1. By: M.Nadeem Akhtar1 Data Communication Ch 10

2. By: M.Nadeem Akhtar2 Networks?  LAN  MAN  WAN

3. By: M.Nadeem Akhtar3 Local Area Networks (LAN)  A local area network (LAN) is a group of computers and other devices (such as printers) that are connected together by a common medium.  LANs typically join computers that are physically close together, such as in the same room or building.  Only a limited number of computers and other devices can be connected on a single LAN.  The limitations vary based upon the medium connecting the computers and devices as well as upon the LAN software being used.

4. By: M.Nadeem Akhtar4 Local Area Networks (LAN)  As a general rule, a LAN will cover a total distance of only about one-half mile.  The distance between computers linked by the communications medium is typically at least two feet and no more than 60 feet.  These distances are only guidelines since the specifications imposed by the type of communications medium, the network interface card used, and the LAN software dictate actual distances.  The current transmission speed of data along a LAN generally runs from 10 Mbps to100 Mbps.

5. By: M.Nadeem Akhtar5 Metropolitan Area Networks (MAN)  A metropolitan area network (MAN) covers an area large enough to include a whole city or several small, contiguous cities.  The physical distance is roughly 30 miles.  The MAN came about as the need to link computers grew past the distance limits of LANs.  Linking several buildings of an organization, such as building on a campus, is the most common application of a MAN.  MANs use the topologies described for LANs as well as some protocols associated with wide area networks.  Common MANs transfer data at speeds of 100 Mbps because they frequently use fiber optics as the communications medium

6. By: M.Nadeem Akhtar6 Wide Area Networks  Wide area networks (WANs) are used to connect computers and other devices when the distances exceed constraints of LANs and MANs.  The public telephone system, or common carrier, is used for wide area networks.  The great disadvantage of using the public telephone system is the reduction in transmission speed. The speed limitations are due to protocols for telephone equipment.  Most data is currently transmitted on the public telephone system at between 9,600 bits per second (the speed at which fax machines operate) and 1 Mbps.  However, an advantage of wide area network is that, unlike LANs, multiple network protocols can be used over a single WAN.

7. By: M.Nadeem Akhtar7 LAN Topologies: LAN use one of the following physical layout designs. These designs are referred to as 'topologies  BUS TOPOLOGY  STAR TOPOLOGY  RING TOPOLOGY  TREE TOPOLOGY

8. By: M.Nadeem Akhtar8 BUS TOPOLOGY  For the bus, all stations attach, through appropriate hardware interfacing known as a tap, directly to a linear transmission medium, or bus.  Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received from the bus.  A transmission from any station propagates the length of the medium in both directions and can be received by all other stations.  At each end of the bus is a terminator, which absorbs any signal, removing it from the bus.

9. By: M.Nadeem Akhtar9 BUS TOPOLOGY

10. By: M.Nadeem Akhtar10 STAR NETWORK  In the star topology, each station is directly connected to a common central node/ hub.  Typically, each station attaches to a central node, referred to as the star coupler, via two point-to-point links, one for transmission and one for reception.  A transmission of a frame from one station to the node is retransmitted on all of the outgoing links.  In this case, although the arrangement is physically a star, it is logically a bus.  A transmission from any station is received by all other stations, and only one station at a time may successfully transmit.

11. By: M.Nadeem Akhtar11 STAR NETWORK

12. By: M.Nadeem Akhtar12 3-RING TOPOLOGY  In this the network consists of a set of repeaters joined by point-to point links in a closed loop.  The repeater is a comparatively simple device, capable of receiving data on one link and transmitting them, bit by bit, on the other link as fast as they are received, with no buffering at the repeater.  The links are unidirectional; that is, data are transmitted in one direction only and all are oriented in the same way. Thus, data circulate around the ring in one direction (clockwise or counterclockwise).  Each station attaches to the network at a repeater and can transmit data onto the network through that repeater.  A data frame circulates past all the other stations, the destination station recognizes its address and copies the frame into a local buffer as it goes by.  The frame continues to circulate until it returns to the source station, where it is removed.

13. By: M.Nadeem Akhtar13 RING TOPOLOGY

14. By: M.Nadeem Akhtar14 4-TREE TOPOLOGY  The tree topology is a generalization of the bus topology.  The transmission medium is a branching cable with no closed loops  The tree layout begins at a point known as the head end, where one or more cables start, and each of these may have branches.  The branches in turn may have additional branches to allow quite complex layouts.  Again, a transmission from any station propagates throughout the medium and can be received by all other stations.  Two problems present themselves in this arrangement.  First, because a transmission from any one station can be received by all other stations, there needs to be some way of indicating for whom the transmission is intended.  Second, a mechanism is needed to regulate transmission.

15. By: M.Nadeem Akhtar15 TREE TOPOLOGY

16. By: M.Nadeem Akhtar16 OSI reference Model In the 1980s, the European-dominated International Standards Organization (ISO), began to develop its Open Systems Interconnection (OSI) networking suite

17. By: M.Nadeem Akhtar17 OSI reference Model

18. By: M.Nadeem Akhtar18 OSI reference Model

19. By: M.Nadeem Akhtar19 OSI reference Model

20. By: M.Nadeem Akhtar20 OSI reference Model

21. By: M.Nadeem Akhtar21 OSI reference Model

22. By: M.Nadeem Akhtar22 Communications Hardware  Modem  Hub  Router  Switch

23. By: M.Nadeem Akhtar23 Modem  Modem: A hardware device that converts analog signals to digital signals and vice versa.  Data rates for various communications systems: –Telephone lines: 56 kbps –Cable modem: up to 2 Mbps –Local Area Networks: 10 to 100 Mbps

24. By: M.Nadeem Akhtar24

25. By: M.Nadeem Akhtar25 Hub  A hub is a device that receives a data packet from a computer at the end of one spoke of the star topology and copies the contents to all other devoices.  Hubs are not sophisticated/ intelligent communication equipment.  A device not physically connected to the hub via a wire can be excluded from the hub network.  Hubs are becoming more complicated. When the term hub is used in communications it generally refers to a passive device that simply copies and passes along data.  As vendors try to differentiate their product from others they have added features to the simple hub.  Hubs are also known as manageable hubs even they are capable of monitoring the data flowing through the hub

26. By: M.Nadeem Akhtar26 Router  A router is a device that connects many LANs.  This is the basis for establishing a wide area network.  An earlier, less sophisticated communications device was bridge, which simply connects two LANs.  Routers extend the communications management facility.  Unlike hubs that only disperse data to a connection port, routers can process the header information of a packet and determine to which LAN the data should be communicated.

27. By: M.Nadeem Akhtar27 Switch  Equipment that filters out data communications not destined for a computer on a particular network and performs routing control to the receiving computer is called switch.  Switches, like routers, are associated with wide area networks.  A switch can improve the communications transmission rates on a network by filtering out (disallowing) data communications to go down paths of a network that cannot contain the computer destination.  By limiting unnecessary data communications, more communication transmission capacity is made available for other communications.