The ipsumdump program summarizes TCP/IP dump files into a self-describing
ASCII format easily readable by humans and programs.

Ipsumdump can read packets from network interfaces, from tcpdump files, and
from existing ipsumdump files.  It will transparently uncompress tcpdump or
ipsumdump files when necessary.  It can randomly sample traffic, filter
traffic based on its contents, anonymize IP addresses, and sort packets from
multiple dumps by timestamp.  Also, it can optionally create a tcpdump file
containing actual packet data.

WWW: http://www.cs.ucla.edu/~kohler/ipsumdump/