Which service allows initiating a Telnet session by hostname?

DNS (Domain Name System) lookup is correct because it translates human-readable hostnames (like "router1.example.com") into IP addresses that devices use to communicate. When you initiate a Telnet session using a hostname, your device performs a DNS lookup to resolve that hostname to its corresponding IP address before establishing the connection. SNMP (Simple Network Management Protocol) is incorrect because it's used for network device management and monitoring, not hostname resolution. Syslog is incorrect as it's a protocol for sending system log messages to a central server. NTP (Network Time Protocol) is incorrect because it synchronizes the clocks of computer systems over a network.