F5 Networks Big-IP 6400

There may a wide choice of vendors in the load balancing, or application delivery, market but F5 Networks has been a clear leader for some time now. And it's easy to see why as its Big-IP boxes offer more features that you can shake a stick at.

On review we have the Big-IP 6400 LTM (Local Traffic Manager), which is delivered as a 2U rack appliance solution capable of handling a 2Gbps traffic throughput. The pair of single-core Opteron processors and DDR memory are looking dated considering the starting price but the rest of the hardware package does include dual SSL accelerator cards.

F5 uses a multi-layered approach to traffic management as the appliance runs its proprietary TMOS kernel, which is essentially a TCP proxy and traffic inspection engine. One of the system processors is dedicated to TMOS, while the second looks after a separate Linux kernel, which provides all the management, monitoring and reporting functions. All traffic passing through the appliance is handled by F5's TMOS and, where appropriate, it will decide to use its own hardware to switch traffic but in the case of SSL traffic, for example, it will hand this over to the accelerator cards.

The appliance protects against threats such as DDoS attacks and offers tools for implementing application security. Resource cloaking stops information being leaked out that hackers may be able to use to gain information about a network, encryption can be applied selectively to protect content and the appliance can act as an authentication proxy. Other features include TCP Express - a proprietary network stack written by F5 to broker connections between hosts and applications.

We found installation in the lab a pleasantly simple affair and aided admirably by the appliance's well-designed web interface. All licensed options are displayed in a tree to the left and each one expands to show their related features. You can start by sorting out administrative access as the appliance has a dedicated port for this and then you can move onto configuring the main Gigabit network ports where you create VLANs and assign port memberships.

The Big-IP uses the common concept of grouping multiple physical servers together and presenting them as a single virtual server, where it performs load balancing across them. The process of setting these up is very simple as you create pools and add your physical servers to them as members. Next, you choose the load-balancing scheme and F5 offers no less than fifteen different methods.

Naturally, you get the standard round robin mode, which intercepts incoming requests and distributes them to each server in strict rotation. At the other end you have options including F5's unique predictive balancing, which analyses traffic to individual pool members over time and predicts future patterns to avoid any one member server becoming overloaded.

Weightings, or ratios, can be applied to pool members that will also affect load balancing. The higher a server's ratio is the more likely traffic is to be sent to it. Dynamic ratios look interesting as these are based on SNMP queries, which poll the servers, look at system utilisation and automatically reduce traffic sent to overloaded servers.

F5 goes one step beyond with its priority groups as these can be used to add extra levels of redundancy to virtual servers. If, for example, you have ten member servers, you can give five a higher group priority, which means only they will have traffic directed at them. If one fails then a server from the lower priority group will be brought in to replace it.