TCP/UDP

Current Layer 4 Protocols

• TCP

• UDP

• SCTP

What does TCP stand for and basics overview?

• Transmission Control Protocol

• Connection-oriented, reliable

What does UDP stand for and basic overview?

• User Datagram Protocol

• Connectionless, outdated

What does SCTP stand for and basic overview?

• Stream Control Transmission Protocol

• New protocol designed to offer reliable transmission over connectionless network

What is TCP and what does it include?

• Provides reliable host-to-host connection

• Ensures no data is loss

• Includes:

  • controls for initiation

  • basic prioritization

  • flow control

  • congestion avoidance

  • termination of connection

What is in the TCP Header?

• Sequence Number

• Acknowledgement Number

• Data Offset

• Control Fields

• Window

• Checksum

What is the Sequence Number in the TCP Header?

• the identifier of the segment being transferred

What is the Acknowledgement Number in the TCP Header?

• the value of the next sequence number expected to be received

• indicates where the data begins

What are the Control Fields in the TCP Header?

• the bits that manage the state and control function of a TCP connection

• examples:

  • SYN

  • SCK

  • FIN

  • RST

  • PSH

  • URG

What is the Window in the TCP Header?

• number of data bytes beginning with the one indicated in the ACK field that this device is able to accept

What does the netstat -a command do?

• displays network information

What is UDP?

• connectionless communication model

• provides minimal capabilities to deliver segments to a given destination

What are the limitations of UDP?

• not a reliable delivery mechanism

• lacks nearly all robust mechanisms used in TCP

• data can be lost

What are the UDP header fields?

• Length

• Checksum

What is length in the UDP header?

• entire length of the segment

What is the checksum in the UDP header?

• a 16-bit value used to detect errors

• accomplished through summing all bits in the segment and taking one's complement

What is a flaw with the UDP header?

• no delivery verification with headers

• aka no handshake

Which is faster, UDP or TCP?

• UDP because no connection, acknowledgement, or retransmission is set up