name: Service Mesh Interface (SMI) Vocabulary
description: |
  Normative vocabulary of the Service Mesh Interface specification, covering the four
  API groups (access, specs, split, metrics) and the core concepts they introduce.
  SMI was a CNCF Sandbox project archived on 2023-10-03; this vocabulary is preserved
  for historical reference and for migration tooling targeting Kubernetes Gateway API
  GAMMA, the de facto successor.
version: '0.6.0'
status: archived
archivalDate: '2023-10-20'
successor: Kubernetes Gateway API (GAMMA)
successorUrl: https://gateway-api.sigs.k8s.io/mesh/gamma/

concepts:
  - term: Service Mesh
    definition: A dedicated infrastructure layer for managing service-to-service communication, observability, and security in a microservices system, typically implemented via sidecar proxies.
  - term: Traffic Policy
    definition: Authorization rules governing which workloads (service identities) may send which kinds of traffic to which other workloads.
  - term: Traffic Management
    definition: Runtime control over how traffic flows between services, including weighted splitting, mirroring, and progressive delivery.
  - term: Traffic Telemetry
    definition: Metrics, traces, and logs describing observed traffic between service mesh participants.
  - term: Service Identity
    definition: In SMI, a Kubernetes ServiceAccount used as the cryptographic identity of a workload for authorization purposes.
  - term: Canary Deployment
    definition: Progressive delivery pattern that routes a small percentage of traffic to a new version of a service before full cutover.
  - term: Traffic Edge
    definition: A directed pairing between two workloads (e.g. pod A talking to pod B) for which metrics are collected.

resourceKinds:
  - kind: TrafficTarget
    apiGroup: access.smi-spec.io/v1alpha3
    definition: Associates a set of traffic rules with a service identity allocated to a group of pods; the unit of authorization in SMI.
  - kind: HTTPRouteGroup
    apiGroup: specs.smi-spec.io/v1alpha4
    definition: A named collection of HTTP route matches (pathRegex, methods, headers) consumed by TrafficTarget and TrafficSplit.
  - kind: TCPRoute
    apiGroup: specs.smi-spec.io/v1alpha4
    definition: A spec resource matching TCP traffic by destination port.
  - kind: UDPRoute
    apiGroup: specs.smi-spec.io/v1alpha4
    definition: A spec resource matching UDP traffic by destination port.
  - kind: TrafficSplit
    apiGroup: split.smi-spec.io/v1alpha4
    definition: Incrementally directs percentages of traffic between backend services for canary, blue/green, and A/B testing rollouts.
  - kind: TrafficMetrics
    apiGroup: metrics.smi-spec.io/v1alpha1
    definition: A per-resource metrics document reporting latency percentiles and success/failure counts over a time window.
  - kind: TrafficMetricsList
    apiGroup: metrics.smi-spec.io/v1alpha1
    definition: Aggregated collection of TrafficMetrics documents, queryable by kind, label selectors, or edges.

metrics:
  - name: p50_response_latency
    unit: seconds
    description: Median (50th percentile) response latency over the time window.
  - name: p90_response_latency
    unit: seconds
    description: 90th percentile response latency over the time window.
  - name: p99_response_latency
    unit: seconds
    description: 99th percentile response latency over the time window.
  - name: success_count
    description: Number of successful responses observed in the time window.
  - name: failure_count
    description: Number of failed responses observed in the time window.

implementations:
  - Linkerd
  - Open Service Mesh (OSM)
  - Consul Connect
  - Traefik Mesh
  - Gloo Mesh
  - Flagger
  - Meshery
  - Argo Rollouts
  - Istio (via smi-adapter-istio)

relatedStandards:
  - name: Kubernetes Gateway API
    url: https://gateway-api.sigs.k8s.io
    relationship: successor
  - name: Gateway API GAMMA Initiative
    url: https://gateway-api.sigs.k8s.io/mesh/gamma/
    relationship: direct successor for service-mesh use cases
  - name: Kubernetes Ingress
    url: https://kubernetes.io/docs/concepts/services-networking/ingress/
    relationship: predecessor (north-south) to Gateway API
  - name: Envoy xDS
    url: https://www.envoyproxy.io/docs/envoy/latest/api/api
    relationship: underlying data-plane API used by most SMI implementations

archivalNotice: |
  CNCF archived the Service Mesh Interface project on 2023-10-03. The maintainers stated:
  "the maintainers have decided to consolidate efforts on a service mesh under the auspices
  of GAMMA under the Kubernetes SIG Network initiative." The GitHub organization and all
  repositories were marked read-only on 2023-10-20. New service-mesh configuration work
  should target Kubernetes Gateway API GAMMA, which reached GA in the Standard Channel
  with Gateway API v1.1.0.