Port 5555 is only for communication between the call manager , and the clients, and uses TCP. It is not used for passing data from the disk agent to the media agent
DP uses what is called Dynamic Port Addressing. After all systems contact, and acknowledge each other using port 5555, then DP will use any port that is available. This can be controlled by using OB2PORTRANGE
The number of ports required are in a chart in the document I sent to you, but, of course, being DP 5.5, there is no mention of VEPA backup requirements. I checked online help, and didn't find any additional information there
If you woul dlike to get some additional documentation published, you can create an Enahncement REquest at thsi URL
https://support.openview.hp.com/enhancement/do/main