Cabletron Systems DMS-100 Manual De Usuario

106   Chapter 4: EIU maintenance

297-8991-910 Standard 03.01 August 1999

Table 27 summarizes the preset bucket parameters for reported LAN faults.

In an overload situation, the EIU overload control discards packets at the
interrupt level rather than at the process level.

The feedback scheme is devised such that packets received either from the
Ethernet interface or F-bus interface are discarded when the EIU resources
reach critical condition. The EIU can withstand a broadcast storm or a
babbling node due to overload controls that have been implemented. This level
of robustness follows standard DMS maintenance philosophy: a node must be
maintainable even under overload conditions.

Lab tests show that a moderately loaded LAN with broadcast messages
resulted in the workstation and the router locking up while the EIU remained
functional. The workstations were overloaded to the point that all activity
within the operating system stopped:

•

the on-screen clock stopped ticking

•

the cursor did not respond to mouse movements

•

keystrokes were ignored

•

outgoing LAN activity stopped

•

programs were not aware that a period of time had elapsed

•

the router stopped routing packets

Receive
framing error

3000

3000

2970

1000

1

Receiver
overflow

3000

3000

2970

1000

1

Receive CRC

3000

3000

2970

1000

1

Transmit
Deferred

60

30

15

1

1

Loss of carrier

30000

30000

29940

10000

1

Late collision

300

300

270

10

1

Transmit
retries
exceeded

300

300

270

10

1