Istio
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An Istio service mesh is logically split into a data plane and a control plane.
The data plane is composed of a set of intelligent proxies () deployed as sidecars. These proxies mediate and control all network communication between microservices. They also collect and report telemetry on all mesh traffic.
The control plane manages and configures the proxies to route traffic.
The following diagram shows the different components that make up each plane:
Envoy proxies are deployed as sidecars to services, logically augmenting the services with Envoy’s many built-in features, for example:
Dynamic service discovery
Load balancing
TLS termination
HTTP/2 and gRPC proxies
Circuit breakers
Health checks
Staged rollouts with %-based traffic split
Fault injection
Rich metrics
This sidecar deployment allows Istio to enforce policy decisions and extract rich telemetry which can be sent to monitoring systems to provide information about the behavior of the entire mesh.
The sidecar proxy model also allows you to add Istio capabilities to an existing deployment without requiring you to rearchitect or rewrite code.
Some of the Istio features and tasks enabled by Envoy proxies include:
Traffic control features: enforce fine-grained traffic control with rich routing rules for HTTP, gRPC, WebSocket, and TCP traffic.
Network resiliency features: setup retries, failovers, circuit breakers, and fault injection.
Security and authentication features: enforce security policies and enforce access control and rate limiting defined through the configuration API.
Pluggable extensions model based on WebAssembly that allows for custom policy enforcement and telemetry generation for mesh traffic.
Istiod provides service discovery, configuration and certificate management.
Istio can support discovery for multiple environments such as Kubernetes or VMs.
Istiod acts as a Certificate Authority (CA) and generates certificates to allow secure mTLS communication in the data plane.
Istio uses an extended version of the proxy. Envoy is a high-performance proxy developed in C++ to mediate all inbound and outbound traffic for all services in the service mesh. Envoy proxies are the only Istio components that interact with data plane traffic.
Istiod converts high level routing rules that control traffic behavior into Envoy-specific configurations, and propagates them to the sidecars at runtime. Pilot abstracts platform-specific service discovery mechanisms and synthesizes them into a standard format that any sidecar conforming with the can consume.
You can use Istio’s to instruct Istiod to refine the Envoy configuration to exercise more granular control over the traffic in your service mesh.
Istiod enables strong service-to-service and end-user authentication with built-in identity and credential management. You can use Istio to upgrade unencrypted traffic in the service mesh. Using Istio, operators can enforce policies based on service identity rather than on relatively unstable layer 3 or layer 4 network identifiers. Additionally, you can use to control who can access your services.