Overlay Networks Explained.
An overlay network is a virtual network of nodes (a connection point that can receive, create, store or send data along distributed network routes) and logical links (which manage the flow and error control of data transmission from one node to another so that the receiving node isn’t overwhelmed with data from the transmitting node), built on top of a network that already exists. It aims to enable a new service or function without having to reconfigure the entire design of the network.
The most widely used overlay network is the internet itself. Before it became commercial, the internet was a research network which ran on top of the physical infrastructure of the Public Switched Telecommunications Network (PSTN). Today, most overlay networks run on top of the internet though other examples of overlay networks include virtual private networks, peer-to-peer networks and VoIP (voice over internet protocol) services.
Most overlay networks use encapsulation which is the process of taking data from one protocol (a method of exchanging data over a computer network) in which one packet (a unit of data) resides inside of another packet while being forwarded to its destination. The encapsulated packet is then de-encapsulated upon arrival. Clever.
The advantage of overlay networks is that they enable developers to create and implement protocols on the web easily and flexibly. Additionally, with overlay networks, virtual machines can be moved to different locations without being restricted by the physical network.
However, there are disadvantages too. Multiple layers of software and processing provided by overlay networks can increase performance overhead (the resources, such as memory and processing time, required to achieve the required result) and make the network more complicated. Also, the process of encapsulating and de-encapsulating packets can demand a significant amount of computing power and the physical network isn’t able to adjust automatically to changes in virtual networks.
But, in the end, how would we manage without overlay networks when traditional networks can’t keep pace with the cloud’s requirements?
The challenge moving forward is to be able to bring overlays at scale and without adding complexity whilst being cost effective and managing, deploying and maintaining a data centre network that allows workloads to be executed and access to the data they produce, managed.