WAN Acceleration devices have grown in popularity in the last 10 years firstly driven by the opportunity to reduce WAN costs and more lately due to latency and sluggish response timing issues. There are basically three different technologies used by almost all the players in the market place:-
• Reduction in the amount of traffic passed across the links
• Prioritisation in the traffic types to ensure certain applications always have the bandwidth
they need
• Application “acceleration”
In this report we will expand on each of these technologies and summarize the key manufacturers in the market place.
Reduction in Traffic
This part of the solution is the one which generally is successful, however different manufacturers have different ways of achieving it. Some use techniques similar to compression on modems, whilst others quote removing common bit patterns and looking across multiple packets to remove recurring data streams.
All these techniques can work very well and hence all the manufacturers can quote figures of up to 10:1 data reduction, but typically in a friendly environment figures of about 4:1 are realistic. These numbers are generally achieved when you have remote terminal session applications with common screen formats for customer records.
There are quite a few catches here though which can reduce these improvements down to about zero:-
• Encryption techniques
• Pre-compressed data
• Images
In Summary, when these solutions work they can be very effective, but in quite a few situations bandwidth was never the issue in the first place so the user sees no difference. WAN service providers are not keen to see them on site so discounts become common to try and get them out.
Prioritisation or Shaping Techniques
This technology is aimed at changing the order of the data, not the volume, that is transmitted. The idea here is that traffic is prioritised into Groups or Classes and then it can be specified how much bandwidth each application has as a minimum if the link gets over-subscribed.
The other side of the story is that low priority applications can and will get zero bandwidth in a period of busy traffic and that the application profile needs to be realistic in how it specifies high medium and low priorities. The various manufacturers have different ways of labelling these techniques with numbers often quoted in the 1000’s for the number of Classes you can configure, but typically around 25 options are all you need.
One advantage of this technique it that it can be done one ended, with a shaping device in the core site but no need for reciprocal devices at the remote sites.
Application Acceleration
The emerging issue in application performance is caused by latency, rather than just bandwidth. This is due to the fact that certain protocols do not wait long enough for the packets to travel across WAN links (they were never designed to do so). This causes the application to send them again leading to a downward spiral of performance issues.
There are a few techniques employed by manufacturers to try and get around this and solutions vary here:-
• Spoofing slow protocols – The most common protocol discussed here is CIFS (part of Windows File Sharing) and the solution tends to be not to send the CIFS packets across the WAN link but use the local devices to send the expected replies.
• TCP manipulation – TCP protocols transmit data in blocks (known as Windows) which is a direct factor in the latency they can cope with. Some of the solutions try and increase the Window size and send data in larger blocks and this helps overcome the latency issues.
There are no standards for these technologies so each manufacturer has to work out the hand shaking procedures for the applications they wish to intercept and program their units to respond. This means that there is little consistency in the performance between manufacturers and the applications they claim to support.
Key Manufacturers in the Market Place
Riverbed
This was the first company to target the growing trend in removing remote servers in offices and sending them back to the data centres. Their technology is specifically aimed at allowing remote users to work on distant file servers.
Juniper (who acquired Peribit)
This company originally had some very unique techniques for removing duplicate data across multiple packets and have since looked to implement acceleration techniques.
BlueCoat (who acquired Packeeter)
They purchased the Packeteer brand over a year ago which was the market leader in packet shaping and managing the order that your data gets handled. They have been looking to catch up in the other areas and the market is expecting the product to be integrated into the security range that Blue Coat are best known for.
Cisco WASS
This is Cisco’s move into the market place and has gained traction in the lager accounts. The range of techniques they claim is large but the units do need very specific installation to get the most out of them.
SilverPeak
One of the newer players in the market place, but appear to have all the above techniques in place and are well priced.
Summary
There are quite a few options in this market place and experience has shown that since most of the ways of achieving the techniques described above are proprietary, the performance of these solutions can vary quite markedly depending of the traffic types in use. Therefore the usual recommendation is to try a few and measure carefully what improvements are seen.