How to design a network for Openstack or cloud deployment

Designing a network is a topic within itself and there is no way we can cover all of it in this single post. Cisco has its own certification path path CCDE for these who want to know more.

Cisco design and implementation guide - old best practices

In a very simplistic view back in the old days a network used to be design similar to the picture below (although it is hard to say when the new era started ;)). Every big network had to have a core, distribution(sometimes called aggregation) and access layer. The network was engineered mainly to help with North to South traffic in the data center or in another words to help get the data out and into the data center.

New cloud friendly data center design best practice

With the advent and popularization of new networking devises that support layer 2 routing, commonly know as networks fabrics (more info about TRILL and fabric) the network design has shifted in data centers. The way we design the networks today is to maximize the East to West traffic instead of the North to South ( old design above). The purpose of the new network is to allow more efficiently exchange data between the servers within the rack or data center.

They say that a picture is worth more than a thousand words. To help us to visualize how a new data center network/cloud network is designed these demonstration pictures (taken from Cisco document: Cisco Massively Salable Data Center) will shed some more light on it. Please note that we no longer use the core, distribution or access keyword but instead: spine, leaf or superspine to describe the different network layers :).

Network operating system architecture

In my previous posts we took a look at how hardware networking vendors design and build modern systems. We concentrated mainly on the OS and software integration on the appliance:

• Arista network operating system switch architecture
• Network appliance architecture

Today I found another good article on Arista blog that takes this one step further and again advocates an open operating system design: Linux as a Switch Operating System: Five Lessons Learned. This is what Arista says:

• It’s okay to leave the door unlocked - get net admin access to the underlying Linux operating system tools
• Preserve the integrity of the Linux core - keep your product specific changes as small as possible to allow integration with already existing software out there
• Focus on state, not messages - being only maybe an average programmer I will not comment on this as this is clearly not my area of expertise
• Keep your hands out of the kernel - why to complicate your code if it doesn't bring any revolutionary benefit; besides it is much easier to find developers who know how to program in linux/libc than in Linux kernel.
• Provide familiar interfaces to ease adoption - everyone knows the IOS CLI so why to invent something new.

Lesson learned from Arista: reuse, integrate and trust your customers.

The company success would not be possible without a clear and consistent OS and tools set design. From my experience they are the second company (I saw this first on BigIP - F5 load balancers).