Network Fundamentals

Network Fundamentals

Network Definition • Two or more computers connected together to share information (e.g., files) or resources (e.g., printers)

Network Services • File Services – Allows multiple users access to sets of files for distribution or collaboration. • Print Services – Allows multiple users to connect to, and use, centralized printers. • Mail Services (including IM) – A server on the network acts as an E-mail server, receiving all E-mail for the domain.

Network Services • Directory and Name Services – Enables users to connect to particular files and devices without knowing the physical location of the resource.

The Internet • A network of networks • The Internet itself is nothing more than a set of facilities that connect separate, little networks together into one gigantic network. • The Internet doesn't provide the information you're looking for, one of the smaller networks does.

Network Administration • Setting up user accounts and services • Monitoring network performance • Repairing network failures • Enforcing security • Providing fault tolerance (backing up)

Network Modes of Transmission • Simplex – One direction only • Over the air television • Burglar, Fire Alarms • Half-Duplex – One direction at a time • Two-way radios • Full-Duplex – Transmit & Receive at the same time. Network connections allow full-duplex transmission.

Types of Networks • Peer-To-Peer • All computers are equal partners • Each user responsible for access to resources on his/her computer • Each workstation acts as either a server or a client in each transaction • Easy to install and operate • No extra equipment or software • Because each person controls access, network security can be a problem.

Types of Networks • Client-Server • Centralized administration of resources • Users must authenticate themselves to use network resources • Server is equipped to handle requests from multiple users at the same time • There is a cost for ease of administration (software, hardware, a trained staff)

Types of Networks • Local Area Network (LAN) • Computers connected over a relatively small geographic area (a home, an office, a building or a campus). • Wide Area Network (WAN) • Designed to work over a larger area than a LAN, across a city, state, country or the planet. • Use either a circuit-switched or packet-switched network.

Connecting a Computer to a Network • Network Interface Card (NIC) • Different cards for different types of network (Ethernet or Token Ring) and for different types of media. • Each card has a particular Media Access Control (MAC) address to uniquely identify it. • Each card is programmed with a TCP/IP address so that other computers can connect to it.

TCP/IP Address • Four series of numbers from 0 – 255 • Every network-connected device has to have a unique address. • There are only 4.3 Billion addresses available.

Dynamic Host Configuration Protocol (DHCP) • On large networks, you can run into problems if you let everyone administer their own IP addresses. • DHCP centralizes the administration of IP addresses on the network. • A DHCP server doles out unique IP’s to requesting computers. • The IP is leased to the device for a specified period of time (72 hours).

Domain Name System • When a network is connected to the Internet, it’s difficult to remember the IPs of all the computers you want to connect to. • Hosts are identified by human-friendly names (www.nku.edu, support.microsoft.com). • A DNS server translates the name into the IP address.

Physical Network Characteristics • Network Topologies • Networking Media • Common Network Devices

Network Topologies • Star – Each device is connected to a centralized point, like spokes in a wheel. • Extended Star – Additional networking devices added to some spokes. Typical in schools, large corporations. • Bus – Single cable running from server. All workstations connect to cable.

Network Topologies • Ring – Devices connected in a circle. A signal (token) is passed from device to device, and only the device with the token may transmit. • Double Ring – Two complete circles. Provides for fault tolerance. If one circle gets broken, the other takes over.

Networking Media • Coaxial Cable • Similar to video cable • Maximum speed is 100 MB/s • Maximum run is 500 meters.

Networking Media • Shielded Twisted Pair • Pairs of wires are twisted together and have a foil shield around them for noise and interference cancellation.

Networking Media • Unshielded Twisted Pair (UTP) • The most common LAN cabling. • Category 3 used for telephone service. • Categories 5, 5e, 6 used for networks. • Rely solely on twisting for interference cancellation.

Networking Media • Fiber Optic Cable • Transmits beams of light instead of electrical impulses. • Much higher bandwidth, less subject to electrical interference. • Much more expensive to deal with.

Networking Media • When any kind of wiring is going to be too expensive, wireless connections are the answer. • Wireless connections come with a whole new set of security concerns. • Home wireless routers and equipment should not be used in a commercial environment.

Network Devices • Hubs • Connect multiple network clients together. • Not very smart, send everything to everyone.

Network Devices • Switches • Similar to a hub, but intelligent. • Switches know the IP addresses of the devices attached to it, and send the message only to the correct device. • Bridges – connect segments of a network together. • Routers – connect different types of networks together, like LAN to WAN.

Network Utilities • ping – Test connectivity to another computer. • arp – Displays mapping between IP addresses and MACs. • nslookup – Displays IP address for a given host name. • netstat – Displays information about active network connections. • ipconfig – Displays TCP/IP configuration information.

Connecting to the Internet • Dialup • DSL • Cable • Satellite

Connecting to the Internet • Dialup • Not always on • Customer does not get an IP address • Ties up the phone line. • Communicates with ISP via low speed modem. • ISP groups many low speed connections together for transmission to the internet.

Connecting to the Internet • Digital Subscriber Line (DSL) • High speed connection using telephone lines. • Generally, customer must be within 18,000 feet of a telco central office. • Customer becomes a remote computer on the ISP's network, and does get an IP address.

Connecting to the Internet • Cable • Generally, anyone who has cable TV service can get cable high speed internet, but not all cable companies provide service. • Like DSL, always on, customer becomes a remote computer on ISP's network, gets an IP address. • All customers in your neighborhood share the same bandwidth.

Connecting to the Internet • Satellite • Provided by satellite TV companies. • Good for people in rural areas who can't get cable or DSL service. • Because satellite TV is really one way service, extra stuff has to be added to make service 2-way. Upload speeds are one tenth of download speeds. • Expensive

Network Fundamentals