Which are the two primary modes for Service discovery within a Kubernetes cluster?

Kubernetes services are discoverable by client Pods primarily through two mechanisms: environment variables, which are automatically populated with service details for newly created Pods, and a cluster DNS service that provides stable DNS entries for all Services.

While the Kubernetes API can be queried for service information, it is not considered a primary direct service discovery mode for applications, and LDAP is unrelated to Kubernetes service discovery.

Labels are used by Kubernetes to organize and select resources, including Pods for a Service, but they are not a direct service discovery mechanism for applications, and Radius is an authentication protocol, not for service discovery.

Selectors are used to define which Pods belong to a Service, but they are not a service discovery mechanism, and DHCP is a protocol for IP address assignment, unrelated to Kubernetes service discovery.