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1. Connectionless - different paths for different datagrams belonging to the same message - independency between pakcets - 패킷사이의 관련성이 없다 2. Connection-oriented - dependency between packets - 패킷사이의 관련성이 있다 - A connection-oriented protocol uses both flow and error control - The sender sends one packet at a time and waits for an acknowledgement before sending the next one - To detect corrupted pack..

- process-to-process communication; addressing; multiplexing and demultiplexing; error, flow, and congestion control - UDP - TCP : connection-oriented service using a transition diagram - It provides a process-to-process communication between two application layers, one at the local host and the other at the remote host - Legend - Point-to-point WAN - LAN switch - WAN switch - Router - The trans..

1. distatnce-vector routing 2. link state routing 3. path-vector routing 1. RIP - distance-vector routing 2. OSPF - link state routing 3. BGP - path-vector routing - a packet is routed, hop by hop - The source host does not need a forwarding table -> its packet to the 'defualt router' - one of the ways to interpret the best route from the source router to the destination router is to find the le..

1. Transmission Delay = (packet length) / (transmission rate) 2. Propagation Delay = (distance) / (propagation speed) 3. Processing Delay = time required to process a packet in a router or a destination host 4. Queuing(대기열) Delay = time a packet waits in input and output queues in a router - the number of bits(=payload) passing through the point in a second - the number of packets lost during tr..

- Multiple-access protocols 1. Random-access protocols - ALOHA - CSMA/CD - CSMA/CA 2. Controlled-access protocols - Reservation - Polling - Token passing 3. Chanelization protocols - FDMA - TDMA - CDMA - collision : to avoid access conflict - earlist random access method - it can be used on any shared medium - potential collisions in this arrangement - The data from the two stations collide and ..

- Flow control at the data link layer - The date-link layer at the sending node tries to push frames toward the data-link layer at the receving node - If the receving noce can not process and deliver the packet to its network at the same rate that the frames arrive, it becomes overwhelmed with frames - Buffers(완충기) - One of the solutions is to use two buffers; one at the sending data-link layer ..

- data rate : the number of data elements(bits) sent in 1s[bps] = bit rate - signal rate : the number of signal elements sent in 1s[baud] = baud rate - 주파수 대역폭(width)이 넓어질수록 데이터 전송속도가 떨어지고, 주파수 대역폭이 좁아질수록 데이터 전송속도가 빨라진다 - BW 는 1/bit rate에 비례 - Goal : increasing the data rate while decreasing the signal rate - Digital data bit(pulse shape)를 전송하기 위해서는 이상적으로는 무한대의 통신 채널 대역폭이 필요하다 -> 현시적으로 불가능. 즉, 항..

- Digital Original - Transmission medium - Attenuated - Amplifier -> Amplified - Attenuated = signal + noise - Attenuated + Amplifier = regenerator(재생) *Amplifiers : 증폭기 *Repeater : 중계기 - 신호의 모양이 변경(signal changes its form or shape) - Each signal frequency component has its own 'propagation(전파) speed' -> 신호가 이동하면서 신호의 모양이 변경 - 위상(phase)이 발생(Components out of phase) -> 시간차이 때문 - 원래신호(Compositive ..

- We use a few criteria such as 'size, geographical coverage, and ownership' to make this distinction - LAN에 대해서 설명하시오 - A local area network (LAN) is usually privately owned and connects some hosts in single office, building or campus -> 컴퓨터 갯수가 적고, 짧다 - Each host(컴퓨터) in a LAN has an identifier, and address, that uniquely defines the host in the LAN *IP address, MAC address, 휴대폰번호 - A packet s..

- When we communicate, we are sharing information. This sharing can be local(지역) or remote(원격) - The term telecommunication(통신), which includes telephony, telegraph, and television, means communication at a distance - Data communications are the exchange of data between two devices(장치) via some form of transmission(전달) media(매체) *Communication(통신) : Broadcasting(방송) - 통신 : 양방향으로 데이터를 주고받음 - 방송 :..