Google’s datacenter network is the magic behind what makes much of Google really work. But what is “bisectional bandwidth” and why does it matter? We talked about bisectional bandwidth. In short, bisectional bandwidth refers to the networks Google servers use to talk to each other.
Historically datacenter networks were oriented around talking to users. Let’s say a request for a web page came in from a browser. The request would go to a server and a reply was crafted by talking to just a few other servers, or perhaps even none at all, and the reply would be sent back to the client. This style of network is called a North/South oriented network. Very little internal communication was needed to implement a request.
That all changed as website and API services grew richer over time. Now literally thousands of backend requests can be made to create a single web page. Mind blowing. This meant communication shifted from being dominated by talking to users to talking to other machines within a datacenter. So these are called East/West oriented networks.
The shift to East/West dominate communication patterns meant a different topology was needed for datacenter networks. The old traditional fat tree network designs were out and something new needed to take its place.
Google has been on the forefront of developing new rich service supportive network designs largely because of their guiding vision of seeing The Datacenter as a Computer. Once your datacenter is the computer then your network is equivalent to a backplane on a single computer, so it must be as fast and reliable as possible so remote disk and remote storage can be accessed as if they were local.