A likely substantial but unknown number of internet users have been cut off from the parts of the internet, unable to send or receive emails or access various websites as a result of a feud between two big backbone internet companies, reports CNET. One company, Level 3 Communications, has cut off direct communications with rival Cogent Communications.

In theory, the internet network is large enough to offer alternate routes when a connection is severed, but sometimes connections between networks are direct and no backup is in place.

In this case, the problem is a type of network connection called "peering," which the biggest network companies engage in by agreeing to establish direct connections between their networks, typically without charge if the companies are of equal size.

But Level 3 says it is substantially larger than Cogent and wants it to pay access fees; Cogent says it's just as big and won't pay. Both sides are adamant about being big. It's a tossup who the biggest losers are - the companies, or their customers.