Each endpoint maintains a packet number, starting at 0 and increasing by one for each packet sent. This is an input to the packet encryption IV. Note that unli

Each endpoint maintains a packet number, starting at 0 and increasing by one for each packet sent. This is an input to the packet encryption IV. Note that unlike TCP retries do not re-use the packet number, they get a higher packet number on re-transmit. This lets endpoints differentiate packet retries from delayed packets, which isn’t possible in TCP (and the ambiguity of which is a problem in TCP stacks that want to react differently to each).