This document discusses different types of communication networks including LANs, MANs, and WANs. It then describes two main switching techniques - circuit switching and packet switching. Circuit switching involves establishing a dedicated communication path between two stations, while packet switching involves breaking messages into packets that are transmitted independently and reassembled at the destination. The document provides details on how each switching technique works.

1. Er. Jay Nagar
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Communication Networks
www.jaynagarblog.wordpress.com

2. Outline
 LANs, MANs, and WANs.
 Switching Techniques
 Circuit Switching.
 Packet Switching.

3. LANs, MANs, and WANs.
 Local area networks (LANs)
 Metropolitan area networks (MANs)
 Wide area networks (WANs) are all examples of
communications networks.

4. Wide Area Networks
 WANs cover a large geographical area.
 WAN consists of a number of interconnected switching
nodes. A transmission from anyone device is routed
through these internal nodes to the specified destination
device.
 Data rates of 64,000 bps or less have been common.
 Optical fiber facilities has led to the standardization of
much higher data rates for WANs.
 These high-speed WANs provide user connections in the
10s and 100s of Mbps, using a transmission technique
known asynchronous transfer mode (ATM).

5. Local Area Networks

6. Metropolitan area networks
 As the name suggests, a MAN occupies a middle ground
between LANs and WANs.
 The primary market for MANs is the customer that has
high-capacity needs in a metropolitan area.
 A MAN is intended to provide the required capacity at
lower cost and greater efficiency than obtaining an
equivalent service from the local telephone company.

7. Switching Techniques
 For transmission of data beyond a local area,
communication is typically achieved by transmitting data
from source to destination through a network of
intermediate switching nodes.
 We will refer to the switching devices whose purpose is to
provide communication as nodes.
 The nodes are connected to each other in some topology by
transmission links.
 Each station attaches to a node, and the collection of nodes
is referred to as a communication network.

8. Switching Techniques

9. Switching Techniques
 Two quite different technologies are used in wide
area switched networks: circuit switching and
packet switching.
 These two technologies differ in the way the nodes
switch information from one link to another on the
way from source to destination.

10. Circuit switching
 Circuit switching has been the dominant technology for
both voice and data communications.
 Communication via circuit switching implies that there is a
dedicated communication path between two
stations.
 The most common example of circuit switching is the
telephone network.
 Circuit switching involves three phases.
1. Circuit establishment.
2. Information transfer.
3. Circuit disconnect.

11. Circuit switching - Circuit
establishment.
 Circuit switching was developed to handle voice traffic but is now
also used for data traffic. The best-known example of a circuit-
switching network is the public telephone network.
 A public telecommunications network can be described using
four generic architectural components:
1. Subscribers: The devices that attach to the network.
2. Subscriber line: The link between the subscriber and the
network, also referred to as the local loop.
3. Exchanges: The switching centers in the network. A switching
center that directly supports subscribers is known as an end
office.
4. Thunks: The branches between exchanges. Trunks carry
multiple voice-frequency circuits using either FDM or
synchronous TDM

12. Packet Switching
 A key characteristic of circuit-switching networks is that
resources within the network are dedicated to a particular
call. For voice connections, the resulting circuit will enjoy a
high percentage of utilization since, most of the time, one
party or the other is talking. two shortcomings became
apparent:
1. In a typical terminal-to-host data connection, much of the
time the line is idle.
2. In a circuit-switching network, the connection provides
for transmission at a constant data rate. Thus each of the
two devices that are connected must transmit and receive
at the same data rate as the other,

13. Packet Switching
 Summarize packet-switching operation.
 The control information, at a minimum, includes the
information that the network requires in order to be able to
route the packet through the network and deliver it to the
intended destination.
 At each node en route, the packet is received, stored briefly,
and passed on to the next node.

14. Packet Switching

15. Packet-switching advantages
 Line efficiency is greater, since a single node-to-node link
can be dynamically shared by many packets over time.
 A packet-switching network can carry out data-rate
conversion. Two stations of different data rates can
exchange packets, since each connects to its node at its
proper data rate.
 When traffic becomes heavy on a circuit-switching network,
some calls are blocked; On a packet-switching network,
packets are still accepted, but delivery delay increases.
 Priorities can be used. Thus, if a node has a number of
packets queued for transmission, it can transmit the
higher-priority packets first.