A network load balancer is one of the core components in a network edge that is connected to a private or public cloud and is responsible to distribute the Internet traffic workload among the WAN (Wide Area Network) resources. Even though at a high level network load balancers have a common strategy in accomplishing this, the devil is usually in the details to achieve an effective and successful load balancing method. In this article, we will look at the various types of network load balancers, compare and contrast them so that you can guide your buying decision when you are upgrading your network.
Why do you need a network load balancer to begin with?
This is a very fair question and may sound logical on the surface, but as anyone who worked with wide area network connectivity will quickly realize, bulletproof connectivity is a utopic goal and unless you design for it, redundancy, agility and dynamic failover will not be part of your plain vanilla WAN connectivity services. In essence what we are saying is that the single transport that your service provider hands you over is prone to errors, fluctuations, brownouts and blackouts. This is sometimes even out of the service provider control as various different aspects of the Internet creates scenarios that may be outside of the service provider control. As an example a performance degradation of a WAN link because of uplink cross traffic, or other parallel local traffic, can impact the performance of your mission critical web applications and this is not your service providers fault. And if you tried to resolve this issue by contacting your service provider, you will quickly realize that it is also not their concern, as their “tests” will quickly show that everything is working as expecting on their end.
What is the alternative to having one ISP?
Ok, so hopefully by now, you are convinced that having a single WAN connection is risky and possibly costly to your business, especially if connectivity to the cloud is an essential part of your business. To keep those essential web services humming, spreading your eggs over various service providers is a smart and proven strategy and a network load balancer can accomplish that goal. In doing so, you would want to consider a few important elements that will impact how well the network load balancer will enhance and protect your network.
Session management of your network load balancer is critical.
Web applications and services are composed of various sessions. Take a browser session to a banking site as an example. The single browser window will have numerous sessions between the browser and various end-points in the Internet. If the network load balancer is not aware of application level classification, in other words, if it cannot understand and “lump” the TCP sessions that belong to the banking site together, it may try to load balance those sessions on different WAN links and therefore present different IP addresses to the bank servers. This will break the application semantics and therefore break the browser session.
The solution to this, is what we call, “intelligent load balancing”, whereby the grouped sessions can be forced onto a single WAN link and therefore represent a single IP address to the banking servers. Another more advanced approach is to use Broadband Bonding, where the sessions are funneled through a bonded tunnel and proxy out from a single IP address and therefore still preserve the application semantics and also add bonded speed in the process. Advanced modern network load balancers will have either one of those options available, preferably both.
Passthrough / transparent install options.
It is surprising to note that there are multi-wan solutions out there that require you to rearchitect your network, or will require you to use their network services (such as firewall, UTM, IPS etc) alongside of their network load balancing solution. Fortunately, modern network load balancers support transparent passthrough installation whereby as an IT manager you have all the other vendor options available to you for various other network services. You can pick and choose from any brand of vendors so that you can build your network from the best of breed components.
Load balancing algorithms are important as well.
Be it round robin, weighted round robin or some other algorithm, the efficiency and effectiveness of the load balancing gets directly effected by the load balancing algorithm. In an ideal scenario, your network load balancer is capable of true packet level bonding, i.e. has the ability to spread the packets of the same session among various WAN links. Since this provides a finer granularity, the network load balancer will have the best chance to optimize the utilization, not to mention the increased peak rates and speed of you WAN connectivity.
Other intelligent overlays.
There are other applications that may not benefit from an increased speed, but rather “care” about other network metrics such as latency, jitter or packet loss. A good example of such applications are real-time applications such as VOIP, video, Unified Communications or chatty applications. If the network load balancer has the capability to identify and funnel those type of traffic into overlay tunnels that are designed to take of those metrics, then you will create a much better Quality of Service within your network.
QoE (Quality of Experience) is what matters.
At the end of the day, Quality of Service from the end-user’s perspective is what matters. All the effort to add a network load balancer to the edge of your network is to maximize your QoE and eliminate down-time. Modern network load balancers are equipped with application centric overlay tunnels that provides the basis for this type of a setup where packets from different applications are treated with respect to what they care about and that directly impacts the performance perceived by the end users.
So if you are serious about your WAN performance and your organization’s connectivity to the cloud, an advanced network load balancer is an integral part of your design. We outlined some of the crucial capabilities and features that you should take into consideration in that decision.
Cahit Akin, CEO, Mushroom Networks, Inc.
Mushroom Networks is the provider of Broadband Bonding appliances that put your networks on auto-pilot. Application flows are intelligently routed around network problems such as latency, jitter and packet loss. Network problems are solved even before you can notice.
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