reading CCO documentation for OER it is not so clear to me the difference between backoff timer (3 values used for dampening) anf holddown timer
BTW which are the triggers for OER to evaluate the MTCs and in turn move them to another exit link (if that is the case...)
thanks for your help !
from PFR configuration guide for 15.0M the following definitions of the timers are provided:
PfR Timers Parameters
Three types of timers can be configured as PfR policy operational parameters:
The backoff timer is used to adjust the transition period that the master controller holds an out-of-policy
traffic class entry. The master controller waits for the transition period before making an attempt to find an
in-policy exit. A minimum, a maximum, and an optional step timer value can be configured.
The holddown timer is used to configure the traffic class entry route dampening timer to set the minimum
period of time that a new exit must be used before an alternate exit can be selected. To prevent the traffic
class entry from flapping because of rapid state changes, the master controller does not move the traffic
class entry to a different exit even if it goes out-of-policy during the holddown timer period. PfR does not
implement policy changes while a traffic class entry is in the holddown state. A traffic class entry will
remain in a holddown state for the default or configured time period. When the holddown timer expires,
PfR will select the best exit based on performance and policy configuration. However, an immediate route
change will be triggered if the current exit for a traffic class entry becomes unreachable.
The periodic timer is used to find a better path for a traffic class entry, even if the traffic class entry is inpolicy
on the current exit. When the periodic timer expires, the master controller evaluates current exit
links for the traffic class entry and, if a better exit exists based on the current measurements and priorities,
the traffic class entry is moved to a new in-policy exit link.
When adjusting PfR timers note that a newly configured timer setting will immediately replace the existing
setting if the value of the new setting is less than the time remaining. If the value is greater than the time
remaining, the new setting will be applied when the existing timer expires or is reset.
Hope to help
Thanks for the reply....
Let me ask about some point:
- backoff timer: consider a traffic class (TC) that at a point in time goes out-of-policy and currently exist another in-policy exit: does PFR moves the TC to the available in-policy exit or, anyway, moves it into OOP state until backoff timer expire ?
- Periodic timer: from configuration guide it seem to me it make sense only if mode select-exit best is operation (in other words: if in mode select-exit good upon timer expires PFR basically does nothing.. )
thanks in advance