8.1
Chapter 8
Switching
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Switching-Data Communication and Computer Networks-Lecture Slides, Slides of Data Communication Systems and Computer Networks
These are a set of Lecture Slides on the subject of Data Communication and Computer Networks at Univeristy of Delhi by Dr. Sonam Zinta. It includes: Switching, Link, Channels, Efficiency, Delay, Circuit-Switched, Phases, Routing, Table
Typology: Slides
2011/2012
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Chapter 8
Switching
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Figure 8.1 Switched network
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8-1 CIRCUIT-SWITCHED NETWORKS
A circuit-switched network consists of a set of switches connected by physical links. A connection between two stations is a dedicated path made of one or more links. However, each connection uses only one dedicated channel on each link. Each link is normally divided into n channels by using FDM or TDM.
Three Phases Efficiency Delay Circuit-Switched Technology in Telephone Networks
Topics discussed in this section:
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A circuit-switched network is made of a
set of switches connected by physical
links, in which each link is
divided into n channels.
Note
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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.
Note
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As a trivial example, let us use a circuit-switched network to connect eight telephones in a small area. Communication is through 4-kHz voice channels. We assume that each link uses FDM to connect a maximum of two voice channels. The bandwidth of each link is then 8 kHz. Figure 8.4 shows the situation. Telephone 1 is connected to telephone 7; 2 to 5; 3 to 8; and 4 to 6. Of course the situation may change when new connections are made. The switch controls the connections.
Example 8.
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As another example, consider a circuit-switched network that connects computers in two remote offices of a private company. The offices are connected using a T-1 line leased from a communication service provider. There are two 4 × 8 (4 inputs and 8 outputs) switches in this network. For each switch, four output ports are folded into the input ports to allow communication between computers in the same office. Four other output ports allow communication between the two offices. Figure 8. shows the situation.
Example 8.
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Figure 8.5 Circuit-switched network used in Example 8.
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Switching at the physical layer in the
traditional telephone network uses
the circuit-switching approach.
Note
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8-2 DATAGRAM NETWORKS
In data communications, we need to send messages from one end system to another. If the message is going to pass through a packet-switched network, it needs to be divided into packets of fixed or variable size. The size of the packet is determined by the network and the governing protocol.
Routing Table Efficiency Delay Datagram Networks in the Internet
Topics discussed in this section:
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Figure 8.7 A datagram network with four switches (routers)
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Figure 8.8 Routing table in a datagram network
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The destination address in the header of
a packet in a datagram network
remains the same during the entire
journey of the packet.
Note
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Figure 8.9 Delay in a datagram network
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