Networking in Private and Public Clouds

This section defines typical cloud services, from SaaS to IaaS, provides an overview of network-related IaaS services, and describes typical multi-tenant requirements.

Every cloud environment must provide the basic network-related IaaS services: attach a VM to a segment, and assign an IP address to a VM. Most IaaS clouds also provide at least rudimentary tenant isolation.

Virtual tenant networks are the hardest challenge when designing the network services in an IaaS cloud:

• You could use VLANs or overlay virtual networks;
• Virtual tenant networks could be implemented in hypervisors or in ToR switches;
• The choices you make will have significant impact on the scalability of your infrastructure.

You could build virtual tenant networks on top of an IaaS infrastructure that doesn't provide them. The same solutions can also be used to connect workloads runninng in multiple cloud environments (hybrid clouds).

Deploying redundant network virtual appliances in a public cloud virtual network is one of the hardest challenges you'll have to tackle in your public cloud networking journey.

Most network services appliances rely on tricks like layer-2 forwarding, IP address sharing, or static routing toward floating next-hop address to implement seamless failover. None of those tricks work in a typical public cloud environment... but don't despair; this section will outline most of the challenges you'll be facing, and give you a few design alternatives.