• Network Interface Card (NIC)

• Connecting DevicesHubs/switches, routers

• Network CablesTwisted-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

http://computing.concord.edu/Networking/networking.htm

Hub Only one computer can talk at a time.

SwitchComputers 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 ModemHub/ Switch

Internet

Bridge

A bridge connects segments of a LAN or LANs of the same type into an aggregated network.

Wireless bridgehttp://kb.netgear.com/app/answers/detail/a_id/9587/~/bridging-and-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 LAN’s 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 LineActually, 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 Connectors 1 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 fiberBundles of optical fibersforming 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)

• 802.11b 11Mbps• 802.11g 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 routerhttp://salestores.com/linksy05.htmlLinksys 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 LAN’s (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 School’s 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 : MMLC’s / BCR

- Switch/ Hub cabinets at Library, MMLC1/2, Staff Rooms ...