/usr/sbin/fddi_config -i interface_name
Changes or displays the FDDI characteristics for interface_name. You must provide interface name. Determines how often the driver counters are updated by the DEFTA adapter. The default is 1 second. Setting the interval time to zero (0) disables counter updates. (For the fta FDDI interface only.) Displays the FDDI interface parameters you can set. Sets the error rate threshold of Link Error Monitor (LEM). The range for the LEM error rate threshold is an integer power of 10 from 1x10^-5 and 1x10^-8. The default LEM threshold is 1x10^-8. Sets the ring purger state for the specified FDDI interface. A value of 1 enables the ring purger ability; a value of 0 disables it. Sets the Restricted Token Timeout parameter, defining how long a single restricted mode dialog can last before being terminated. The range for this parameter is from 0 to 10000 milliseconds. The default value is 1000 milliseconds. Sets the Request Token Rotation Time (T_req) for interface_name. T_req is used during the ring initialization process to negotiate a Target Token Rotation Time (TTRT) for the ring. The range for this parameter is from 4.0 milliseconds to 167.77208 milliseconds. The default value is 8.0 milliseconds. Sets the Valid Transmission Time (TVX) timer for a specific FDDI interface. The range for the TVX timer is from 2.5 milliseconds to 5.2224 milliseconds. The default is 2.6214 milliseconds. Enables (1) or disables (0) full-duplex operation for the fta FDDI interface. If the full-duplex operation is enabled, the interface can be in one of the following states: Idle, Request, Confirm, or Operational. (For the fta FDDI interface only.)
The fddi_config command allows you to display all the parameters you can set for a specified FDDI interface and to modify one or more parameters depending on your configuration requirements. If you change a parameter, all parameters, including unchanged ones, are displayed as confirmation. You must be superuser to use this command.
Each FDDI interface has a Media Access Control (MAC) entity. As part of token ring initialization, all MAC entities on the ring participate in a Claim Token Process to choose a Target Token Rotation Time (TTRT) value. In this process, each MAC entity bids their own Request TRT (T_req). The lowest T_req value is chosen as the Negotiated TRT (T_neg) or TTRT for the ring. Use the netstat -I fza0 -s command to see the Requested TRT and Negotiated TRT.
The TTRT value dictates an approximate, maximum delay for the token to make a complete loop around the ring. The time it actually takes for a token to complete a loop around the ring is determined by the stations on the ring and whether or not the token is captured by a station. If the difference between the time of the last passing of the token and the current time exceeds TTRT, stations on the ring may no longer capture the token.
With small TTRT values, stations cannot hold a token very long on its loop around the ring. This means that each station can transmit only a small amount of data, but has the opportunity to capture the token more frequently and transmit data. With large TTRT values, stations can hold a token for a longer period of time, enabling them to transmit more data per token capture. However, each station must wait a longer period of time to capture a token. On a heavily loaded ring this might not be desirable.
Each MAC entity also maintains a Valid Transmission Time (TVX) timer to recover from transient ring error conditions. The TVX timer specifies the maximum amount of time that can elapse without receiving a valid frame or nonrestricted token. When this timer expires, the MAC entity assumes that the ring is no longer operational and initiates the Claim Token process to reinitialize the ring.
To show the parameters you can set for a the fza0 interface, enter: fddi_config -i fza0 -d To change the TRT value for the fta0 interface to 10.2, enter: fddi_config -t10.2 -i fta0 To turn the ring purger off, enter: fddi_config -p 0 -i mfa0
Files: fza(7), fta(7), mfa(7) delim off