fddi_config - Displays and modifies the Fiber Distributed
Data Interface (FDDI) parameters
/usr/sbin/fddi_config -i interface_name [-c
valid_counter_interval_time] [-d] [-l link_error_monitor_threshold]
[-p [1 | 0]] [-r restricted_token_timeout_time]
[-t token_request_time] [-v valid_transmit_time]
[-x [1 | 0]]
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 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: fta(7), fza(7), mfa(7)
fddi_config(8)
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