Regarding service providers there are 5 practices to follow.

1. Back up servers that can also be taken to an out of the area server to share with traffic volumes.

2. Updated automation to keep up and keep track.

3. To constantly test all equipment and tasks.

4. Assessments of the existing systems.

5. Keeping the integrity to assist in all aspects and keep confidence with the customers.

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http://www.telecomreseller.com/2014/07/14/top-5-hosted-unified-communications-best-practices/