NT1 PRELIM
COMMUNICATION:
- Act of transmitting and exchanging information between people, people and objects, and objects and objects through various media and actions.
- Delivering an information from source to receiver with giving meaning to Understanding the information from source.
- LATIN word: Communicare
INTERNET:
- is the largest computer network in the world. Its predecessor, Advanced Research Projects Agency Network (ARPAnet) was born in 1969.
NETWORK COMMUNICATON:
- refers to communication between terminal devices through a computer network.
SIGNAL:
- MEANS OF COMMUNICATION: refers to a sign or indication that conveys information about something or that tells someone to do something.
- COMMUNICATED INFORMATION: refers to an event or act, which shows that something exists or that gives information about something.
- ELECTRONICS TRANSMITTED INFORMATION: This refers to a detectable physical quantity or impulse by which messages or information can be transmitted via telegraphy, telephony, radio, radar, or television.
EXAMPLES OF SIGNALS:
• Electrical signals (voltages and currents in a circuit)
• Acoustic signals (audio or speech signals)
• Video signals (intensity variations in an image)
• Biological signals (sequence of bases in a gene)
• Noise (interference – unwanted and undesired form of signal)
WAVES:
- refer to disturbances in that energy to travel through a medium from one location to another.
WAVELENGTH:
- the horizontal distance of a wave from a point to the corresponding point on the next wave.
AMPLITUDE:
- vertical distance from a given point on the wave from the horizontal axis.
PHASE:
- describes the position of the waveform relative to time zero.
FREQUENCY:
- The number of waves made per second or as cycles per second.
- reciprocal of the period to complete one (1) wave cycle. The unit for frequency is in Hertz (Hz)
- 1 Hz means 1 cycle per second (cps).
PERIOD:
- This refers to the amount of time (expressed in seconds) required to complete one (1) full cycle.
GENERAL CATEGORIES OF WAVES
ANALOG WAVE:
- is a wave in which both the amplitude and time continuously vary over their respective intervals
- Results in a wavy characteristic.
- Examples: the human voice and music.
DIGITAL WAVE:
- It is a wave with several discrete (jumpy) states such as high or low, and on or off.
- It has a fixed amplitude, but its pulse width and frequency can be changed.
- Example: the data stored in the memory of a computer in the form of 0s and 1s.
NETWORK MEDIA:
- Computers facilitate information exchange and resource sharing from one
location to another
- through some sort of wiring/cabling or waves that act as a physical path, which
carries electrical or electromagnetic signals between a transmitter and a
receiver.
WIRED or BOUNDED MEDIA:
- Networking media use cables and are limited by physical geography.
WIRELESS or UNBOUNDED MEDIA:
- Networking media do not use any cables in transmitting data and is not bounded by physical geography.
TRANSMISSION MODE:
- SIMPLEX MODE: Connection wherein data flows in one (1) direction only
(unidirectional). This type is either transmit-only or receive-only
- HALF-DUPLEX MODE: Connection wherein data can flow in both directions, but not simultaneously (both at the same time) over a shared physical medium.
- FULL-DUPLEX MODE: Connection wherein data simultaneously flows in both directions
TRANSMISSION TYPE:
- SERIAL TRANSMISSION: which data with each bit lining up in a series as the bits are sent over a single wire at a time. (one at a time)
- PARALLEL TRANSMISSION: wherein a group of bits is sent simultaneously, but each uses a different channel.
WIRED OR BOUNDED MEDIA
SERIAL CABLE:
- The most widely used standard for serial data communications is intended to operate over distances of up to 50 feet and has a communication speed that is equal to or less than 20Kbps.
COAXIAL CABLE:
- refers to two (2) conductors enclosed by an insulating protective coating.
TYPES:
THIN(THINNET) CABLE:
- flexible coaxial cable about 0.25 inches thick.
- It uses British Naval Connector (BNC)-T cable connector attached to LAN Card (NIC).
THICK(THICKNET CABLE):
- relatively rigid coaxial cable about 0.5 inches in diameter.
- It uses vampire tap or piercing tap as connectors.
TWISTED PAIR CABLE:
- consists of two insulated strands of copper wire that are arranged in a regular spiral pattern.
UNSHIELDED TWISTED-PAIR(UTP) CABLE:
- refers to a twisted pair cable that contains no shielding.
- It has eight (8) individual copper wires, in which pairs of them are twisted around each other to form a four-pair color-coded wire
Attenuation - refers to signal loss due to impedance.
Crosstalk - refers to the twisted-wire pairs producing a magnetic field cancellation effect
SHIELDED TWISTED-PAIR(STP) CABLE:
- refers to a twisted pair cable that combines the techniques of twisting wires, cancellation, and shielding.
- Each pair of eight (8) individual copper wires is twisted and then wrapped in a metallic foil.
FIBER OPTIC CABLE:
- A bundle of extremely thin and cylindrically shaped glass fibers surrounded by a concentric layer of glass coating that can conduct modulated light transmissions.
PARTS:
- CORE: the innermost section that consists of one (1) or more very thin strands or fiber made of glass or plastic.
- CLADDING: an outer optical glass or plastic coating that surrounds and traps the light in the core by the principle of total internal reflection.
- COATING: It is made from plastic that helps to shield the core and cladding from damage.
- STRENGTHENING FIBERS: stand as protection for the core against compressive forces or crushing and tension or excessive pulling.
- CABLE JACKET(SHEATH): outermost layer that protects a buffer or a bundle of buffer-coated fibers against moisture, abrasion, crushing, and other environmental dangers.
FIBER OPTIC MODES
- SINGLE-MODE FIBER OPTIC CABLE: allows light waves to travel along a single path or in only one mode. It is used for high-speed transmission over long distances.
- MULTIMODE FIBER OPTIC CABLE: allows light waves to travel into numerous paths through the core of the fiber at various angles.
WIRELES OR UNBOUDED MEDIA
RADIO WAVE:
- A wireless medium that is used for multicast communications and paging systems over long distances.
ANTENNA:
- which is also known as aerial
- refers to a metallic structure that acts as a transducer that converts electrical energy to electromagnetic energy (upon transmission of signal) and vice-versa.
TYPES OF WAVE PROPAGATION:
- LINE OF SIGHT: method by which radio waves travel from the transmitting antenna to the receiving antenna.
- GROUND WAVE(SURFACE): method by which radio waves are radiated directly towards the earth’s surface.
- SKYWAVE(IONOSPHERIC): method by which radio waves radiate upwards from the transmitting antenna of the earth into a direction towards the ionosphere.
- SPACE WAVE: method by which radio waves radiation exceeds 30 MHz up to 300 GHz.
OTHER WIRELESS MEDIUM TECHNOLOGIES:
INFRARED: a wireless medium that is used for short-range communication in a closed area using line-of-sight propagation.
MICROEAVE: a wireless medium that is used for unicast communication
BLUETOOTH: short-range wireless communication technology that allows devices to transmit data or voice wirelessly over a short distance.
NETWORK TOPOLOGY
- It is a schematic description of a network arrangement, connecting various nodes (sender and receiver) through lines of connection.
• Star Topology – in this type of topology, the computers are connected to a single hub through a cable. This hub is the central node while all other nodes are connected to it.
• Bus Topology – a network type in which every computer and network device is connected to a single cable. When it has exactly two (2) endpoints, then it is called Linear Bus Topology. All nodes are connected through a bus (ex. Coaxial cable).
• Ring Topology – forms a ring as each computer is connected to another computer, with the last one (1) connected to the first—exactly two (2) neighbors for each device.
• Tree Topology – has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three (3) levels to hierarchy.
• Mesh Topology – a point-to-point connection to other nodes or devices. All the network nodes are connected.
o Partial Mesh Topology – in this topology, some systems are connected in the same fashion as mesh topology, but some devices are only connected to two (2) or three (3) devices.
o Full Mesh Topology – each node or device is connected.
• Hybrid Topology – it consists of a mix of two (2) different types of topologies merging as one network.
Terminal device
- It is the end-device of the data communication system. It provides the necessary functions required by the user access protocol operations.
• Network interface card (NIC) - is a key component that connects directly to a device that allows access to a network such as an internet or a local network.
Switch
- It is the device closest to end-users, used to access the network and switch data frames.
• Broadcast domain - is a set of nodes that can receive broadcast packets from a node.
Router
- It is a network-layer device that forwards data packets on the Internet.
• Modem - is a device that connects a network to the Internet. It takes signals from your Internet service provider (ISP) and translates them into signals connected to the local devices.
• Gateway - is a term for a router that provides functions such as protocol conversion, route selection, and data exchange when networks using different architectures or protocols communicate with each other.
Firewall
- It is a network security device used to ensure secure communication between two networks.
Wireless Devices
- It is a network that uses radio waves, laser, and infrared signals to replace some or all transmission media in a wired LAN.
o Fat Access Point (Fat AP) - applies to homes. It works independently and needs to be configured separately. It has simple functions and low costs.
o Fit Access Point (Fat AP) - applies to medium- and large-sized enterprises. It needs to work with the AC and is managed and configured by the AC.
o Access Controller (AC) - is generally deployed at the aggregation layer of the entire network. The AC provides wireless data control services featuring large capacity, high performance, high reliability, easy installation, and easy maintenance.
Local Area Network (LAN)
- generally covers an area of a few square kilometers. The main function is to connect several terminals that are close to each other (within a family, within one or more buildings, within a campus, for example). Technologies used: Ethernet and Wi-Fi.
Metropolitan Area Network (MAN)
- A MAN is a large-sized LAN, requiring high costs but can provide a higher transmission rate. It improves the transmission media in LANs and expands the access scope of LANs (able to cover a university campus or city).
Wide Area Network (WAN)
- A WAN generally covers an area of several kilometers or larger (thousands of kilometers for example). It is mainly used to connect several LANs or MANs that are far from each other (for example, across cities or countries). Telecom operators' communication lines use HDLC and PPP.
Open Systems Interconnection (OSI) model - is a descriptive network scheme. The OSI model describes how information or data makes its way from application programs through a network medium to another application program located on another network.
LAYER 7: APPLICATION LAYER - is the OSI layer that is closest to the user. It provides network services to the user’s applications such as spreadsheet programs, word processing programs, and bank terminal programs.
LAYER 6: PRESENTATION LAYER - ensures that the information that the application layer of one (1) system sends out is readable by the application layer of another system.
LAYER 5: SESSION LAYER - defines how to start, control and end conversations (called sessions) between applications. It also synchronizes dialogue between two (2) hosts’ presentation layers and manages their data exchange.
LAYER 4: TRANSPORT LAYER - regulates information flow to ensure end-to-end connectivity between host applications reliably and accurately. This layer segments data from the sending host’s system and reassembles the data into a data stream on the receiving host’s system.
LAYER 3: NETWORK LAYER - defines end-to-end delivery of packets. It defines how routing works (identifying endpoints) and how routes are learned so that the packets can be delivered.
• LAYER 2: DATA LINK LAYER - provides access to the networking media and physical transmission across the media and this enables the data to locate its intended destination on a network.
LAYER 1: PHYSICAL LAYER - deals with the physical characteristics of the transmission medium. It defines the electrical, mechanical, procedural, and functional specifications for achieving, maintaining, and deactivating the physical link between end systems.
TCP/IP Model
- It is a networking model with a set of communication protocols for the Internet and similar networks. It is commonly known as TCP/IP because its Transmission Control Protocol and Internet Protocol (IP) were the first networking protocols defined in this model. Internet Protocol (IP) provides basic communication. Transmission Control Protocol (TCP) provides key functions that applications need.
• APPLICATION LAYER - represents an interface through a variety of protocols that enable services to be applied to end-user application processes.
• TRANSPORT LAYER - is responsible for reliable end-to-end data delivery from the source host to the destination host.
• INTERNET LAYER (Network) - is responsible for the delivery of service requests that respond from the transport layer and have them arrive at their destination through the “virtual network” image of the Internet.
• NETWORK ACCESS LAYER - is also called the host-to-network layer, which is concerned with all the issues that an IP packet requires to make a physical link to the network media.
• The OSI Model - is a logical and conceptual model that defines network communication used by systems open to interconnection and communication with other systems.