Week_2_Class_1,2.pdf

Wide Area Networks (WANs) Wide Area Networks (WANs) Long distances Provide connectivity over large areas Wider geographical span than a LAN Spans a city, state, country or even world. Interconnects connecting devices such a switches,...

Wide Area Networks (WANs) Wide Area Networks (WANs) Long distances Provide connectivity over large areas Wider geographical span than a LAN Spans a city, state, country or even world. Interconnects connecting devices such a switches, routers or modems. Normally created and run by communication companies. Three types of WAN 1.1  WANs: a switched WAN and a point-to-point WAN 1.2  A heterogeneous network made of four WANs and two LANs 1.3 Transmission Mode The term transmission mode is used to define the direction of signal flow between two linked devices. Or The way in which data is transmitted from one device to another device is known as transmission mode. Types of Transmission Mode The Transmission mode is divided into three categories: Simplex Mode In simplex mode the communication is unidirectional as a one-way street. Only one of the two stations on a link can transmit the other can only receive. Radio, TV. Half-duplex Mode In half duplex mode, both station can transmit and receive but not at the same time. When one device is sending the other can only receive. wakitaki. Full-duplex Mode In full-duplex mode (also called duplex), both stations can transmit and receive simultaneously. Telephone.  Connecting Devices Hosts and networks do not normally operate in isolation. Connecting devices connect hosts together to make a network or connect networks together to make an internet. Connecting devices can operate in different layers of the Internet model. 7.9 Networking Devices Repeaters Hubs Switches Bridges Routers The purposes of having devices 1. They allow a greater number of nodes to be connected to the network. 2. They extend the distance over which a network can extend. 3. They localize traffic on the network. 4. They can merge existing networks. 5. They isolate network problems so that they can be diagnosed more easily. What internetworking devices operate at the physical layer (layer 1) of the OSI model? A repeater can provide a simple solution if either of these two problems exists. When signals first leave a transmitting station, they are clean and easily recognizable. However, the longer the cable length, the weaker and more deteriorated the signals become as they pass along the networking media. Location of Repeater Hub Hub is a Multi-port device. Hubs are very common internetworking devices. Hub device that serves as the center of a star topology network. Hub is not an intelligent device. A hub (repeater) receives a signal, before it becomes too weak, regenerates it. Hub is a device that operates only in the physical layer.  Hubs 7.17  Hubs 7.18  Link-Layer Switches A link-layer switch (or switch) operates in both the physical and the data-link layers As a physical-layer device, it regenerates the signal it receives As a link-layer device, the link-layer switch can check the MAC addresses (source and destination) contained in the frame 7.19  Link-Layer Switches Switch has the ‘Filtering’ capability Unlike hub, a switch can check the destination address of a frame and decide on outgoing port Switches connect heterogeneous devices 7.20  Link-Layer Switches 7.21  Learning Switch 7.22 Bridge Device that connects and passes packets between two network segments. More intelligent than hub – analyze incoming packets and forwards based on addressing information. How many types of Bridges? Describe the types and working of the bridges. At what layer of the OSI model do bridges operate? Because bridges operate at the data link layer, layer 2, they are not required to examine upper-layer information. How do bridges filter network traffic? How are bridge data-forwarding decisions limited? Although bridges use tables to determine whether or not to forward data to other segments of the network, the types of comparisons and decisions they make are relatively low level, simple ones. What types of network traffic problems is a bridge incapable of solving? Bridges work best where traffic from one segment of a network to other segments is not too great. However, when traffic between network segments becomes too heavy, the bridge can become a bottleneck and actually slow down communication. How many addressing schemes are there in networking? First on is the MAC address. The second addressing scheme in networking makes use of what is called the IP address. How do IP addresses differ from MAC addresses? Like MAC addresses, every IP address is unique. No two IP addresses are ever alike. However, while MAC addresses are physical addresses that are actually hard-coded into the NIC card and occur at the data link layer IP addresses are implemented in software and occur at the network layer of the OSI model. What are routers? Routers are another type of internetworking device. These devices pass data packets between networks based on network protocol or layer 3 information. Routers can make intelligent decisions as to the best path for data delivery on the network. What network problems can routers help resolve? The problem of excessive broadcast traffic can be solved by using a router. Routers are able to do this, because they do not forward broadcast frames unless specifically told to do so How do routers differ from bridges? Routers differ from bridges in several respects. 1. Bridging occurs at the data link layer or layer 2,while routing occurs at the network layer or layer 3 of the OSI model. 2. Bridges use physical or MAC addresses to make data forwarding decisions. Routers use a different addressing scheme that occurs at layer three How do routers work? Routers are used to connect two or more networks. For routing to be successful, each network must have a unique network number The port where a router connects to network A would have an IP address of A5. The IP address of the router's second interface would be B5.  Router vs. Switch Three differences between a router and a repeater or a switch: 1.A router has a physical and logical (IP) address for each of its interfaces. 2.A router acts only on those packets in which the link-layer destination address matches the address of the interface at which the packet arrives. 3.A router changes the link-layer address of the packet (both source and destination) when it forwards the packet. 7.52  Redundant Network? Network redundancy is a duplicated infrastructure where additional or alternate instances of network devices and connections are installed. 7.53 7.54  Loop Problem in a Switch Redundant switches create Loops in the system Created when two or more broadcasting LANs are connected by more than one switch 7.55  Loop Problem in a learning Switch (Part a) 7.56  Loop Problem in a learning Switch (Part b) 7.57  Loop Problem in a learning Switch (Part c) 7.58  Loop Problem in a learning Switch (Part d) 7.59  Assignment # 1 What is the method to overcome loop problem in Switch? Implement the solution in any programming language (as per your choice). Write down the proposed algorithm/method Pseudo code (step by step). 7.60  Transmission Media 7.61  Transmission medium and physical layer 7.62  Figure 7.2 Classes of transmission media 7.63  GUIDED MEDIA Guided media, which are those that provide a conduit from one device to another, include twisted-pair cable, coaxial cable, and fiber-optic cable. Signal traveling along any of these media is directed and contained by the physical limits of the medium 7.64  Twisted-pair cable Consists of 2 copper conductors, each with its own plastic insulation, twisted together One wire carries signals and other is ground reference Receiver uses difference between the two Interference (Noise) & Crosstalk 7.65  Twisted-pair cable 7.66  UTP and STP cables Unshielded vs. Shielded Twisted Pair Cable 7.67  Categories of unshielded twisted-pair cables 7.68  UTP connector (RJ45-Registered Jack) 7.69  Figure Coaxial cable Carries signals of higher frequency ranges than those in twisted pair cable 7.70  Table 7.2 Categories of coaxial cables (RG-Radio Guide) 7.71  Figure BNC (Bayonet Nut Coupling) connectors 7.72  Fiber optics Made of glass or plastic and transmits signals in the form of light Light travels in a straight line as long as it is moving through a single uniform substance If a ray of light traveling through one substance suddenly enters another substance (of a different density), the ray changes direction 7.73  Bending of light ray 7.74  Optical fiber 7.75  Propagation modes 7.76  Modes 7.77  Fiber construction 7.78  Fiber-optic cable connectors 7.79  Advantages & Disadvantages of Fiber Higher Bandwidth Less Attenuation Less EM Interference Light Weight Installation/Maintenance Unidirectional Cost 7.80  7-2 UNGUIDED MEDIA: WIRELESS Unguided media transport electromagnetic waves without using a physical conductor. This type of communication is often referred to as wireless communication. Signals are normally broadcast through free space and thus are available to anyone who has a device capable of receiving them 7.81  Figure Electromagnetic spectrum for wireless communication 7.82  Figure Propagation methods The ionosphere is a shell of electrons and electrically charged atoms and molecules that surrounds the Earth 7.83  Table 7.4 Bands 7.84  Figure 7.19 Wireless transmission waves 7.85