Editor's note: In part two of our three-part series on buying WAN optimization appliances, we look at a variety of WAN optimization techniques you should consider to improve WAN link performance before you buy. Part one of the series looked at some of the leading appliance vendors that you may want to consider, and part three addresses how different vendors combine WAN optimization techniques to help you assess which products will meet the needs of your organization.
A number of techniques are used to optimize wide area network (WAN) performance, and the greater the number of techniques used, the more WAN link performance can be improved. To get what they need, buyers should be looking at products that employ multiple WAN optimization techniques to gain different advantages. Check out the options below.
Data deduplication is a compression technique that eliminates the need to transmit redundant data to users across the WAN by analyzing data patterns and storing unique data. Data that matches it is replaced with an index reference that points to the stored data. By working at the byte level, benefits are achieved across IP applications. Where users regularly access the same data over and over, deduplication is an effective technique that reduces the amount of data that needs to be stored or transmitted.
Compression reduces the size of data files by encoding and transmitting the data using fewer bits, without losing information. Compression techniques are similar to those used by file compression programs and can be applied to data passing through hardware- or software-based WAN acceleration appliances. Compression techniques work across all applications and traffic but generally provide only incremental improvements.
Optimizing network latency can include TCP refinements including window-size scaling, selective acknowledgements, Layer 3 congestion control algorithms, and even colocation strategies in which the application is placed in close proximity to the endpoint. In some implementations, the WAN optimizer will answer the requests locally instead of forwarding the request to the remote server to leverage write-behind and read-ahead mechanisms. This technique works only if some applications or data are stored locally to regular users.
Caching involves staging data in local memory caches to speed data transfer over the WAN. Caching relies on the concept of data proximity, in that applications tend to access the same data over and over. Caching is extremely effective for locations that continually access the same database or application.
Error correction mitigates packet loss by adding an additional loss-recovery packet for a set number of packets sent. This can reduce the need for retransmissions on congested WAN links. This approach is effective primarily on high-traffic WANs.
Equalizing makes intelligent assumptions about which traffic needs immediate priority based on data usage. It essentially makes decisions based on usage patterns. As a result, some users may get significantly slower response times.
Connection limits set the amount of time allowed for a transaction on the WAN to prevent access gridlock and denial of service. On congested networks, however, this could effectively cut off certain classes of users from ready access to bandwidth.
Traffic shaping controls data flow for specific applications or transport protocols. This gives network professionals the flexibility to decide which applications take precedence over the WAN. A common use case of traffic shaping would be to prevent one protocol or application from hogging a link over other protocols deemed more important by network IT. Some WAN acceleration devices can traffic shape with a high level of granularity.
Next: In part three, find out how to figure out which vendor's WAN optimization appliance you should buy
Get the guide: Improve service delivery with WAN application optimization
Read the primer: WAN bandwidth tools and techniques
Video: Industry trends drive WAN optimization performance demands
And more video: Optimize your WAN for changing end-user needs
Testing WAN optimization tools before buying – an essential step
As WAN technologies evolve, classic optimization takes back seat