Network Topology(网络的铺排) Star a central computer(server).PPT

* WHAT IS A NETWORK? a group of = 2 computers/devices linked together.BENEFITS Information sharing(分享資料)-e.g.database, data and files Hardware sharing (分享硬件) -e.g. printer Software sharing (分享軟件)-a license purchased to install a copy for many users Data Communication(數據溝通) Collaborative environment(共同作業) – work together in group project online Cut costs(減成本) 2 TYPES LAN (local area network) (區域網絡)– limited geographical area WAN(wide area network) (廣域網絡)- large geographical area DATA COMMUNICATON-data transmission from one place to another. Requirements: A sending device (a computer) A communication hardware(modem, cable modem)a network transmission hardware ( NIC , Hub, Bridge, Gateway, Router) A communication media (twisted pair, coaxial or fiber optic cable) radio, microwaves, satellites signals) A receiving device(a computer) Communication software (email, icq) USES OF COMMUNICATION TECHNOLOGIES – Voice Mail, Fax, Email, Instant Messaging, Chat rooms, newsgroups,telephony, videoconferencing, collaboration, groupware, Global Position System Data Communication Digital signals (數碼 訊息) (e.g. bits 101010) are used by computers.Analog signals (類比 訊息) (electrical wave) are used by telephone line.A modem converts digital signals from the sending computer into analog signals to be used by telephone line.(modulate) Data travels through telephone lines to sender’s ISP server. Data are divided into packets (細訊息郵包) which are then routed (路由) through Internet to the ISP server of the receiver. Data are then reassembled(重新整合).Another modem converts analog signals back into digital signals to be used by the receiving computer. (demodulate) Sending computer Receiving computer modem modem Digital signals Digital signals Analog signals Telephone lines ISP Analog signals Telephone lines ISP Internet Radio signals Broadcast radio/cellular radio Travel in straight line Used in mobile communication Slow, susceptible to noise Provide portability and flexibility M