Which of the following is primarily used for logging network devices?

Syslog is a standardized system logging protocol used to send different types of messages from various devices over a network to a centralized logging server. This allows for the collection, storage, and analysis of log data from devices such as routers, switches, and firewalls. It plays a crucial role in network management and security, enabling administrators to monitor device activity, troubleshoot issues, and ensure compliance with security policies.

The other options have different functions: DHCP is used for dynamic IP address allocation, HTTP is a protocol for transferring web pages, and FTP is used for transferring files. While these protocols serve their specific purposes, they do not specialize in logging device messages or activities like Syslog does.