Service mesh is an important set of capabilities that solve some difficult service-to-service communication challenges when operating a services-style architecture. Just as Kubernetes and containers helped to provide a nice set of abstractions to deploying and running workloads on a fleet of computers, so too is service mesh emerging to abstract the network in a way that gives operators and developers control over request routing, observability, and policy enforcement. This provides a lot of potential.
The only problem is, although Kubernetes has emerged as a powerful API for abstracting underlying infrastructure for scheduling workloads, there is no one, single pragmatic API that surfaces the capabilities needed in a service mesh.