One of the surest ways for companies with expensive data links to save money is to install WAN-acceleration devices. Users report the gear pays for itself in as little as a few months.The primary way these devices save money is by making fixed-size links appear larger. This puts off the need to buy more bandwidth, which is a money-saver, particularly when the bandwidth is expensive, as is the case with international direct circuits.WAN optimizers sit at both ends of connections and tune traffic so more of it crosses the wire more efficiently. The results are increased throughput and faster application response time and database access. A long list of vendors make such appliances, which tap a range of technologies to achieve results (see graphic below). The vendors include Blue Coat, Expand Networks, F5 Networks, Juniper Networks, NetScaler, Orbital Data, Packeteer, Riverbed and Silver Peak .Many ways to be fasterWAN-acceleration devices use a variety of technologies, with each vendor picking its own to make the connections perform better.Compression: Reduces the volume of bits needed to represent files before they reach the WAN.Pattern reduction: Reduces the volume of bits by recognizing patterns in bit streams that are independent of file structures and sending an abbreviated version.Application optimization: Anticipates responses that applications need and provides them locally, reducing WAN traffic.TCP optimization: Running customized TCP that responds more moderately to congestion reduces slowdowns when congestion does occur.Caching: Stores local copies of frequently accessed files so they don't have to cross the WAN and syncs just the changes with the originals.These devices can have a quick ROI, for domestic links as well as international ones. For example, the payback for Lititz, Pa., financial-services firm Susquehanna Bancshares was less than a year when it placed Expand's WAN accelerators on a DS-3 connection between its Pennsylvania data centers 120 miles apart, says Rod Lefever, the firm's senior vice president and CTO.The company used to outsource a disaster-recovery site where tapes would be shipped, replicated and brought online if the primary data center failed, but it was a lengthy process to bring up the site. "The best case was 36 hours," Lefever says.The company replicates several gigabytes of data per day, much of it the images of checks the company processes. That time was getting longer as the data center handled more traffic, so the company decided to set up a second company-owned data center to continuously replicate the first.With the then-existing bundle of five T-1 circuits bonded into a logical 7.5Mbps link, the backup could be online in half an hour. Much of that delay was caused by some switchovers the firm decided to keep manual as a security precaution, Lefever says. The problem, though, was that total traffic over the link had increased to an average 6M to 7Mbps, with peak traffic spiking to nearly 45Mbps. "We used the vast majority of our available bandwidth for average traffic," he says.So the company tested devices from Expand and Peribit (now part of Juniper). Susquehanna found for its particular mix of traffic, the Peribit gear didn't improve performance on the link, Lefever says. But the company says the Expand product improved traffic throughput enough so even spikes in traffic could be handled on the 7.5Mbps logical linkThe setup was tight, however, and allowed no room for growth. Lefever says over time, traffic spikes increased to highs of 80M to 150Mbps, depending on the day."The peaks are very short, but they would cause congestion and a backlog of traffic," he says. Those peaks required an OC-3 connection, so the company bought a DS-3. The company had thought about putting in more T-1s rather than jumping to a DS-3, but it turned out the DS-3 was less expensive than multiple extra T-1s, he says.Once the DS-3 was installed, the average traffic volume before compression was about 8Mbps. After compression, it was 4M to 5Mbps, and traffic peaked at 30Mbps. Susquehanna could have gotten by with the DS-3 and no WAN optimization, but Lefever says he knew more application traffic was inevitable, so in mid-2005 he purchased and installed the Expand devices to give room for growth."Now we are looking at four or five other major data sources looking to replicate between the data centers," Lefever says. "Without the Expand [devices] we would be looking at putting in an additional DS-3 circuit or more."At $5,500 per month, that is a pricey prospect and makes the Expand optimizers attractive. "With them we can get twice, probably three times the utility out of the DS-3, and the ROI on that is just under one year," he says.He says the company is considering another pair of Expand boxes to connect two other sites closer than the data centers are, so the links are less expensive. "It would be closer to two to three years' ROI on the one being considered," he says.The DS-3 failed once, but with the Expand boxes in place, daytime network traffic was maintained using just the five T-1 circuits that have remained in place for other uses, as well as backup when the DS-3 fails. That allowed business to go on unimpaired and even some replication traffic squeezed in, he says. "If the failure had been at night [when most of the replication is done] we would have fallen behind, but not so much that we couldn't catch up," he says.International appealAnother user of WAN-acceleration gear, Internet gaming company Electronic Arts in Redwood City, Calif., found the ROI so compelling it started a massive program to install them on all the company's international connections, says Ruben Cortez, the company's chief network architect.The company wanted to consolidate its servers at fewer sites to reduce capital and administrative costs and decided it needed better-performing WAN connections so server access didn't become so slow it got in the way of doing business, he says.Used initially on a connection between Brisbane and Sydney, Australia, the Riverbed WAN optimizers cost the company $147,000. New file servers for the consolidation project and maintenance for a year cost $44,000, he says. The performance increase the Riverbed gear brought about let the company put off buying more bandwidth for a year - a savings of $78,528, he says, and the company estimates a productivity increase of $216,000 in the first year.That gave the project an ROI of 8.3 months, Cortez says, adding that some of the ROI is real but hard to quantify. "If I had to do it again, I'd put more emphasis on the opportunity cost of people having to wait for a file to get across. We have situations where now it's not five minutes for the next window, it's 10 to 15 seconds," he says.