Another Internet backbone outage on Monday left as many as 5.7 million Charter Communications customers without reliable Internet access.

Charter, the third-largest Internet Service Provider in the United States, lost service from one of its backbone networks. Backbone networks are the systems that connect ISPs to each other around the world.

Late last week, Sunflower Broadband Internet customers experienced similar problems when Level 3 Communications, a backbone network for Sunflower, conducted scheduled maintenance that went awry.

For Charter customers, the Internet service outage was sporadic and varied, with some customers reporting no problems, according to messages to Charter on Twitter, while others reported extremely slow connections or no connection at all.

Charter also said the outage was affecting several other major ISPs across the country.