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 :
- Datagram
- 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.