:

Controlling the Transmission Timer

You can set the FDDI control transmission timer to control the FDDI TL-Min time, which is the

minimum time to transmit a Physical Sublayer or PHY line state before advancing to the next Physical

Connection Management or PCM state as defined by the X3T9.5 specification. To do so, use the

following command in interface configuration mode:

Modifying the C-Min Timer

You can modify the C-Min timer on the PCM from its default value of 1600 microseconds by using the

following command in interface configuration mode:

Command Purpose

fddi token-rotation-time microseconds

Sets the FDDI token rotation time.

Command Purpose

fddi valid-transmission-time microseconds

Sets the FDDI valid transmission timer.

Command Purpose

fddi tl-min-time microseconds

Sets the FDDI control transmission timer.

Command Purpose

fddi c-min microseconds

Sets the C-Min timer on the PCM.

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Cisco Systems IC-23 Manual do Utilizador Página 19