1. Explain different network devices in detail. Or Explain NIC (Network Interface Card) in detail. Network interface cards are add on cards as hardware cards on the motherboard. This is additional hardware card require to install physically in to the slot on the motherboard. This type of card consists of different types of network ports, to communicate with other machine (node) and server. NIC is small printed circuit board that is installed in mother board of CPU. This card provides the connectivity between computer internal system resources and external resources connected to the network. Each NIC has a unique address (physical address) that differentiates from any other NIC. NIC consists of different types of network ports to communicate with other device or server. Backside of NIC card, it contains a physical interface for a specific connector type. Each connector type is designed for specific transmission media. Types of NIC : Basically there are two types of NIC: 1. ARCNET Card 2. ETHERNET Card ARCNET Card : This card consists of eight Dual Inline Package (DIP) Switches. These switches are used for defining address of nodes. If all switches are off then address is 00H and if the all are on then the address is FFH. Thus we can connect 256 nodes with it. It supports MCA (Micro Channel Architectural) Bus. The cable used with ARCNET card is Co-axial usually it is RG-62. The maximum length of the cable used is 20,000ft [6680mt]; i.e. the length between server and node. This type of NIC supports BUS topology and star topology but usually implemented on star topology. It has an 8 bit or 16 bit port. It consists of a boot ROM. Transmission rate is 2.5 mbps. It also has a BNC connector and a jumper on a card. The name of the driver for this card is TURBO RXNET (TRXNET). If the stations are wired in the Bus topology the maximum trunk length of the bus segment is 1000 ft. ARCNET card uses a token ring bus access method but it is not IEEE standard. ETHERNET Card : This card consists of PCI (Peripheral Component Interconnected) bus. The slots available are 8, 16, 32 bit. Node address is between 0 to 1023. DIP switches are not available. The cable used is RG-58. This type of NIC supports Bus topology and star topology but unlike ARCNET card is usually support Bus topology. Thick and thin Ethernet are available. Data transfer rate is 10 mbps. Thick Ethernet uses AUI connector 25-pin female connector. Then Ethernet uses BNC connector. There are no switches for port address settings. 1 Dept: CE Computer Networking(3340702) Chintan Kanani
2. Explain Repeaters in detail. Repeater is an electronic device, which operates, only in physical layer of the OSI model. Signal that carry information within a network can travel a fixed distance before noise can affect integrity of the data. Repeater installed on a link receives the signal before it becomes too weak or corrupted, regenerates the original bit pattern & puts the new refreshed copy back onto the link. A repeater allows us to extend only the physical length of a network. A repeater does not change the functionality of the network. Repeater does not have idea to keep the frame from passing to the right side when it is meant for a station on left side. The difference is that, with the repeater, stations C and D receive a truer copy of the frame that would otherwise have been possible. Repeater is not an Amplifier : An amplifier cannot differentiate between the intended signal and noise signal, means it amplifiers equally everything fed into it. A repeater does not amplify the signal, it regenerates it. When it receives a noise signal or corrupted signal, it creates a copy bit for bit at the original strength. The location of a repeater on a link is important. A repeater must be placed so that a signal reaches it before any noise changes the meaning of any of any of bits. 2 Dept: CE Computer Networking(3340702) Chintan Kanani
If the corrupted bit travels much farther, its meaning can totally change. So, repeater placed on link before signal is corrupted. 3. Explain Bridge in detail. Bridges operate in both the physical and data link layer of the OSI model as shown in fig. A bridge connects two or more LANs. Bridges can divide a large network into smaller segments. Bridges contain logic (software) that allows them to keep the traffic for each segment separate, in this way they filter traffic. Repeaters retransmit frames to the entire connected device. Bridges transmit frames only to the separate segment. Like this way bridges filter the traffic (handle traffic). Bridges can also provide security through this partitioning of traffic (Means preventing unauthorized access). Bridges operates at the data link layer, so giving it access to the physical addresses of all stations connected to it. When a frame enters a bridge, it regenerates the signal and it checks the address of the destination and forwards the new copy only to the segment to which address belongs. As a bridge found frame, it reads the address contained in the frame & compares that address with a table of all stations on both segments. When the bridge finds corrects match, it find to which segment the station belongs and send the frame only to that segment. Bridge must have a look up table that contains the physical addresses of every station connected to it. The table also indicates to which segment each station belongs. 3 Dept: CE Computer Networking(3340702) Chintan Kanani
A C D B Bridge E G H F From fig if packet from A passed to the device D through the bridge. In this case, both devices are on the same segment (upper segment). So packet is blocked from crossing into the lower segment. Because no need to pass on lower segment. Suppose packet generated by device A is send to device G. At this time bridge allows the packet to cross and send packet to the lower segment. So finally it is received by station G. Types of Bridges: 1. Simple Bridge. 2. Multiport Bridge. 3. Transparent Bridge. Simple Bridge : A simple bridge is the most primitive and least expensive types of bridge. A simple bridge links two segments. It contains a table that lists the physical addresses of all stations connected with the bridge. In this bridge, physical addresses must be entered manually that makes them primitive. Before a simple bridge can be used, an operator enters the addresses of every station. In this bridge, updating of the devices is time consuming process. Whenever a new station is added, the table must be modified means new entry for new device. If station is removed then also address must be deleted from the table. So, installation and maintenance of simple bridges are time consuming. Multiport Bridge : Multiport bridge can be used to connect more than two LANs. In this bridge three tables are created, each one holding the physical address of stations reachable 4 Dept: CE Computer Networking(3340702) Chintan Kanani
through the corresponding port. Transparent Bridge : Transport Bridge builds its table of physical station addresses on its own as it performs its bridge functions. Table is automatically built by frame movements in the network. When transparent bridge is first installed, its table is empty. When it receives packet it looks at source & destination address. Destination address is used for forwarding decision to the particular segments. Source address is used for adding entries to the table and for updating table. As it reads source address it notes which side the packet came from and the segment to which it belongs. It checks destination address to decide where to send packet. If it is not inside table, it sends the packet to all of the station on both segments excepting sender (source) station. The first packet transmitted by each station, the bridge makes entries inside the table with corresponding segment. So, at last table completed with all station addresses and segment. Next packet send by each station refers the table entry. Transparent bridge has self updating feature. Suppose two devices exchanging their place. Now its entry, inside the table for segment is wrong, because both devices are now replacing their segment, but this bridge updating its table automatically. Bridge is constantly checking source address of received. So, it updates entry for devices according to change. 4. Explain HUB in detail. Hub is used to create connections between stations in a physical star topology. Hub is a central network device that connects network nodes as shown in fig. It is also referred as concentrators. It enables central network management. It can have multiple inputs & outputs all active at one time. It permits large numbers of computer to be connected on a single or multiple LANs. It enables high speed communication. Provide connection for several different media types. (coaxial, fiber optic, twisted pair) Basically three types of hub : 1. Active Hub. 2. Passive Hub. 3. Hybrid Hub. Active Hub: Most hubs are active in that they regenerate and retransmit the signals the same way a repeater does. In fact, because hubs usually have eight to twelve ports for computers to connect to, they are often called multiport repeaters. Active hubs need electrical power to run. It contains a repeater which is h/w device that regenerates the received bits before sending to the link. Passive Hub: It provides physical connection between the attached devices. Passive hubs act as connection points and do not amplify or regenerate the signal; the signal passes through the hub. Passive hubs do not require electricity to run. Intelligent Hubs: Intelligent hubs are enhanced active hubs. It will accommodate several different types of cables. A hub-based network can be expanded by connecting more than one hub. It also has functions which can add intelligence to a hub like hub management (control the hub) and switching hub (which includes circuitry that very quickly routes signals between ports on the hub). 5 Dept: CE Computer Networking(3340702) Chintan Kanani
5. Explain Switch in detail. Switches provide bridging functionality with greater efficiency. It acts as multiport bridge to connect devices or segments in a LAN as shown in fig. Switch has a buffer for each link to which it is connected. Switch operates in Data Link Layer of the OSI model. When it receives a frame, it stores the frame in buffer of receiving link & checks address to find outgoing link. If the outgoing link is free the switch sends the frame to that particular link. Two different Strategies of switch : 1. Store and Forward switch. 2. Cut-through switch. Store and Forward Switch: This switch stores the frame in the input buffer until the whole packet has arrived. Cut-through Switch: It forwards the frame to the output buffer as soon as the destination address is received. 6. Explain Router in detail. Routers operate in the physical, data link and network layers of the OSI model as shown in fig. It is most active in network layer. Routers are able to access network layer address (logic address) of the device. It contains software that enables them to determine which of several paths between those addresses is best for particular transmission. A packet sent from a station on one network to a device on a neighbouring network goes first to the jointly device router which switches packet to the destination network. 6 Dept: CE Computer Networking(3340702) Chintan Kanani
Router consults with a routing table when packet is ready to be forwarded. Simplest function of routers is to receive packets from one connected network and pass them to second connected network Router is capable of determining which of its connected networks is the best next relay point for the packet. Once a router has identified the best route for a packet to travel, it passes packet along the appropriate network to another router. Routing Concepts : Least-cost Routing : Which path does it select? This decision is based on efficiency of network, means which of the available path is cheapest or shortest? In routing, shortest means the combination of cheapest, fastest, more secure, more reliable and so on. Non-adaptive Routing : In non-adaptive routing in which once a pathway to a destination has been selected, the router sends all packets for that destination along that one route. Adaptive Routing : In adaptive routing, a router may select a new route for each packet. In response to changes in condition and topology of the networks. Routers send the packets depending on which route is most efficient at that moment. According to the information inside the routing table the router select the best path. Routing table lists the following information. N/W addresses of each device, how to connect to other nodes (device), possible paths between routers, the cost of sending data over those paths. Basically two types of Routers are there : 1. Static Router. 2. Dynamic Router. Static Router: Routing table s information s are entered manually. Means this administrator enters the route for each destination into the table. It cannot update automatically when there is change (shutdown of routers or breaking of link or some fault in connection) in the internet. It is more secure. It always uses the same route. Dynamic Router: Routing table is created automatically. Table is updated using one of the dynamic routing protocols whenever there is change (shutdown of routers or breaking of link or some fault in connection) in the internet. 7. Explain Gateway in detail. Gateways operate in all seven layers of OSI model as shown in fig. A gateway is also called as protocol converter. Gateway is used to connect two different network systems. A Router is used to transfers, accepts and relays packets only across networks using similar protocols. A gateway can accept a packet formatted for one protocol and converts into a packet formatted for another protocol before forwarding it. 7 Dept: CE Computer Networking(3340702) Chintan Kanani
Gateway must adjust data rate, size and format. It converts the protocol from one network to another. Access point is hardware device or computer software that acts as a communication hub for users of a wireless device to connect to a wired LAN. Workstation (Client or Node) : Workstation is an individual single user computer which is connected with the server. It has communication capabilities. Two types of workstations are there Diskless: A node which has no floppy drive, no hard disk is referred as diskless node. It has add on card is added into CPU as a hardware device. So there is a one boot ram for temporary data storage. Computer with hard disk: Program can be loaded in hard disk. It is computer memory for permanent data storage. 8. Explain Network Software in detail. Network software is defined as a collection of program s that can be installed on file server or node. Without network operating system the computer is dead machine, it is loaded in main computer called server. It accepts the command and manipulates the data and prepares the result and sends it to that node. A network operating system can do the things like 1. Ties together all computer and peripherals in network. 2. It provides security for an access to data and peripherals in network. Software Components : All network operating system used to be application program that were loaded on top of stand alone operating system. Client Software : In the stand alone system when the user types the command, which makes a request for computer to perform some task, the request goes over the computers local bus to the CPU. Server Software : Server software makes it possible for users at other machines to share server s data and peripherals. 8 Dept: CE Computer Networking(3340702) Chintan Kanani
9. Explain Wireless Network in detail. Wireless having no wires In networking terminology, wireless is used to describe any computer network where there is no physical wired connection between sender and receiver. Network is connected by unguided media like radio wave, microwave, infrared, or satellite to maintain communications. Wireless requires specific equipment such as NIC (Network Interface Card). AP (Access Point) and routers in place of wires. Advantages of Wireless Networks : Wireless network saves the cost of installation of LAN cabling. Easy to relocate the network. Easy to modify the network structure. We can easily expand the wireless network compare to wired network. Disadvantages of Wireless Networks : Troubleshooting is difficult. It is expensive compared to wired network. Types of Wireless Network : 1. Local Area Network. 2. Extended LAN. 3. Mobile Computing. 10 Define Unicasting, Multicasting, Broadcasting. UNICASTING : In computer networks, Communication that takes place over a network between single sender and single receiver is called unicast. MULTICASTING : Multicasting is used to transmit a single message to a select group of recipients. A simple example of multicasting is sending an e-mail message to mailing list. Teleconferencing and videoconferencing also use multicasting, but require more robust protocols and networks. Note that multicasting refers to sending a message to a select group whereas broadcasting refers to sending a message to everyone connected to a network. BROADCASTING : In computer networking, broadcasting refers to transmitting a packet that will be received by every device on network. Broadcasting is a useful feature in e-mail systems. Satellite television also use broadcasting for their program. Broadcasting is used to simultaneously send the same message to multiple recipients, without requiring an acknowledgement. In networking, a distinction is made between broadcasting and multicasting. Broadcasting sends a message to everyone on the network whereas multicasting sends a message to a select list of recipients. 11 Give the difference between layer 2 switches and layer 3 switches. Layer 2 switches Layer 2 switches works at datalink layer. It does not provide routing facilities. It is cheap compare to layer 3 switches. It is less efficient. It does not work like a router. Layer 3 switches Layer 3 switches works at datalink layer as well as network layer. It provides routing facilities. It is costly compare to layer 2 switches. It is more efficient. It is work like a router. 9 Dept: CE Computer Networking(3340702) Chintan Kanani