said. A router receives an update only when the status of a link in the area changes or something important occurs outside the area.

However, Levchenko noted, cre-ating areas is a complicated process that requires precise configuration. In addition, he said, it doesn’t enable direct communication among routers that aren’t in the same area and thus is not very efficient.

The XL algorithm works by letting each router automatically determine which of its neighboring routers—

and even more distant routers in some cases—actually need a specific update.

The routers make these determi-nations based on a set of rules. The rules require updates only when a change in link status increases rout-ing overhead, when it occurs along what would normally be the short-est path from sender to recipient, or when an alternative routing would reduce overhead significantly.

With XL, routers also decide whether to send updates based on

Externalview

Externalview

Externalview

Internalview

Forwardtable

Externalview

Externalview

Externalview

From neighbors

To neighbors Source: Associate professor Stefan SavageUniversity of California, San Diego

Researchers have developed a new algorithm that makes network routing more efficient. Currently, if there are problems along potential data routes, the system notifies all routers, even those that are unaffected. This creates heavy network traffic. With the new algorithm, a router receives and sends “external view” network information from and to neighboring routers. This helps each router build an “internal view” of the information its neighbors have. If the router receives important network information, it forwards it only to the neighbors that need but don’t already have it.

New Algorithm Makes Routers More Efficient

A n academic research team has developed a new algo-rithm that makes network routing more efficient. This would be important

in large heterogeneous corporate networks in which the oldest, slow-est routers make the others wait while they absorb updates and recalculate path tables.

A team led by University of Cali-fornia, San Diego, associate professor Stefan Savage developed the Approxi-mate Link (XL) State algorithm.

XL makes networks more efficient by automatically limiting the number of route or link-state updates they receive from other routers, explained Kirill Levchenko, a UCSD postdoc-toral researcher who worked on the project.

Currently, if there is a problem along potential data routes, algo-rithms inform all network routers about information such as link-state updates, which identify whether a network link is working. This enables the system to reroute traffic along available paths.

However, notifying every network router, including those not affected by a specific problem, can cause problems. For example, in extensive systems such as backbone routing networks, many updates would go to a large number of routers. This could make the routers, and thus the network itself, slow or unresponsive, Levchenko explained.

Systems currently try to limit the number of updates by manually dividing the network into isolated groups of routers called areas, he

23FEBRUARY 2009

NEWS BRIEFS

Published by the IEEE Computer Society0018-9162/09/$25.00 © 2009 IEEE

NEWS BRIEFS

compUtER 24

information that neighboring rout-ers have about the network. They receive this information regularly from the neighboring routers. If they determine that the other routers don’t know about something impor-tant, they inform them.

Either way, XL lets the system send updates only to the routers affected by specific updates. This enables the

network to operate more efficiently, according to Levchenko.

XL, which the researchers are still testing, works with the Intermediate System-to-Intermediate System and Open Shortest Path First protocols, currently used by most routers.

Router makers like Cisco Sys-tems—which helped fund the UCSD research—will have to implement XL

in their software for the technology to become an important part of net-work technology, noted Levchenko.

Cisco is involved with this project because it is interested in innova-tions that could improve corporate networking efficiency, noted Linda M. Horiuchi, the company’s senior public relations manager for corpo-rate communications.

Researchers Work on First Optical- Network Firewall

A European research group is developing what it cla ims would be the world’s first optical fire-wall, designed to be fast

enough to secure high-speed optical networks.

The WISDOM (Wirespeed Security Domains using Optical Monitoring) project—which includes Ireland’s Tyndall Institute, Greece’s Founda-tion for Research and Technology, the UK’s CIP Technologies, French opti-cal-equipment vendor Avanex, and UK network operator BT—expects to finish its work on the firewall this May.

The demand for optical band-width is approximately doubling each year, according to Graeme Max-well, project coordinator and CIP vice president for hybrid research and development.

He said this is due to the growing demand for data-intensive services such as video-on-demand and online gaming, as well as the increased introduction of fiber-to-the-home networks.

Telecommunications providers are thus expanding the Internet’s high-speed fiber-optic backbone.

However, the electronic processes and algorithms used in firewalls to filter data for security threats are too slow, expensive, and power-hungry to keep pace with rising network speeds.

Manufacturers have tried to address this problem via custom electronic firewalls, which increase performance by using more proc-essors or networking line cards. These firewalls are very fast but also increase cost and power consump-tion, Maxwell said.

The WISDOM optical firewall uses innovative, custom algorithms to perform conventional threat-identification tasks—such as packet recognition and the interrogation and manipulation of data streams—in high-speed networks.

The system will offer the fast per-formance of optical processing: up to 40 gigabits per second, comparable to the speed of today’s commercial opti-cal networks, Maxwell said.

WISDOM has developed inte-grated optical components, such as logic gates, that enable high-speed, programmable pattern matching. The firewall can thus examine optical packet headers, including IP address

and other fields, for information that indicates potential security problems. For example, it might filter out pack-ets with information in their headers that indicate they are going to recipi-ent TCP/IP ports that are typically attack targets.

In essence, WISDOM would work as a high-speed filter that recognizes suspect data packets. Traditional electronic firewall approaches would then decide how to dispose of the fil-tered packets.

Because of its bandwidth and abil-ity to quickly recognize and filter out suspect packets, the optical firewall would be highly scalable, Maxwell noted.

Veteran hardware analyst and consultant Peter Glaskowsky said the WISDOM firewall appears useful but may not have much short-term significance and could have trouble competing with current commercial products, which are more afforda-ble, widely available, and mature.

Maxwell said the WISDOM fire-wall will be ready for commercial implementation in perhaps five years and will be used primarily in core and metropolitan-area net-works.

T he World Wide Web Con-sortium has adopted an improved and updated ver-sion of a standard designed to help Web designers and

developers create sites that are easier for older and disabled users to work with.

The W3C’s Web Content Acces-sibi l it y Guidelines 2.0 (www.w3.org/TR/WCAG20) improves upon the initial standard, adopted in May 1999. WCAG 2.0 addresses problems that people with visual, auditory, physical, cognitive, and neurological difficulties caused by disabilities or

age have in accessing the Web. WCAG 2.0 explains how to make

content easier for disabled users to more easily perceive, under-stand, and work with, and easier for various technologies to inter-pret correctly, explained University of Wisconsin-Madison professor Gregg Vanderheiden, director of the school’s Trace Research and Devel-opment Center, which studies the communication needs of people with disabilities. He is also cochair of the W3C’s WCAG Working Group.

The new standard, for exam-ple, addresses the provision of text

instead of images for blind users, the use of captions instead of audio for deaf users, ways to make input and navigation easier, and compatibility with existing assistive technologies.

He said one of WCAG 2.0’s notable improvements is that it can be applied to any Web technology, such as Adobe Flash or Microsoft Silverlight.

WCAG 1.0 works only with HTML and thus is incompatible with Flash, PDF, and many types of scripting. WCAG 1.0 can be applied to some con-tent not written in HTML. However, for example, if a Web page includes non-HTML scripting, that feature

W3C Adopts Web-Accessibility Specifications

A start-up has added a twist to videoconferencing by developing a device that combines affordable robotics and telepresence.

RoboDynamics has created TiLR (pronounced “Tyler,” short for telepresence Internet-connected low-cost robot), a robot with videocommunications capabilities.

Like videoconferencing, this could eliminate some costly travel for meetings, said CEO Fred Nikoghar.

TiLR’s mobility, which videoconferencing doesn’t offer, would also let a person in one place communicate bidirec-tionally with multiple workers at different places in a building that’s in another location. The device’s mobility also offers spontaneity in communications because users aren’t stuck behind a stationary computer, Nikoghar noted.

TiLR stands 46 inches tall, weighs 60 pounds, and is made of aircraft-grade aluminum and highly durable polycarbonate resin thermoplastic.

It runs a Mini-ITX PC and any processor that works on the computer’s motherboard. So far, RoboDynamics has used a 2-GHz VIA Technologies C7 chip. TiLR has 1 gigabyte of RAM and runs Windows XP Professional and proprietary telepresence software. It also has an 8-inch LCD touch screen and a high-reso-lution Canon camera.

The robot provides videoconferencing services by connecting to the Internet. It works with multiple wireless technologies, including cellular and WiMax, as long as they provide at least 200 kilobits per second of bandwidth. The ideal is at least 500 Kbps. The company’s current implementation uses the IEEE 802.11g flavor of Wi-fi. Users could change the networking technologies they employ by installing different add-in cards.

Remote users control the robot via the TiLR Command Center, a software component that installs on most PCs and works with broadband connections.

According to RoboDynamics, TiLR will be particularly helpful in corporate, manufacturing, and educational settings.

For example, Nikoghar said, the device could be used for the maintenance of large, specialty equipment. In lieu of a visit, tech-nicians could employ TiLR to remotely look at machinery, diagnose problems, and instruct on-site mechanics how to make the neces-sary repairs, saving time and money in the process.

The TiLR system’s price is $10,000, said Nikoghar. This would be less expensive in the long run than some high-end telepres-ence systems that cost up to $5,000 a month.

DEvicE ADDs RoBotics to tElEpREsEncE

25FEBRUARY 2009

RoboDynamics has created TiLR, a robot with communications capabilities that enable expanded videoconferencing.

Editor: lee Garber, Computer, l.garber@computer.org

NEWS BRIEFS

compUtER 26

would have to be turned off.Because the new standard can

handle material not written in HTML, it will work with all types of Web con-tent—including text, images, audio, and video—and all types of Web appli-cations—such as those for e-mail, e-commerce, financial management, authoring, and social networking.

The new standard will also be more precise than its predecessor.

For example, the older guidelines stated that the color combinations used on a site should “provide suf-ficient contrast when viewed by someone having color deficits or when viewed on a black and white screen” without specifically stating what is considered sufficient. The new standard specifies a minimum level of contrast and the proper use of images and logos.

This clarity and precision also lets individuals and automated tools more easily test sites for compliance.

According to Vanderheiden, WCAG 2.0 doesn’t specify which technolo-

gies Web developers must use to comply with it. This enables flexibil-ity and innovation in implementation and also lets vendors of Web-devel-opment software conform to the standard while continuing to use their own technologies.

Third-party vendors are already creating techniques that would let their products and technologies con-form to WCAG 2.0.

To upgrade Web sites from WCAG 1.0 to WCAG 2.0 compliance gen-erally won’t require significant changes, said Vanderheiden. For example, developers would have to ensure that audio on their sites could be turned off so that it doesn’t inter-fere with screen readers and that their input controls are described clearly enough for people with dif-ferent disabilities.

The WCAG 2.0 is part of the W3C’s Web Accessibility Initiative, which works with organizations around the world to develop and promote adap-tive technologies.

According to Vanderheiden, the consortium developed the stand-ard with considerable input from industry, disability and research organizations, and IT policy makers worldwide. The W3C also tested it extensively.

Nadège Riche, the European Disa-bility Forum’s policy officer in charge of information and communication technology and standardization, said her group supports WCAG 2.0.

However, she added, the standard alone won’t deliver a fully accessible Web. Even if Web content conforms, she explained, user equipment may not be able to support accessibility. She said legislation will be necessary.

News Briefs written by Linda Dailey Paulson, a freelance technology writer based in Ventura, California. Contact her at ldpaulson@yahoo.com.

Silver Bullet Security PodcastIn-depth in ter v iews w i th secur i t y gurus . Hos ted by Gar y McGraw.

w w w.computer.org /secur i t y /podcastsSponsored by