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The above trends made it extremely difficult to implement a successful disaster recovery plan. With a thin-client architecture, we did not have to worry about backing up remote offices. But we wanted to ensure that all data centers where protected in near real-time, with failover capabilities between them. We had some of the most sophisticated tools in the industry to achieve this objective, such as EMC's SRDF application. These tools required dedicated and cost network lines to support the replication.

Taking A Long, Hard Look at the WAN

Linklaters took a long hard look at all of our applications to determine how best to overcome our scalability and performance challenges. We acknowledged that there was a need for more bandwidth, but the upgrade process had to be better controlled.

At the same time, we recognized that more bandwidth would not solve all of our problems and is extremely costly. Network quality, not bandwidth, was the main reason why our VoIP and Citrix traffic was not living up to our expectations. We quickly came to the conclusion that we needed WAN optimization.

The IT team decided to take a comprehensive look at what we determined were the leading WAN optimization vendors at the time, which initially led us to products from Cisco, Riverbed, Silver Peak Systems, Blue Coat, and Citrix. Because we were using Packeteer for traffic shaping on our VoIP traffic, we decided to see if they too could meet our broader WAN optimization requirements (this was before Packeteer was acquired by Blue Coat.)

We were quickly able to pare down this list when we could not get Cisco and Citrix to work in our evaluation scenario. Bluecoat and Packeteer were also eliminated since both lacked performing disk-based deduplication for Citrix, which we thought was critical given the repetitive nature of our WAN traffic. Our employees send thousands of versions of the same documents back and forth, much of which is identical. We therefore quickly established that deduplication would have a significant reduction in our WAN bandwidth.

That left Riverbed and Silver Peak Systems, which we moved into live production tests over a several week period. We evaluated these products on a primary WAN connection between our Hong Kong and UK data centers. Then, they went to a live test in our Bangkok office, which has more than 30 attorneys.

While both Riverbed and Silver Peak Systems performed well on a variety of different applications, the real difference came down to the Citrix application. Silver Peak optimizes this traffic while Riverbed did not. Silver Peak has an enormous impact on Citrix's reliability across the WAN; in addition, once we turned off compression and encryption on our Citrix servers, Silver Peak was able to dedupe our Citrix traffic. Its performance with Citrix was a pleasant surprise to us as other WAN optimization vendors told us they could not dedupe Citrix traffic due to its low latency requirements. With Silver Peak, we are seeing 7GB Citrix sessions reduced to 3GB on the WAN, which is an average reduction of 56 percent.