Exinda

WAN Optimisation Techniques

WAN optimization solutions are used to improve the performance of applications ("accelerate") by employing a variety of technologies on network data flows: eliminating duplicate data transmissions, storing data in localized caches, compressing the data, prioritizing data, and streamlining chatty protocols (i.e. CIFS).

In the table below I've listed some of these technologies, the benefit they provide, and how they work.

Technology	Benefit	How it Works
Windows Scaling	Link bandwidth is fully utilized.	TCP connection window is adjusted to suit the Bandwidth Delay Product of the link.
Selective ACK	Better handling of packet loss & retransmissions. Deals with loss on the LAN.	Notifies the host of what packets have been received subsequent to packet loss. Avoids retransmission of successfully received data.
Packet Aggregation	Better performance by reducing acks from lots of small packets.	Small packets are aggregated into large packets before being sent on the WAN. This is especially important when data is compressed and de-duplicated.
Congestion Control	More suitable congestion control for a variety of environments	Ability to select a congestion control that best suits a customer environment. i.e. High speed low latency etc.
Fast Start	Connection throughput increases very early into the connection	High Speed TCP congestion control
Delayed ACK	Speed up packet transmission by acknowledging multiple packets at a time	Reduce roundtrips by Ack’ing multiple packets at a time
Data De-Duplication	Reduces the amount of data sent across the network virtually expanding the WAN. Serves data to users at LAN speeds from disk cache.	Repetitive data patterns are recognized and stored in a cache. When these patterns are seen on the network they are replaced with a “symbol” and reconstructed on the other side of the WAN.
Compression LZO	Reduces the amount of data sent across the network virtually expanding the WAN	All non repetitive data patterns are compressed, this interacts with WAN memory and creates even greater reduction and speed benefits.
Bi-Directional Data Store Cache	Data stored in the cache is immediately available for matching in both directions. Opening and saving files is faster	Data is stored one and is available for matching and reducing repetitive data in both directions.
Persistent Data Store Cache	Cache data is available after power outage or reboot	Data is stored on disk along with the index.
Universal Data Store Cache	No multiple copies of the same data, better scaling of disk storage	Data is stored once in the cache and available to all peers. No cache segmentation is needed

WAN Optimization technologies are quickly becoming a required component for an organization to successfully deliver applications over a wide area network.