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Question

Difficulty: MediumCommon Ports and Protocols

A network administrator is organizing security auditing profiles and intermediate firewall access rules for essential enterprise infrastructure services. Match each network protocol on the left with its corresponding default port and transport layer protocol on the right.

  • NTP (Network Time Protocol)UDP 123
  • IMAPS (Internet Message Access Protocol Secure)TCP 993
  • TelnetTCP 23
  • SMTPS (Simple Mail Transfer Protocol Secure)TCP 465

Answer

NTP matches with UDP 123; IMAPS matches with TCP 993; Telnet matches with TCP 23; SMTPS matches with TCP 465.
Each network service is matched directly to its official transport protocol and default listening port: NTP uses UDP 123, IMAPS uses TCP 993, Telnet uses TCP 23, and SMTPS uses TCP 465.

Step-by-Step Solution

1
Identify the transport protocol and default port for time synchronization services (NTP).
NTP operates over UDP port 123.
Time synchronization relies on low-latency, connectionless transmission over UDP 123.
2
Identify the transport protocol and default port for secure mailbox access (IMAPS).
IMAPS operates over TCP port 993.
Standard unencrypted IMAP uses TCP 143, whereas secure IMAPS wraps the session in TLS on TCP 993.
3
Identify the transport protocol and default port for unencrypted legacy command-line management (Telnet).
Telnet operates over TCP port 23.
Telnet establishes cleartext command-line communication using TCP port 23.
4
Identify the transport protocol and default port for secure mail submission (SMTPS).
SMTPS operates over TCP port 465.
Standard SMTP uses TCP 25, while implicit TLS-encrypted SMTPS uses TCP port 465.

Key Concept

Common Network Ports and Protocols
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Topics

Common Ports and Protocols

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