Transport layer

Transport layer

1. Transport layer protocols

   • Transport of data
     • Transport layer function
       • responsible for establishing a temporary communication session between two applications and for transmitting data between them
     • Responsibilities of the transport layer
       • At the destination, the transport layer must be able to reconstruct the data portions in a complete data stream that is useful for the application layer.
     • Multiplexing conversations
       • Sending some types of data (for example, a video transmission) through a network, such as a complete flow of communication
     • Reliability of the transport layer
       • It is considered a reliable and complete transport layer protocol, since it guarantees that all data reaches the destination.
     • TCP
       • If a shipment order is divided into several packages, the customer can review the order of delivery online.
     • UDP
       • There is a tradeoff between the value of reliability and the burden it implies for network resources.
     • Protocol of the correct transport layer for the appropriate application
       • For some applications, the segments must arrive in a very specific sequence so that they can be processed correctly.
   • General description of TCP and UDP
     • Characteristics of TCP
       • the specific characteristics of reliability and the way they track conversations
     • TCP Header
       • A protocol with status information is a protocol that tracks the status of the communication session.
     • UCP features
       • it is such a simple protocol that, in general, it is described in terms of what it does not do compared to TCP.
     • UDP Header
       • If reliability is required when using UDP as a transport protocol, it must be administered by the application.
     • Multiple and independent conversations
       • The transport layer must be able to separate and manage several communications with different needs of transport requirements
     • Port numbers
       • The source port number is associated with the application that originates communication on the local host
     • Pair of sockets
       • The source and destination ports are placed within the segment. The segments are encapsulated within an IP packet.
     • Groups of port numbers
       • these numbers are reserved for services and applications
     • The netstat command
       • TCP connections not described can represent a significant security threat.

2. TCP y UDP

   • TCP communication process
     • TCP server processes
       • Each application process that runs on the server is configured to use a port number
     • Establishment of TCP connections
       • In some cultures, when two people meet, they usually wave at each other
     • End of the TCP session
       • To close a connection, the completion control marker must be set
     • Analysis of the three-way TCP link
       • exchange information about what data is received through the TCP header information
   • Reliability and flow control
     • TCP Reliability: orderly delivery
       • The TCP segments can reach their destination untidy.
     • TCP flow control: window size and acknowledgments
       • the amount of data that the destination can receive and process with reliability.
     • TCP flow control: congestion prevention
       • When congestion occurs in a network, the overloaded router starts discarding packets.
   • UDP communication
     • Comparison of low overhead and reliability of UDP
       • UDP is a simple protocol that provides the basic functions of the transport layer.
     • Reassembly of UDP datagrams
       • They often take different routes and arrive in the wrong order.
     • Processes and requests of the UDP server
       • they are assigned known or registered port numbers
     • UDP client processes
       • As in TCP, client-server communication is initiated by a client application that requests data from a server process.
   • TCP or UDP
     • Applications that use TCP
       • TCP is an excellent example of how different layers of the TCP / IP protocol suite have specific functions
     • Applications that use UDP
       • Although DNS and SNMP use UDP by default, both can also use TCP.