LEKSWAP: BASIC NETWORKING

LEKSWAP: BASIC NETWORKING: "An Introduction to Computer Networking First we had the industrial revolution in the 19th and 20th centu..."

BASIC NETWORKING

An Introduction to Computer Networking
First we had the industrial revolution in the 19th and 20th century, which swept the whole world. The computer revolution is said to be the next big thing which is going to downsize the achievements of the earlier revolution.
Computer revolution has arrived in part and parcels in the 21st century and it is just going to grow bigger by the minute. Every minute at least a hundred PC's are bought all around the world, and majority of them are nowadays connected to the internet. When its all about connecting two or more computer systems, in different parts of the world, bang comes the need for networking.
Networking allows various intelligent devices like computers, PDA, mobile phones to communicate with each other either through physical wires or wireless signals. This is nothing but the much used word "convergence" of technology.
We all send emails, don't we? But have we ever wondered how this email knows where to go? Well devices like routers act like postmen, who look at the IP address the email address originated from and they then forward it to the destination IP address, who is the actually intended recipient of the email. Networking basically explains one how this sequence of occurs happens in real time world and as to how the data packets reach where they have to.
Software and Networking are inter-dependant. A Client Server application created by the tireless programmer can run only on a network, formed by your hardware guy, whose majority of the time goes into tripping about CAT5 cables and sorting them out. The operating system (network operating system) used by the system administrator is actually the successful execution of the code of a software programmer, at runtime.
Currently the software field is very much saturated, as all that one requires in the software field is good logic, imagination and creativity. Hence even if you are not from a technical background as such, still you can pick up a course on say CC++ or Java and climb the steps of being a coder from day one itself. But networking is all about troubleshooting in real life situations. No matter how badly one messes up with a computer system, the networking guy has to get the machine up and running ASAP.
In the forthcoming articles in this section, you will get to know more about the standard models over which the internet was built, a preview on the various devices that make a network work, like your hub, router, repeater, switch and also about the various networking operating systems. Useful tips regarding cracking certifications like CCNA, MCSE will also be given.
So watch out for this space, where you can quench your thirst for technical knowledge, with a cherry of philosophy and real life examples on top.   
Computer Network – Basics
An internet work is a collection of individual networks, connected by intermediate networking devices, that functions as a single large network. The networking devices are the vital tools for communication.  Whenever you have a set of computers or networking devices to be connected, you make the connections, depending on the physical layout and your requirements Depending on the physical layout or topology of the network, there are three types of networks.
LAN
LAN stands for Local Area Network. These networks evolved around the PC revolution. LANs enabled multiple users in a relatively small geographical area to exchange files and messages, as well as access shared resources such as file servers.
WAN
WAN stands for Wide Area Network. The interconnection of various LAN’s through telephone network, which unites geographically distributed users is achieved through WAN. In short when we log on to the internet, we become a part of a WAN.
MAN
MAN stands for Metropolitan Area Network. It is usually the interconnection between various LAN’s in a particular geographical area like a metropolitan city like Bombay. Hence the name.
Internetworking evolved as a solution to three key problems: isolated LANs, duplication of resources, and a lack of network management. Isolated LANS made electronic communication between different offices or departments impossible. Duplication of resources meant that the same hardware and software had to be supplied to each office or department, as did a separate support staff. This lack of network management meant that no centralized method of managing and troubleshooting networks existed.
Open Systems Interconnection Model
The OSI model is the basic model describing the data movement through a network. The Open Systems Interconnection (OSI) reference model describes how information from a software application in one computer moves through a network medium to a software application in another computer. The OSI reference model is a conceptual model composed of seven layers, each specifying particular network functions. The OSI model divides the tasks involved with moving information between networked computers into seven smaller, more manageable task groups. A task or group of tasks is then assigned to each of the seven OSI layers.
The following list details the seven layers of the Open System Interconnection (OSI) reference model:

• Layer 7—Application layer (A)
• Layer 6—Presentation layer (P)
• Layer 5—Session layer (S)
• Layer 4—Transport layer (T)
• Layer 3—Network layer (N)
• Layer 2—Data Link layer (D)
• Layer 1—Physical layer (P)

Tip To Remember
People Do Need To Send Packets Away.
The first letter of each word is related to the alphabet associated with the name of the OSI layer. P of People stands for Physical Layer of the OSI model and so on.
Protocol
The OSI model provides a conceptual framework for communication between computers, but the model itself is not a method of communication. Actual communication is made possible by using communication protocols. In the context of data networking, a protocol is a formal set of rules and conventions that governs how computers exchange information over a network medium. A protocol implements the functions of one or more of the OSI layers. A wide variety of communication protocols exist, but all tend to fall into one of the following groups: LAN protocols, WAN protocols, network protocols, and routing protocols. LAN protocols operate at the network and data link layers of the OSI model and define communication over the various LAN media. WAN protocols operate at the lowest three layers of the OSI model and define communication over the various wide-area media. Routing protocols are network-layer protocols that are responsible for path determination and traffic switching. Finally, network protocols are the various upper-layer protocols that exist in a given protocol suite.
This being the beginning session, I haven’t dwelled into the details. Lets start small and end big! So till then get these fundamentals ingrained in your mind.
Are you Safe on Network?

As an user of computer you must have seen messages for alerts for viruses, worms, Trojan horses and many other related to security of your computer, or you must be getting emails even phone calls making you alert about computer security. They must be telling you so many buzzwords like “your computer is being monitored and used by somebody else, we can solve the problem by installing some software…” and so on.

Now the bottom line is this:

Should you really worry about security issue?
Can someone really use your computer?

Answer is simple and straight “Yes”.

You must be thinking why anybody would like to intrude your system? Reason can be anything like:

• May be someone is interested in getting your personal information or a person wants to steal some data from your system.
• May be some one wants to cause damage to your system.
• May be someone wants to test his or her computer skills?

Someone may be interested in your personal information for financial gain, may be the person is interested in your credit card number or your bank account number or even your SSN number.
Most credit card thieves are interested in cracking databases maintained by merchants, financial firms like banks and credit reporting services. How hacker can get my password or credit card information? Hacker can install some malicious code that could also track your keystrokes and send the data to remote attacker all usernames and passwords it obtained when you visited an online banking site.
A person could be interested in causing damage to your system, reason can be anything like the person is not having good relations with you, so by damaging your system he or she wants to take revenge from you for any reason.
Its not always that person who is cracking your system (crackers) is for wealth and revenge. Most crackers see the process as a game; an exiting challenge that let them uses their knowledge of computer.
There are some cases where cracker wants to break into a “secure” system to demonstrate its vulnerabilities to its owners.
Reason can be there where cracker wants to use your system for doing illegal work. They don’t want them to be traced down, so they may want to put you in all illegal activities.
If you have high-speed Internet access with wireless router then the risk of getting exposed to the hackers is more. Some of the security risks for wireless Internet access are Insertion Attacks, Interception and monitoring wireless traffic, Configuration change, and Network Jamming etc.

With so many reasons and so many cases regarding network security and so many threats coming from so many different angles, a question arises how are you supposed to protect yourself?

You cannot get 100% protection, some of the risk is impossible to avoid, you can’t control what comes from outside.

But still we can take some measures to minimize the disasters and risk of losing personal information.
Plan in advance for your system recovery. Like you should have back up for all your important data, pictures, songs etc.

Do not forget the Basics of Security
Regardless of how much protection you have in place, or whether you use a Mac, Windows XP, or Firefox browser etc, all the security precautions should be taken.

Spend some money in buying good anti virus software, hardware or software based firewall, latest intrusion detection system, anti spy ware, install them in your system and keep updating these protection software, security patches from vendors regularly, because in every new version these software’s have new features for new possibilities.

Keep changing your password regularly and most important thing, password should be unpredictable. You should not keep your name your pet’s name or any other related name or number as your password. If you are giving your password to anyone like to your computer consultant then change it immediately after your work is being done.

E-mails are the most common source of virus. Do not open any suspicious mail attachments, which comes with any mail even from your friends or relatives, it can be a program to get into your system and take out all your data. Email worms routinely spoof the sender information. Some of the recent virus file extensions are exe, inf, url, vbs, vbe, wsf, wsh, wsc, zip etc.

Disconnect your system from Internet when you don’t use it. If you are using wireless router then keep the password security or Wi-Fi Protected Access (WPA) enabled.

These are few measures, which when combined with your common sense can serve you as tools for preventing your system from outside raiding to some extent. 
Bluetooth

In this article I will talk about Bluetooth. You must be thinking what is this Bluetooth? Is it something related to cosmetics or something related to teeth or may be something…
Well to begin with, Bluetooth is a new technology named after the 10th century Danish king Harald Bluetooth Blatand who ruled part of Scandinavia in 960 AD .He helped unite his part of the world. As the name implies that Bluetooth would be the technology to unite the mobile world.
Bluetooth device is the revolutionary device launched by L.M Ericsson, to integrate its phone with all Internet enabled devices. Two L.M Ericsson telephone employees, the Swedish born Sve Mattison and his Dutch colleague, Jaap Haartsen, originally designed Bluetooth technology in 1994.

The term Bluetooth refers to an open specification governed by the Bluetooth special interest group (SIG) for wireless personal area networks (PANs). This technology provides a way to connect and exchange information between devices like personal digital assistants (PDAs), mobile phones, laptops, PCs, printers and digital cameras via a secure, low cost, globally available short-range radio frequency.

Lets look at some examples where we can use Bluetooth technology.
Nowadays, you have to either manually enter the names and phone numbers of all your contacts or in other advance way you can use a cable to connect your phone and PC and can run some application to synchronize the contact information.
With this new technology you could see this happens automatically, without your involvement, whenever phone will come in the range of PC data will automatically updated.
With Bluetooth there are so many exciting applications like, nowadays whenever you come to office, you have to do so many setup to get to start to work, like you have to connect your notebook to USB port, you switch it on, then your notebook gets boot up and after that only you are able to log in. All this process takes some of your time. Now think about the situation where you walk into the office switch on the notebook and get ready to do work. This is possible with Bluetooth, it makes your notebook to start communicating with your server via radio signals, not require you to connect it to the USB port.
Even car manufacturers are not left behind; car manufacturers such as BMW, Lexus and Toyota have equipped some of their models with Bluetooth car kits. This allows you to use the features of your cell phone through the car’s audio system while the phone itself stored in the trunk for instance.
Now the question arises, how the Bluetooth technology works?

The Bluetooth system consists of an RF (Radio Frequency) transceiver, baseband and protocol stack. It uses radio standards to enable file-sharing and data transfers between devices like PDA and desktop. These radio frequencies are present in all directions and their range varies between 10cm to 10m, further it can be extended to 100m depending on the power class of the product, again this power transmission rates varies in many Bluetooth products depending on the power saving features available in particular unit, bandwidth requirements, transmission distance, etc.
Because this Bluetooth technology uses radio signals, the walls in our house will not impede a Bluetooth network. Also we can control devices in the different rooms very easily.
Bluetooth operates in globally available low radio frequency at 2.4 GHz and supports data speed of up to 721 Kbps, as well as three voice channels.
To make use of Bluetooth technology you have to make sure the new device which you buy is Bluetooth compatible, Bluetooth compatible devices comes with software to configure Bluetooth to share data by implementing specific profiles, these profiles will determine what type of information or resources the device can store.
When you want two new Bluetooth device should communicate, first you have to introduce them to share data, this is known as pairing (authorizing the device to communicate with each other).
It is also possible to configure the devices to have password protection, so that other people cannot take part in your communication. One more thing is also there, you can set up the device to constantly announce their presence to the device in its range, and the connection can be automatically establish.

Conclusion
As this is the emerging technology today and is widely adopted by industry leaders, in every version new features are included, the next version of Bluetooth includes a number of features to increase security, usability and value of Bluetooth.

 I Model and TCP/IP Model
The OSI model by IBM is the biggest boon that systems developer can have had for their karma in the past life.

What exactly is the OSI model?
As I had mentioned it is actually a layered stack, with 7 layers. Each of these 7 layers are implemented by different protocols for each layer. But keep in mind, its not necessary that all these layers have to be used, when trying to device a system. A system can also make away with any of the 7 layers like say the Session Layer or the Application Layer.

Consider a Router for example. A Router is a device, which works in the Network Layer of the OSI Model. Its main function is to route packets that arrive at its ports. Router takes a routing decision for each of the packet that arrives at its port, on the basis of Routing Tables.

Routing Tables are somewhat similar to the Time Table we follow while attending our courses in college. Depending on the subject scheduled in the timetable for a particular day, we decide whether to attend the lecture or not. In a similar way the Router looks at the destination address (which is the IP address) of the packet that is to be routed.

Now remember that an IP address is made up of a Host ID and a Network ID (I will cover IP addresses in depth in the future articles). The Router looks at the Network ID and compares it with the other Network ID’s present in its Routing Tables. If the particular Network ID is found to be present in the Router’s Table, the packet is routed to the appropriate destination successfully. If the Network ID of the packet is not present in the Router’s Routing Table, then the router forwards the packet to the next nearest router and this process continues till the packet reaches its intended destination.

This is very similar to what you do when you are asked where someone stays, while walking on the road. You are shown the address by the person, who wants to reach a place (Consider this Address as the Destination IP address). Now what you do is directly look at the name of the street. This is because the name of the building is not something you will be immediately familiar with, as a building with the same name will surely exist in thousand different streets.

If you are very well aware of the geography of the place, then by looking at the Street (Network ID) you tell the person where the street is. ( similar to a Router finding that the Network ID field of the IP address of the packet is present in its Routing Table). If you don’t know the street or the address, you tell the person to ask some one else ( that is you forward him to the next nearest Router).

OSI model doesn’t say you do things this way. It just tells you “ Hey keep in mind that these things should be covered while designing a feasible network solution “.

TCP/IP Model
The TCP/ IP model superseded the OSI model. This is the model that is currently most widely used. The various layers in the TCP/IP model are :

5) Application
4) Transport
3) Internet work
2) Data Link
1) Physical

Note that the Sessions and Application Layer present in the OSI Model are absent in the TCP/IP Model.

In the 1990’s, TCP/IP has become firmly established as the dominant commercial architecture and as the protocol suite upon which the bulk of new protocol development is to be done.

There are a number of reasons for the success of the TCP/IP model over the OSI model:

1. Internet is built on the foundation of the TCP/IP suite. The tentacles of the Internet and the World Wide Web have spread throughout the world and that is the main reason for the success of TCP/IP model over the OSI model.
2. TCP/IP protocols were initially researched under a project in the Department of Defense (DOD). DOD was committed to international standards and most of its operational requirements couldn’t be met by the OSI model. So it started to develop the TCP/IP. Since the DOD is the largest consumer of software products in the world, the vendors were encouraged to develop TCP/IP based products.

In the next article I will cover more about the various layers in the OSI Model and the TCP/IP Model.
Layer One of OSI Model
Physical Layer
In the last article I explained in depth about the OSI and TCP/IP Models. Now in this layered protocol structure, we have to see what each layer does. Basically in the OSI Model, we have two layers:
1) Upper Layer – Comprising of Sessions, Presentation and Applications Layers.

This layer basically deals with the application issues (basically software). Application Layer is the closest to the end user. For eg: Applications like Microsoft Word, Powerpoint on which we work can be said to be closer to the end user like us.

2) Lower Layer – Comprising of the Physical, Data Link, Network and Transport Layers.

This layer deals with the data transport issues. The Physical and Data Link layers basically deal with hardware and software. Other Lower Layers are generally implemented using software.

Lets have a look at some of the Lower Layer Protocols in detail :

1) Physical Layer:

The Physical Layer defines the Mechanical, Electrical, Procedural and Functional specifications for activating, maintaining and deactivating the physical link between communication network systems.  These specifications define characteristics such as:

• Voltage levels and timings of voltage changes.
• Physical data rates and maximum transmission distances
• Physical Connectors.

Devices in this layer copy frames or data from one network to another, depending upon the device in operation like a Hub or a Repeater. This layer basically deals with the network components that you can touch. Any device or protocol that operates at the Physical Layer deals with the physical components of the network. It deals with medium like Copper Wires, UTP cables, Coaxial cables or Fiber Optic Cables. When a protocol at the physical layer receives information from the upper layers, it translates all the data into signals that can be transmitted on a transmission medium. This is called Signal Encoding. That is the ones and zeros of data are converted into electrical on –off’s by the physical layer protocols.
Physical Layer also specifies how much of the media will be used during the data transmission.
1. Base band Signaling: Technology in which a network uses all available signal frequencies or the entire bandwidth. Eg: Most LAN technologies like Ethernet.

2. Broad band Signaling: Technology in which a network uses only one frequency or a part of the entire bandwidth i.e multiple signals can be transmitted over a media simultaneously.Eg: TV signals, where you have various channels like CNBC, ZEE, BBC, each on a different frequency and hence each occupies a part of the bandwidth.
Physical layer also specifies the topology or layout of the transmission media. There are four possible kinds of topologies:

• Bus
• Star
• Ring
• Mesh

Devices used in the Physical Layer are

• Network Interface Cards (NIC)
• Transceivers
• Repeaters
• Hubs
• Multi Station Access Units (MAU’s)

Implementations in the Physical Layer :

• LAN specifications and
• WAN specifications

Remember that the physical layer is the same for TCP/IP Model so all the above applies to TCP/IP Model too. I will cover all the subtopics like the devices, topologies, implementations and transmission media in the forthcoming articles. In the next article, lets have a look at the Data Link Layer and also some part of the Network Layer.    

Wireless Technologies:
Voice and Messaging
by Ruchi Gupta
Whether its because you made a call using a mobile phone, received a message on your pager, checked your email from a PDA or even just seen a advert related to it, we have all come across a wireless data or voice network. Wireless technologies represent a rapidly emerging area of growth and importance for providing ubiquitous access to the network for all those who want to use wireless services.

There are numerous applications for the different wireless technologies. In broader ways application of wireless technologies are divided into the following:

• Voice and Messaging.
• Hand-held and other Internet-enabled devices.
• Data Networking.

All the above classifications are based on the cost, network model, bandwidth, and coverage areas. In this article we will discuss about Voice and Messaging part of wireless technologies.
Mobile phones, pagers, and two-way business radios comes under voice and messaging services. These devices can further be divided into two categories depending on what standards they are based on either it can be analog or digital which again depends on in the way in which they process signals and encodes information.
The analog standard is Advanced Mobile Phone System (AMPS). Digital standards are Global System for Mobile Communications (GSM), or Code Division Multiple Access (CDMA).
These devices operate within networks and different carriers operate these network. In USA there are carriers like AT&T, Sprint, Verizon, local phone companies etc. and operate in different frequency band, which are allocated by Federal Communication Commission (FCC), this commission regulates interstate and international communications by radio, television, wire, satellite and cable.
Advance Mobile Phone System (AMPS)
This is the analog mobile phone system standard developed by Bell Labs, and officially introduced in USA in 1984. Now a day analog is not considered advanced but at that time it was considered quit advanced and its introduction is what made today’s mobile world practical.
This standard is based on the initial electromagnetic radiation spectrum and allocates frequency ranges within the 800 and 900 Megahertz (MHz) spectrum to cellular telephone.
Each service provider can use half of the frequency range for receiving signals from cellular phones and half for transmitting to cellular phones. The bands are divided into 30 kHz sub-bands called channels. The receiving channels are called reverse channels and the sending channels are called forward channels.
This division of the spectrum into sub-band channels is achieved by using Frequency Division Multiple Access (FDMA).
FDMA is the technique where available bandwidth is divided into a multitude of channels where each user occupies a separate channel.
Global System for Mobile Communications (GSM)
With analog system there were many disadvantages with cellular communication like it didn’t support encryption, compression, and ISDN compatibility. In early 80s European realized that new mobile system should be developed that should be digital, ISDN compatible with good speech quality. From here the introduction of GSM to the world started.
GSM network operates in the frequency range of 1,850 to 1,990 MHz, and the separation between adjacent carrier frequencies is 200 kHz.
GSM utilizes the time division multiple access concept (TDMA). TDMA is a technique in which several different calls may share same carrier and each call is assigned a particular time slot.
In United States T-mobile and Cingular etc. are the carriers of GSM network on 1,900 MHz band.
Code Division Multiple Access (CDMA)
CDMA is a digital wireless technology that works by converting speech into digital information, which is then transmitted as a radio signal over a wireless network. Using a unique code to distinguish each call, CDMA uses spectrum efficiently, enabling more people to share the airwaves simultaneously without static, cross talk or interference. The foremost application of CDMA is the digital cellular phone technology from QUALCOMM that operates in the 800MHz band and 1.9GHz PCS band. CDMA phones are noted for their call quality.
CDMA optimizes use of the radio spectrum, which is an increasingly scarce resource worldwide. CDMA requires fewer cell sites than the GSM and TDMA digital cell phone systems. CDMA's single cell frequency re-use capability and non-contiguous bandwidth requirement, along with its extended coverage range, simplifies RF planning and implementation. This allows providers to deploy faster, and giving the opportunity to service provider for increased and quicker return on investment. In United States CDMA Network Operators are ALLTEL, Verizon Wireless, US Cellular and the Qwest communications.
So which is better? Its like comparing AM and FM radio they both do the same thing but differently.
The wireless world offers broad choices among service providers, calling plans and phones. Low-priced equipments and rates make wireless affordable. Today’s cell phones comes with so many other features besides talking like you can take photos, surf the Internet, send emails, play games and many more. With so many options available in the market, its only you who have to decide which one is suitable for you.    

By

Engr. Lekan Quadri

+2328088982857