The bad news is that the cracks in the cloud structure have already started to show. The good news is that this has been recognised in time and the industry has launched the CloudEthernet Forum and is already rallying to tackle fundamental issues and ensure a reliable, scalable and secure cloud for the coming generation.
A more detailed analysis of the challenges and suggested steps to their resolution is available in the CEF white paper The Benefits and Challenges Ahead for Cloud Operators . There are, however, two main factors that need first to be understood to provide context for the technical challenges.
The first is scale. It is understood that the market is rapidly expanding, even more rapidly than expected - but this is a familiar challenge in the IT world with lots of new users coming on line. What is different is the explosion in virtual machines that is unbounded by the physical limitations usually imposed by the requirement to install hardware. In a virtualised environment every VM is equivalent to a new location added to the network and, even in a low-density datacentre we could be speaking of many tens of thousands of such "locations". Already we hear of new giant datacentres hosting over a million VMs: string a few of these together and we will very soon be addressing tens of millions of new network locations.
Ethernet has, quite rightly so far, proved itself as the optimal technology for these datacentres, but it is worth remembering that it is based on a concept designed in the 1970s to string a few computers in the Palo Alto research centre together so they could share a printer. It has developed over 3 decades by adding switches to extend the service from tens to many thousands of locations. This is a natural evolution in response to growing demand. But the coming VM explosion is way beyond natural, and today's switch designs simply don't have the memory to hold tables for tens of millions of locations. And a move to create new generation "super-switches" would go against the basic economics that makes Ethernet so suitable.
Doesn't SDN point the way to a solution - keeping the switches simple and centralising this massive routing burden onto the network controller? It's an attractive idea and may well be a part of the solution, but it is not really what SDN is fundamentally about. The real attraction of SDN is to use central control as a basis to deliver smart new functionality and flexibility to the overall network by virtualising it and creating a more nimble communications infrastructure. Forcing an additional massive "heavy lifting" administrative burden onto the controller in this way shifts the emphasis from software-defined towards software-relieved - reducing what could have been a breakthrough into a sticking plaster solution. NFV, similarly, may have a role to play, but its immediate effect would be to increase the number of functions running on VMs.
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