Deep down, the key for a connection is the concatenation of SA DA SP DP. DA and DP are constant for a given service in the simple case and the others are 4 oct

Deep down, the key for a connection is the concatenation of SA DA SP DP. DA and DP are constant for a given service in the simple case and the others are 4 octets [although not all of it usable] for IPv4 and 2 octets (for port).