Short route to a faster wan
Optimization can add speed without boosting bandwidth
- By John Moore
- Aug 10, 2007
'We extended our capability, without spending more money.' ' Clifford Clarke, Fort Wayne, Ind.
WPN Photo by Clint Keller
You know what happens when your e-mail and file servers are on the other side of the country and the people who use them are just down the hall? That's right ' they'll come to you when their e-mail client takes time to update or their files are slow to open. And it won't be a friendly visit.
As more agencies centralize and distribute information technology services, administrators are increasingly finding application performance being hampered by the laws of physics: It takes time for packets to fly back and forth across this great land of ours.
And even if the transport time of data can be measured in milliseconds, enough journeys back and forth will present the appearance of inactivity and annoy users. A long wait for a graphics-laden presentation is a test of patience and a productivity drain. Slow wide-area networks also expand backup windows and hinder continuity-of-operations plans.
The problem is multifaceted. The protocols underlying the Internet and network usage patterns contribute to bogged-down IP WANs. The law of unintended consequences also plays a role. Server and storage consolidation, designed to boost efficiency, may actually create situations in which users endure slow data access. Industry executives cited consolidation as a key driver behind government WAN optimization projects.
And where consolidation doesn't play a role in the sluggishness, distributed operations do. Branch offices and other operations located away from the central data center could be candidates for a WAN boost, too.
Fortunately, the answer doesn't always involve procuring more network capacity, which is always an expensive option. A number of different companies offer software and hardware that can help you make better use of your existing bandwidth.
That was the approach taken by Fort Wayne, Ind., when remote facilities had trouble accessing data housed in the city's data center. The fire department's training academy, for example, found it slow going when it reached over the WAN for training material, which included large files such as PowerPoint presentations.
The fire department 'did have problems getting [large files] across the link,' said Clifford Clarke, Fort Wayne's chief information officer.
Clarke considered upgrading the city's T1 line, but opted for a WAN optimization solution. This product class targets protocol weaknesses that hinder WAN performance and employs other techniques, such as caching and compression.
Fort Wayne conducted a proof-of-concept project last year using Cisco Systems' Wide Area Application Services (WAAS) product. The city found that WAAS could decrease access time by 40 percent to 60 percent. The technology also helped the county avoid an expensive bandwidth purchase.
'We extended our capability, without spending more money on that particular link,' Clarke said.Distance or congestion
David Smith, federal systems engineering manager at Citrix Systems, which has an optimization product called WANScaler, said the WAN lag boils down to 'a problem of distance or a problem of congestion.'
On the distance side, latency generally crops up as an issue over distances greater than one or two states, Smith said.
With Transaction Control Protocol, which accounts for the bulk of Internet traffic, latency is measured as the time it takes the following sequence to occur: A packet travels the network from sender to receiver and an acknowledgement of receipt flows back to the sender. Naturally, the longer the distance, the greater the latency.
Mark Urban, director of product marketing at WAN optimization vendor Packeteer, said latency of 5 milliseconds is typical for a good network in which a sender and a recipient are 200 miles apart. Latency over thousands of miles will reach 600 milliseconds, or just more than half a second.
The round-trip time affects TCP communication because it waits for an acknowledgement before moving more data across the wire. This delay has little impact on small transactions, but the story is different for bigger chunks of data ' a 100M file, for instance.
'You get into constraints when you're trying to move large amounts of data from one endpoint to another via TCP,' Urban said.
Smith said TCP was originally devised for smaller networks and thus harbors inefficiencies in WAN environments.
TCP isn't the only protocol with WAN issues. The Common Internet File System, a file-sharing protocol, is 'even more sensitive to latency,' Urban said. CIFS subjects files sent via the WAN to multiple round trips.
Technology aside, how organizations use a network can also contribute to performance problems. An enterprise that consolidates servers and storage and expects to have remote users accessing data via the WAN may be setting themselves up for trouble, industry executives say.
'People are treating the WAN as they would a LAN and, unfortunately, the laws of physics work against us on that assumption,' said Steve Picot, regional manager of federal data center solutions at Cisco.Speeding the WAN
WAN optimization products typically employ multiple performance-improving methods.
Most products in the category offer protocol acceleration to mitigate latency. Essentially, vendors tweak TCP to boost efficiency. Quality-of-service and bandwidth management techniques prioritize traffic so mission-critical applications get precedence, said Amichai Lesser, director of product marketing at Shunra Software, which recently launched a WAN optimization product selection service.
Another technique, data compression, aims to increase throughput.
The Marine Forces Reserve found compression to have a significant impact on its backup strategy. The New Orleans-based organization saturated a 155 megabits/sec OC-3 line when sending backup data to a COOP center in Kansas City, Mo.
'We started looking around for WAN acceleration to help compress our data,' said Glenn Voges, a senior network engineer who works as a contractor for the Marine Forces Reserve.
The reserve opted for Riverbed Technology's Steelhead 5010 WAN optimization appliance. Voges said compression lets the organization move 30G of Exchange data in six to eight hours. Before compression, that task took nearly two days.
In addition, WAN optimization solutions use caching to reduce the amount of data that must travel the WAN. Frequently accessed data can be stored on a WAN optimization appliance housed in a remote office, for example. Wide-area file service technology, considered a subset of WAN optimization, uses local caching and CIFS acceleration. The objective is to let organizations centralize applications without sacrificing file access speed in remote offices.
Solutions typically consist of an appliance set. One appliance might reside in the data center, while the other is housed in a remote facility.
'WAN optimization is a symmetrical solution ' you have a box on each end of the network and between those is where the traffic is optimized,' Smith said. Appliances may be installed in pairs at each end of the line, for redundancy purposes.
As for pricing, entry-level appliances can be had for less than $4,000, while enterprise-class products can run into the six figures. Customers believe faster WANs and cost avoidance justify the investment.
In Fort Wayne, Clarke said the WAN optimization deployment generated a 10-month return on investment. As for a bandwidth upgrade, 'we've pushed that off into the future.'
The Marine Forces Reserve, meanwhile, also avoided the pitfall of throwing more bandwidth at a lagging WAN. Although bandwidth is a recurring expense, the organization's appliance purchase represented a one-time outlay, Voges explained.
'That was the way to go,' he said.