ITGD4103 Data Communications and Networks Lecture-2 Dr. Anwar Mousa University of Palestine Faculty of Information Technology

ITGD4103 Data Communications and Networks

Lecture-2

Dr. Anwar Mousa

University of PalestineFaculty of Information Technology

Dr. Anwar M. Mousa [email protected]

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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.


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Types of Networks

Point-to-Point Connection via:

Wires

Cables

Satellite

Microwave


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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.


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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)


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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.


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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


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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

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3

4

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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


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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


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Star Topology


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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


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Tree Topology

A variation of star


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Advantages Same as star. Increase the distance. Can isolate/group together sections of the

network. Disadvantages

Same as star. Example

Cable TV


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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).


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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.


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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.


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Advantages

Easy to install

Easy to cope

with fault

Disadvantages

Not robust


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Hybrid Topologies

Larger networks often combine several topologies connected via central hub.


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Classification of networks


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• 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.


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• 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.


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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.


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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


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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.


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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.


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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


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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.


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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.


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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.


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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.


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WANs to interconnect LANs


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(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.


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Internetworks

Network of networks Connection via

interconnecting devices

(Routers&Gateway) LANs and WANs are

connected together.


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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.


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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.

Documents

ITGD4103 Data Communications and Networks Lecture-2 Dr. Anwar Mousa University of Palestine Faculty of Information Technology