Cisco Systems IC-23 Setting the Token Rotation Time, Setting the Transmission Valid Timer, IC-41

Configuring LAN Interfaces

Configuring a Fiber Distributed Data Interface

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:

Command	Purpose
fddi token-rotation-time microseconds	Sets the FDDI token rotation time.

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:

Command	Purpose
fddi valid-transmission-time microseconds	Sets the FDDI valid transmission timer.

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:

Command	Purpose
fddi tl-min-time microseconds	Sets the FDDI control transmission timer.

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 c-minmicroseconds	Sets the C-Min timer on the PCM.

Cisco IOS Interface Configuration Guide

IC-41