What are the differences between container communication inside and outside a pod in Kubernetes?

  • Each Pod is assigned a unique IP address for each address family.
  • Every container in a Pod shares the network namespace, including the IP address and network ports.
Inside a Pod Outside a Pod
Network namespace Containers share the same network namespace, IP address, and port space. Containers have distinct IP addresses and separate network namespaces.
Communication method Containers communicate with each other via localhost. Containers must use IP networking to communicate.
IPC (Inter-process Communication) Containers can use SystemV semaphores or POSIX shared memory for communication. OS-level IPC is not possible between Pods without special configuration.
Hostname The system hostname is the same for all containers in the Pod (configured as the Pod's hostname). Each Pod has its own distinct hostname.
Port management Containers share the same port space and must coordinate usage within the Pod. Each Pod manages its own port space; no conflict between Pods unless specific networking configurations apply.

In this version, the key differences between the two contexts are emphasized by using bold formatting for clarity.