chap 7

• Transport Layer Protocols

  Establish a data channel for an application to achieve end-to-end data exchange

  
• Basic elements of all networks

  • Devices
  • Media
  • Messages
  • Rules
• Protocols

  Rules or procedures that define how messages are sent, directed, received, and interpreted
• Layered Network Models

  Structuring technique that groups network protocols according to their functions
• Layered Network Models

  • Simplifies the network model
  • Enables specialization
  • Provides design modularity
  • Encourages interoperability
  • Allows for standardized interfaces
• Layered network models

  • OSI Seven Layer Model
  • TCP/IP Model
• The OSI Seven Layer Model was created to unify networks
• The OSI Seven Layer Model is an accepted International Standard for data communication networks
• OSI Seven Layer Model layers

  • Application Layer
  • Presentation Layer
  • Transport Layer
  • Session Layer
  • Network Layer
  • Data Link Layer
  • Physical Layer
• Encapsulation


  Process of adding headers to the data
• De-encapsulation


  Process of removing headers from the data
• Encapsulation increases the size of the data packet
• The TCP/IP model was developed by DARPA in the late 1960s
• Internet Protocol Suite

  Set of communication protocols for the internet
• TCP/IP Model layers

  • Application Layer
  • Transport Layer
  • Internet Layer
  • Network Access Layer
• TCP

  Transmission Control Protocol
• IP

  Internet Protocol
• Transport Layer

  • Establishes a data channel
  • Application addressing
  • Segmentation of data
  • Error control
  • Flow control
  • Congestion control

  
• Transmission Control Protocol (TCP)

  Connection-oriented communication
• User Datagram Protocol (UDP)

  Connectionless communication
• TCP

  • Connection establishment
  • Flow-control
  • Reliable transmission
• TCP provides a mechanism to keep track of data transmission
• Receiving host sends acknowledgement to sending host upon receiving data successfully
• Unsuccessful transmission can be detected, and re-transmission will be carried out
• Transport Layer Protocols

  • Transmission Control Protocol (TCP)
  • User Datagram Protocol (UDP)

  
• Transmission Control Protocol (TCP)

  • Connection-oriented
  • Connection establishment
  • Flow-control
  • Reliable transmission
• User Datagram Protocol (UDP)

  • Connectionless
  • No connection establishment
  • No flow-control
  • Unreliable transmission
• TCP connection establishment

  1. Establish connection before communication

  2. Provide flow-control

  3. Track data transmission

  4. Send acknowledgements

  5. Detect unsuccessful transmission and re-transmit
• TCP provides a mechanism to keep track of the data transmission between the hosts
• Receiving host sends acknowledgement to sending host upon receiving incoming data successfully
• Unsuccessful transmission can be detected, and re-transmission will be carried out to resend the data
• TCP header is a minimum of 20 bytes long
• TCP header can be up to 60 bytes long
• Compulsory fields in TCP header

  • Source Port
  • Destination Port
  • Sequence Number
  • Acknowledgement Number
  • Header Length
  • Reserved
  • Window
  • Checksum
  • Urgent
• UDP header is 8 bytes long
• Fields in UDP header

  • Source Port
  • Destination Port
  • Length
  • Checksum
• Comparison between TCP and UDP

  • TCP is reliable but slow
  • UDP is unreliable but fast
  • TCP has a longer header than UDP
• When to use TCP or UDP

  • Use TCP if reliability is important
  • Use UDP if speed is critical
• Transport Layer uses the concept of the port for application addressing
• Port numbers

  • Source Port
  • Destination Port