The Internet Metrics post in December was a good starting point for my research on backbone traffic, but I'm struggling to get more specific information.  Specifically, I am trying to find out the market share for the major backbone providers (so far I've found WorldCom 37% and Sprint 16% of traffic).  Boardwatch has this breakdown, but by ISP connections (WorldCom 24% & Sprint 14%).  Is the percent of ISP connections a good estimate of the percent of traffic a backbone carries? 

Also, for the major backbones, is there any kind of breakdown of the percent of a backbone's traffic that is for a corporate end user vs. a personal dial-up or broadband account.  Specifically, does WorldCom, Sprint, C&W, ATT, Genuity, Level 3's traffic have a strong tendency to be for corporate or personal accounts?

Finally, Is there any source or estimate for the current total amount of Internet traffic carried by all networks?

Any information or sources would be greatly appreciated.
Thanks,
Eric
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Eric Lemond
Interdiciplinary Telecommunications Program, CU Boulder
Intern, FastIdeas