Cisco standard NetFlow version 5 defines a flow as a unidirectional sequence of packets that all share seven values which define a unique key for the flow:
+ Ingress interface (SNMP ifIndex)
+ Source IP address
+ Destination IP address
+ IP protocol
+ Source port for UDP or TCP, 0 for other protocols
+ Destination port for UDP or TCP, type and code for ICMP, or 0 for other protocols
+ IP Type of Service
Note: A flow is a unidirectional series of packets between a given source and destination.

The FMC and managed devices communicate using a two-way, SSL-encrypted communication channel, which by default is on port 8305.
Cisco strongly recommends that you keep the default settings for the remote management port, but if the management port conflicts with other communications on your network, you can choose a different port. If you change the management port, you must change it for all devices in your deployment that need to communicate with each other.