A circuit-switched network is made of a set of switches connected by physical links, in which each link is divided into n channels.
In circuit switching, the resources need to be reserved during the setup phase; the resources remain dedicated for the entire duration of data transfer until the teardown phase.
Three Phases
The actual communication in a circuit-switched network requires three phases:
Connection Setup, data transfer, and connection teardown.
Efficiency
Not efficient as other two types of network because resources are allocated during the entire duration of the connection.
Delay
Low efficiency, the delay is minimal
In a packet-switched network, there is no resource reservation;
resources are allocated on demand.
Data transmitted in a short packets (few kbytes)
A longer message is broken up in a series of packets
Every packet contains some control information in its header (required for routing and some other purposes)
As mentioned earlier, packet switching networks breaks up a message into packets
Two approaches are commonly used for handling theses packets:
Virtual circuit
datagram
Virtual Circuit Approach
A preplanned route is established before any packets are sent
Call Request and Call Accept packets are used to establish the connection
Route is fixed for the duration of the logical connection (like circuit switching)
Each packet contains a virtual circuit identifier as well as data
Each node on the route knows where to forward the packets
A Clear Request packet issued by one of the two stations terminates the connection
DATAGRAM:
Each packet is treated independently, with no reference to packets that have gone before
Every intermediate node has to take routing decision
Every packet contains source and destination addresses
Intermediate nodes maintains routing tables Each packet treated independently
Packets can take any practical route
Packets may arrive out of order
Packets may go missing
Up to receiver to re-order packets and recover from missing packets
In circuit switching, the resources need to be reserved during the setup phase; the resources remain dedicated for the entire duration of data transfer until the teardown phase.
Three Phases
The actual communication in a circuit-switched network requires three phases:
Connection Setup, data transfer, and connection teardown.
Efficiency
Not efficient as other two types of network because resources are allocated during the entire duration of the connection.
Delay
Low efficiency, the delay is minimal
In a packet-switched network, there is no resource reservation;
resources are allocated on demand.
Data transmitted in a short packets (few kbytes)
A longer message is broken up in a series of packets
Every packet contains some control information in its header (required for routing and some other purposes)
As mentioned earlier, packet switching networks breaks up a message into packets
Two approaches are commonly used for handling theses packets:
Virtual circuit
datagram
Virtual Circuit Approach
A preplanned route is established before any packets are sent
Call Request and Call Accept packets are used to establish the connection
Route is fixed for the duration of the logical connection (like circuit switching)
Each packet contains a virtual circuit identifier as well as data
Each node on the route knows where to forward the packets
A Clear Request packet issued by one of the two stations terminates the connection
DATAGRAM:
Each packet is treated independently, with no reference to packets that have gone before
Every intermediate node has to take routing decision
Every packet contains source and destination addresses
Intermediate nodes maintains routing tables Each packet treated independently
Packets can take any practical route
Packets may arrive out of order
Packets may go missing
Up to receiver to re-order packets and recover from missing packets
