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Saturday, 16 February 2013

Host-to-Host Layer Protocols

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Transport Layer Protocols:

The main purpose of the Host-to Host layer is to shield the upper-layer application from the complexities of the network i.e this layer begin the  processing of the gathered information ready to send.

Three protocols mainly work at this layer:
  1.  Transmission Control Protocol (TCP)
  2.  User Datagram Protocol (UDP)
  3.  Stream Control Transmission Protocol (SCTP)
Transmission Control Protocol (TCP):


  1.  TCP is a byte-oriented protocol: It receives a message or messages from a process layer, stores them as a stream of bytes, and sends them in segments.
  2.  Sequenced: It number and sequences each segment so that the destination's TCP stack can put the segments back into the order the application intended.
  3.  Connection-Oriented: Before a transmitting host starts to send segments down the model, the sender's TCP stack contacts the destination stack to establish a connection. The connection which is created is known as virtual-circuit.
  4.  Reliable Service: Connection created between source and destination then data is transferred with acknowledgement and then connection is terminated.
  5.  Acknowledgements:  After data is send to the destination, acknowledgement is received whether data is reached or not.
  6.  TCP is a full-duplex, connection-oriented. reliable, and accurate protocol.
  7.  Flow Control: The receiver of the data controls the amount of data that are to be sent by the sender.
  8.  Error Control: To provide reliable service, TCP implements an error control mechanism.
  9.  Congestion control: The amount of data sent by a sender is not only controlled by the receiver(Flow control), but is also determined by the level of congestion in the network.
  10.  Port no.= 6
User Datagram Protocol (UDP):

  1.  UDP is a message-oriented protocol: A process delivers a message to UDP, which is encapsulated in a user datagram and sent over the network.
  2.  Unsequenced: UDP does not sequenced the segments and does not care in which order the segments arrive at the destination.
  3.  Connectionless: UDP doesn't create a virtual-circuit between source and destination thats why it is connectionless.
  4.  Unreliable Service: In this protocol, data is transferred directly i.e there is no surity whether data is reached or not to the destination.
  5.  No Acknowledgements
  6.  No Flow control, Congestion control
  7.  UDP also provide error control(Checksum).
  8.  Port no.= 17 
Stream Control Transmission Protocol (SCTP):

  1.  SCTP combines the best features of UDP and TCP.
  2.  SCTP is a message-oriented protocol, it preserves the message boundaries and at the same time detects lost data, duplicate data, and out-of-order data.
  3.  Full-Duplex Communication: SCTP offers full-duplex service, in which data can flow in both directions at the same time.
  4.  Connection-Oriented Service: SCTP is a connection-oriented protocol.However, a connection is called an association
  5.  Reliable Service: It uses an acknowledgement mechanism to check the safe and sound arrival of data. 
  6.  Port no.= 2905
  7.  Multihoming: A TCP connection involves one source and one destination IP address. This means that even if the sender or receiver is a multihomed, only one of IP address per end can be utilized during the connection whereas SCTP supports multihoming service i.e sending and receiving host can define multiple IP addresses.        
  8.  Multiple Streams: An association in SCTP involve multiple streams. 
  9.  It also Provide Error control, Flow control, Congestion control.

                                                                   Multihoming





Multiple Streams



                                                                                                         Made By: P & V

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