Which one of the following is not a client-server application?

Concept

A client-server application has an application-layer client process that requests a service from an application-layer server process. The classification depends on the communicating processes and protocol layer, not merely on whether two hosts exchange packets.

A network diagnostic can exchange control messages directly through the network stack without constituting an application-layer client-server service.

Application

Classify each choice by identifying the protocol and the endpoints that exchange its messages.

• Internet chat: a chat client connects to a chat service that relays messages and maintains shared state.

• Web browsing: a browser requests resources from a web server through HTTP or HTTPS.

• E-mail: a mail user agent communicates with mail servers through SMTP, IMAP, or POP.

• Ping: the utility sends an ICMP Echo Request, and the target host’s network stack returns an Echo Reply; ICMP operates at the network layer rather than as an application-layer service.

Cross-check and result

HTTP, SMTP, IMAP, and POP are application-layer protocols used by client and server processes. ICMP carries network-layer control and diagnostic messages. Therefore, Ping is the choice that is not a client-server application.