Zoom, zoom, zoom
WAN acceleration brings Seattle transit system up to speed
- By Doug Beizer
- Mar 10, 2007
Traffic on state Route 518 whizzes past a light-rail platform in Tukwila, Wash., near the Seattle-Tacoma International Airport. The mass transit system recently got a boost from wide-area network acceleration devices.
Seattle's famed monorail isn't the only mass transit system operating in the Pacific Northwest.
Commuter trains ferry thousands of people to and from work over 74 miles of tracks between Everett and Tacoma. Buses move people about the areas' three counties. And a light rail system under construction will connect downtown Seattle to the Seattle-Tacoma International Airport.
The entire system is managed by Sound Transit, a state entity founded to build the transportation network. With three core sites and several remote locations, Sound Transit officials depend on a wide-area network to keep projects moving forward and to communicate with the organization's contractors. However, about a year and a half ago, the WAN was sometimes running as slow as the morning rush hour.
To speed the network, Sound Transit officials installed WAN acceleration devices. The devices were necessary because applications such as LiveLink Enterprise Content Management and Microsoft Office SharePoint were running at unacceptably slow speeds, said Garv Nayyar, senior integration engineer at Sound Transit.
"So we have all these remote sites, plus folks who work from their own remote offices, wanting to access things like LiveLink," Nayyar said. "It was taking them forever to upload and download documents because everything was located at our headquarters. The servers and access to the Internet were here."
Computer-assisted design drawings ranging from 1M to 50M were taking up to nine minutes to open. High-quality digital photos were also slow to upload, taking as long as four minutes.
Even using an Exchange e-mail server was slow, said Jeff Aaron, director of product marketing at Silver Peak Systems Inc., a provider of WAN acceleration appliances based in Santa Clara, Calif.
"Things were taking two or three minutes over the WAN, whereas on a local-area network they would only take a few seconds," Aaron said.
Connecting geographically dispersed offices brings unavoidable problems, WAN experts said. The distance limits bandwidth and creates slowdowns in data transfer rates. And as the number of routers and other devices that data flows through increases, the packet loss rate inevitably rises.
In addition, the trend toward moving servers out of offices and into data centers makes it harder to avoid using WANs for routine tasks. Agencies make those moves for many reasons, including reducing management costs, freeing building space and aiding disaster recovery.
One of Sound Transit's contractors complained that the network slowdowns were costing time and could lead to delays in completing projects, Nayyar said. The transportation entity decided to find a way to mitigate the problems.
A number of options can help improve WAN speeds. One is to simply deploy servers at every office location, but that is usually costly. In addition to the equipment costs, that approach requires employees at each location to manage the servers, synchronize their data, back them up and store backups in remote locations.
Increased bandwidth can also improve overall speed, but that doesn't always solve packet loss or latency problems. Network technologies can compress data or implement a priority system that designates which data is higher priority.
Finally, a relatively new technology called data reduction stores the data traffic that flows into each office and keeps a running tab of the data's location. When someone tries to send a file to a location that already has it, the data-reduction system stops it and sends a pointer to the destination location. That allows the recipient to get the right file without the file data actually having to be transmitted, Aaron said.
"It's similar to a cache, but the biggest difference is data reduction will work across all different types of applications," he said. "So let's say I'm e-mailing a PowerPoint file to you that's leaving my office and entering your office. The appliances in [both] offices will see that and store that information, so the next time I e-mail that PowerPoint file to you, it won't go across the WAN, it will just be delivered locally."
Sound Transit officials decided to use several methods to accelerate WAN traffic, all bundled into the Silver Peak appliance. Silver Peak appliances are installed at each Sound Transit location to filter traffic going to each office's WAN router.
"Literally, all it is doing is sitting in the path and fingerprinting the traffic, and whenever anything is sent that has already been seen, it intercepts that and sends a pointer instead of the data itself," Aaron said.
In some cases, Sound Transit's WAN traffic is down by about 95 percent because redundant information has been eliminated.
Sound Transit officials tested Silver Peak at one of its remote sites that had the most complaints. Staff members at the site noticed an improvement immediately.
"Even on their busiest days they noticed a huge difference," Nayyar said. "The files that were taking 10 to 15 minutes to open now take about 10 or 20 seconds."
An unexpected benefit of the acceleration appliance is that it gives Sound Transit officials a view of what kind of traffic is going in and out of the remote sites. If people are streaming radio stations and slowing the WAN, administrators can stop that.Staff Writer Doug Beizer can be reached at firstname.lastname@example.org.