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Chapter 7: Transport Layer, DIFFA MAHARANI NINGTYAS, 201710893, MINDMAP…

- - - - The Transport Layer is responsible for establishing a temporary communication session between two applications and delivering data between them. TCP/IP uses two protocols to achieve this:
        
        Transmission Control Protocol (TCP)
        
        User Datagram Protocol (UDP)
      - Primary Responsibilities of Transport layer Protocols
        
        Tracking the individual communication between applications on the source and destination hosts
        
        Segmenting data for manageability and reassembling segmented data into streams of application data at the destination
        
        Identifying the proper application for each communication stream
    - - Segmenting the data
        
        Enables many different communications, from many different users, to be interleaved (multiplexed) on the same network, at the same time.
        
        Provides the means to both send and receive data when running multiple applications.
        
        Header added to each segment to identify it.
    - - Different applications have different transport reliability requirements
        TCP/IP provides two transport layer protocols, TCP and UDP
        
        Transmission Control Protocol (TCP)
        
        Provides reliable delivery ensuring that all of the data arrives at the destination.
        
        Uses acknowledged delivery and other processes to ensure delivery
        
        Makes larger demands on the network – more overhead
        
        User Datagram Protocol (UDP)
        
        Provides just the basic functions for delivery – no reliability
        
        Less overhead
        
        TCP or UDP
        
        There is a trade-off between the value of reliability and the burden it places on the network.
        
        Application developers choose the transport protocol based on the requirements of their applications.
- - - - Transmission Control Protocol (TCP)
        
        RFC 793, Connection-oriented – creating a session between source and destination, Reliable delivery – retransmitting lost or corrupt data, ordered data reconstruction – numbering and sequencing of segments, Flow control - regulating the amount of data transmitted and Stateful protocol – keeping track of the session.
    - - User Datagram Protocol (UDP)
        
        RFC 768, Connectionless, Unreliable delivery, No ordered data reconstruction, No flow control and Stateless protocol.
      - Applications that use UDP:
        
        Domain Name System (DNS), Video Streaming, and Voice over IP (VoIP).
    - - Port Numbers are used by TCP and UDP to differentiate between applications
    - - Netstat
        
        Used to examine TCP connections that are open and running on a networked host
  - - - Three-Way Handshake
        
        Establishes that the destination device is present on the network.
        
        Verifies that the destination device has an active service and is accepting requests on the destination port number that the initiating client intends to use for the session.
        
        Informs the destination device that the source client intends to establish a communication session on that port number.
    - - Step 1: The initiating client requests a client-to-server communication session with the server.
    - - Step 2: The server acknowledges the client-to-server communication session and requests a server-to-client communication session.
    - - Step 3: The initiating client acknowledges the server-to-client communication session.
  - - - Sequence numbers used to reassemble segments into original order
    - - The sequence number and acknowledgement number are used together to confirm receipt.
      - Window Size - The amount of data that a source can transmit before an acknowledgement must be received.
  - - - UDP
        
        Simple protocol that provides the basic transport layer functions
        
        Used by applications that can tolerate small loss of data
        
        Used by applications that cannot tolerate delay
      - Used by
        
        Domain Name System (DNS)
        
        Simple Network Management Protocol (SNMP)
        
        Dynamic Host Configuration Protocol (DHCP)
        
        Trivial File Transfer Protocol (TFTP)
        
        IP telephony or Voice over IP (VoIP)
        
        Online games
    - - UDP-based server applications are assigned well-known or registered port numbers.
      - UDP client process randomly selects port number from range of dynamic port numbers as the source port.
  - - - (HTTP, FTP, SMTP, TELNET) <-> TCP <-> IP
      - (DCHP, DNS, SNMP, TFTP, VolP, IPTV) <-> UDP <-> IP