ITGD4103 Data Communications and Networks Lecture-2 Dr. Anwar Mousa University of Palestine Faculty...
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ITGD4103 Data Communications and Networks
Lecture-2
Dr. Anwar Mousa
University of PalestineFaculty of Information Technology
Dr. Anwar M. Mousa [email protected]
2
DATE TOPICSWeek 1 Course introduction-Data Communications
Week 2 network models
Week 3 Data and signals
Week 4 Data Transmission Techniques
Week 5 Digital and Analog Signals
Week 6 Bandwidth Utilization and multiplexing
Week 7 Transmission Media
Week 8 Mid-Term Exam
Week 9 Wired LANs: Ethernet
Week 10 Wireless LANs
Week 11 Wireless WANs
Week 12 SONET/SDH
Week 13 Frame Relay
Week 14 ATM
Week 15 Switching
Week 16 FINAL EXAM
EE 541/451 Fall 2006 [3]
Textbook and SoftwareTextbook and Software
Require textbook: “Data Communications and Networking,” Behrouz A. Forouzan, 4th ed,
Mc-Graw Hill, 2007.
Reference“Data and Computer Communications,” W. Stallings, 7th ed., Prentice Hall,
2004.
Dr. Anwar M. Mousa [email protected]
4
Types of Networks
Point-to-Point Connection via:
Wires
Cables
Satellite
Microwave
Dr. Anwar M. Mousa [email protected]
5
Point-to-Point Network
Point-to-point connections provides a dedicated link between two devices.
Each device can communicate only with those that are directly connected to it.
To communicate with other computers not directly connected they must do so via intermediate nodes.
Dr. Anwar M. Mousa [email protected]
6
Types of Networks Multi-point
Spatially shared: several devices can use the link
simultaneously.
Timeshared: users must take turn
1. one-to-many (broadcast)
2. many-to-many (multipoint)
3. many-to-one (client/server)
Dr. Anwar M. Mousa [email protected]
7
Multipoint Network In multipoint networks many devices share a single
link or communication medium.
All nodes must “fight” for their turn to speak
(connection) or wait to be granted a turn.
Dr. Anwar M. Mousa [email protected]
8
Topology
The way a network is physically or logically layout. Two or more devices connected to a Link.
Two or more links form a Topology.
Basic Topologies: Mesh Star Bus Tree Ring Hybrid
Dr. Anwar M. Mousa [email protected]
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Mesh Topology
Each device has a dedicated point-to-point link. A fully connected mesh network with n devices
has n(n-1)/21
2
3
4
5
Dr. Anwar M. Mousa [email protected]
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Advantages High throughput Robust High Security Simple fault identification and isolation
Disadvantages Number of cables –space &cost (material,install). Number of I/O ports. Difficult to reconfigure.
Usage Backbone connecting
Dr. Anwar M. Mousa [email protected]
11
Star Topology
Each device has a dedicated point-to-point link to a central controller (Hub)
The hub controls all traffic by switching individual devices in or out.
• A star configuration is not only used to interconnect workstations on a LAN. It is also used to interconnect LANs via an exchange or switch,
• however, emerging asynchronous transfer mode (ATM) technology (and other high-speed networks) may make the use of star configurations a more common occurrence
Dr. Anwar M. Mousa [email protected]
13
Advantages Less expensive (cable)than Mesh One I/O port Easy to install and reconfigure. Robust Easy to cope with fault.
Disadvantages More cabling used than for other topologies Hub failure disables entire network
Usage Ethernet
Dr. Anwar M. Mousa [email protected]
15
Advantages Same as star. Increase the distance. Can isolate/group together sections of the
network. Disadvantages
Same as star. Example
Cable TV
Dr. Anwar M. Mousa [email protected]
16
Bus Topology
Consists of series of computers connected along a single cable segment
Each node connects to the Bus (a long cable running as a backbone).
Dr. Anwar M. Mousa [email protected]
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Advantages Easy to install. Less cable compare to other topologies. Failure of any device does not shut network down.
Disadvantages Limited backbone length. Backbone failure causes complete network failure. Fault isolation difficult.
Dr. Anwar M. Mousa [email protected]
18
Ring Topology
Each device has a dedicated point-to-point with its neighbors.
Eliminating switching by routing all traffic in a circle from device to device.
The cable is connected to form a closed loop Signals passed in one direction.
Dr. Anwar M. Mousa [email protected]
19
Advantages
Easy to install
Easy to cope
with fault
Disadvantages
Not robust
Dr. Anwar M. Mousa [email protected]
20
Hybrid Topologies
Larger networks often combine several topologies connected via central hub.
Dr. Anwar M. Mousa [email protected]
22
Classification of networks
• Communication networks are usually defined by their size and complexity. We can distinguish three main types:
• Local area networks (LAN). These networks connect computer equipment and other terminals distributed in a localised area,– e.g. a university campus, factory, office. The connection is
usually a cable or fibre, and the extent of the cable defines the LAN.
Dr. Anwar M. Mousa [email protected]
23
Classification of networks
• Metropolitan area networks (MAN). These networks are used to interconnect LANs that are spread around, say, a town or city. This kind of network is a high speed network using optical fibre connections.
• Wide area networks (WAN). These networks connect computers and other terminals over large distances. They often require multiple communication connections, including microwave radio links and satellite.
Dr. Anwar M. Mousa [email protected]
24
Classification of networks: LAN• LANs may have a number of different physical
configurations,– i.e. the manner in which workstations on the LAN are
physically connected. • The physical configuration will often reflect the media access
control (MAC) method used to allow the workstation to gain access to the connection media.
• Most LANs are shared medium networks,– i.e. there is effectively one link between all the
workstations on the LAN and each must wait its turn for the use of the media.
Dr. Anwar M. Mousa [email protected]
25
Classification of networks: LAN• There are various methods of controlling how and when a
workstation gets its turn to use the media,
– e.g. carrier sense multiple access with collision detect (CSMA/CD).
– .One of the most popular configurations is the bus arrangement for example Ethernet
Dr. Anwar M. Mousa [email protected]
26
Local Area Network (LAN)
LANs mainly designed for computers to share
resources such as printers, scanners,etc.
A LAN will generally use only a single type of
transmission medium.
Topologies: bus, star, or ring.
Data rates range from 10 Mbps to 100 Mbps.
Usually privately owned &operated.
Dr. Anwar M. Mousa [email protected]
27
Backbone Networks
A larger,central network connecting several LANs.
Typically span up to several Km.
Typically data rates from 64 Kbps to 45 Mbps.
Usually privately owned & operated.
Dr. Anwar M. Mousa [email protected]
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Dr. Anwar M. Mousa [email protected]
29
Backbone interconnecting LAN segments
• LAN segments may be interconnected by use of a backbone LAN that allows communication between the segments. The segments help to localise traffic, e.g. within an office or a single floor in a building. Each segment is a LAN in itself, but is connected to the backbone via a bridge
Dr. Anwar M. Mousa [email protected]
30
Metropolitan Area Network (MAN)
Extend over an entire city (5 –50 Kms). Mainly used for interconnecting private LANs.
located at different areas to each other. Normally owned and operated by someone else.
An independent or government service provider.
Dr. Anwar M. Mousa [email protected]
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Dr. Anwar M. Mousa [email protected]
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Wide Area Network: WAN• WANs often exploit public networks such as the
public telephone system
• There are two types of public network: 1. Public switched telephone network (PSTN).
– This is the ordinary telephone system. This system exists in all countries of the world. It was designed specifically for the transmission of voice communication. Digital systems employing this network must produce a "voice-like" signal, and accept the low transmission rates.
Dr. Anwar M. Mousa [email protected]
33
Classification of networks: WAN2. Public switched data network (PSDN).
• This is a public network designed specifically for the transmission of digital data.
• They arose from privately owned WANs that required higher performance than the PSTN.
• Many countries of the world are introducing PSDN services.
• They can support much higher transmission rates.
Dr. Anwar M. Mousa [email protected]
34
Classification of networks: WAN• An integrated services digital network (ISDN) is the term
given to all-digital networks that can carry simultaneously voice and data communication,
• and offer additionally a variety of teletex services. ISDN services are being introduced all round the world.
Dr. Anwar M. Mousa [email protected]
36
(WAN characteristics)
Extend over a large geographical area.
(entire country,continent or globe).
Make use of public carrier transmission media such as Leased line.
Public switched data network (PSDN)/(ISDN)
WANs that are wholly operated by a single company
sometimes referred as an enterprise network.
Dr. Anwar M. Mousa [email protected]
37
Dr. Anwar M. Mousa [email protected]
38
Internetworks
Network of networks Connection via
interconnecting devices
(Routers&Gateway) LANs and WANs are
connected together.
Dr. Anwar M. Mousa [email protected]
39
Types of switching
• Switching describes the method by which the corresponders are connected.
• Public networks employ two types of switching.
1. A circuit switched network (CSN)
– establishes a connection through the network that is then used exclusively by the two correspondents.
– The PSTN is a circuit switched network.
Dr. Anwar M. Mousa [email protected]
40
Types of switching
2. A packet switched network (PSN)
– divides the message into packets, that are addressed to the recipient.
– The packets are then forwarded through the network, together with many other packets.
– The outstanding advantage of the PSN is that the two correspondents can communicate at different rates, permitting much more efficient use of the communication channel.