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3.18 Maintenance windows
Maintenance works are on everybody’s agenda in current fast paced and continuously evolving networks. During maintenance network engineers are very busy and will welcome any help their systems can offer in carrying out those works with the least amount of headaches. IRP instances are clearly not in the top of network engineer’s priorities and asking to suspend or shutdown providers immediately before a maintenance window starts and restart the provider back once the maintenance works end is not very helpful if not even annoying.
GMI offers the facility to plan maintenance windows in advance for providers on the connected IRP instances. Knowing when a maintenance window starts and ends, the IRP instances exclude specific provider links from either performance optimization or bandwidth control. More so, there is a capability to reshape the traffic flowing in and out of a network to anticipate any downtime on a link.
Properly configured maintenance windows allows IRP instances the time to move most of the outbound traffic and deflect most of inbound traffic away from the provider link that is scheduled for maintenance. Having only a small fraction of traffic or none at all on the maintenance link before the downtime starts avoids any (shall we say, catastrophic) spikes, possible overloads and consequently unpredictable behavior of the remaining live network equipment.
Specifically the following applies:
- a maintenance window is configured in advance and can be removed/revised at any time
- a maintenance window sets details for single provider. If needed multiple maintenance windows can be setup and even overlapping maintenance windows are OK
- GMI highlights maintenance windows in the Frontend, so that it is easy to spot current maintenance window status
- optionally GMI can instruct IRP instances to preserve existing improvements so that once the maintenance window ends improvements are reimplemented. It is advised that this feature is used only when the maintenance window is very short (a few minutes long)
- an unloading period can be setup. During unloading IRP instances actively re-route outbound prefixes through other available providers. While IRP instances are able to make most of the unloading improvements fast, consideration shall be given to the announcement rate limitations setup in Bgpd in order for all the improvements to reach network routers in time for maintenance window starting time
- a prepend time can be setup. This is only applicable if Inbound optimization is operational. If this time is setup then an IRP instance will prepend configured inbound prefixes with the maximum allowed number of prepends through the provider link under maintenance in order to deflect inbound traffic towards other providers.
To review Maintenance windows, navigate to the corresponding left side bar menu option.
Figure 3.18.1: Maintenance windows menu button
The list displays all the current and future maintenance windows configured for providers in various IRP instances.
Figure 3.18.2: Maintenance windows
As shown in the screen-shot above, the list highlights:
- Current color-coded status of the maintenance window. Red and Orange depict unloading and actual maintenance phases while Blue and Green depict future planned windows and past finished windows correspondingly
- Begin and End date-times of maintenance windows
- Provider under maintenance
- Withdraw Improvement option enables or disables withdrawal of existing Outbound Improvements to that provider
- Seconds to Unload defines time interval in seconds prior to beginning of the maintenance window when a particular IRP instance starts to unload outbound traffic from provider
If Seconds to Unload/Seconds to Prepend time intervals set to zero the IRP instance does not perform corresponding action
When seconds to unload is specified it should be at least 5 minutes (300 seconds) long with larger time intervals allowing IRP more time to assess and reroute traffic flowing through provider with scheduled maintenance window. Very short time intervals might not have the desired effect since usually an IRP optimization cycle takes 2-3 minutes to finish- Seconds to Prepend defines time interval in seconds prior to beginning of the maintenance window when IRP announces all inbound prefixes with maximum prepends to provider in order to deflect inbound traffic towards other providers.
Maintenance windows can be added, edited or deleted using the designated action buttons.
A maintenance window is added by specifying the following:
Figure 3.18.3: Maintenance window popup