COMPUTER NETWORKS
Computer Networks
A series of electronic devices connected together through copper cables, fiber optics, and radio waves.
There are many types of computer networks, including:
Local-Area Networks (LAN's): The computers are geographically close to each other (in the same building).
Wide-Area Networks (WAN's): The computers are farther apart and are connected by telephone lines or radio waves.
Metropolitan-Area Networks (MAN's): A MAN is usually not privately owned by the user or the company.
Computer Networks
Local-Area Networks (LAN's):
two buildings with 4 departments connected as a LAN.
Wide-Area Networks (WAN's):
A WAN would be most useful for large companies with offices or factories in widely separated areas
INTERNET – A type of WAN
Computer Networks
In addition to these types, the following characteristics are also used to categorize different types of networks:
topology architecture protocol
topology : The geometric arrangement of
a computer system. Common topologies include a
mesh,star,bus, ring,tree.
Computer Networks
Topology refers to the shape of a network, or the network's layout.
Topologies are either physical or logical.
Physical TopologyThe physical layout of devices on a network.
Every LAN has a topology, or the way that the devices on a network are arranged and how they communicate with each other.
The way that the workstations are connected to the network through the actual cables that transmit data.
Logical Topology
The way that the signals act on the network media,
or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices.
Network Topology
The five most common network topologies. MeshStarBus Ring Tree
Mesh Topology
In a true mesh topology every node has a connection to every other node in the network.
Star Topology
Nodes communicate across the network by passing data through the hub.
All devices are
connected to a
central hub.
Bus Topology All devices are connected to a central cable, called the bus or backbone.
Ring Topology
All devices are connected to one another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either side of it.
Tree Topology
A hybrid topology. Groups of star-configured networks are connected to a linear bus backbone.
Computer Networks
architecture
Networks can be broadly classified as using either a
peer-to-peer or client/server
Network Architecture
Sharing single computers with
each other. peer-to-peer
peer-to-peer One individual can access and
save files to another individuals computer.
This can be slow when large files are being transferred.
client/server
A single computer is set aside to only save files and run programs.
Each computer in the network can run any program, or save files, to this single computer, which is named the server.
Computers on a network are sometimes called nodes, a processing location.
Every node has it's own unique network address.
Computers and devices that allocate resources for a network are called servers.
Computer Networks
protocolsFor two computers to talk to each other, they must agree on some kind of standard way of communicating.
Computer Networks
computers on a network will not be able to communicate unless they are able to speak the same "language."
The languages by which computers communicate over a network are called protocols.
protocol
Protocols tell computers how to send and receive data and what to do with the data after they receive it.
The protocol defines a common set of rules and signals that computers on the network use to communicate.
Computer Networks
Modern computer networks use standard protocol called Ethernet to communicate with one another.
Ethernet
One of the most popular protocols for LAN's is called Ethernet, a local-area network (LAN) protocol developed by Xerox Corporation in cooperation with DEC and Intel in 1976.
Ethernet
Ethernet uses a bus or star topology and supports data transfer rates of 10 Mbps.
It is one of the most widely implemented LAN standards.
Another popular LAN protocol for PC's is the IBM token-ring network.
EthernetEthernet is a technology used to connect multiple devices together to form a "network", it consists of physical cables, connectors, and a protocol that allows clear communications between devices.
Ethernet run at either 10, 100 or 1000 megabits per second.
Cable and Hardware
Ethernet has several wiring standards that dictate the speed and the communications medium the computers will use.
Cable Type & Speed
Name
10Base-2
10Base-T
10Base-F
100Base-T (Fast Ethernet)
1000Base-T (Gigabit Ethernet)
Cable Type
Coaxial
CAT3 or CAT5
Twisted Pair
Fiber optic
CAT5 Twisted Pair
Fiber optic
Speed
10Mbps
10Mbps
10Mbps
100Mbps
1000Mbps
Network Channels
There are three main cable types:
Coaxial, which looks like TV antenna wire,
Twisted pair; which looks like phone wire; and
Fiber optic wire.
Types of cables
Coaxial Coaxial cable is
classified into two categories: baseband (uses
digital signals) and
broadband (uses analog signals) coaxial cable
Coaxial
A single insulated inner wire is surrounded by a cylindrical conductor which is covered with a shield; it transmits electromagnetic signals.
Types of cablesTwisted Pair
two insulated copper wires twisted together in a regular spiral pattern; one pair establishes one communication link; it transmits electromagnetic signals.
Twisted pair
Twisted pairs are distinguished between shielded (STP) & unshielded (UTP)twisted pairs according to their protection against electromagnetic fields
Types of cables
Fiber optic
transmits optical signals, which must be transformed to electromagnetic signals
consists of three concentric sections,the core (a fibre conducting optical rays), the cladding (reflecting optical rays) and the jacket (surrounding one or many fibres to protect them)
Fibre Optic
Wireless Networks Wireless networks are perfect when you don’t feel like stringing a bunch of cable over you floor. They also have the added advantage that your computer (or laptop) can be “on the go” anywhere in the house. However, they are quite expensive.
Other network hardware
Besides wire, you will need network cards for each machine on a network, and a hub
Hub
The most important piece of your network is the hub.
It is the heart of any 10/100 Base-T network.
All computers on the network are connected to the hub.
HubIt is the job of the hub to broadcast a signal send from one machine to all the machines on the network.
The hub also isolates a computer if it detects a cable fault.
HubHubs come in many sizes, ranging from 4 ports all the way up to 36 ports.
Each port can be used to connect a computer. The more ports, the more computers you can connect.
Obviously, the more ports, the higher the price.
The network card
The last piece of hardware you will need is network interface cards (or NICs) for each machine in your house.
The network card
This card is used to communicate on the network.
Some computers, such Macintoshes, already come pre-installed with network cards.
The network card
You can tell if your computer has a network card build in by looking in the rear of the case for a jack that looks kind of like a phone jack, only bigger.
Network cards come in three flavors: 10Base-T, 10/100Base-T 100Base-T.
The network card
10Base-T Ethernet
The primary type of Ethernet in use today is 10Base-T, which operates at 10 Mbps and follows a star topology using unshielded twisted-pair cabling.
10Base-T Ethernet networks are very easy to set up. This flavor of Ethernet relies on hubs.
The network card100Base-T cards cost only a little more than ones that operate at 10 Mbps, and give you much more flexibility for upgrading your network in the future.
Most 100Base-T hubs will automatically sense whether the card connected to each port is 10 or 100 Mbps and operate accordingly.
ARCNETShort for Attached Resource Computer network, ARCnet is one of the oldest, simplest, and least expensive types of local-area network.
ARCnet was introduced by Datapoint Corporation in 1977.
It uses a token-ring architecture, supports data rates of 2.5 Mbps, and connects up to 255 computers.
Token ringis a local area network (LAN) in which all computers are connected in a ring or star topology and a bit- or token-passing scheme is used.This prevents the collision of data between two computers that want to send messages at the same time. The Token Ring protocol is the second most widely-used protocol on local area networks after Ethernet.
ARCNET
A special advantage of ARCnet is that it permits various types of transmission media i.e twisted-pair wire, coaxial cable, and fibre optic cable
to be mixed on the same network.
Summary
Types of Networks:
LAN
WAN
MAN
Network Topology:
Mesh
Star
Bus
Ring
Tree
Channels:
Twisted pair
Coaxial
Fibre opticNetwork Interface Card:
Ethernet
Arcnet
Server
Nodes
Hubs