Network Interface Card (NIC) Connecting Devices Hubs/switches, routers Network Cables Twisted-pair cable, Coaxial cable, Optical fiber Wireless Networks Connecting to a Computer Network

Each NIC has a MAC (Medium Access Control) address –An unique hardware number to identify a computer in the network –In Windows, to locate the MAC of a NIC: run > cmd > ipconfig /all MAC = physical address (A hex code)

Connecting Devices Hub/Switch –provides a central connection points for cables in a network and direct the data flow among them –A typical client-server configuration a cable connects the hub/switch to a server other computers are connected to the hub/switch Hub/ Switch Client-server network connected with a hub/ switch Hub/ Switch

Connecting Devices Hub

Hubs and Switches Hub Only one computer can talk at a time. Switch Computers can talk with each other on private connections so that multiple conversations can be carried on at the same time. 1st computer sends a print job to the printer

Routers & Modems Hub/ Switch Client-server network connected with a hub/ switch Router Modem Hub/ Switch Internet

Bridge A bridge connects segments of a LAN or LANs of the same type into an aggregated network. Wireless bridge repeating-using-wndap330

Router A router connects a LAN to a different LAN A router is connected to another router. A huge network of routers connects the LANs together to form the Internet. is needed to connect a LAN and the Internet (a WAN) Routes (forwards/ directs) packets (of data) between networks (LANs). i.e. direct data flow. Most home-use routers have LAN ports and also act as hubs/switch. (router + hub/switch)

Bridge vs Router bridge: - simple, link up to form a aggregated LAN router: - complicated, direct traffic between two different LANs - idea: one LAN is not under control of the other LAN (ip address)

Modem (modulator demodulator) Refer to textbook Types of modem Dial-up modem (telephone line) Cable modem (cable TV network) ADSL modem (broadband telephone network) –Asymmetric Digital Subscriber Line DSL modem (broadband telephone network) –Digital Subscriber Line Actually, an ADSL/ DSL modem is not a D-A-D but a D-D device.

Network Cables Unshielded twisted-pair (UTP) cable Use RJ45 connector Twisted to reduce interference Category 5 UTP –100Mbps (=1,000,000 bps; not 1024 x 1024bps) –Commonly used in LANs (Shielded twisted-pair)

Network Cables Shielded twisted-pair (STP) cable Metallic foil shielding

Straight through cable Cut evenly across ½ inch left Clip down Insert fully in

Coaxial Cable (coax) commonly used for VCR and cable TV connections use BNC jack/ connector transmit more signal over longer distance than twisted-pair cable

BNC Connectors Male Connectors1 Male – 2 Female Connectors

Fiber optics (optical fibers) are long, thin strands of very pure glass about the diameter of a human hair. They are arranged in bundles called optical cables and used to transmit light signals over long distances. Parts of a single optical fiber Bundles of optical fibers forming optical cables

Wireless Networks Access point (AP) (= wireless hub) A device that transports data between a wireless LAN and a wired LAN (forming one unified LAN) Wireless Local Area Network (WLAN) uses Radio Frequency (RF) technology

Hardware Access Point Wireless LAN adaptors

AP13 outside 5/F Staff Room

Wireless Fidelity (Wi-Fi) protocols (rules/ standard) b 11Mbps g 54Mbps Wireless Equivalent Privacy (WEP) security protocol encrypt data for wireless transmission

Wireless Broadband Router (+ hub + AP) - connect to a modem (then to the Internet/ other LANs) - connecting nodes in the LAN Google search: internet sharing router Linksys WRT54G All-In-One Wireless-G Broadband Router Access Point (= wireless hub) - connect to a switch/hub (the LAN) - connecting nodes in the LAN

Cable or DSL/ADSL Modem Internet

Revision of Concepts Functions of devices - hub/switch/AP connecting equipment in the LAN - Router connect a LAN to another LANs (Internet) - Modem perform conversion to enable computer data signal to be sent over telephone/ cable TV / ADSL network.

Revision of Concepts Home use devices > AP (wireless hub) > AP + wired-hub/ switch > router + AP + wired-hub (3 devices in a case, most popular, market name: wireless internet sharing router) > cable/ ADSL modem (for broadband connection) At school > switch/ hub, router, broadband modem are separate devices > one router for the whole school LAN > one broadband modem

Network in our school Network OS: Windows, Linux Some functions/ services –Account management (logging on/ off) –Accessing network drives –Using network printers –File transfer –Routing to the Internet connecting the school LAN to the Internet

Diagram of school LAN

Visiting Schools Server Room What to look for? - UTP cables, Optical Fibre - Hubs, Switches and Router - Modem, Cable Modem - Servers : File (FTP), Web, SAMS, … - Backup magnetic tape system - Patch panel - UPS (uninterruptible power supply) systems Other network facilities - other servers : MMLCs / BCR - Switch/ Hub cabinets at Library, MMLC1/2, Staff Rooms...