What is a Service Mesh?

Modern applications are typically architected as distributed collections of microservices, with each collection of microservices performing some discrete business function. A service mesh is a dedicated infrastructure layer that you can add to your applications. It allows you to transparently add capabilities like observability, traffic management, and security, without adding them to your own code. The term “service mesh” describes both the type of software you use to implement this pattern, and the security or network domain that is created when you use that software.

As the deployment of distributed services, such as in a Kubernetes-based system, grows in size and complexity, it can become harder to understand and manage. Its requirements can include discovery, load balancing, failure recovery, metrics, and monitoring. A service mesh also often addresses more complex operational requirements, like A/B testing, canary deployments, rate limiting, access control, encryption, and end-to-end authentication.

Service-to-service communication is what makes a distributed application possible. Routing this communication, both within and across application clusters, becomes increasingly complex as the number of services grow. Istio helps reduce this complexity while easing the strain on development teams.

What is Istio?

Istio is an open source service mesh that layers transparently onto existing distributed applications. Istio’s powerful features provide a uniform and more efficient way to secure, connect, and monitor services. Istio is the path to load balancing, service-to-service authentication, and monitoring – with few or no service code changes. Its powerful control plane brings vital features, including:

• Secure service-to-service communication in a cluster with TLS encryption, strong identity-based authentication and authorization
• Automatic load balancing for HTTP, gRPC, WebSocket, and TCP traffic
• Fine-grained control of traffic behavior with rich routing rules, retries, failovers, and fault injection
• A pluggable policy layer and configuration API supporting access controls, rate limits and quotas
• Automatic metrics, logs, and traces for all traffic within a cluster, including cluster ingress and egress

Istio is designed for extensibility and can handle a diverse range of deployment needs. Istio’s control plane runs on Kubernetes, and you can add applications deployed in that cluster to your mesh, extend the mesh to other clusters, or even connect VMs or other endpoints running outside of Kubernetes.

A large ecosystem of contributors, partners, integrations, and distributors extend and leverage Istio for a wide variety of scenarios. You can install Istio yourself, or a number of vendors have products that integrate Istio and manage it for you.

How it Works

Istio has two components: the data plane and the control plane.

The data plane is the communication between services. Without a service mesh, the network doesn’t understand the traffic being sent over, and can’t make any decisions based on what type of traffic it is, or who it is from or to.

Service mesh uses a proxy to intercept all your network traffic, allowing a broad set of application-aware features based on configuration you set.

An Envoy proxy is deployed along with each service that you start in your cluster, or runs alongside services running on VMs.

The control plane takes your desired configuration, and its view of the services, and dynamically programs the proxy servers, updating them as the rules or the environment changes.