By Art Reisman
Editor’s note: Art Reisman is the CTO of APconnections. APconnections designs and manufactures the popular NetEqualizer bandwidth shaper.
Although there is no way to actually make your true WAN speed faster, here are some tips for corporate IT professionals that can make better use of the bandwidth you already have, thus providing the illusion of a faster pipe.
1) Caching — How does it work and is it a good idea?
Caching servers have built-in intelligence to store the most recently and most frequently requested information, thus preventing future requests from traversing a WAN/Internet link unnecessarily.
Caching servers keep a time stamp of their last update to data. If the page time stamp has not changed since the last time a user has accessed the page, the caching server will present a local stored copy of the Web page, saving the time it would take to load the page from across the Internet.
Caching on your WAN link in some instances can reduce traffic by 50 percent or more. For example, if your employees are making a run on the latest PDF explaining their benefits, without caching each access would traverse the WAN link to a central server duplicating the data across the link many times over. With caching, they will receive a local copy from the caching server.
What is the downside of caching?
There are two main issues that can arise with caching:
a) Keeping the cache current –If you access a cache page that is not current you are at risk of getting old and incorrect information. Some things you may never want to be cached. For example, the results of a transactional database query. It’s not that these problems are insurmountable, but there is always the risk the data in cache will not be synchronized with changes. I personally have been misled by old data from my cache on several occasions.
b) Volume – There are some 300 million websites on the Internet. Each site contains upwards of several megabytes of public information. The amount of data is staggering and even the smartest caching scheme cannot account for the variation in usage patterns among users and the likelihood they will hit an uncached page.
We recommend Squid as a proxy solution.
2) Protocol Spoofing
Historically, there have been client server applications developed for an internal LAN. Many of these applications are considered chatty. For example, to complete a transaction between a client and server, tens of messages may be transmitted when perhaps one or two would suffice. Everything was fine until companies, for logistical and other reasons, extended their LANs across the globe using WAN links to tie different locations together.
To get a better visual on what goes on in a chatty application perhaps an analogy will help. It’s like sending family members your summer vacation pictures, and, for some insane reason, putting each picture in a separate envelope and mailing them individually on the same mail run. Obviously, this would be extremely inefficient, just as chatty applications can be.
What protocol spoofing accomplishes is to “fake out” the client or server side of the transaction and then send a more compact version of the transaction over the Internet (i.e., put all the pictures in one envelope and send it on your behalf, thus saving you postage).
For more information, visit the Protocol Spoofing page at WANOptimization.org.
At first glance, the term compression seems intuitively obvious. Most people have at one time or another extracted a compressed Windows ZIP file. If you examine the file sizes pre- and post-extraction, it reveals there is more data on the hard drive after the extraction. Well, WAN compression products use some of the same principles, only they compress the data on the WAN link and decompress it automatically once delivered, thus saving space on the link, making the network more efficient. Even though you likely understand compression on a Windows file conceptually, it would be wise to understand what is really going on under the hood during compression before making an investment to reduce network costs. Here are two questions to consider.
a) How Does it Work? — A good and easy way to visualize data compression is comparing it to the use of short hand when taking dictation. By using a single symbol for common words a scribe can take written dictation much faster than if he were to spell out each word. The basic principle behind compression techniques is to use shortcuts to represent common data.
Commercial compression algorithms, although similar in principle, can vary widely in practice. Each company offering a solution typically has its own trade secrets that they closely guard for a competitive advantage. However, there are a few general rules common to all strategies. One technique is to encode a repeated character within a data file. For a simple example, let’s suppose we were compressing this very document and as a format separator we had a row with a solid dash.
The data for this solid dash line is comprised of approximately 160 times the ASCII character “-�. When transporting the document across a WAN link without compression, this line of document would require 80 bytes of data, but with clever compression, we can encode this using a special notation “-� X 160.
The compression device at the front end would read the 160 character line and realize,”Duh, this is stupid. Why send the same character 160 times in a row?” So, it would incorporate a special code to depict the data more efficiently.
Perhaps that was obvious, but it is important know a little bit about compression techniques to understand the limits of their effectiveness. There are many types of data that cannot be efficiently compressed.
For example, many image and voice recordings are already optimized and there is very little improvement in data size that can be accomplished with compression techniques. The companies that sell compression based solutions should be able to provide you with profiles on what to expect based on the type of data sent on your WAN link.
b) What are the downsides? — Compression always requires equipment at both ends of the link and results can be sporadic depending on the traffic type.
4) Requesting Text Only from Browsers on Remote Links
Editors note: Although this may seem a bit archaic and backwoods, it can be effective in a pinch to keep a remote office up and running.
If you are stuck with a dial-up or slower WAN connection, have your users set their browsers to text-only mode. However, while this will speed up general browsing and e-mail, it will do nothing to speed up more bandwidth intensive activities like video conferencing. The reason why text only can be effective is that most Web pages are loaded with graphics which take up the bulk of the load time. If you’re desperate, switching to text-only will eliminate the graphics and save you quite a bit of time.
5) Application Shaping on Your WAN Link
Editor’s Note: Application shaping is appropriate for corporate IT administrators and is generally not a practical solution for a home user. Makers of application shapers include Packeteer and Allot and are typically out of the price range for many smaller networks and home users.
One of the most popular and intuitive forms of optimizing bandwidth is a method called “application shaping,” with aliases of “traffic shaping,” “bandwidth control,” and perhaps a few others thrown in for good measure. For the IT manager that is held accountable for everything that can and will go wrong on a network, or the CIO that needs to manage network usage policies, this is a dream come true. If you can divvy up portions of your WAN/Internet link to various applications, then you can take control of your network and ensure that important traffic has sufficient bandwidth.
At the center of application shaping is the ability to identify traffic by type. For example, identifying between Citrix traffic, streaming audio, Kazaa peer-to-peer, or something else. However, this approach is not without its drawbacks.
Here are a few common questions potential users of application shaping generally ask.
a) Can you control applications with just a firewall or do you need a special product? — Many applications are expected to use Internet ports when communicating across the Web. An Internet port is part of an Internet address, and many firewall products can easily identify ports and block or limit them. For example, the “FTP” application commonly used for downloading files uses the well known “port 21.”
The fallacy with this scheme, as many operators soon find out, is that there are many applications that do not consistently use a fixed port for communication. Many application writers have no desire to be easily classified. In fact, they don’t want IT personnel to block them at all, so they deliberately design applications to not conform to any formal port assignment scheme. For this reason, any product that aims to block or alter application flows by port should be avoided if your primary mission is to control applications by type.
b) So, if standard firewalls are inadequate at blocking applications by port, what can help?
As you are likely aware, all traffic on the Internet travels around in what is called an IP packet. An IP packet can very simply be thought of as a string of characters moving from Computer A to Computer B. The string of characters is called the “payload,” much like the freight inside a railroad car. On the outside of this payload, or data, is the address where it is being sent. These two elements, the address and the payload, comprise the complete IP packet.
In the case of different applications on the Internet, we would expect to see different kinds of payloads. For example, let’s take the example of a skyscraper being transported from New York to Los Angeles. How could this be done using a freight train? Common sense suggests that one would disassemble the office tower, stuff it into as many freight cars as it takes to transport it, and then when the train arrived in Los Angeles hopefully the workers on the other end would have the instructions on how to reassemble the tower.
Well, this analogy works with almost anything that is sent across the Internet, only the payload is some form of data, not a physical hunk of bricks, metal and wires. If we were sending a Word document as an e-mail attachment, guess what, the contents of the document would be disassembled into a bunch of IP packets and sent to the receiving e-mail client where it would be re-assembled. If I looked at the payload of each Internet packet in transit, I could actually see snippets of the document in each packet and could quite easily read the words as they went by.
At the heart of all current application shaping products is special software that examines the content of Internet packets, and through various pattern matching techniques, determines what type of application a particular flow is. Once a flow is determined, then the application shaping tool can enforce the operators policies on that flow. Some examples of policy are:
The list of rules you can apply to traffic types and flow is unlimited. However, there is a downside to application shaping of which you should be aware. Here are a few:
- The number of applications on the Internet is a moving target. The best application shaping tools do a very good job of identifying several thousand of them, and yet there will always be some traffic that is unknown (estimated at 10 percent by experts from the leading manufacturers). The unknown traffic is lumped into the unknown classification and an operator must make a blanket decision on how to shape this class. Is it important? Is it not? Suppose the important traffic was streaming audio for a Web cast and is not classified. Well, you get the picture. Although theory behind application shaping by type is a noble one, the cost for a company to stay up to date is large and there are cracks.
- Even if the application spectrum could be completely classified, the spectrum of applications constantly changes. You must keep licenses current to ensure you have the latest in detection capabilities. And even then it can be quite a task to constantly analyze and change the mix of policies on your network. As bandwidth costs lessen, how much human time should be spent divvying up and creating ever more complex policies to optimize your WAN traffic?
6) Test Your WAN-Link Speed
A common issues with slow WAN link service is that your provider is not giving you what they have advertised.
For more information, see The Real Meaning of Comcast Generosity.
7) Make Sure There Is No Interference on Your Wireless Point-to-Point WAN Link
If the signal between locations served by a point to point link are weak, the wireless equipment will automatically downgrade its service to a slower speed. We have seen this many times where a customer believes they have perhaps a 40-megabit backhaul link and perhaps are only realizing five megabits.
8) Deploy a Fairness Device to Smooth Out Those Rough Patches During Contentious Busy Hours
Yes, this is the NetEqualizer News Blog, but with all bias aside, these things work great. If you are in an office sharing an Internet feed with various users, the NetEqualizer will keep aggressive bandwidth users from crowding others out. No, it cannot create additional bandwidth on your pipe, but it will eliminate the gridlock caused by your colleague in the next cubicle downloading a Microsoft service pack.
Yes, there are other devices on the market (like your fancy router), but the NetEqualizer was specifically designed for that mission.
9) Bonus Tip: Kill All of Those Security Devices and See What Happens
With recent out break of the H1N1 virus, it reminded me of how sometimes the symptoms and carnage from a vaccine are worse than the disease it claims to cure. Well, the same holds true for your security protection hardware on your network. From proxies to firewalls, underpowered equipment can be the biggest choke point on your network.
Created by APconnections, the NetEqualizer is a plug-and-play bandwidth control and WAN/Internet optimization appliance that is flexible and scalable. When the network is congested, NetEqualizer’s unique “behavior shaping” technology dynamically and automatically gives priority to latency sensitive applications, such as VoIP and email.
Links to other bandwidth control products on the market.
Packet Shaper by Blue Coat
Exinda Packet Shaper and Riverbed tend to focus on the enterprise WAN optimization market.
Cymphonix comes from a background of detailed reporting.
Very solid product for bandwidth shaping.
Exinda from Australia has really made a good run in the US market offering a good alternative to the incumbants.
For those of you who are wed to Windows NetLimiter is your answer