What would I be looking at to differentiate computers on the same network? (using Ruby/Rails code) Also considering computers that are assigned a different ip over a wireless office network. Would I be looking at extracting the MAC address or is there a better way?
Unsure what you're trying to do here, but you perhaps want to be looking at using session or cookie information to identify unique users of a rails app.
If however, you are asking a more generic networking question...then IP's are non-unique. Take for example multiple computers (CPE's) behind a NAT-router. They will all appear as the same IP on the WAN side. MAC addresses are unique. However, they can be spoofed/modified and as such are not a secure way to identify 'unique-ness' either. Take the same example of the CPE's behind a NAT-router. They will all appear to the WAN side as a single MAC address for their network traffic. (This is in-fact how Internet routing works).
So basically MAC addresses will not transit a router in the network as they are Layer 2 entities. IP's are Layer 3+ and will transit routers, but not NAT routers (which are very common). I'm sure it is possible to get MAC information via a cookie or some such inquiry, but that is no guarantee of uniqueness considering that MAC's can be modified.
-Dale
