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In a typical codec application, Codec X will send a packet from Address A Port B, to Address C Port D on the Destination
Codec Y. A codec that has multiple applications running (like streaming audio while simultaneously serving a
configuration web page) would deliver these applications from, and to, different port numbers, but perhaps to the same
IP address. Port numbers are also used by NAT routers in segmenting applications flowing through them and they may
change source port numbers at will.
Network Address Translation (NAT) refers to the ability of a router to translate requests from computers (or codecs)
within its LAN onto the public internet. On its most basic level, this involves replacing the private “source” or return
IP address in each packet with the true public IP and remembering where that packet was sent. This insures that any
response can be forwarded back to the proper device.
