A useful script file I wrote called zplog is available for free download from the SILICON CHIP website. In case you're wondering where the name came from, I have convention of starting all my programs and scripts with "z" so I know that they are "home grown" (not many commercial programs start with "z"). The "plog" bit stands for "packet log".
I will not attempt to explain how it works as it contains a lot of diabolical "awk" code. However, if you read the "man" pages on "awk", you should be able to make some sense of it.
The script can be run with or without arguments. The optional arguments are:
zplog[-a][-e string][-f fn][-i][-m nm][-n][-p][-s][-v]