How does Openflow, SDN help Virtualization/Cloud (Part 3 of 3) – Why Nicira had to do a deal?
The challenges faced by Openflow and SDN
This is the 3rd and final article in this series. As promised, lets look at some of the challenges facing this space and how we are addressing those challenges.
Challenge 1 – Which is why Nicira had to get a big partner
I have seen a lot of article about Nicira being acquired. The question no one has asked is – if the space is so hot, why did Nicira sell so early? The deal size (1.26B) was hardly chump change but if I were them and my stock was rising exponentially, then I would have held off in lure of changing the world. So what was the rush? I believe the answer lies in some of the issues I discussed in article 2 of this series a few months back–the difference between server (Controller-based) and switch (Fabric-based) approaches. The Nicira solution was very dependent on the server and the server hypervisor. The world of server operating systems and hypervisor is so fragmented that staying independent would have been a very uphill battle. Tying up with one of the biggest hypervisors made sense to ensure that their technology keeps moving forward. And Vmware is good company driven by solid technology. So, perhaps, the only question is how long before the Vmware/EMC and Cisco relationship comes unhinged?
Challenge 2 – The divide between Control place and Data Plane
The current promise of having a standard way of controlling networking and a controller that is platform independent is huge. It provides simplified network management and rapid scale for virtual networks. Yet the current implementations have become problematic.
Since the switches are dumb and do not have global view, the current controllers have turned into a policy enforcement engine as well i.e. new flow setup requires a controller to agree which means every flow needs to go through the controller which instantiates them on the switch. This raises several issues:
- A controller which is essentially an application running on a server OS over a 10gbs link (with a latency of tens of milli-second) is in charge of controlling a switch which is switching 1.2 Tbps of traffic at an average latency of under a micro second and deals with 100k flows with a 30% being setup or torn down every second. To put things in perspective, a controller takes tens of millisecond to set up a flow while the life of a flow transferring a 10Mb data (typical web page) is 10 msec!!
- To deal with 100k flows, the switch chips need to have that kind of flow capability. The current (and coming generation) of chips have no where near such capability so one can only use the flow table as a cache which brings the 3rd issue.
- Flow setup rate is anemic at best on the existing hardware. You are lucky if you can get 1000 flows per second.
So what is lacking is a Network Operating system on the switch to support the controller App. If you look at the server world, the administrator specified the policies and its the job of the OS working very closely with the H/W to enforce the policies. In the current scenario it feels like a application running on the bare metal with no Operating System support. Since this is a highly specialized application, it needs a specialized Operating system – a Network Operating system which can also be virtualized.
Challenge 3 – The Controller based Network
For a while, people were just tried to their inflexible networks which didn’t see any innovation in last two decades while the server and storage went through major metamorphosis. That frustration gave birth to Openflow/SDN which has currently morphed into a controller mania. Moving the brain from body and separating them creates somewhat of a split brain problem since the body (or switch in this case) still needs somewhat of a brain. What we need is a solution that encompasses the entire L2 fabric and the controller and Fabric work as one while providing easy abstractions for user to achieve their virtualization, SLA and monitoring needs.
A Distributed Network Hypervisor or Netvisor to the rescue
So what we (at Pluribus) saw early on that the world of servers is a very good example. The commoditization of chips and value moving to software is pretty much whats happening in the world of storage and is bound to happen in the world of networking. So we decided to do things in the right order i.e. get the bleeding edge commodity chips and create a Network Operating System with the following properties:
- Network OS – since a switch chip is very specialized and powerful chip.
- Distributed – There are always more then 1 switches in the network which need to work in tandem to support end-to-end flow
- Virtualized – Ability to run physical and Virtual Networking applications – As I mentioned before, a switch is not the network. We need to deal with all network services in physical and virtual form and the network OS needs to support that
Hence we created a Distributed Network Hypervisor called Netvisor or nvOS for short. Its designed to run on the switches and support virtual and physical network services. It also runs a controller on itself where the controller is a policy distribution engine and no longer a policy enforcement engine.
As the above figure shows, the current line drawn between the control plane and data place is not going to scale and perform. The line we originally drew (the founding principle of PLuribus Networks) need to be delivered for SDN and Openflow to deliver its true promise.
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