Distributed load sharing with virtual appliances

Cloud computing has been a revolution in the recent past. All network device manufactures are evolving their products to meet the new requirements. We can see lot many networking appliances for firewall, load balancers, IPS etc., now available to the market.

Load Distributors:

Even though VM appliances provide lot of flexibility for the network administrators in maintaining them, one setback in most of the cases is the scalability, performance and reliability. Hardware appliances gain over software appliances in this regard by considerable edge.

To increase the scalability, either we need to increase the resources of the virtual appliance or add multiple instances which can share the load.

In case of multiple instances, load sharing must be done to make use of it most. We can do it by deploying load distributor appliance. It takes care of distributing the traffic between the network appliances.


One such architecture is released by Embrane. Here is short overview of their products.
But, this Load distributor must not be bottleneck by itself in performance and scalability. One way is to add more CPUs/resources to the load distributor.

There is a good article that talks about the same problem and suggests to add more functionality like ALG like intelligence for the load distributors and make use of openflow and create flows in the L2 switches(openflow enabled switches will be widely used in future). Thus, a fast path gets created and traffic flows from L2 switches to network service appliances directly. For the new connections, the openflow switches send the traffic to Load distributor to get flow created.

There is a still challenge of single point of failure. VmWare has an option of VMotion. The load distributor VM will be transferred to other ESX server. For other virtualization solutions it will be challenging to handle it.

One would ask about the failures on L2 openflow switch. It is interesting to see what solution fits here. Traditional VRRP solutions are for L3 and above. In future, we would see backup switches too??

SoftADC as load distributor:

Coming back to the load distributors, I feel softADCs can be tuned for that role. The feature rich softADC can be stripped to play like load distributor. A simple L7 load balancer appliance can be best bet to act as openflow controller. They can provide advantages in persistence, fail over handling by VRRP etc., The time to market and ROI will be good as they can be easily tuned to act as load distributor. The vendors like Radware, Citrix etc., should think of adding open flow controller capabilities and L2 switches with openflow enabled data paths for the same.

SoftADC - Future is here! (Part -1)

In my last article, I wrote about different types of virtualization and which is best for ADC. SoftADC, is a software version of ADC product. It can be classified further into
1) Software that can be run as a virtual appliance on a generic hardware on top of hypervisor like vmware, xen or hyper-v
From Vmware's website, three vendors provide softADC.
- Zeus
- JetNexus
- Citrix Netscaler

2) Software that can be run on a environment that provides virtualization customized to run networking appliances.
- Nortel/Radware Virutal services switch

Most of ADC vendors have shown inclination towards the first type of softADC. The customized virtualization environment solution seems to have not been successful so far. The reason could be the attempt is not so well executed or due to Nortel financial crisis. I will leave that to your analysis.

But, I back the idea of the customized networking virtualization as it is designed to provide high efficiency for networking virtual appliances like firewalls, SSL acceleration, Application Delivery controllers, IPS etc.,
- Built in Hardware support for SSL acceleration
- Advantage of Resource virtualization and network virtualization
- Simplified hyervisor to suit networking appliances, so less overhead.
- Ability to run thread of virtual appliances for a given client connection ( For example: Firewall - SSL - Firewall - IPS - SSL)

SoftADC has its own advantages. The fact that is running on generic hardware and work with established cloud computing infrastructure, it is simple to configure and manage from administrator point of view. The performance it could generate suits for small to medium scale businesses. And, it is also scalable by adding more cores and gain the performance.

Some softADCs seems to have identified the bottlenecks associated when running on generic hardware. For example, Zeus has support for SSL acceleration on hardware when used.

SoftADC are here to stay especially in this era of cloud computing. The business requirements will define what type of SoftADC to deploy.