Because VoIP calls are routed through computer servers, that information is automatically logged by the software. This can be both a convenience and a business tool. VoIP automatically logs each call number, caller ID, date, duration, and whether the call was connected or went to voice mail. The call logs can also be sorted by each of the aforementioned details.

The call logs are integrated into many of the other UCC tools of Voice over Internet Protocol. When viewing the call logs, the user can select a call and add that number to the contact list. If the VoIP provider supports this option, the user can click2dial the number right from the computer. The information itself can be exported to XML or CSV files to be plotted into graphs.

Additional Reading
What are the Differences between Business and Residential VoIP?
What is Simultaneous Ring?