Hurricane Harvey: A Test-Bed For Internet Resilience

Amid the wreckage inflicted by Hurricane Harvey, south Texas is measuring the crisis in numbers of homes flattened or flooded, hospitals closed, refineries stalled, and storm refugees saved by brave neighbors with small boats.

A significant part of the damage, however, can be hidden in the soggy underground—in the conduits that house the major trunk lines and tributaries of the Internet backbone in Houston, says Paul Barford, one of the experts who have been studying hurricanes for years to gauge the resilience of the Internet. Barford, a computer sciences professor at the University of Wisconsin-Madison, says “last mile” connections to homes and buildings, such as DSL and modem lines that often run above ground, were also at risk from the storm’s high winds.

Interruptions in Internet service soon cropped up in the coastal areas of Texas that were whipped by hurricane-force winds starting on Aug. 25, and then soaked in rainfall so relentless that it had to be measured in feet rather than inches. But the long-term impact of the storm on the region’s Internet capabilities can’t be gauged until the floodwaters have fully drained away from the highways, buildings, and bayous, and power restored, Barford says.

“The full extent of the damage remains to be seen,” Barford says.

Major Internet service providers kick in emergency plans and deploy backup equipment to get customers back online as quickly as possible in these circumstances, and government agencies including the Department of Homeland Security lend support, Barford says.

But the cost could be significant, Barford says. He declined to make any ballpark projections, but says, “I can tell you, it’ll start in the billions.” Data firms are estimating the total financial impact of the hurricane at $70 billion to $108 billion, the New York Times reported.

Barford is known for spearheading the ongoing “Internet Atlas” project, which maintains a map of the big long-haul cables that funnel online traffic across the nation, from city to city. The streams of data then get picked up by regional Internet service providers, which bring it to individual users and offices.

Houston, as the fourth-largest city in the United States, is a nexus of major Internet trunk lines, as well as hubs that allow data from different service providers and data centers to enter the network so it can be dispatched to its destinations. Barford says Houston has three hubs called Internet Exchange Points or I.X.P.s, and 26 points of presence—Internet gateways that use components such as routers, servers, and Ethernet switches to direct online traffic.

“All of these facilities are at risk due to Harvey,” says Barford, whose research has been funded by U.S. government agencies, including the Department of Homeland Security, and private companies such as Intel and Cisco.

On Aug. 29, at the peak of the storm’s impact, service was out for at least 283,593 Internet and cable TV subscribers across 55 counties in Texas and Louisiana, according to disaster impact reports by the Federal Communications Commission. That number had changed to at least 164,544 subscribers in 13 counties of Texas by Sept. 3 (Sunday). AT&T and Comcast are major consumer providers in the region.

In spite of the outages, Internet communications played a key role in rescue and recovery efforts in Texas, as Xconomy’s Texas editor Angela Shah reported. Flood victims were connected with emergency responders and volunteers through social media channels.

Many of the Internet outages could have been caused simply by the loss of electrical power, Barford says, and in that case could be resolved fairly quickly. But his main interest is in buried fiber infrastructure, where damage could be harder to repair and more likely to have long-term consequences, if only for the Houston region.

Even though Houston’s cables and hubs are interconnected with the national Internet system, as well as the global Web, Hurricane Harvey is likely to have a minimal effect on overall U.S. Internet traffic, Barford says. That’s because the system is designed to route digital data around any disruptions, so it can get to its destination through an alternate path. “It’s very, very good at that,” he says.

The robustness of the Internet in preventing local events from cascading into larger regional or nationwide outages is borne out by another researcher’s study of a comparable storm. Hurricane Sandy made landfall on New York and New Jersey on Oct. 30, 2012, and caused significant outages in those two states, a team led by University of Southern California computer science professor John Heidemann found.

The hurricane increased the overall outage rate of U.S. networks from 0.2 percent to 0.43 percent in the day following landfall, Heidemann’s team discovered. Although that represented a doubling of the nationwide outage rate, it’s still not a drastic erosion of Internet performance. The U.S. outage rate routinely hovers at around 0.3 percent, as estimated by Heidemann. However, after Sandy, the nationwide outage rate took four days to return to the rate prevailing before the storm hit, he found.

Heidemann released some preliminary assessments of Hurricane Harvey on Friday from the ANT Lab, a multi-center project that studies Internet stability and security. The Harvey study looked at the Internet’s viability at the edge of networks, where end users are affected, rather than its backbone of major cables. The team sends out pings to a sampling of Internet addresses mapped to U.S. regions, then tracks the responses—and responses that don’t come back. After Harvey’s landfall in Corpus Christi, TX, at least 40 percent of home networks dropped off the Internet, followed by the downing of many networks in Houston as the storm moved up the coast, according to the ANT Lab report. The outages in Houston, however, took out a smaller fraction of the city’s total networks compared with the failures in Corpus Christi.

Heidemann’s method can’t distinguish between a loss of service due to power failures or due to damage to Internet infrastructure itself, but the data can be useful as a remote measurement of physical storm damage, the team said in its preliminary report.

“Observations about Internet outages due to storm damages provide unique details about the geographic scope and seriousness of damage,” the report says. The team is now working to achieve real-time reporting of outages, to add to information gathered from storm scenes by news organizations and utilities busy with efforts to restore and maintain service.

As for the Internet backbone, Barford wondered whether Harvey could have had unusual consequences because it drenched Houston in record rains that lasted for days. The Internet’s long-haul cables are carried in conduits buried in soil, or threaded through city utility lines. The conduits are packed with materials that make them resistant to moisture, but “not necessarily weather-proof,” he says. Some of Houston’s cables and other infrastructure might have been immersed for the better part of a week, he says.

“They’re not designed to be underwater for extended periods of time,” Barford says. Possible exposure of some lines to salt water, which is more … Next Page »

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Bernadette Tansey is Xconomy's San Francisco Editor. You can reach her at Follow @Tansey_Xconomy

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