Siemens RUGGEDCOM ROS User Manual page 85

RUGGEDCOM ROS
User Guide
3
Figure 30: Link Detection Form
1. Fast Link Detection Box
2. Configure the following parameter(s) as required:
NOTE
When Fast Link Detection is enabled, the system prevents link state change processing from
consuming all available CPU resources. However, if Port Guard is not used, it is possible for
almost all available CPU time to be consumed by frequent link state changes, which could have a
negative impact on overall system responsiveness.
Parameter
Fast Link Detection
Link Detection Time
Configuring Link Detection
2. Link Detection Time Box
Description
Synopsis: { Off, On, On_withPortGuard }
Default: On_withPortGuard
This parameter provides protection against faulty end devices generating an improper
link integrity signal. When a faulty end device or a mis-matching fiber port is connected
to the unit, a large number of continuous link state changes could be reported in a short
period of time. These large number of bogus link state changes could render the system
unresponsive as most, if not all, of the system resources are used to process the link
state changes. This could in turn cause a serious network problem as the unit's RSTP
process may not be able to run, thus allowing network loop to form.
Three different settings are available for this parameter:
• ON_withPortGuard - This is the recommended setting. With this setting, an extended
period (~2 minutes) of excessive link state changes reported by a port will prompt Port
Guard feature to disable FAST LINK DETECTION on that port and raise an alarm.
By disabling FAST LINK DETECTION on the problematic port, excessive link state
changes can no longer consume substantial amount of system resources. However if
FAST LINK DETECTION is disabled, the port will need a longer time to detect a link
failure. This may result in a longer network recovery time of up to 2s. Once Port Guard
disables FAST LINK DETECTION of a particular port, user can re-enable FAST LINK
DETECTION on the port by clearing the alarm.
• ON - In certain special cases where a prolonged excessive link state changes
constitute a legitimate link operation, using this setting can prevent Port Guard from
disabling FAST LINK DETECTION on the port in question. If excessive link state
changes persist for more than 2 minutes, an alarm will be generated to warn user
about the observed bouncing link. If the excessive link state changes condition is
resolved later on, the alarm will be cleared automatically. Since this option does not
disable FAST LINK DETECTION, a persistent bouncing link could continue affect the
system in terms of response time. This setting should be used with caution.
• OFF - Turning this parameter OFF will disable FAST LINK DETECTION completely.
The switch will need a longer time to detect a link failure. This will result in a longer
network recovery time of up to 2s.
Synopsis: 100 ms to 1000 ms
Default: 100 ms
3. Apply Button 4. Reload Button
Chapter 3
Device Management
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