Layer 5 is the best place to attack WAN optimization

By managing traffic sessions at Layer 5 (the session layer), application performance and WAN optimization can reach an entirely new level.

As companies become more distributed and remote workers using bandwidth-intensive applications over the WAN more numerous, the need for better WAN optimization and application acceleration techniques has become glaringly apparent. Most approaches to solving this problem focus on either Layer 3 (the network layer) or Layer 7 (the applications layer) of the Open Systems Interconnection model. However, by combining the best of both of these approaches and then managing traffic sessions at Layer 5 (the session layer), application performance and WAN optimization can reach an entirely new level.

The other side: Layer 5 is not the answer

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Technologies aiming to solve the bandwidth problem at Layer 3 accelerate all traffic over the WAN by reducing the duplication of data in the datastream as it enters the WAN. These technologies have two key shortcomings: First, they require significant processing resources and, in some cases, actually can slow down traffic. Second, Layer 3 technologies are not aware of the functions of the applications merged into the datastream, so they are unable to speed up traffic for any specific application.

Other technologies focus solely on accelerating the performance of individual applications by compressing data and streamlining protocols at Layer 7. However, because these "accelerated" applications are mixed in with uncompressed WAN traffic, it is impossible to guarantee that the compressed application consistently will perform as required. Also, application-layer technologies only increase the performance of a single application - they suffer a dramatic performance drop-off when working with two or more applications, as they tend to favor the application for which they were designed.

Combining WAN optimization and application acceleration by managing traffic at Layer 5 provides the ability to examine application datastreams before they merge, which finds and removes more redundancies than Layer 3 methods. This eliminates data transfer redundancy by grouping data by session and sending only once, which reduces the number of data roundtrips over the WAN.

By looking at all application datastreams and automatically determining which streams can benefit from compression and protocol optimization, WAN optimization technologies that operate at Layer 5 also can accelerate more traffic types than Layer 7 technologies. And by reusing the compression dictionaries, technologies that operate at Layer 5 greatly reduce the number of needed updates. This optimizes the WAN connection for ROI while guaranteeing the behavior of networked applications under a variety of WAN conditions.

The volume of enterprise WAN traffic continues to grow as applications become ever more sophisticated, and the old rules can no longer handle this new, speedier data flow. By converging application acceleration with WAN optimization and managing it at Layer 5, WAN optimization products let applications used over the WAN experience true, LAN-like performance.

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Foss is CEO of Swan Labs, an enterprise application company. He can be reached at

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Copyright © 2005 IDG Communications, Inc.

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