Internet-Security.com TCP port 15443 details

Istio service mesh uses TCP port 15443 on its gateways (istio-ingressgateway and east-west gateway) for SNI-based TLS/mTLS passthrough handled by Envoy.
In default Istio installs on Kubernetes, the istio-ingressgateway Service includes port 15443 (name: "tls") to route HTTPS traffic to in-mesh services without terminating TLS.
Istio multi-cluster/east-west gateways expose 15443 to accept cross-cluster mTLS traffic (e.g., for *.local hostnames) and route it within the mesh.
Managed Istio distributions—Google Anthos Service Mesh and Red Hat OpenShift Service Mesh—use the same 15443 gateway port for TLS passthrough.
Example: On GKE with Anthos Service Mesh, the istio-ingressgateway container listens on 15443/TCP and accepts SNI-based TLS passthrough connections to mesh services.

TCP 15443