Clever Gizmos at the edge of the network

The world of professional network managers is filled with minutia and arcana.  There are hundreds of acronyms to keep track of, a constant onslaught of protocols and technologies, performance bottlenecks and security threats, software patches and, generally, many more problems than solutions.  Think Dante's fifth level of Hell, the one where you are forced to have lunch with Cisco1 salesmen every day.  Forever.

The rare occasion when a straightforward answer to a pressing need presents itself can feel like heavenly grace bathing you in a warm radiant light.  I'm not trying to invoke divine intervention on behalf of edge appliance, but these unassuming little workhorses increasingly present themselves as quick and cool solutions in a chaotic world.  

In the article below, I'm going to tell you how edge appliances solve a few of the problems that some harried network manager is worrying about in your behalf right at this very moment.

So what the are they?

Edge appliances are dedicated networking devices that combine hardware and software to elegantly solve a specific problem, or perform a single task very efficiently.  Typically they take the physical form of a 1U Intel-based server that resides on the "edge" of a network and provides a shared function or resource . They are designed to be rack mounted, right alongside the web servers and routers they work with.  To keep costs down, many edge servers run a version Linux or Unix that has been stripped of all functions except those that will be used for the task at hand.  

Even though they all look pretty similar, these skinny metal boxes handle jobs that are all over the map, and new ones seem to appear everyday.  The appeal of these devices2 is that they focus on a single job and do it really well.  The downside is that you can easily end up with a bunch of them, and each one has its own idiosyncrasies that you have to know in order to set them up and maintain them.  

Here are a few examples of network edge appliances:

Traffic Managers

Packets are the lingua franca of the Internet and edge appliances that inspect these electronic envelopes and move them along to their proper destinations are a mainstay of the industry.  In some sense, traffic managers invented the category of edge devices as Cisco and other networking companies introduced a flood of customized routers and switches as the Internet began to grow exponentially in the early 1990's.  More recently packet inspection and packet shaper devices with cute names like the Packeteer, allow network managers to test and troubleshoot networks by simulating real world traffic. 

Storage Devices

It may not be apparent to "civilians," but any computer professional will tell you that we are currently experiencing a tidal wave of data.  The Internet has presented us with an unprecedented ability to gather usage, demographic and sales information and most businesses are determined to gather all that they can, even if they don't know what they're going to do with it.  This presents the network manager with a never-ending quest for devices on which to capture that flood, and manage it once you've got it.  Network Attached Storage (NAS) devices are compact servers dedicated to providing loads of easily managed disk space at a low price.  On another front, devices like the HP SureStore AutoBackup Appliance contain tape drives and other archival storage devices that assist in the process of moving older data into long term storage.

Security Appliance

Keeping the bad guys out of the network probably keeps more network managers awake at night than any other topics.  Edge appliances such as firewalls, intrusion detection and prevention appliances use a variety of approaches to securing the network.  Extreme performance is required here because whether your firewall is directing packets from a hacker into the bit bucket, or the intrusion-detection appliance is checking for suspicious activity, they have to be capable of handling all the network traffic between your network and the rest of the Internet.

Performance Enhancers

When you hit the "Buy It" button on your favorite e-commerce website, you should see the little padlock icon (or whatever) on your browser appear to assure you that your purchase information is being encrypted over a secure connection.  This moment of warm and fuzzy consumer security is brought to you at a price.  The server overhead involved in processing an encrypted SSL session can be as much as 10 times normal.  If you multiply this times the thousands of encrypted sessions currently running on a large commercial website, you can understand the market for SSL accelerators.

Along these same lines are XML accelerators that are beginning to appear on the market. These devices are designed to manage the growing volume of XML data generated as web services increase in popularity.

Load Balancers

Designing an e-commerce website that can scale from a modest introduction to the almost unimaginable volume of traffic experienced by an international Internet presence like is one of the most challenging tasks a networking professional can encounter.  Load balancers help to solve one of those problems by carefully monitoring the status of the individual servers and routing inbound traffic to the server most able to handle it.

Content Caches

Internet businesses with a worldwide presence must address the problem of delivering their content to customers who may be a very long way away.  One way to handle this problem is to distribute copies of the content to servers that are physically located around the globe and then directing incoming customer requests to the closest server.  Content cache devices like the NetCache, from Network Appliance Company3, manage this process by detecting changes in content and automating its distribution.


1 Cisco, the mother of all appliance vendors:
2 InfoWorld magazine just did a nice eval of edge appliances:
3 Network Appliance website: