Load Balancer Buying Guide 2013

Load Balancer Buying Guide 2013


By Jay Dobbs (updated 10/2013)

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High availability, acceleration, flexibility, and capacity sum up the four key qualities of server load balancers today. Some refer to this as the layer 4-7 networking space while Gartner uses the term ADC (Application Delivery Controllers) to describe these devices.

While high availability and application scalability was the original goal of server Load balancing devices, it has become a commoditized feature. It is a given today that any decent load balancing device can check the health of servers and applications via pings, TCP port checks, and HTTP GETs. Extra credit is earned by load balancing devices that can also execute custom health checks the load balancer administrator creates. This too gives application developers, who tend to know their own applications the best, the ability to automate accurate, timely, health checks.

Once users can get to content reliably, they then demanded getting it faster. Many load balancing vendors are able to deliver this through the use of a handful of technologies. Caching and compression can speedup delivery of some types of HTTP content. TCP multiplexing and optimization lets servers operate more efficiently at layer 4. If a good portion of your traffic is HTTPS, then offloading SSL processing from the servers' general purpose CPU to the load balancing device's dedicated SSL ASIC can dramatically increase server efficiency. This frequently results in faster connections.

Load balancing flexibility is judged by the device's capacity to manipulate traffic passing through it at layers 3-7. As load balancing devices gain in sophistication, their ability at traffic manipulation is increasing by leaps and bounds. You don't want hackers to know what O/S your web servers are running? No problem, the load balancing device can erase select server response headers. Are search engine crawlers slowing down your site? Modern load balancing device can identify them and load balance crawlers to a dedicated server. Your banking site just decided to go 100% SSL encrypted? Not to worry, the LB device can easily rewrite all HTTP requests to HTTPS requests. The devices with the best flexibility tend to utilize user customizable scripts. These scripts are fairly easy to understand and open up the world of possibilities for the application owner and network administrator.

With the top Load Balancers in the market having very similar features, the tie breaker often comes down to price/performance. The ever increasing capacity of these devices is amazing. Back in the mid 90s, when server load balancers were just hitting the market, passing 100Mbps was a big deal. The enterprise class load balancers today can push close to line speed through their 10 Gigabit interface. 10Gigabit is the new 1Gigabit. Devices with plain 1Gigabit interfaces are still going strong, but a host of new applications on the internet is eager to push the envelope. The proliferation of video, P2P protocols, IPTV, voice over IP calls, photo/file sharing sites, broadband to the home and cell phone are all driving the demand for higher capacity load balancers in the data center. This is all good news for the IT shopper. As capacity increases, the cost per connection has been steadily dropping.

The icing on the cake may be the ease of management. The most competent Load Balancers have a straight forward CLI and a user friendly GUI. Once again, the top players all pass with flying colors. Personal preference plays a large role in this area, so make sure to evaluate the management interface thoroughly. Just because the network administrator uses the CLI today, six months from now it may be the application owner (who prefers the GUI) is in charge of the load balancing device. So test both interfaces during your evaluation period.

Security is another area load balancers are increasingly addressing today. Providing DDoS protection, limiting connections by abusive IPs, and throttling connections to servers are just some of the ways they help secure the overall network.


Know your traffic. Having a good idea of your current network traffic level will help you size the right model to fit your needs. If you don't have this information handy, check with the person in charge of paying your monthly bandwidth bill. Also consider your traffic growth pattern and buy a device that will not only meet your needs today, but for 12 to 24 months in to the future.

Try it out first. Even though the top brands all have similar features, they tend to do things slightly differently. Also this is a chance to see which management interface you and your staff prefer. Any decent load balancing vendor should be able to provide you with an evaluation unit quickly. This gives you a glimpse in to their future responsiveness.

Which features will you use? Deciding which features are important to your company will significantly cut down on your task of evaluating the product. Load Balancers today have a cornucopia of features. Don't fall in to the trap of kicking the tires on all the bells and whistles! Decide which features are must haves, which ones are nice to haves, and which ones you'll most likely never use. Prioritize your time accordingly. Otherwise, it can take six months or more to test a load balancing device. With proper prioritization, it shouldn't take more than two weeks to evaluate a load balancing device.

Cost. Cost. Cost. As we mentioned earlier, price per connection or price per megabit has been steadily decreasing. However, some vendors are willing to give you more connections per dollar. Make sure you compare apples to apples when making your buying decision. The industry standard metrics are:

-New layer 4 connections per second (the device can process)

-New layer 7 connections per second (the device can process)

-Layer 7 transactions or requests per second (applicable to HTTP traffic only)

-Maximum throughput (the device can handle)

-SSL Transactions Per Second (or TPS)

Be careful not to confuse layer 7 connections per second (or CPS) with transactions per second (or TPS). Specifically to HTTP, it is possible to pass multiple HTTP TPS or requests (RPS) over a single TCP connection. Some vendors use the term TPS and others use RPS to describe HTTP traffic. The most honest vendors are more inclined to disclose all five of the above metrics openly on their website. These devices aren't cheap, so in order to know what you're getting, insist on the above standard metrics.


The field of enterprise load balancing continues to evolve in 2013. Cisco announced their exit from the ADC space with a well-defined end of support schedule for their ACE platform. The Foundry acquisition by Brocade has been a huge win for the rest of the ADC vendors as their market share continue to plummet. Riverbed's acquisition of Zeus (now Stingray) seems to have made small gains outside of their core customer base. On the other hand, these are exciting times for both A10 and F5 Networks. They're locked in a hardware arms race with both companies releasing fresh new hardware platforms over the summer. Seattle based F5 Networks is one of the early players in this space. But with a lengthy 4-6 year hardware refresh cycle, it opened the door for A10, the smaller faster moving challenger, an opportunity to go after F5's install base. With a slew of new platforms like the LTM 4000, 5000, and 7000 series, F5 is hoping to prove their hardware chops to their sizable customer base. Silicon Valley based A10 Networks has never been known to resting on their laurels. With an aggressive 1-2 year hardware refresh cycle, they answered F5's new offerings by introducing a whole new Thunder series in late summer. With an all-you-can eat no licensing model, A10 is working harder than ever to increase their market share in preparation for an eventual IPO. To round out the top 3 ADC vendors, we talked to a number of brick and mortar resellers about the state of Citrix/Netscaler. It seems there aren't aggressive efforts to win ADC market share on pure load balancing projects. The focus seems to be bundling Netscalers with other Citrix product deployments.

Whichever vendor you choose to go with, make sure you do your homework. A good place to start is the vendor's website.


Happy Load Balancing!

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