Designing a Private Cloud Network Infrastructure

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The data center networking team in a large enterprise (the Customer) has been tasked with building the network infrastructure for a new private cloud deployment.

They approached numerous vendors trying to figure out how the new network should look like, and got thoroughly confused by all the data center fabric offerings, from FabricPath (Cisco) and VCS Fabric (Brocade) to Virtual Chassis Fabric (Juniper), QFabric (Juniper) and more traditional leaf-and-spine architectures (Arista). Should they build a layer-2 fabric, a layer-3 fabric or a leaf-and-spine fabric?

Collect the Requirements

Talking with vendors without knowing the actual network requirements is a waste of time – the networking team can start designing the network when they collect (at least) the following requirements:

• End-to-end connectivity requirements (L2 or L3 connectivity between edge ports);
• Required services (IP transport, lossless IP transport and/or FCoE transport);
• Total number of edge ports (GE/10GE/FC/FCoE)
• Total north-south (traffic leaving the data center) and east-west (inter-server traffic) bandwidth.

Private Cloud Planning and Design Process

Planning and design of a new (private or public) cloud infrastructure should follow these logical steps:

• Define the services offered by the cloud. Major decision points include IaaS versus PaaS and simple hosting versus support for complex application stacks^[1].
• Select the orchestration system (OpenStack, CloudStack, vCloud Director…) that will allow the customers to deploy these services;
• Select the hypervisor supported by the selected orchestration system that has the desired features (example: high-availability);
• Select optimal server hardware based on workload requirements;
• Select the network services implementation (physical or virtual firewalls and load balancers);
• Select the virtual networking implementation (VLANs or overlay virtual networks);
• Design the network infrastructure based on the previous selections.

Quick Overview of Results

Most reasonably sized private cloud deployments require few tens of high-end physical servers and associated storage – either distributed or in form of storage arrays. You can implement the network infrastructure meeting these requirements with two ToR switches having between 64 10GE and 128 10GE ports.

1. Does it make sense to build new clouds with overlay networks?
   http://blog.ipspace.net/2013/12/does-it-make-sense-to-build-new-clouds.html

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