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Computer Networking 숙명여자대학교 컴퓨터 과학과 최 종원.

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Presentation on theme: "Computer Networking 숙명여자대학교 컴퓨터 과학과 최 종원."— Presentation transcript:

1 Computer Networking 숙명여자대학교 컴퓨터 과학과 최 종원

2 What is the Internet? A world-wide computer network
hosts or end systems network application program protocol communication link router packet switching

3 Service Description The Internet allows distributed applications running on its end-systems to exchange data with each other The Internet provides two services to its distributed applications: a connection-oriented service and a connectionless service. Currently the Internet does not provide a service that makes promises about how long it will take to deliver the data from sender to receiver.

4 Soom Good Hyperlinks Internet Engineering Task Force (IETF):
The World Wide Web Consortium (W3C): The Association for Computing Machinery (ACM) the Institute of Electrical and Electronics Engineers (IEEE): Connected: An Internet Encyclopedia: Media History Project:

5 What is a Protocol? A Human Ananlogy : Fig 1.2 Network Protocols
a protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event

6 The Network Edge End Systems, Clients and Servers Figure 1.3-
Connectionless andConnection-Oriented Service Connection-Oriented Services reliable data transfer Flow control congestion control TCP Connectionless Service UDP

7 The Network Core Figure 1.4circuit switching packet switching
Message Switching

8 Routing in Data Networks
Classes of packet-switched networks datagram networks and virtual circuit networks route according to host dest addr or to vc number datagram net : Internet vc network : X.25, frame relay and ATM VC network a path vc numbers, one # for each link along the path entries in VC number translation table in each packet switch

9 Why vc numbers are changed?
The length of the vc field is reduced a network management function is simplified Datagram network ananlogous to postal services do not maintain connection-state information in the switches

10 Access Networks and Physical Media
Access network - the physical link(s) that connect an end system to its edge router residential access network institutional mobile Residential access networks use of a modem over POTS twisted-pair phone line

11 Narrowband ISDN ADSL and HFC all digital transmission of data
adsl uses frequency division multiplexing a hig-speed downstream channel, 50kHz-1MHz a medium-speed upstream channel, 4kHz to 50kHz an ordinary POTS two-way telephone channel, 0 to 4kHz data rate : a function of the distance between the home modem and the ISP modem HFC : extensions of the cable network cable modem, 10-Base T Ethernet port the rates are shared among the homes

12 Company access network
Lan is used to connect an end system to an edge router twisted-apir copper wire or coxial cable shared Ethernet and switched Ethernet Mobile access networks use radio spectrum to connect a mobile end system to a base station cellular digital packet data

13 Physical Media Guided media and unguided media
twisted pair copper wire UTP : category 3 and 5 coaxial cable : baseband and broadband fiber optics terrestrial and satellite radio channels


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