What we talk about when we talk about cloud network performance

Infrastructure-as-a-Service ("Cloud") data-centers intrinsically depend on high-performance networks to connect servers within the data-center and to the rest of the world. Cloud providers typically offer different service levels, and associated prices, for different sizes of virtual machine, memory, and disk storage. However, while all cloud providers provide network connectivity to tenant VMs, they seldom make any promises about network performance, and so cloud tenants suffer from highly-variable, unpredictable network performance. Many cloud customers do want to be able to rely on network performance guarantees, and many cloud providers would like to offer (and charge for) these guarantees. But nobody really agrees on how to define these guarantees, and it turns out to be challenging to define "network performance" in a way that is useful to both customers and providers. We attempt to bring some clarity to this question.