packettester.py is a python script which relies on the scapy library.
It loads a pcap file and finds unique packets in a session. It is helpful to trim your pcap file prior to using this tool, by limiting the packet list to the stream that you wish to analyze.
For more information on this tool, read the corresponding blog post: http://www.digitalbond.com/blog/2014/10/15/protocol-differential-analysis/