Packet Switching

Packet Switching

  • In packet switching messages are divided into smaller piece called PACKET
  • Each packet includes source and destination address information so that individual packets can be routed through the internetworks independently.
  • The packet that makes up a message can take very different routs through the internetworks.
  • Packet Switching looks concededly like messages switching but the different characteristic is that packets are restricted is that packets to a size that enables the switching device to manage the packet. The packet data entirely in memory.
  • This eliminates the need for switching device to store the data temporary on disc.
  • Packet switching routes packets through the networks much more rapidly and efficiently then is possible with messages switching.

Two Common methods of packets as follow :

  1. Datagram
  2. Virtual Circuits

1. Datagram

  • It service treat each packets as an independently message.
  • Each packet is routed through the internetworks independently and each switch mode determines which network segment should be used for the next step in packets rout.
  • This capability enables switches to bypass busy segment and take other step to speed packets through the internetworks.
  • Datagram is frequency used on LAN's (Local Area Network).
  • Network layer protocols are responsible for delivering the frame to the appropriate networks.
  • Each datagram include destination address information device on the local network can recognize and receive appropriate datagram.
  • Packet switching needs the need to transmit large message with the small frame size that can be accommodate by the physical layer.
  • The network layer is responsible for fragmenting messages from upper layer into smaller datagram that are appropriate for physical layer.
  • The network layer is also responsible for reconstruction messages from datagrams as they are received.

2. Virtual Circuits  

  • It's operate by established by formal connection between two devices in communication.
  • When devices begin a season they negotiate communication parameters such as maximum messages size, communication window and network path.
  • This negotiation established virtual circuits which are a well define pat through the internetworks by which the device communicate.
  • This virtual circuits remains in effect until the devices stop communicating.
  • Virtual circuits are define by the establishment of a logical connection
  • Virtual means that the network behaves as through a dedicated physical circuits has been established between the communication device.

Even through no such physical circuits actually exists the network presents the appearance of a physical connections to the devices at the end of the circuits.