computer networking

                                           

                                                     COMPUTER NETWORKING

            Computer network is a collection of computers and other hardware devices so that network users can share hardware, software, data and they can communicate with each other electronically.  Computer networking is connecting a computer with other computers or other devices to enable them to communicate with each other, between:

1. computer devices/equipments

2. transmission media to send/control data/signals

3. communication devices to transmit/send data from

    sources to destinations

4.  softwares

                    TYPE OF NETWORK

v  LAN

v  MAN

v  WAN

v  PAN

1. LAN

• Covers relatively small geographical area. Eg. Home,

schools, office building

• Client/ server network is example of LAN

• Allows file exchange, emails, printer sharing or accessing

the internet.

2. MAN

• Network designed to service a metropolitan area, a city or

a county

• Owned or provided by a city or network provider

• For local people’s access to internet

• Example in Malaysia? 3 network of LAN for Mid Valley City

3. WAN

• network that covers large / broad geographical area

• Ex: telecommunications network that links across metropolitan,

regional, or national boundaries) using private or public network

transports.

• In essence, this mode of telecommunication allows a business to

effectively carry out its daily function regardless of location.

• Internet: world’s largest WAN

NETWORK COMPONENT

1. Hots/End nodes

• Refers to the data source and the data destination.
• Examples:
– Personal computers
– Terminals
– Workstations

– Automatic Teller Machine

2. Transmission media

• For transmitting data and control signals
• Responsible for sending electric or signal through spesific
media. It can be bounded (wired) or unbounded (wireless)

media.

Unbounded (wired)	Bounded (Wireless)
·         Coaxial cable            ·         Twisted pair            ·         Fibre optic	·         Radio signals                 ·         Satellite transmission                 ·         Infrared transmission

3. Network electronic devices

• Responsible to control data from source to destination

• Provide interface between different media transmitter or for

different protocol

• To connect multiple network together or to connect

computer or network to the internet

• Examples:

– Bridges

– Routers

– Multiplexers

– Switches

– Hubs

– Gateways

– Front End Processors

4. Software/Application

• The applications at the end nodes (what is end node?)

normally involves technique and protocols

• The protocol determines the rules and procedure to send

data, terminate data, interpret data, present data and

control mistakes

• Software in the network functions to ensure data is

delivered at respective destination

• to control data transmission

5. Network architecture standard and protocols

• NAS: The blueprint of standards that define:

– How device in a network typically connect

– How the device can communicate

• To ensure interoperability between various

devices and equipment made by different

vendors.

• To enable devices made by different companies to

work or communicate with each other.

Example : TCP/IP, Ethernet (802.3), Wi-Fi

(802.11), WiMAX etc

• Network architecture is the way they are design to

communicate

• 2 types :

1. Client/Server Networks

• Client = computers that request or utilize network

resources

• Server = processing the request by client

• What is network server? Provide access to software, files

etc being shared in the network

• Retrieves file from server: download

• Transfer from client to server : upload

2. Peer to Peer Networks

• No central server

• Have direct access to other devices attached to the

network

• As long as they are declared as ‘shared devices’

• Internet peer to peer: eg. iTunes, Bluetooth between hand

phone.

NETWORK TOPOLOGY

Physical	Logical
Linear bus	Shared media
Star	Token based
Ring
Tree
Mesh

1. Physical topology
• The physical layout of devices on a network.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 thenetwork through the actual cables that transmit       data

1. Linear Bus
􀂃 consists of central cable to which all devices are connected
with a terminator at each end.
􀂃 All nodes (file server, workstations, and peripherals) are
connected to the linear cable.
􀂃 Data transmitted through the bus line from one device to
the other
􀂃 Network cannot function when the bus line fails
􀂃 Ethernet and LocalTalk networks use a linear bus topology.
􀂃 The message is transmitted along the cable and is visible
to all computers connected to that cable.

2. Ring
• Each of the systems is connected to its respective
neighbor forming a ring.
• Sometimes called “star-wired network”
• The main difference between the bus and ring is that the
ring topology does not require termination. Because the
systems are connected all together in a loop, there is no
beginning and end point as there is with the bus topology.
• No terminator and no bounce back signal.

3. Star
• All networked devices are connected directly to the
central device (hub) / concentrator
• From central device, all network transmissions are sent
• Data on a star network passes through the hub or
concentrator before continuing to its destination. The hub
or concentrator manages and controls all functions of the
network. It also acts as a repeater for the data flow.

4. A tree (hybrid)
• Can incorporate structures such as ring, star and bus
network in one large network
• It consists of groups of star-configured workstations
connected to a linear bus backbone cable.
• Allow for the expansion of an existing network, and enable
schools to configure a network to meet their needs.

5. Mesh
• Computers have redundant physical connections to one
another
• When the mesh network is a WAN (such as the Internet),
or a LAN that is divided into multiple subnets, routers make
decisions about which of the multiple available paths will
be taken.
• Decide based on which one is the most ‘effective’

2. Logical topology
• how the systems communicate across the physical
topologies
• 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.
• 2 types:

1. Shared media topology

• In a shared media topology, all the systems have the
ability to access the physical layout whenever they need it.
• Advantage : the systems have unrestricted access to the
physical media.
• Disadvantage : Collisions - If two systems send information
out on the wire at the same time, the packets collide and
kill both packets. If add more systems to the network, there
is a greater opportunity for collisions.
• To help reduce the number of collisions, many
networks are broken up into several smaller
networks with the use of switches or hubs, and
each network is then referred to as its own
collision
• Example: Ethernet


2. Token-based topology

• Have a token that travels around the network.
• When a system needs to send out packets, it grabs the
token off of the wire, attaches it to the packets that are
sent, and sends it back out on the wire.
• As the token travels around the network, each system
examines the token.
• When the packets arrive at the destination systems, those
systems copy the information off of the wire and the token
continues its journey until it gets back to the sender.
• When the sender receives the token back, it
pullsthe token off of the wire and sends out a new

empty token to be used by the next machine.
• Advantage : Do not have the same collision problems that
Ethernet-based networks do because of the need to have
possession of the token to communicate.
• Disadvantage : Latency – Because each machine has to
wait until it can use the token, there is often a delay in
when communications actually occur.
• Token-based network are typically configured in physical
ring topology because the token needs to be delivered
back to the originating machine for it to release.
• The ring topology best facilitates this requirement

WIRELESS TECHNOLOGY

Wireless technology

This week I learn wireless technology which is different with last week. This technology does not use wire as the medium of connection. This technology use  signal (radio) signals to send data through the airwaves between devices. Wireless technology is generally used for mobile IT equipment. It encompasses cellular telephones, personal digital assistants (PDA's), and wireless networking. For the example, GPS units, garage door openers and or garage doors, wireless computer mice and keyboards, satellite television and cordless telephones are the technology that’s use wireless technology.

Cisco’s Wireless data initiatives:

·         Point-point/ Multipoint wireless

·         Wireless LAN

·         Wireless local loop

·         Mobile cellular voice/data communications

There are many uses of the wireless technology that  helps our daily life to be more easier. Mobile users can use their cellular phone to access e-mail anywhere and anytime. Travelers with portable computers can connect to the Internet through base stations  installed in airports, railway stations, and other public locations. At home, users can connect devices on their desktop to synchronize data and transfer files.

Type of wireless technology

ü  Wireless wide area networks (WWANs)

ü  Wireless metropolitan area networks (WMANs)

ü  Wireless local area networks (WLANs)

ü  Wireless personal area networks (WPANs

This is the example of the type wireless technology:

           

1.Infra Red

•  Do not use signals in radio frequency

•Send data as infrared light rays in short distance

•IrDA (Infrared Data Association) is an industry standard for wireless communication with infrared light.

•Many laptops sold today are equipped with an IrDA-compatible transceiver that enables communication with other devices, such as printers, modems, LANs, or other laptops. The transfer speed ranges from 2400 bps to 4 Mbps

2.Wireless local area networks (WLANs) , WiFi

•WLANs are based on the IEEE 802.11 standard.

•IEEE 802.11 standard is a standard that has been developed by IEEE (Institute of Electrical and Eletronic Engineers) to differentiate between the various technology families

•There are three physical layers for WLANs: two radio frequency specifications (RF - direct sequence and frequency hopping spread spectrum) and one infrared (IR).

•Wi-Fi underlying this technology

•WLAN configurations vary from simple, independent, peer-to-peer connections between a set of PCs, to more complex, intra-building infrastructure networks.

•Wireless solutions :

i. A point-to-point solution is used to bridge between two local area networks, and to provide an alternative to cable between two geographically distant locations (up to 30 miles).

ii. Point-to-multi-point solutions connect several, separate locations to one single location or building

 3.Broadband wireless.

•Broadband wireless access is a technology aimed at providing high-speed wireless access over a wide area from devices such as personal computers to data networks.

•According to the 802.16-2004 standard, broadband means 'having instantaneous bandwidth greater than around 1 MHz and supporting data rates greater than about 1.5 Mbit/s

•It is planned to be used in the next few years

and is estimated to have a range of

50km (30 miles).

4.Bluetooth,

•Bluetooth is an industrial specification for wireless personal area networks (PANs).

•Designed for very short range <10 m

•Connect and exchange information between devices such as mobile phones, laptops, PCs, printers, digital cameras and video game consoles over a secure, globally unlicensed short-range radio frequency.

•Data speed up to 3Mbps

5.WiMax

• To extend the range of wireless network

•Speed up to 70Mbps, Range 30 miles

•Provides access to internet access to fixed location with larger coverage

I also learn about the generation of mobile phone. I hope this picture make you understand the evolution of mobile phone from 1G to 4G.

WIRED TECHNOLOGY

Connecting a cable

So what I learned in chapter last week is “Connecting a cable : cabling and hardware”. In this chapter, I learned more to wired connection because wireless connection will be explain in next chapter. Generally, cable is the medium through which information usually moves from one network device to another.

There are 3 types of cables which is

Ø  Coaxial

Ø  Twisted pair

i. unshielded

ii. shielded

Ø  Fibre optic

There are the difference between these three types of cable :

There are also cable connectors that use to connect the cable, but there are several types of connectors.

1.Coaxial cable connector

•The most common type of connector used with coaxial cables is the Bayonet-Neill-                              Concelman       

(BNC) connector

•Different types of adapters are available for BNC connectors, including a T-connector, barrel

connector, and terminator.

2. Fibre optic cable connector

•The most common type of connector used with fiber optic cable is the ST & SC connector

3. UTP cable connector

•The standard connector for unshielded twisted pair cabling is an RJ-45 connector

(RJ=Registered Jack)

•Look like a large telephone-style connector

•A slow allows RJ-45 to be inserted only one way

                When we use the topology, there are some type of cable that suitable to some topology :

Physical topology	Cable used
Linear bus	Coaxial                     Twisted pair                     Fibre optic
Star	Twisted pair                     Fibre optic
Star wired ring	Twisted pair
Tree	Coaxial                     Twisted pair                     Fibre optic

                In this chapter also, I also learned network hardware. What is network hardware?. Networking hardware includes all computers, peripherals, interface cards and other equipment needed to perform data-processing and communications within the network.

             
 There are 8 hardware or equipment that I learn which is:

ü  File server

ü  Workstation

ü  Network interface card

ü  Concentrator or hubs

ü  Switch

ü  Repeaters

ü  Bridges

ü  Routers

1. File server

•A file server stands at the heart of most networks.

•very fast computer

•large amount of RAM and storage space,

•a fast network interface card.

•network operating system software resides on this computer, along with any software applications and data files that need to be shared.

2. Workstation

•user computers that is connected to a network are called workstations.

•configured with a network interface card, networking software, and the appropriate cables.

•do not necessarily storage capability , files can be saved on the file server.

•almost any computer can serve as a network workstation.

3. Network Interface Card (NIC)

•provides the physical connection between the network and the computer workstation.

•major factor in determining the speed and performance of a network

•Most NICs are internal, with the card fitting into an expansion slot inside the computer.

•Some computers, such as Mac Classics, use external boxes which are attached to a serial port or a SCSI port.

•Laptop computers - built-in NIC or network cards that slip into a PCMCIA slot.

•The three most common network interface connections are

–Ethernet cards,

–LocalTalk connectors

–Token Ring cards.

4. Concentrator/Hubs

•Central connection point

•Transmit all data received to all node connected to the hub. Regardless to which device the data being sent to

•Lots of extra network traffic, network less efficient

5. Switch

•Switch vs Hubs : Both devices contain ports to connect the devices together via networking cables and to facilitates communication between the devices, but they differ in how they transfer data.

•Identifies the device on the network for which the data is intended and sends the data to that node only

•Can connect Ethernet, token ring, Fiber Channel or other types of packet switched network segments together to form an internetwork

6. Repeater

•to boost the signal with a device called a repeater. The repeater electrically amplifies the signal it receives and rebroadcasts it.

•can be separate devices or they can be incorporated into a concentrator.

•used when the total length of your network cable exceeds the standards set for the type of cable being used.

7. Bridges

•A bridge monitors the information traffic on both sides of the network so that it can pass packets of information to the correct location. The bridge manages the traffic to maintain optimum performance on both sides of the network

•It keeps information flowing on both sides of the network, but it does not allow unnecessary traffic through.

•Can be used to connect different types of cabling, or physical topologies. They must be between networks with the same protocol.

•A network bridge connects multiple network segments

•Bridges are similar to repeaters or network hubs, devices that connect network segments at the physical layer, however a bridge works by using bridging where traffic from one network is managed rather than simply rebroadcast to adjacent network segments.

8. Routers

•Connectors that used to link different networks

•translates information from one network to another; it is similar to a superintelligent bridge.

•select the best path to route a message, based on the destination address and origin.

•direct traffic to prevent head-on collisions, and is smart enough to know when to direct traffic along back roads and shortcuts.

•While bridges know the addresses of all computers on each side of the network, routers know the addresses of computers, bridges, and other routers on the network. Routers can even "listen" to the entire network to determine which sections are busiest -- they can then redirect data around those sections until they clear up.

•Also determines the best route to send the data over the Internet.

        
   •Routers can:

ü  Direct signal traffic efficiently

ü  Route messages between any two protocols

ü  Route messages between linear bus, star, and star-wired ring topologies

ü  Route messages across fiber optic, coaxial, and twisted-pair cabling

That’s all that I learned in this chapter. Thank you.

Data Communication

DATA?
- “raw data” that had been processed, arranged, stored and will be used to get information

Data communication?
- Process of change / transfer information in a form of a digital data (binary) in between two or more devices using electronic delivery system.
- Data communication is transmitted via mediums such as wires, coaxial cables, fiber optics, or radiated electromagnetic waves such as broadcast radio, infrared light, microwaves, and satellites.

Type of signal
•Data comes in variety styles : text, voice, picture and video
•All this type of information needs to be converted into signal that can be understood by the      communication media in order to transmit the data from one place to another location.
•Data comes in two type of formation

1.Analogue signal
2.Digital signal

1. Analogue
•Is like the human voice
•Formed by continuously varying voltage level that create wave than be grasped by an analogue transmitter like microphone.
•Typically presented by their characteristics sine wave
•Analogue signal is transmit through PSTN line such as phone line
•Involves 2 parameters ;

Frequency : number of completed wave’s cycles. Measured in Hertz (Hz), which is cycle per second
Amplitude : wave’s height that measured in voltan(V) or decibel (dB). A strong signal will create higher amplitude.



2. Digital
-Transmission of binary electrical or light pulses that only have two possible states, 0 and 1 (language of computers)
-Digital format is ideal for electronic communication as the string of 1s and 0s can be transmitted by a series of "on/off" signals represented by pulses of electricity or light
-Presented as a square wave

-Digital signal need to be change into analogue signal to be transmitted through PSTN lines.

-The process of changing ;
1. Analogue to digital signal : modulation
2. Digital to analogue signal : demodulation
-Modem is the hardware that used to do this changing process

Data transmission mode

-Data need to be digitized before it can be transmitted through the electrical transmission medium.
-When we enter data into a computer via keyboard (alphabet or numeric), the data is encoded into an equivalent binary coded using standard coding scheme such as;
 1. Extended Binary Coded Decimal Interchange Code (EBCDIC)

 2. American Standards Committee for Information Interchange (ASCII)

-The digitized data are then transmitted through

1. Parallel transmission
- data is sent at least one byte at a time, each bit in the byte taking separate path
- means that a group of bits is transmitted simultaneously by using separate line for each bit

2. Serial transmission
- data sent one bit at a time, one after another a long a single path
-A bit slower compared to parallel transmission,
-used for short communication e.g between computer to printer

3 Seriel Transmission Modes

1. Synchronous Transmission
•data transmitted into blocks called “framed” or groups and transferred at regular specified interval
•Both sending device and receiving device are operated simultaneously and are resynchronized after each few thousand data signals bits are transmitted
•Only the start and end of the entire frame is mark with the start and stop bit
•This type of transmission mode are more efficient as fewer control bits involves

2. Asynchronous Transmission
•Used when the bits are divided into small group (bytes) and sent independently.
•The group of bits can be sent at any time and the receiver never knows when they will arrive (e.g: keyboard)
•Usually required a “start bit” to alert the receiver of incoming data and a “stop bit” to indicate the
end of transmission.

3. Isochronous Transmission
•data is sent at the same time as other related data to support certain types of real time applications e.g streaming voice, video and music


Directions/ Flow of Data Transmission

1. Simplex
•One way communications / one direction
•Role of transmitter and receiver are fixed

•Ex: radio station – transmits the signal to its listeners and listener never allows transmitting back

2. Half Duplex
•Flow in 2 direction but never at the same time
•One station transmits information to another station without any interruption
•The other station will response after that transmission has been completed
•Ex: Walkie-talkie

3. Full Duplex
•Data can moves in both directions at the same time
•Both station can transmit and receive simultaneously
•Consists of two simple channels; 1 channel used to forward while another as the reverse channel, linking at the same point
•Ex: Telephone
•Many networks and most internet connections are full duplex

Data Compression







Example of file compression formats, such as ARC and ZIP.

Elements of computer and communications technology

               Hye and assalamualaikum, today i just learned about elements of computer . There are 6 elements involved which is:


1. People
2. Procedure
3. Data
4. Hardware
5. Software
6. Communications/ Connectivity


But, when i search at the internet  about this information, there are a little bit different with what i learned. There are seven major elements of communication process are

1. sender
2. ideas
3. encoding
4. communication channel
5. receiver
6. decoding
7. feedback

http://www.yourarticlelibrary.com/business-communication/7-major-elements-of-communication-process/25815/

There are two videos that can help you understand more about this element in communications process

Wait! i want to share a video that i found that i think very useful and many tips that can help us as a teacher soon.

Introduction to telecommunication

Communication
•imparting, conveying or exchange of thoughts, messages, ideas, knowledge or information by sign and sounds like speech, signals, writing or behavior. According to wikipedia:

Communication (from Latin commūnicāre, meaning "to share"^[1]) is the act of conveying intended meaning to another entity through the use of mutually understood signs andsemiotic rules. The basic steps of communication are the forming of communicative intent, message composition, message encoding, transmission of signal, reception of signal, message decoding and finally interpretation of the message by the recipient.

The study of communication can be divided into communication studies, which concerns only human communication, and biosemiotics, which examines the communication of organisms in general. Communication is usually visual, auditory, or biochemical, while human communication is unique for its extensive use of language.
 You might be interested with the history of information technology. So, you can click this link below. What can I summarized from this page is there are four stage of development age which is premechanical, mechanical, electromechanical, lastly is electronic.

http://openbookproject.net/courses/intro2ict/history/history.html

Click this link below to watch video  about history of communication.

https://www.youtube.com/watch?v=ytUymzVJMZU



Communication process involves 6  basics elements 

1. Sender
2. message
3. channel
4. receiver
5. noise
6. feedback