active backup link的用法和样例：
- Backup Link A resilient (fault tolerant) link which is not used until the primary link fails.
- It can be argued that having a backup link that's significantly smaller than your main one is a bit pointless, but at least you can set filters to let only the vital traffic through if your primary link fails.
- The orient has been playing an active role in the world economy.
- Do you have any backup if this machine fails?
- We should always have a backup plan.