Increasingly popular social-networking sites such as MySpace, YouTube and Facebook are accounting for such huge volumes of DNS queries and bandwidth consumption that carriers, universities and corporations are scrambling to keep pace.

The trend is prompting some network operators to upgrade their DNS systems, while others are blocking the sites altogether. Moreover, the "MySpace Effect" is expected to hit many more nets soon, as these network-intensive interactive features migrate from specialty sites to mainstream e-commerce operations and intranets.

"Social media is not just going to be in pure-play sites like MySpace and Facebook. It's going to become increasingly prevalent across retailers, media and entertainment," says Mike Afergan, CTO of US-based Akamai, a content delivery network company that supports MySpace, Facebook and Friendster. "It drives a lot more requests and a lot more bit-traffic across these networks."

The demanding nature of social-networking sites was highlighted in May when the US Department of Defence announced it was blocking worldwide access to 13 Web sites, including MySpace and YouTube.

"The Commander of DoD's Joint Task Force, Global Network Operations has noted a significant increase in use of DoD network resources tied up by individuals visiting certain recreational Internet sites," Army General B.B. Bell said in a memo. "This recreational traffic impacts our official DoD network and bandwidth availability, while posing a significant operational security challenge."

The Defence Department began blocking access to these sites on May 14 on its unclassified IP network, which is called NIPRNET for Non-secure Internet Protocol Routed Network.

The military isn't the only organization to notice how taxing these sites are on network resources.

"One of the things we're hearing more and more from carriers is that social-networking sites like MySpace and YouTube are contributing to an exponential increase in DNS traffic," says Tom Tovar, president and COO of US-based Nominum, which sells high-end DNS software to carriers and enterprises.

Social-networking sites create large volumes of DNS traffic because they pull content from all over the Internet. Most of these sites use content-delivery networks to extend the geographical reach of their content so users can access it closer to home.

"A single MySpace page can have anywhere from 200 to 300 DNS lookups, while a normal news site with ads might have 10 to 15 DNS lookups," Tovar says. "It's an exponential increase."

Virgin Media, a UK cable service provider with 10 million subscribers (including 3.5 million broadband users) in the United Kingdom, has found that the amount of DNS traffic generated by social-networking sites has grown dramatically in the past 10 months. YouTube and Facebook traffic has doubled in that time frame but still represents a fraction of Virgin Media's overall DNS traffic. YouTube grew from 0.5 percent to 0.75 percent of the carrier's DNS traffic, while Facebook grew from 0.5 percent to 1 percent.

In contrast, MySpace now represents 10 percent of Virgin Media's DNS traffic, up from 7.2 percent last northern autumn.

The social-networking sites "are generating many more DNS queries per user than other sites", says Keith Oborn, network systems product architect with Virgin Media. "Because of the way MySpace pages are structured, a single page can generate hundreds of DNS queries."

Oborn says the fact that many of these social-networking sites, including MySpace and YouTube, are served by content-delivery networks adds to the DNS traffic.

"They're making use of an awful lot of short TTLs [time to live values]," Oborn says. "That increases the load on the DNS servers. The same thing would happen for an enterprise customer as you see happening on a service provider network."

Oborn says it's rare for one Web site to account for 10 percent of DNS traffic.

"MySpace is the one that everybody knows about," he says. "It's the thing we need to keep a careful eye on in DNS land."

Virgin Media is addressing this phenomenon by upgrading its DNS infrastructure to the latest version of Nominum's software, which uses a technique called Anycast to provide load balancing for improved redundancy. Virgin Media will complete the upgrade this summer.

With the new configuration, Virgin Media says it "could do 2.5 million DNS queries per second, but all we need is 50,000 or 60,000," Obort says. "We have a lot of overcapacity in DNS, which is both cheap and good to have. ... It cost us a few hundred thousand pounds at most."

Virgin Media is anticipating continued growth in its DNS traffic, driven in part by social-networking sites. "Overall our DNS traffic is growing twice as fast as the number of users," Oborn says.