1.4 Core Ports, Protocols & Transport Layer Mechanics
Details standard well-known TCP and UDP service ports, secure encrypted protocol replacements, and transport layer reliability trade-offs.
🎯 Key CompTIA Network+ Exam Takeaways
- TCP provides reliable, ordered connection-oriented delivery; UDP provides lightweight, connectionless low-latency transmission.
- Critical administrative ports: SSH (TCP 22), Telnet (TCP 23), RDP (TCP 3389), SNMP (UDP 161/162).
- Secure service replacements: replace HTTP (80) with HTTPS (443), LDAP (389) with LDAPS (636), and unencrypted email with SMTPS (587) and IMAPS (993).
Network services utilize standardized port numbers (0 to 1023 are Well-Known ports) managed by IANA. Secure protocols wrap application traffic in Transport Layer Security (TLS) or SSH cryptographic tunnels to ensure confidentiality.
Network management systems rely on Simple Network Management Protocol (SNMP), where agents listen on UDP port 161 and send event traps to the NMS on UDP port 162. Network Time Protocol (NTP) uses UDP 123 to synchronize clocks for cryptographic operations and log auditing.
Directory services utilize LDAP on TCP port 389, which transmits credentials in cleartext unless upgraded to LDAPS over TCP port 636.
⚠️ Common Pearson VUE Exam Traps
- Believing DNS only uses UDP 53; it uses TCP 53 for zone transfers (AXFR) and responses over 512 bytes.
- Allowing unencrypted administrative protocols (Telnet, FTP, HTTP) on enterprise production networks.
Knowledge Checkpoint
A firewall engineer is writing security rules for an internal recursive DNS resolver. Under normal operational standards, which ports and transport protocols must be permitted through the firewall for standard name resolution queries and zone transfers?