Chapter 3. Wireless Networks and Wan Technologies 1398-2-24-14-59
Chapter 3. Wireless Networks and Wan Technologies 1398-2-24-14-59
Chapter 3. Wireless Networks and Wan Technologies 1398-2-24-14-59
WIRELESS NETWORK
AND
WAN TECHNOLOGIES
Wireless LAN?
• A wireless LAN or WLAN is a wireless local area
network that uses radio waves as its carrier.
• To give a network connection to all users in a
building or campus, the last link with the users
is wireless.
• The backbone network usually uses cables
Wireless-LAN
• A WLAN is a wireless computer network
that links two or more devices using a
wireless distribution method within a
limited area such as a home, school,
computer laboratory, or office building.
• This gives users the ability to move around
within a local coverage area and yet still be
connected to the network.
Wireless-LAN
• A WLAN can also provide a connection to the
wider Internet.
• Wireless LANs have become popular for use in
the home, due to their ease of installation and
use.
• They are also popular in commercial complexes
that offer wireless access to their customers
(often without charge).
Common Topologies
Physical Layer:
• The wireless NIC takes frames of data from the link layer,
scrambles the data in a predetermined way, then uses the
modified data stream to modulate a radio carrier signal.
Data Link Layer:
• Uses Carriers-Sense-Multiple-Access with Collision
Avoidance (CSMA/CA).
• CSMA/CA in computer networking, is a network multiple
access method in which carrier sensing is used, but nodes
attempt to avoid collisions by transmitting only when the
channel is sensed to be idle
Integration With Existing Networks
• Wireless Access Points (APs) - a small device that
bridges wireless traffic to your network.
• Access point is designed to broadcast a wireless
signal that computers can detect and "tune" into.
• Most access points bridge wireless LANs into
Ethernet networks
Integration With Existing Networks
Roaming
• Users maintain a continuous connection as they roam from
one physical area to another
• Mobile nodes automatically register with the new access
point.
• Methods: DHCP, Mobile IP
• Roaming refers to the ability for a cellular
customer to automatically make and
receive voice calls, send and receive data,
or access other services, including
home data services, when travelling
outside the geographical coverage area of the home network.
WLAN Security
• Handheld terminals
• Access points
Hardware
✓Point-to-Point
✓ISDN
✓ATM
✓Frame relay
✓DSL
✓X.25
Common WAN Terminology
• Dialup modem
• Access Server
• Broadband modem
• Router
• Core Router
Devices in WAN technology
CSU-Channel Service Unit/ DSU-Digital Service Unit
• A CSU/DSU is a digital-interface device(two
separate digital devices) that adapts the physical
interface on a data terminal equipment (DTE)
device to the interface of a data circuit-terminating
equipment (DCE) device in a switched-carrier
network.
• The CSU/DSU terminates the digital signals at
customer location.
• WAN Switch-
• a multiport internetworking device used in service provider
networks
Devices in WAN technology
Devices in WAN technology
• Circuit Switching
• a circuit switched network is one that establishes a
dedicated circuit or channel between nodes and terminals
before the users may communicate
• Circuit switching dynamically establishes a dedicated virtual
connection for voice or data between a sender and a
receiver
• Before communication can start, it is necessary to establish
the connection through the network of the service provider
• The two most common types of circuit switched networks
• The Public Switched Telephone Network (PSTN)
• The Integrated Service Digital Network (ISDN)
Circuit Switching
Devices in WAN technology
• Packet Switching
• Packet switching splits traffic data in to packets that are
routed over a shared network
• Packet switched network do not require a circuit to be
established
• The switched in packet switched network (PSN)
determine the links that packets must be sent over
based on the addressing information in each packet
• Two approaches in this link determination
• Connectionless system
• Connection oriented system
Packet Switching
Devices in WAN technology
• Packet Switching
• When the circuit is established temporarily while
a packet is travelling through it, and then breaks
down again, it is called a virtual circuit (VC)
• Because the internal links between the switches
are shared between many users, the cost of
packet switching network is lower than that of
circuit-switching network
WAN Technologies
✓Point-to-Point
✓ISDN
✓ATM
✓Frame relay
✓DSL
✓X.25
PPT-Point-to-Point Protocol
• A point-to-point link provides a pre-established WAN
communications path from the customer sites through
the provider network to a remote destination.
• Point-to-point lines are usually leased from a carrier and
are called leased lines because its established path is
permanent and fixed for each remote network reached
through the carrier facilities
• PPT is commonly used as a layer 2 protocol on dedicated
Leased lines.
• Leased lines provide direct point-to-point connections
between enterprise LANs and connect individual
branches to a packet-switched network.
ISDN-Integrated Services Digital Network
• ISDN is a set of communication standards for
simultaneous digital transmission of voice, video,
data, and other network services over the
traditional circuits of the public switched telephone
network (PSTN).
• Prior to ISDN, the telephone system was viewed as
a way to transport voice, with some special services
available for data.
• The key feature of ISDN is that it integrates speech
and data on the same lines, adding features that
were not available in the classic telephone system.
Integrated Services Digital Network