According to a new report by data analysis firm Renesys, while the very largest provider networks (the Internet backbones) were apparently unaffected by the blackout in North America, many thousands of significant networks and millions of individual Internet users were offline for hours or days.
Banks, investment funds, business services, manufacturers, hospitals, educational institutions, ISPs, and government units were among the affected organisations, says the research.
According to Renesys' estimates, on 14 August -- when the North American blackout hit -- there were over 9,700 globally advertised customer networks in the affected area, belonging to over 3,500 organisations. A third of these networks -- 3,175 -- suffered from "abnormal connectivity outages" during the blackout, Renesys says. Of those, more than 2,000 networks suffered severe connectivity outages for longer than four hours, and over 1,400 networks for longer than 12 hours (some even more than 48 hours).
The networks suffering from abnormal connectivity outages belonged to over 1,700 organisations. More than 1,000 organisations had outages of all of their networks lasting longer than four hours.
Nearly half of those organisations involved in global Internet routing lost connectivity to some or all of their networks in the blackout area.
However, the specific effects of the blackout on Internet availability were geographically well-localised, said the report authors, and no evidence was found of cascading failures affecting global Internet stability.
This is backed up by the London Internet Exchange (LINX), which is the largest Internet exchange point in Europe, through which over half of all Internet traffic in Europe passes. A spokeswoman for LINX said that in mid-August there was a slight dip in traffic flowing through the LINX routers, but that this dip was too small to be significant.
"We route a lot of traffic from ISPs in the US, so if the traffic had affected them we would see it," she said. "We saw no problems for August -- the network traffic continued to flow."
Besides, she said, none of the serious operators have their equipment running without backup generators. "The backup generators at Telehouse on Broadway in New York can provide enough power to run a small city."
