Wide Area Network
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What is a WAN?
• A wide area network (WAN ) is a data
communications network that covers a
relatively broad geographic area and that
often uses transmission facilities provided
by common carriers, such as telephone
companies.
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LANs and WANs
LAN
• A LAN connects
computers, peripherals,
and other devices in a
single building or other
small geographic area.
• LANs typically are owned
by the company or
organization that uses
them.
WAN
• A WAN allows the
transmission of data
across greater
geographic distances.
• An enterprise must
subscribe to a WAN
service provider to use
WAN carrier network
services.
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WAN
• Here are the three major characteristics of WANs:
– WANs generally connect devices that are separated
by a broader geographic area than can be served by
a LAN.
– WANs use the services of carriers, such as telephone
companies, cable companies, satellite systems, and
network providers.
– WANs use serial connections of various types to
provide access to bandwidth over large geographic
areas.
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WAN Users
• WANs are used to connect local area networks
(LANs) together, so that users and computers in
one location can communicate with users and
computers in other locations.
• Many WANs are private that uses either
dedicated or switched communication link.
• Others are public that use the global Internet
infrastructure.
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WAN and OSI
• WAN technologies generally function at
the lower three layers of the OSI
reference model: the physical layer, the
data link layer, and the network layer.
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How to Build a WAN?
• WANs are most often built using leased
lines. At each end of the leased line, a
router connects to the LAN on one side
and a hub within the WAN on the other.
• A set of switches and routers are
interconnected to form a Wide Area
Network. The switches can be connected
in different topologies such as full mesh
and half mesh.
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Internet
WAN
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1- Dedicated (Point-to-Point)
Connection
• A point-to-point link provides a single, pre-established
WAN communications path from the customer premises
through a carrier network to a remote network (It is a
permanent full time connection).
• Point-to-point lines are usually leased from a carrier and
thus are often called leased lines.
• For a point-to-point line, the carrier allocates pairs of wire
and facility hardware to this user only.
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1- Dedicated (Point-to-Point)
Connection
• These circuits are generally priced based
on bandwidth required and distance
between the two connected points.
Advantage:
Line is always reserved for the user
Disadvantage:
Expensive
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2- Switched Network
• Switched network - Several users share
the same line or the bandwidth of the line.
There are two types of switched networks:
– Circuit switching
– Packet switching
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2.1 - Circuit Switching
• Circuit Switching allows data connections to be
established when needed and then terminated when
communication is complete.
• This works like a normal telephone line works for voice
communication.
• When a router has data for a remote site, the switched
circuit is initiated.
• When the two networks are connected and
authenticated, they can transfer data.
• When the data transmission is complete, the call can be
terminated.
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2.1 - Circuit Switching
• Cost is determined by the connection time.
• Examples: ISDN
Advantage:
Cheap
Disadvantage:
• Network is reserved for the connection even if no data is
sent.
• Any failure in circuits will stop the connection, and
require another call to reserve a new circuits.
• Some times you wait until network is ready.
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2.2 - Packet Switching
• Many WAN users do not make efficient use of the fixed
bandwidth that is available with dedicated or switched
circuits, because the data flow fluctuates.
• Packet switching is a WAN technology in which users
share common carrier resources.
• It splits traffic data into packets that are routed over a
shared network.
• Packet-switching networks do not require a circuit to be
established, and they allow many pairs of nodes to
communicate over the same channel
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2.2 - Packet Switching
• Because this allows the carrier to make more efficient
use of its infrastructure, the cost to the customer is
generally much better than with point-to-point lines.
• Examples of packet switching technologies:
X.25, ATM, Frame relay
Advantages:
– Fast, but slower than circuit switching.
– Cheap
– Connection is always there , due to many paths that data can move
through
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3- Public WAN connection
• Public connections use the global Internet
infrastructure.
• Until recently, the Internet was not a viable
networking option for many businesses because of
the significant security risks and lack of adequate
performance guarantees in an end-to-end Internet
connection.
• However, with the development of Virtual private
network (VPN) technology, the Internet is become
an inexpensive and secure option for connecting.
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Virtual private network (VPN)
• Is a technology widely used in a public
network to provide private and secured
WAN for an organization.
• VPN uses encryption and other techniques
to make it appear that the organization has
a dedicated network, while making use of
the shared infrastructure of the WAN.
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