A network load balancer is one of the core components in a network edge. It is connected to a private or public cloud and is responsible for distributing 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 and 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 works with wide area network connectivity will quickly realize, bulletproof connectivity is a utopian goal. Careful design is required or else important network characteristics such as 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 obtained through your service provider is prone to errors, fluctuations, brownouts and blackouts. Often, these network performance issues are outside of the service provider’s 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 essential. To keep those essential web services humming, spreading your eggs over various service provider baskets 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. Application semantics are therefore preserved, and the Broadband Bonding process will also add significant speed to the session. Advanced modern network load balancers will have either one of those options available, preferably both.
Passthrough and transparent install options are not guaranteed.
It is surprising to note that there are multi-WAN solution vendors out there that require you to rearchitect your network, or 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 which requires no changes at all to your current network. This allows the IT manager to have all the other vendor options available 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 is directly affected 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 network utilization, as well as realizing increased peak rates and speed of your 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 optimize traffic flow with respect to 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 Experience 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 facilitates packet-level routing decisions based on each application’s critical metrics. This improves overall network performance and provides for an improved Quality of Experience for 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.