Homework:
4th Oct, 2016 16.1 Basic Concepts of Computer Networks Internet is the world's largest computer network 16.2 Local Area Networks and Wide Area Networks
Intercept: steal the data when it transmit in the network. Peer to Peer (P2P). e.g. BT is a P2P services. Each computer upload/download files. - suitable to small network. - No need to setup a server. Client /Server - suitable to large network. In our school campus, we have around 10 server (Physical and Virtual), over 200 desktop computers as client computer. - need to set up a server.
Home network Share Internet (via modem, router) Share data (Share a folder in your PC to others) Smart home (Able to control home appliance via network or Internet) Share printer IP cam. Procedure of sharing a Printer/Folder in a peer to peer network 1. Connect Printer to computer A 2. Share the printer/folder (e.g. PrinterShare/FolderShare) and set sharing permission in computer A. (In home network, set the same account user name and password in Both Computer) 3. In the other computer, map the printer share. (e.g. \\<IP address>\PrinterShare) or the folder share (e.g.\\<IP address>\FolderShare) 16.3 Network services - Hardware Sharing (Harddisk, printer, scanner) - Software Sharing (web services) Count the number of simultaneous sign-in - Data/ File sharing (Centralized Data Management, information backup, security) - Communications (Internet Access service sharing, Network conference) Class work You have 3 computers at home. You want to share one broadband connection, printer, network drive. Draw a network diagram at your home. Common Server: FIle server Print server. Log-on/sign-in server (Windows: Domain server) Directory Server (LDAP), authentication server Single Sign-on (Similar to Google. You can sign on App Inventor using Google account) VPN server. Logon a VPN server in school over the Internet. The sign-in account can map network drive, browse the internal network. Just like working in school Transmission of data is encrypted. (Tunneling) 16.4 Connecting to a computer network 16.4.1 A network interface card: RJ45 - Media Access Control (MAC) Access, used within a LAN segment. In the switch, a table of MAC address and IP address is stored. also called Hardware address. 48 bits address. The first 24 bits can used to identify the manufacturer. http://aruljohn.com/mac.pl (Exercise) Security issue: MAC spoofing. (Demonstration) - Obtain an IP address from DHCP server - common bandwidth: 100Mbps, 1Gbps - connector: RJ45 (common) , BNC (outdated), fiber. - Expansion bus: PCI, on board, USB Windows Networking Commands: ipconfig, arp, nslookup, ping, netstat Network Connecting devices
16.4.2 Modem Dial up modem. It converts digital signals from your computer into analog signals that can travel over telephone lines and vice versa. Maximum speed: 56 kbps Still used in fax machine. Cable modem. via cable TV line DSL, ADSL modem: also via telephone line. 16.4.3 Cables
Transmission over Power line. (Demonstration) 16.4.4 Radio Connections Satellite broadband. in plane, cruise. Microwave: up to km, direct line of sight is needed. Wi-Fi Connections: up to 100m, use radio signal. WLAN 16.5 Methods of Internet Access Internet Service Provider. Dial up connection: up to 56 kbps (56000 bit per second) Dial up modem: convert digital signal into analog signal and vice versa. ISDN (Integrated Services Digital Network) - not popular in HK. - up to 128 kbps Broadband - 10Mbps, 100 Mbps, 1000Mbps is common in HK. (Bandwidth connected to ISP) - DSL (Digital subscription line) modem (SDSL, ADSL) using telephone line Many years ago, PCCW only provides ADSL to school, upload speed is 1.5Mbps. Download speed is 10Mbps. We switch to use HGC because of symmetric bandwidth. - Cable modem (using TV network) - Direct Ethernet (Fast Ethernet) T-carrier (Leased line) - Nowadays, no school using it to connect to Internet. It is not cost effective. It is very expensive. - It connect two points in a WAN with guarantee bandwidth. With better security. - can be leased by hours, days etc. Suitable for video conference meeting. or connect 2 offices in different area. Wireless Internet Access. - Wi-Fi hot spots - provided by different ISP. Usually free for 3G/4G subscriber. 11Mbps, 54Mbps, can be over 100Mbps. - Mobile phone, GPRS/2.5G (115.2 kbps), 3G (2-28Mbps), 4G LTE (up to 100Mbps) Homework P.216 Self Assessment Corner Q1-10 Do it in exercise book P.218 Short questions Q1-3 workbook P.45 - P.49 MC Q2 A bridge is a switch but with two ports only Q10 WAP Short Questions Q1. P.181 Q2. P.193 - 194 Q3 a) fibre not affect by EMI STP / coaxial : fairly resistant to EMI b) c) Q5 MC answer
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