This acticle is part of Datacenter Desing Practices.
A key goal of network virtualization is to provide a virtual-to-physical network abstraction.
To achieve this, the physical fabric must provide a robust IP transport with the following characteristics:
- Simplicity
- Scalability
- High bandwidth
- Fault-tolerant transport
- Support for different levels of (QoS)
Simplicity and Scalability
Simplicity and scalability are the first and most critical requirements for networking.
Simplicity:
Configuration of the switches inside a data center must be simple. General or global configuration such as AAA, SNMP, syslog, NTP, and others should be replicated line by line, independent of the position of the switches. A central management capability to configure all switches at once is an alternative.
Scalability:
Scalability factors include, but are not limited to, the following:
- Number of racks supported in a fabric.
- Amount of bandwidth between any two racks in a data center.
- Number of paths from which a leaf switch can select when communicating with another rack.
The total number of ports available across all spine switches and the oversubscription that is acceptable determine the number of racks supported in a fabric. Different racks may host different types of infrastructure, which can result in different bandwidth requirements.
- Racks with storage systems might attract or source more traffic than other racks.
- Compute racks, such as racks hosting hypervisors with workloads or virtual machines, might have different bandwidth requirements than shared edge and compute racks, which provide connectivity to the outside world.
Link speed and the number of links vary to satisfy different bandwidth demands. it can vary for each rack without sacrificing other aspects of the leaf-and-spine architecture.