Some packet handlers (such as RTCP) may need access to the parent
object or they may require some additional data from outside the
packet handler that is required when processing the packet.
Because most packet handlers do not require the raw UDP datagram
received through the socket, it makes little sense to relay those
parameters to them.
Additionally, there's a clear distinction between crafting
an RTP frame and operating on it so having one handler type
for both operations is not the best design choice.
Thus the packet handlers are divided into primary and auxiliary
handlers. Primary handlers are responsible for creating a packet
that the auxiliary handlers can operate on and auxiliary handlers
are responsible for doing all other operations on the packet such as
gathering sessions statistic information or decrypting the packet.
Aaro Altonen