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

2 DATETOPICS Week 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][3] Textbook and Software Require textbook: “Data Communications and Networking,” Behrouz A. Forouzan, 4th ed, Mc-Graw Hill, Reference “Data and Computer Communications,” W. Stallings, 7th ed., Prentice Hall, 2004.

Dr. Anwar M. Mousa 4 Types of Networks  Point-to-Point  Connection via:  Wires  Cables  Satellite  Microwave

Dr. Anwar M. Mousa 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 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 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 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 9 Mesh Topology  Each device has a dedicated point-to-point link.  A fully connected mesh network with n devices has n(n-1)/

Dr. Anwar M. Mousa 10  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 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 12 Star Topology

Dr. Anwar M. Mousa 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 14 Tree Topology  A variation of star

Dr. Anwar M. Mousa 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 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 17  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 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 19  Advantages  Easy to install  Easy to cope with fault  Disadvantages  Not robust

Dr. Anwar M. Mousa 20 Hybrid Topologies  Larger networks often combine several topologies connected via central hub.

Dr. Anwar M. Mousa 21 Classification of networks

Dr. Anwar M. Mousa 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 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 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 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 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 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.

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Dr. Anwar M. Mousa 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 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.

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Dr. Anwar M. Mousa 32 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 33 Classification of networks: WAN 2.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 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 35 WANs to interconnect LANs

Dr. Anwar M. Mousa 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.

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Dr. Anwar M. Mousa 38 Internetworks  Network of networks  Connection via interconnecting devices (Routers&Gateway)  LANs and WANs are connected together.

Dr. Anwar M. Mousa 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 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.