Lecture: TCP and UDP Protocols for CCNA

Introduction

• Instructor: Jeremy's IT Lab
• Course: Free, complete course for CCNA
• Focus of Lecture: Compare TCP and UDP, two Layer 4 protocols
• Exam Topic: Exam topic 1.5 - Compare TCP to UDP
• Additional Content: Bonus practice question from Boson ExSim

Overview of Layer 4

• Functions:
  • Provides transparent data transfer between end hosts
  • Encapsulates data with a Layer 4 header
  • Uses services of lower layers for data delivery
• Services Provided:
  • TCP: Reliable data transfer, error recovery, data sequencing, flow control
  • UDP: Does not provide these services
• Layer 4 Addressing:
  • Uses "port numbers" for addressing
  • Identifies Application Layer protocol and supports session multiplexing

TCP (Transmission Control Protocol)

• Characteristics:
  • Connection-oriented protocol
  • Reliable communication through segment acknowledgment
  • Provides sequencing and flow control
• Key Concepts:
  • Three-Way Handshake: SYN, SYN-ACK, ACK for connection establishment
  • Four-Way Handshake: FIN, ACK for connection termination
  • Reliable Communication: Acknowledgment and retransmission of unacknowledged segments
  • Flow Control: Window size field manages data transmission rate

UDP (User Datagram Protocol)

• Characteristics:
  • Connectionless protocol
  • Best-effort delivery without acknowledgment or retransmission
  • No sequencing or flow control
• Header:
  • Simplified with only four fields: Source port, destination port, length, and checksum

Comparison of TCP and UDP

• TCP:
  • More features, reliable, at the cost of larger header and potential delays
  • Suitable for applications requiring reliability (e.g., file downloads)
• UDP:
  • Simpler, less overhead, suitable for delay-sensitive applications (e.g., real-time voice/video)
  • Some applications handle reliability within the application itself
• Both Protocols:
  • Provide Layer 4 addressing through port numbers

Important Port Numbers

• TCP Ports:
  • FTP: 20, 21
  • SSH: 22
  • Telnet: 23
  • SMTP: 25
  • HTTP: 80
  • POP3: 110
  • HTTPS: 443
• UDP Ports:
  • DHCP: 67, 68
  • TFTP: 69
  • SNMP: 161, 162
  • Syslog: 514
• Both TCP & UDP:
  • DNS: Uses both protocols depending on the situation

Study Tools and Resources

• Boson ExSim: Recommended for CCNA practice exams
• Anki Flashcards: For memorizing port numbers
• Wireshark Demo: For observing TCP and UDP in a real network

Summary

• Reviewed Layer 4 basics and port numbering
• Detailed comparison of TCP and UDP protocols
• Emphasis on understanding differences for exam preparation
• Quiz questions to reinforce learning

Acknowledgments

• Recognition of JCNP-level channel members for support