001. Network Overview

(1) Information and Communication (정보통신)

: The act of exchanging information with a target using multiple communication methods.

(2) Data (자료)

: Simple data collected for analysis or reference purposes, expressed in numbers, letters, symbols, etc.

(3) Information (정보)

: Data that has been processed and given meaning to achieve a specific purpose.

(4) Goals of Information and Communication (정보통신의 목표)

(i) Accuracy (정확)

: Signals should not be weakened, altered, or lost due to external factors during transmission.

(ii) Efficiency (효율)

: The value of the information obtained should be high compared to the equipment or cost used.

(iii) Security (보안)

: The information exchanged should not be leaked to third parties.

(5) Key Elements of Information and Communication (정보통신의 주요 요소)

(i) Sender (송신자)

: A person, device, computer, or node that creates and sends information.

(ii) Receiver (수신자)

: A person, device, computer, or node that receives and processes information.

(iii) Medium (전송매체)

: The physical path or means used by the sender to transmit information to the receiver.

(iv) Protocol (프로토콜)

: Rules or agreements that ensure smooth communication between multiple senders and receivers.

(6) Network (네트워크)

: A web-like communication system where senders and receivers are connected using communication technology, providing short or long-distance transmission of data.

(7) Internet (인터넷)

: Communication between networks (e.g. WWW: World Wide Web)

(8) Intranet (인트라넷)

: Communication within a single network. A closed communication form only accessible by members of an organization, such as the military or a company (e.g. Military Network).

(9) Network Topology (네트워크 토폴로지)

: Networks are designed in various forms depending on purpose and structure. These design methods are called topologies.

(i) Mesh Topology (망형 토폴로지)

: All devices are connected point-to-point.

: Failure in one communication line does not affect the overall network.

: Requires a lot of workspace and is expensive to install as all devices must be interconnected.

(ii) Star Topology (성형 토폴로지)

: Each device is connected point-to-point to a central system (hub).

: The central control node manages all communication. If it fails, the entire network goes down.

(iii) Tree Topology (트리형 토폴로지)

: Like a tree branching out, the network expands radially from one device to multiple others.

: Easy to connect many networks at once if hubs are available, but failure in a specific device affects all devices below it.

(iv) Bus Topology (버스형 토폴로지)

: All devices in the network are connected to a single cable.

: Simple structure, low installation cost, and easy to add or remove devices.

: Terminators are used at both ends to prevent signal reflection.

: Too many devices on one line can degrade performance, and line failure affects the entire network.

(v) Ring Topology (링형 토폴로지)

: Similar to bus topology but forms a ring by connecting both ends.

: Often used for networks within specific areas such as campuses.

: Pros and cons are similar to those of bus topology.

(vi) Hybrid Topology (하이브리드형 토폴로지)

: A combination of two or more topologies, customized to meet specific needs by compensating for the drawbacks of each.

(10) Network Classification by Data Transmission Method (데이터 전송 방식에 따른 네트워크 분류)

(i) Analog Communication: Circuit Switching (아날로그 통신 : 회선 교환망)

: The caller gives the callee’s info to a telephone operator, who physically connects wires to establish the call. This analog method of establishing a dedicated and physical link is called circuit switching.

: Each line is used independently.

: High installation cost due to the need for dedicated circuits.

: Low bandwidth and poor transmission efficiency.

: Strong security (used in military).

: Suitable for real-time or high-volume data transmission.

: Low network efficiency due to continuous circuit occupancy.

(ii) Digital Communication: Packet Switching (디지털 통신 : 패킷 교환망)

: All computers are connected via lines, and data moves without physically switching or unplugging lines.

: Data is divided into small packets for transmission.

: Multiple packets from different sources can share the same line, each containing its destination address.

: Switches guide packets through the most efficient route.

: Overcomes the limitations of circuit switching.

: Low installation cost.

: High bandwidth and transmission efficiency.

: One transmission line can be shared by many packets.

(11) Network Classification by Communication Method (통신 방식에 따른 네트워크 분류)

(i) Unicast (유니캐스트)

: One-to-one communication between a server and a client.

(ii) Broadcast (브로드캐스트)

: Sends data to all devices within the same local LAN (router-segmented area).

: One-to-all communication.

(iii) Multicast (멀티캐스트)

: Sends data to a specific group all at once.

: One-to-specific-many communication.

(12) Network Classification by Size and Scope (규모와 범위에 따른 네트워크 분류)

(i) LAN (Local Area Network = Campus Network) (근거리 통신망)

: A communication network for devices within 10 km, such as in a home, school, or office.

: Topology is configured according to the purpose.

: Called Campus Network due to its typical scale (e.g. university campus).

(ii) MAN (Metropolitan Area Network) (대도시 통신망)

: A network connecting devices within a city, typically composed of multiple LANs.

(iii) WAN (Wide Area Network) (원거리 통신망)

: A network connecting very large areas, such as countries or continents, typically composed of multiple MANs.

(13) Ethernet (이더넷)

: Wired LAN network standard.

: Typically built using coaxial or UTP cables and configured in a bus topology.

(14) Network Classification by Transmission Medium (전송 매체에 따른 네트워크 분류)

(i) Wired Transmission Medium (유선 전송 매체)

(a) Twisted Pair (꼬임선, 이중 나선 케이블)

: Two thin copper wires twisted and wrapped with plastic insulation, used for both analog and digital transmission.

: Inexpensive and widely used.

: Not suitable for high-speed transmission and sensitive to external interference.

(a-1) UTP (Unshielded Twisted Pair) (보호되지 않은 꼬임선)

: No shielding foil; simply twisted and wrapped in plastic insulation. Most common due to low cost.

(a-2) FTP (Foiled Twisted Pair) (포일 피복 처리된 꼬임선)

: Entire cable wrapped in shielding foil to reduce interference, then insulated with plastic.

(a-3) STP (Shielded Twisted Pair) (강하게 피복 처리된 꼬임선)

: Each twisted pair is individually shielded in addition to overall shielding for maximum interference protection.

(b) Coaxial Cable (동축 케이블)

: Consists of a central wire and a surrounding shield (mesh), separated by an insulator. Similar to DVI connectors.

: Easy to install, supports higher bandwidth than twisted pair, enabling faster data transfer.

: Generally more expensive than twisted pair.

: Thin glass fiber sends data by converting signals to light pulses at the transmitter, then reconverts at the receiver.

: Composed of Core, Cladding, and Coating.

: Transmits large volumes of data over long distances with minimal signal loss.

: Not affected by moisture or electromagnetic interference due to its non-conductive material.

: Expensive and complex to install; prone to breakage, thus usually buried underground.

: Supports only one-way transmission.

(ii) Wireless Transmission Medium (무선 전송 매체)

: Uses radio waves to transmit data through the air.

: Characteristics vary depending on wavelength and frequency band, so suitable frequencies are selected for each use case.

(15) Hz

: A unit that indicates the number of sine waves generated per second.

(i) Low Frequency (저주파)

: Fewer sine waves per second.

: Signal travels farther with a single wave.

(ii) High Frequency (고주파)

: More sine waves per second.

: Signal travels a shorter distance per wave.

(iii) Bandwidth (대역폭)

: The amount of information that can be sent at once is inversely proportional to transmission distance. A higher bandwidth allows more data but shorter range.

: To send large amounts of information over long distances using wide bandwidth, many base stations are required.