New networking paradigm

Lately Open Flow and SDN have generated lot of buzz. Many startups are already touting to have open flow switches and SDN applications that can simplify and change the data center networking landscape. But apart from commoditizing switching hardware and speed of innovation in the networking space, not that they are not enough, what else Open Flow and SDC promise to solve? So let’s look at the current DC problems first.

So what are the problems….

Well, the problem is traditional Data Center design doesn’t scale when companies like Google, Facebook, and Amazon  are designing MSDC( Massively Scalable Data Center) with an objective of putting any workload at any place. Workloads can move, thanks to server virtualization, but traditional network is the bottleneck.

So what are the problems with traditional networking…

Let’s start with listing out the problems

1. Static networking prevents workload mobility

2. Server to Server traffic causes computational bottleneck

3. Scale up model doesn’t serve today’s workload elasticity


Let me explain one by one what I mean.

1. Static networking: If we look at the traditional deployment model, the common practice is to map a VLAN to an application. This rigid vlan mapping model breaks workload mobility. In addition, vlan spanning concentrates traffic at aggregation layer where router links are overbooked. Not to mention VLAN provisioning takes weeks,

2. Server to Server traffic: With new type of applications, there is an explosion of server to server traffic.  According to some study(don’t remember the name), north-south bound and east-west bound traffic consist of 25% and 75% of the total data center traffic respectively. In traditional networking model, different server-farms are placed in different L2 domain and communication among them go through a L3 aggregation switch,which is grossly over-subscribed, at times it can be as high as 1:250 at the top of the hierarchy. Here network becomes the bottleneck for computation.

3. Scale up model: Traditional networking model is based on the scale up model.More performance can be added through an under subscribed hardware,and once the maximum hardware capacity is reached, a new  hardware is required to replace the old hardware. In contrast, with Scale Out model additional performance demand can be met by adding one more unit. Many virtual appliances are now built with scale out model rather scale up model, providing efficient resource utilization and elasticity needed in today’s data centers.

Open Flow and SDN promise to solve the above problems by having a global view of the network. I will explore Open Flow and SDN more in my next blog.


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