1. Circuit Switched
The most typical circuit switching networks: telephone network
Circuit switched in three stages:
- Establishing a connection (call / circuit established)
- communication
- Releasable connection (circuit removal)
The characteristics of circuit switching is monopolizing resources .
Circuit-switched network using multiplexed shared trunk.
2. The message exchange
Message: The overall message is sent.
Packet switching: the entire one-time packets to the next node application.
Application: telegraph communication.
3. Packet Switched
Packet: A series of relatively small data packets out of the packet splitting.
Each small packet must add a header information.
Packet switching need message splitting and recombination , which results in additional overhead (header information including time and resource costs).
When the first intermediate router to forward a packet to the destination host at the same time, also the source host transmits the second packet to router, until all packets are sent to the destination host.
Uplink shared packet switching is not previously allocated, is random, depending on how much data the user sends, using DAMA, called a statistical multiplexing.
FIG link is shared users A and B, A more packet data transmission, the shared link bandwidth occupied more A, B at this time if no data is transmitted, then A link bandwidth is almost all occupied.
Packet switching and packet switching are used in storage - forward exchange.
Differences:
message switching to a full packet "store - forward."
Packet switching performed in small groups "store - forward"
Packet switching packet delivery time:
T = M/R+(h-1)L/R = M/R+nL/R
Packet transmission delay (delay) = L (bits) / R (bits / sec)
packets: M bits
link bandwidth (data transfer rate): R bps
packet length (size): L bits
number of hops: h
the number of routers : n
Circuit switched packet switched VS
Compared with the circuit switching, packet switching allows more users to simultaneously use the network, allows full sharing of network resources.
Packet-switched data transmission network in burst
- Full sharing of resources
- Simple, no call setup
Packet switched congestion may occur, i.e. packet loss and delay, reliable data transfer protocol processing required and congestion control.
