As has been shown, the predominant way that availability of a network can be improved is to improve its MTBF by using devices that have redundant components and by engineering the network to be as redundant as possible, leveraging many of the technologies discussed in the previous sections.
However, glancing back to the general availability formula, another approach to improving availability is to reduce MTTR. Reducing MTTR is primarily a factor of operational resiliency.
MTTR operations can be significantly improved in conjunction with device and network redundant design. Specifically, the capability to make changes, upgrade software, and replace or upgrade hardware in a production network is extensively improved due to the implementation of device and network redundancy. The capability to upgrade individualdevices without taking them out of service is based on having internal component redundancy complemented with the system software capabilities. Similarly, by having dual active paths through redundant network devices designed to converge in subsecond timeframes, you can schedule an outage event on one element of the network and allow it to be upgraded and then brought back into service with minimal or no disruption to the network as a whole.
You can also improve MTTR by reducing the time required to perform any of the following operations:
- Failure detection
- Notification
- Fault diagnosis
- Dispatch and Arrival
- Fault repair
Some technologies that can help automate and streamline these operations include the following:
- General Online Diagnostics (GOLD)
- Embedded Event Manager (EEM)
- In Service Software Upgrade (ISSU)
- Online Insertion and Removal (OIR)
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