There are different types of whois servers. Some are 'referrers', which will refer the query onward to another registrar if it's not their domain (like Netsol do) and some are not referrers, in which case they will just tell you 'not found'. The top level whois servers can be queried to find out who the registrar is for a domain name. This 'top level' whois server will accept a query on port 43:
http://rs.internic.net, but NOT via a browser. You'll need a proper Linux or Win32 command line client. I wrote one myself for Win32 so that's what I use for casual use and I use a Linux scripting method for more intensive querying.
Network Solutions are not 'in charge' of all the .coms, but they are responsible (Verisign) for the zone files which contain all the DNS entries for .com/.net/.mil/.edu but note that whois information is NOT part of their assets -- these are owned by the individual registrars who 'sell' the domain.
If you compare zone files twice per day and submit differences to top level whois queries, you can start to understand how name 'snaps' work.
Get yourself a command line whois client and I'll give you some more examples.
Regards!