GUID Uniqueness

This is an article explaining how GUID can be almost certainly (if not totally certainly unique).

Link: http://blogs.msdn.com/b/oldnewthing/archive/2008/06/27/8659071.aspx

This is done by including the following information in the GUID:

1. Machine ID (network card Mac address)
2. Timestamp
3. Counter to differentiate entries generated within the same timestamp
4. Algorithm version identifier

This is the "Version 1" algorithm for GUID generation. There are other versions which rely more on random number generators. I'm not sure if those are as reliable as version 1 in terms of guaranteeing uniqueness, and will be the topic of future research.