3Com 2200 manual Fddi MACs

Administering FDDI MACs 8-9

Setting maxT-Req

The maxT-Reqattribute specifies the maximum time value of fddiMACT-Req that will be used by any MAC that is configured onto this path. T-Req is the value that a MAC bids during the claim process to determine a ring’s operational token rotation time, T_Opr. The lowest T-Req bid on the ring becomes T_Opr.

When T_Opr is a low value, the token rotates more quickly, so token latency is reduced. However, more of the ring’s available bandwidth is used to circulate the token. Higher values of T_Opr use less bandwidth to circulate the token, but they increase token latency when the ring is saturated.

To set maxT-Req:

Top-Level Menu

system
ethernet	station
➧fddi	➧path
bridge	mac
ip	port
snmp
analyzer
script
logout

1

display tvxLowerBound tmaxLowerBound

➧maxTreq

2

From the top level of the Administration Console, enter:

fddi path maxTreq

You are prompted for a station, path, and value. The Switch 2200 has one station, which appears in brackets.

Press [Return].

3

4

Enter the path ( p = primary, s = secondary).

Enter the new minimum time value.

The default value is 165000 microseconds (∝s)

See the following example:

Select station [1]:

Select path(s) (p,s,all) [p]:

Station 1 Primary - Enter new value [165000]:

Administering	An FDDI MAC uses a token-passing protocol to determine which station has
FDDI MACs	control of the physical medium (the ring). The primary purpose of the MAC
	is to deliver frames (packets) to their destination by scheduling and
	performing all data transfers. You can display MAC statistics and configure
	the following parameters:
■	MAC FrameErrorThreshold
■	NotCopiedThreshold

■ Logical Link Control (LLC) service