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Learn about network types, topologies, protocols, and standards. Discover the advantages and disadvantages of different network configurations.
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NETWORKS A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network.
internet: It is two or more network that can be communicate to each other. Internet: A collaboration of more than hundreds of thousands of interconnected networks. Internetwork: The collection of two or more networks.
Advantages The use of dedicated links guarantees. A mesh topology is robust. Privacy or security. 4. Point-to-point links make fault identification and fault isolation easy.
Disadvantages A mesh are related to the amount of cabling and the number of I/O ports required. 2. Installation and reconnection are difficult. 3. The sheer bulk of the wiring can be greater than the available space (in walls, ceilings, or floors) can accommodate. 4. The hardware required to connect each link (I/O ports and cable) can be prohibitively expensive.
Advantages A star topology is less expensive than a mesh topology. 2. This factor also makes it easy to install and reconfigure 3. Far less cabling needs. 4. Robustness: 5. Easy fault identification and fault isolation.
Disadvantages The dependency of the whole topology on one single point, the hub. If the hub goes down, the whole system is dead. 2. Astar requires far less cable than a mesh, each node must be linked to a central hub. For this reason, often more cabling is required in a star than in some other topologies (such as ring or bus). The star topology is used in local-area networks (LANs)
Advantages Ease of installation. 2. Abus uses less cabling than mesh or star topologies.
Disadvantages Difficult reconnection and fault isolation. 2. Difficult to add new devices. 3. Adding new devices may therefore require modification or replacement of the backbone. 4. Fault or break in the bus cable stops all transmission.
Advantages Easy to install and reconfigure. 2. Fault isolation is simplified. 3. If one device does not receive a signal within a specified period, it can issue an alarm. The alarm alerts the network operator to the problem and its location.
A hybrid topology: a star backbone with three bus networks
PROTOCOLS AND STANDARDS We define two widely used terms: 1] Protocols and 2] Standards. Protocol, which is synonymous with rule. Standards, which are agreed-upon rules.
Protocols Definition:- • Protocol is a set of rules that govern all aspect of data communication between computers on a network. • These rules include guidelines that regulate the following characteristics of a network: access method, allowed physical topologies, types of cabling, and speed of data transfer. • A protocol defines what, how, when it communicated. • The key elements of a protocol are syntax, semantics and timing.
Elements of protocol:- • Syntax The structure or format of the data. Eg. A simple protocol; Sender address Receiver address data 8 bits 8 bits 64bits
ii)Semantics - Refers to the meaning of each section of bits. - how is a particular pattern to be interpreted, and what action is to be taken based on that interpretation. Eg. Does an address identify the route to be taken or the final of the message?
iii) Timing Refers to two characteristics: • When data to be sent • How fast it can be sent Eg. If a sender produces data at 100 Mbps but the receiver can process data at only 1 Mbps, the transmission will overload the receiver and data will be largely lost.
Standards • ‘A set of rules for ensuring quality'. • Standards are developed by cooperation among • standards creation committees, forums, and • government regulatory agencies. • Data communication falls into two categories: • 1] De facto (by fact or by convention) • 2] De jure (by law or by regulation)
Standards Standards Creation Committees:- • International Standards Organization (ISO) • International Telecommunications Union (ITU) • American National Standards Institute (ANSI) • Institute of Electrical and Electronics Engineers (IEEE) • Electronic Industries Association (EIA) • Internet Engineering Task Force (IETF)
A wide area network (WAN) provides long-distance transmission of data, image, audio, and video information over large geographic areas that may comprise a country, a continent, or even the whole world.
A personal area network, or PAN, is a computer network that enables communication between computer devices near a person. PANs can be wired, such as USB or FireWire, or they can be wireless, such as infrared, ZigBee, Bluetooth and ultrawideband, or UWB. The range of a PAN typically is a few meters. Examples of wireless PAN, or WPAN, devices include cell phone headsets, wireless keyboards, wireless mice, printers, bar code scanners and game consoles.
Transmission medium and physical layer
Common network cable types • Coaxial cable • Unshielded twisted pair • Fiber optic
Guided Media 1] Twisted-Pair Cable 2] Coaxial Cable 3] Fiber-Optic Cable Twisted-pair and coaxial cable use metallic (copper) conductors that accept and transport signals in the form of electric current. Optical fiber is a cable that accepts and transports signals in the form of light.
Twisted-pair cable Plastic Copper One of the wires is used to carry signals to the receiver, and the other is used only as a ground reference.
In addition to the signal sent by the sender on one of the wires, interference (noise) and crosstalk may affect both wires and create unwanted signals. If the two wires are parallel, the effect of these unwanted signals is not the same in both wires because they are at different locations relative to the noise or crosstalk sources (e,g., one is closer and the other is farther).
UTP characteristics • Unshielded • Twisted (why?) pairs of insulated conductors • Covered by insulating sheath
Cat 5 cable • Category 5 cable, commonly referred to • as Cat 5, is a twisted pair cable for • carrying signals. • This type of cable is used in structured cabling • for computer networks such as Ethernet. • The cable standard provides performance of up • to 100 MHz and is suitable for most varieties • of Ethernet over twisted pair. • Cat 5 is also used to carry other signals such • as telephony and video.
Cat5e cable • 1000Mbps data capacity • For runs of up to 90 meters • Solid core cable ideal for structural installations (PVC or Plenum) • Stranded cable ideal for patch cables • Terminated with RJ-45 connectors
Cat 6 cable CAT6 or Category 6 is a description of network cabling that consists of four twisted pair wires, has a data rate of 10000 Mbps, and is used in Ethernet and Gigabit Ethernet. It additionally can support 10 Gigabit ethernet connections over a limited distance.(technically, 50 meters or 164 feet for a single cable).
Applications Twisted-pair cables are used in telephone lines to provide voice and data channels. The local loop-the line that connects subscribers to the central telephone office---commonly consists of unshielded twisted-pair cables.
