"In addition to protecting data that reside in database server, please describe how data can be protected during transmission both inside and outside of firewall. "
- The short answer is: "Using Encryption."
One can assume that at some point someone may intercept your transmissions (both inside and outside of firewall). Whether you expect an interception or whether you just generally suspect that interceptions may occur, you should transmit your information in a format that is useless to any interceptors.
Encryption allows any message to be transmitted that will be useless to anyone who intercepts it.
* Private Key ...
The expert examines protection data during transmission.