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Transport Layer Services : Multiplexing And Demultiplexing

  1. Sarvajanik College Of Engineering And Technology Subject Name :- Computer Networks Subject Code :- 2140709 Branch :- Computer Engineering Eve. (COE) 1
  2. Group Members And Topic  170420107559 – Uttam Thummar  170420107560 – Dhriti Uttamchandani  170420107561 – Keyur Vadodariya  170420107562 – Aditya Vaghela Topic:- Transport Layer - Introduction & Services, Multiplexing & Demultiplexing  Guided By :- Prof. Jaydeep Barad Prof. Pariza Kamboj 2
  3. Introduction  Transport layer protocol provides logical communication between application processes running on different hosts.  Transport layer protocol are implemented in the end system but not in network routers.  On sending side , the transport layer converts the application layer messages it receives from sending application process into transport layer packets, known as transport layer segments.  On the receiving side ,the transport layer reassembles segments , into messages ,passes to application layer.
  4. Transport layer in OSI networking system  Another purpose of Transport layer protocol is to ensure data integrity by evaluating checksum. It is the value added to the data on the source, defining data. If the checksum at the recipients end does not match the initial checksum, the data would be retransmitted.
  5. Functions of Transport layer  This layer breaks messages into packets.  It perform error recovery if the lower layer are not adequately error free.  Function of flow control if not done adequately at network layer.  Function of multiplexing and demultiplexing sessions together.  This layer can be responsible for setting up and releasing connection across the network.
  6. TRANSPORT LAYER SERVICES Transport Layer is the second layer of TCP/IP model. It is an end-to-end layer used to deliver messages to a host.  It is termed as end-to-end layer because it provides a point-to-point connection rather than hop-to- hop, between the source host and destination host to deliver the services reliably  The unit of data encapsulation in Transport Layer is a segment. The standard protocols used by Transport Layer to enhance it’s functionalities are  TCP(Transmission Control Protocol),  UDP( User Datagram Protocol),  DCCP( Datagram Congestion Control Protocol) etc.
  7. 1) Process to process delivery – While Data Link Layer requires the MAC address (48 bits address contained inside the Network Interface Card of every host machine) of source- destination hosts to correctly deliver a frame in a similar way Transport Layer requires a Port number to correctly deliver the segments of data to the correct process amongst the multiple processes running on a particular host TRANSPORT LAYER SERVICES
  8. 2. End-to-end Connection between hosts –  Transport layer is also responsible for creating the end-to-end Connection between hosts for which it mainly uses TCP and UDP.  TCP is a secure, connection- orientated protocol which uses a handshake TCP ensures reliable delivery of messages and is used in various applications.  It is a often used in multicasting protocols. TRANSPORT LAYER SERVICES
  9. 3. Congestion Control –  Congestion is a situation in which too many sources over a network attempt to send data and the router buffers start overflowing due to which loss of packets occur.  It uses open loop congestion control to prevent the congestion and closed loop congestion control to remove the congestion in a network once it occurred. TRANSPORT LAYER SERVICES
  10. 4. Data integrity and Error correction –  Transport layer checks for errors in the messages coming from application layer by using error detection codes, computing checksums, it checks whether the received data is not corrupted and uses the ACK and NACK services to inform the sender if the data is arrived or not and checks for the integrity of data. TRANSPORT LAYER SERVICES
  11. 5. Flow control –  Transport layer provides a flow control mechanism between the adjacent layers of the TCP/IP model. TCP also prevents the data loss due to a fast sender and slow receiver by imposing some flow control techniques. It uses the method of sliding window protocol which is accomplished by receiver by sending a window back to the sender informing the size of data it can receive. TRANSPORT LAYER SERVICES
  12. Multiplexing :-  Gathering data from multiple application processes of sender, enveloping that data with header and sending them as a whole to the intended receiver is called as multiplexing. Demultiplexing :-  Delivering received segments at receiver side to the correct app layer processes is called as demultiplexing. 12 TRANSPORT LAYER SERVICES
  13. Multiplexing  The Transport Layer at source collects data from various application process.  These Segments contains :-  Source Port No.  Destination Port No.  Header Files and Data.  These Segment’s are passed to the Network Layer which adds the source & destination IP address to get the Datagram 13
  14. Demultiplexing  Dest. Host receives IP Datagrams  each datagram has source IP address, destination IP address.  each datagram carries 1 transport- layer segment.  each segment has source, destination port number.  Dest. Host uses IP addresses & port numbers to direct segment to appropriate socket. 14
  15. How Multiplexing & Demultiplexing is Done15
  16. Types Of Multiplexing & Demultiplexing 1. Connection Less Multiplexing & Demultiplexing  Protocol - UDP  Unreliable because UDP 2. Connection Oriented Multiplexing & Demultiplexing  Protocol – TCP  Reliable because TCP 16
  17. Connection Less Mux - Demux  Create sockets with port numbers  DatagramSocket mySocket1 = new DatagramSocket(99111);  DatagramSocket mySocket2 = new DatagramSocket(99222); UDP socket identified by two- tuple  dest IP address  dest port number 17  When host receives UDP segment:  checks destination port number in segment  directs UDP segment to socket with that port number  IP datagrams with same destination port but different source IP addresses and/or source port numbers directed to same socket
  18. Connection Less Mux - Demux18
  19. Connection-Oriented Multiplexing and Demultiplexing  TCP socket identified by 4-tuple:  Source IP Address  Source Port Number  Destination IP Address  Destination Port Number  Mux: Server uses all four values along with other data to form a segment for a socket.  Demux: Receiver uses all four values to direct segment to appropriate socket.
  20. Connection-Oriented Multiplexing and Demultiplexing  Two arriving TCP segments with different source IP addresses or source port numbers will be directed to different sockets.  Server host may support many simultaneous TCP sockets.  Each socket identified by its own 4-tuple.  Web servers have different sockets for each connecting client.  Non-persistent HTTP will have different socket for each request.
  21. Refrences  Computer Networking-A Top-Down approach, 5thedition, Kurose and Ross, Pearson.   Data Communications and Networking (4th edition), Behrouz Forouzan, McGraw Hill 22
  22. Thank You23