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What is Networking? : 

What is Networking? A network is a connection between terminals, computers, servers and components which allows for the easy flow of data and use of resources between one another. Sharing is the main purpose of networking. Today, we are going to learn that how a person can communicate through computers viz., Different ways of connecting and Devices used to connect. 2

Network Topology : 

Network Topology The network topology defines the structure of the network. It can be physical or logical. Physical Topology means the physical design of a network including the devices, location and cable installation. Logical Topology refers to the fact that how a data actually transfers in a network as opposed to its design. 3

Main types of Physical Topologies : 

Main types of Physical Topologies The basic topologies you will find in most LANs today include the following: Bus Topology Ring Topology Star Topology Mesh Topology Hybrids 4

Bus Topology : 

Bus Topology A network cabling topology in which each device is connected to the next device, forming a daisy chain with two ends, each of which must be terminated with lots of binary collision. The bus carries the transmitted message along the cable to check the destination address contained in the message to see if it’s matching it's own. If the address does not match, the workstation does nothing more. If it matches that contained in the message , the workstation processes the message. Advantages of a Bus Topology Easy to connect a computer or peripheral to a bus. Requires less cable length. Disadvantages of a Bus Topology Entire network shuts down if there is a break in the main cable. Terminators are required at both ends of the backbone cable. Difficult to identify the problem if the entire network shuts down. Not meant to be used as a stand-alone solution in a large building. 5

Slide 6: 

A network that uses a bus topology is referred to as a “bus network.” Bus networks were the original form of Ethernet networks, using the 10Base5 cabling standard. Bus topology is used for Small workgroup, Trunk cables connecting hubs or switches , Back boning, to form campus-wide networks. Bus topology is the cheapest way of connecting computers to form a workgroup or departmental LAN. 6


RING TOPOLOGY Connects one host to the next and last to the first. Creates a physical ring of cable. The most important thing it is strictly a logical construction. A frame travels around the ring, stopping at each node. If a node wants to transmit data, it adds the data as well as the destination address to the frame. The frame then continues around the ring until it finds the destination node, which takes the data out of the frame. The main features are: Workstations connect to the ring Faulty workstations can be bypassed More cabling required than bus The connectors used tend to cause a lot of problems Commonly used to implement token ring at 4 and 16 Mbps Four wire generally STP or UTP. 7

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Single ring – All the devices on the network share a single cable. Use token passing for their Media Access Control (MAC) mechanism are wired using a ring topology.(Collision) Dual ring – The dual ring topology allows data to be sent in both directions. FDDI uses the token passing Media Access Control (MAC) mechanism and supports a double ring topology that provides fault tolerance in the event of a system disconnection or cable failure. (No collision) 8

Slide 9: 

IEEE 802.5 Token Ring is widely used in ring networks for controlling station access to the ring. Wiring is done in a physical star fashion, with cables wired directly from each workstation back to the MAU. Advantages of a ring topology Cable failure affect limited users Equal access for all users Each workstation has full access speed to the ring As workstations numbers increase performance diminishes slightly Disadvantages a ring topology Costly wiring Difficult connections Expensive adapter cards 9


STAR & TREE TOPOLOGY A star topology in which each device is connected to a central nexus called a hub. Larger networks use the extended star topology also called tree topology. The main features are: All wiring is done from a central point (hub or switch) and each node is connected directly with them. Data on a star network passes through the hub or concentrator before continuing to its destination. The hub or concentrator manages and control all functions of the network. It also acts as a repeater for the data flow. Has the greatest cable lengths of any topology This configuration is common with twisted pair cable: however, it can also be used with coaxial cable or fiber optic cable. Generally STP or UTP. 10

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Advantages of a Star Topology Easy to install and wire. No disruptions to the network then connecting or removing devices. Easy to detect faults and to remove parts. Disadvantages of a Star Topology Requires more cable length than a bus topology. If the hub or concentrator fails, nodes attached are disabled. More expensive than bus topologies because of the cost of the concentrators. The protocols used with star configurations are usually Ethernet or LocalTalk. 11

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Advantages of a Tree Topology Point-to-point wiring for individual segments. Supported by several hardware and software venders. Disadvantages of a Tree Topology Overall length of each segment is limited by the type of cabling used. If the backbone line breaks, the entire segment goes down. More difficult to configure and wire than other topologies 13


STAR-WIRED RING TOPOLOGY A star-wired ring topology may appear (externally) to be the same as a star topology. Internally, the MAU(multistation access unit) of a star-wired ring contains wiring that allows information to pass from one device to another in a circle or ring . The Token Ring protocol uses a star-wired ring topology. 14


MESH TOPOLOGY The topology in which every device connects to every other device is called Mesh topology. The mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance. It is used in WANs to interconnect LANs and for mission critical networks like those used by banks and financial institutions. Implementing the mesh topology is expensive and difficult. It work on the concept of routes. In Mesh topology, message sent to the destination can take any possible shortest, easiest route to reach its destination. 15






ROUTERS Routers are specialized network device that determines the next network point to which to forward a data packet toward its destination. A device that forwards data packets between computer networks. Routers are most often used in large internetworks that use the TCP/IP protocol suite and for connecting TCP/IP hosts and local area networks (LANs) to the Internet. Routers can also be used to join dissimilar media such as unshielded twisted-pair (UTP) cabling and fiber-optic cabling, and different network architectures such as Token Ring and Ethernet. Routers often provide basic firewall functions. It works on the OSI Layer 3 (Network Layer). No collision domain No broadcast domain 18

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Routers are classified as one of the following: Static routers: These must have their routing tables configured manually with all network addresses and paths in the internetwork. Administrator manually assigns path. Dynamic routers: These automatically create their routing tables by listening to network traffic. Path selection depends on the routers protocols. (RIP, EIGRP & OSPL) Default routers: We don’t know the destination. 19


BRIDGING Bridging is a technique used to connect networks at the data-link layer. A bridge is a physical unit that you use to connect network segments. Bridges operates in called promiscuous mode. Bridges operate by sensing the source MAC addresses of the transmitting nodes on the network and automatically building an internal routing table. Three collision domain and one broadcast domain. Bridges come in three basic types: Local bridges: Directly connect local area networks (LANs) Remote bridges: Can be used to create a wide area network (WAN) link between LANs Wireless bridges: Can be used to join LANs or connect remote stations to LANs 20

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The other types are: Transparent Bridging - They build a table of addresses (bridging table) as they receive packets. If the address is not in the bridging table, the packet is forwarded to all segments other than the one it came from. This type of bridge is used on Ethernet networks. Source route bridging - The source computer provides path information inside the packet. This is used on Token Ring networks. 21


BROUTER Any network device having the capabilities of both a bridge and a router is called a brouter. There is a device called a brouter which will function similar to a bridge for network transport protocols that are not routable, and will function as a router for routable protocols. It functions at the network and data link layers of the OSI network model. 22


GATEWAY Gateway is the point where the packets leaves its own area network and enter into another network. Most gateways operate at the application layer, but can operate at the network or session layer of the OSI model. A gateway is usually a dedicated device or a set of services running on a dedicated computer. 23

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Examples include the following: E-mail gateways—for example, a gateway that receives Simple Mail Transfer Protocol (SMTP) e-mail, translates it into a standard X.400 format, and forwards it to its destination. Gateway Service for NetWare (GSNW), which enables a machine running Microsoft Windows NT Server or Windows 2000 Server to be a gateway for Windows clients so that they can access file and print resources on a NetWare server. Gateways between a Systems Network Architecture (SNA) host and computers on a TCP/IP network, such as the one provided by Microsoft SNA Server. A packet assembler/disassembler (PAD) that provides connectivity between a local area network (LAN) and an X.25 packet-switching network. 24


REPEATER A networking component that extends a network by boosting the signal so that it can travel farther along the cabling. A repeater connects two segments of your network cable. Repeaters work only at the physical layer of the OSI network model. Other uses for repeaters include the following: Joining two 16-Mbps Token Ring networks in different buildings over distances up to 3000 meters over multimode fiber-optic cabling or up to 20 kilometers over single-mode fiber Increasing the lobe length between a Token Ring main ring and a remote node Joining dissimilar 10Base2 and 10Base5 segments to form a single Ethernet LAN Boosting signals from mainframe controllers to 3270 terminals over coaxial or UTP cabling to support distances up to 2500 meters Extending the operating distance of T1 lines by placing G.703 repeaters at 2.2-kilometer intervals Extending backbone fiber-optic cable runs in campus wide LANs or metropolitan area networks (MANs) 25


SWITCHES Any device that can control the flow of electrical signals. A number of special-purpose switches are used in networking. Switch splits the network traffic and sends it to different destinations rather than to all systems on the network. Works on Data Link Layer (L2) of the OSI Model. For example, the following types of switches are used to control access to computers by printers, keyboards, and monitors: Matrix switches: Have a keypad for mapping input ports to output ports and are typically used to connect several printers to several workstations Code-operated switches: Use a data string sent by the PC to select the printer port to be used Port-contention or scanning switches: Use several input ports but only one output port and monitor the input ports continually for data to route to the output port KVM switches: Allow one keyboard/video-monitor/mouse to be used for several servers 26

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Types of Switches: Cut-through switch: Cut-through switch forwards packets immediately by reading the destination address as they're received and relaying the packets out through the appropriate port with no additional processing. The switch doesn't even wait for the entire packet to arrive before it begins forwarding it. Cut-through switches use a hardware-based mechanism. Store-and-forward switch: A store-and-forward switch waits until an entire packet arrives before forwarding it to its destination. Verify the data by performing a cyclical redundancy check (CRC). 27

HUB : 

HUB A hub or concentrator is a device used to connect all of the computers on a star or ring network. A hub is generally termed a workgroup hub if it supports up to 50 stations, a departmental hub if it supports up to 250 stations, and an enterprise hub if it supports more than 250 stations. Stackable hubs can be used to provide these various capabilities. Types of hubs: Passive hubs: A hub which does not need an external power source. Passive hubs do not amplify the electrical signal of incoming packets before broadcasting them out to the network. Active hubs: Active hubs which regenerates the signal and therefore needs an external power supply. Intelligent hubs: Intelligent hubs add extra features to an active hub that are of particular importance to businesses. A hub which provides error detection (e.g. excessive collisions) and also does what an active hub does. 28

Slide 29: 

There are numerous types of hubs for various specialized uses. These include the following: Minihubs: Which have only 4 to 8 ports and are used for quick or temporary LAN extensions. Minihubs can be as small as a cigarette packet. Workgroup hubs: Which are the basic building blocks of small workgroup LANs. These typically have 8 or 16 ports on them. Stackable hubs: Which are modular in design and can be mounted in racks and cabinets within the wiring closet and can be connected using special ribbon or DB-50 cables. In configurations of 8, 16, and 24 ports and can be stacked to effectively form a single hub with 48, 72, 144, or more ports. Stackable hubs take less space and are easier to manage than regular workgroup hubs. Dual-speed hubs: Which have autosensing ports that support combinations of both 100-Mbps Fast Ethernet connections and 10-Mbps traditional Ethernet connections. Dual-speed hubs are typically stackable hubs with 8 or 16 ports that can be stacked to support a total of 32 or 48 ports. Fast hubs: Which have 100-Mbps ports only for forming 100BaseTX Fast Ethernet LANs. Supports up to 144 stations, and they might include fiber-optic ports for connecting to a high-speed fiber-optic backbone. Modular hubs: Which are more expensive hubs that provide a backplane or chassis in which cards can be inserted to create custom hub configurations. They are more common in Token Ring or Fiber Distributed Data Interface (FDDI) environments 29


MODEM MODEM: The term “modem” (which actually stands for “modulator/demodulator”). a hardware device that converts the digital signals generated by computers into analog signals suitable for transmission over a telephone line, and back again. A dial-up connection between two computers requires a modem at each end, both of which support the same communication protocols. Modems take the form of internal devices that plug into one of a computer's expansion slots, or external devices that connect to one of the computer's serial ports. The term modem is also used incorrectly, in many cases, to describe any device that provides a connection to a wide area communications service, such as a cable television or DSL connection. These devices are not actually modems, because the service is digital, and no analog/digital conversion takes place. 30

Modem types include the following : 

Modem types include the following Internal modems: which are installed as interface cards inside the computer and functions such as encoding and data compression. External modems: which are generally more expensive and connect to the serial port on the computer using a DB9 or DB25 connector. External modems are useful when several users need to share a modem. PCMCIA modems: which are credit-card-sized modems for laptop computers used by mobile workers. Voice/data/fax modems: which can be used for file transfer, sending and receiving faxes, and voice mail using associated software. 31

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