A switched network consists of nodes called switches that are capable of creating temporary connections between devices linked to the switch. End systems like computers and phones are directly connected to switches, while other switches are used for routing. A circuit-switched network divides links into channels and requires resources to be reserved during setup, remaining dedicated for the duration of the data transfer until teardown. It has three phases: setup to create dedicated channels between switches, data transfer using the dedicated circuit, and teardown when a party sends a signal to release the resources.

2. switching
A switched network consists of a series of interlinked
nodes, called switches. Switches are devices capable of
creating temporary connections
between two or more devices linked to the switch. In a
switched network, some of these
nodes are connected to the end systems (computers or
telephones, for example). The end systems, such as
computers or telephones, are directly connected to a
Switch
Others
are used only for routing. Figure 8.1 shows a switched
network

3. Figure 8.1 Switched network

4. Figure 8.2 Taxonomy ofswitched networks

5. 8.1 CIRCUIT-SWITCHED NETWORKS
A circuit-switched network is made of a set of
switches connected by physical links,
in which each link is divided into n channels.

6. Figure 8.3 A trivial circuit-switched network

7. note
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

8. Figure 8.4 Circuit-switched network used in
Example 8.1

9. Three Phases
•Setup Phase
•Data Transfer Phase
•Teardown Phase

10. Setup phase
connection setup
means creating dedicated channels
between the switches.

11. Data Transfer Phase
After the establishment of the dedicated
circuit (channels), the two parties can
transfer data
Teardown Phase
When one of the parties needs to
disconnect, a signal is sent to each switch to
release
the resources