Physical device fingerprinting with TCP timestamp options. This is an advisory with content that is somewhat similar to a paper released around March 1st 2005 by a student at UC San Diego. The research was apparently conducted independently, though at the same time.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/36815/TCP_Timestamping_Advanced_Fingerprinting.txt
Source: https://packetstormsecurity.com/files/36815/TCP_Timestamping_Advanced_Fingerprinting.txt.html