Untitled Quiz

Transport Layer in Depth

• The transport layer manages the delivery of data between applications
• Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) are two primary protocols in this layer.

Transport Layer Protocols

• TCP (Transmission Control Protocol)

  • Connection-oriented protocol
  • Guarantees delivery of data packets
  • Handles error recovery, retransmission
  • Reliable delivery
  • Useful for applications requiring reliable delivery, e.g. email, file sharing, web browsing

• UDP (User Datagram Protocol)

  • Connectionless protocol
  • No guarantees of delivery
  • Faster than TCP, but less reliable
  • Useful for applications tolerant to occasional data loss, e.g. video streaming, online gaming, DNS

UDP vs TCP

• UDP is connectionless, single packet transfer, no retransmission delay, suitable for real-time applications like VoIP and online games
• UDP does not perform segmentation or error correction
• TCP is connection-oriented, has error correction and reliable delivery, sequencing

Why UDP?

• Fast connection, latency is not an issue (no connection establishment)
• Simple: No connection state at sender/receiver
• Small segment header: Lower overhead per packet

UDP Segment Format

• Comprises Source Port, Destination Port, Length, Checksum, and Data fields
• Source and Destination Ports identify the applications
• Length specifies bytes in the UDP header and payload
• Checksum verifies data integrity, optional in IPv4, but mandatory in IPv6

TCP Header

• Contains Source Port, Destination Port, Sequence Number, Acknowledgement Number, Data Offset, Reserved, Flags, Window, Checksum, Urgent Pointer, and Options.
• Sequence and acknowledgment numbers track data packets
• Window size indicates the amount of data that can be transmitted
• Control flags manage data flow

Features of TCP

• Connection-oriented protocol
• Reliable point-to-point data transfer
• Full duplex
• Flow control (receiver controls sending rate)
• Congestion control (prevents sender from overwhelming network)

Three-Way Handshake Protocol

• Connection establishment process used by TCP
• Client sends SYN, server sends SYN/ACK, client responds with ACK
• Establishes a connection before data transfer

Quality of Service (QoS)

• Leaky Bucket Algorithm

  • Smooths bursty traffic by averaging the data rate
  • Temporarily stores packets
  • Sends packets to the network at a constant rate

• Token Bucket Algorithm

  • Enables more traffic than leaky bucket
  • Provides tokens to regulate the transfer rate, packet can only be sent out when there are available tokens
  • Avoid discarding packets when the network is congested