Digital Telecommunications & Networks

Digital Telecommunications & Networks

Part 1: General Review on Networking

a.) What are two reasons for developing Local Area Network (LANs)?

The main two reasons for developing a Local Area Networks are

1. Information sharing

2. Resource sharing.

Information sharing is a term which explains the process of users ability to access the similar data files, switch information through e- mail, or browse the Internet for the required information. The main advantage of information sharing is better decision making, which makes it usually more important than resource sharing.

Resource sharing is a process of a computer sharing a hardware device like printer, sccaner or software applications with other computers on the same network, in order to decrease the expenditure. Ref. Link [1]

b.) What is the function of LAN monitoring software?

Now a day's LAN Monitoring Software is special software which is mostly use by several business organizations to observe their employees' using the Internet in a correct way during t in office hours. By the use of this software the employers have the benefit of looking at the records provided by the software to evaluate the company's confidential information is compromised or other malicious activities occurring in the office without audit. And also it shows the data flow in the Local Area Network used above the network card, bandwidth management in addition to hardware modification recorded.

Os Monitor Monitoring Software is one type of LAN Monitoring software and it is used by company management to search and supervise all of their staff members computers from his chamber with a secret mode. It can be easily installed on a enterprise networks in a couple of minutes plus permits for easy accessibility from a administrators Personal Computer. All the activities in the Lan are recorded by this software, and also you can block unauthorized activities. It can monitor all users in LAN through a central Server, and also we can change all settings from Server by administrator for all the user computers instead of change settings on the each Client. It is very easy to manage and supervise your employees. All that options care only personalize and manage by company owner.

With the help of LAN monitoring software you can continuously track the user activities of lan computers and also we have a option like you can get screenshots of the user computers like browsing history, usage of programs and files operations etc. Ref.Link [2]

c.) Describe at least three types of servers.

Server types are

File Servers

File server is a type of server which is attached or placed in a network, whose primary function is to provide shared storage or allocation of files such as documents, data base, and multimedia etc. This can be access by any computer which is placed inside the network.

A file server's primary function is to store files and it does not perform any calculations and does not run any applications on behalf of client, but only helps in rapid retrieval of data.

And these file servers are commonly used in educational institutions and big organizations where storage of data is must. Some examples of file servers are LINUX file server, WINDOWS server etc. Ref.Link[3]

Print servers

A print server is used to connect one or more printers for all computers that computers all are connected by a same network. On the network one computer is allocated as a default printer, the server assigns a print job by the print server with the main office server assuming that the primary and backup server allows the printing capability. The print servers can be used at homes instead of printers connected to each individual computer. A printer can be connected at home for home projects. Ref.Link[15]

Application server

Application server is designed to run some specific tasks, the application server is used to run one application which keeps the company's network going on and takes the total RAM and ROM requirement of one server.

For example, your company might have a number of desktop publishing or word processing programs, and all those applications might exist on one type of server. Everyone who wants to access those programs logs on to the Desktop Publishing Server, for example, to use In Design Pages etc that your organisation might have that one. Ref.Link[16]

d.) What is Ethernet? How does it work?

Ethernet is a protocol and is controlled by the way data is transmitted over a LAN which uses wires . The LAN uses RJ-45 jack mostly used for your telephone sets which are double in size. Some of Ethernet networks use coaxial cables and at present large LANs, which connect between buildings. Coaxial cables are thick cables that links your TV antenna to your TV set. Ethernet is the most conventional LAN protocol used today, to connect to computers one has to buy a network card. We get a Ethernet LAN cards with speeds ranging from 100 Mbps – 1000 Mbps. Ref. Link[4]

Ethernet follows simple rules that for its basic operations

•Medium – To transmit electronic signals Ethernet devices uses coaxial copper cable and the medium is generally called as Fiber optic cabling.

•Segment - Single shared medium is called as Ethernet segment.

•Node – Nodes are the devices attached to the segments.

•Frame – The communication channel for the nodes are called frames which vary in sizes.

Frames are similar to sentences in human language which follow the certain rules. There are different lengths for frames and the frames should include the source address and destination address and should identify the sender and receiver of the message. The address independently identifies the node, just as a name identifies a particular names of person. No two Ethernet devices should ever have the same address. Ref. Link [13].

Part 2: General Review on Wireless Local Area Networking

a.) Describe the basic components of a wireless network.

The two important components in a wireless network are

1. wireless access points

2. Wireless clients.

Wireless access points are base stations that are attached like an interface between wired and wireless networks. The coverage provided by an access point is referred as the “coverage cell”. Large areas requires many Access Points for quality coverage and helps the users to overlap setup and enables users to roam between cells without loosing their connection.

Wireless clients are the network interfaces used in computer devices such as PDAs, laptops, PCs that communicate with access points. If a wireless client enters coverage cell it connects to an access point with all permits and proper settings allowed to access the network. Ref. Link [6]

b.) Compare and contrast the two types of antennas.

Omni directional antennas and directional antennas are the two types of antennas that can be used on Acess Points. WLANs are installed using access points having omni directional antennas which transmits in all directions at the same time and a common omnidirectional antenna is the dipole antenna. Directional antenna Transmits a signal only in single direction. Because the signal is stronger than the signal from an access points when using an omnidirectional antenna. Omnidirectional antennas transmit in all directions like vertically and horizontally. The signal goes in all directions, as well as downs and ups and there is a small place above antenna where there is is no signal. The directional antenna projects signals in one direction and are frequently used on the walls of a building which benefits the range of access point.

c.) How does roaming work?

The client switches between access points while moving physically or as a result of balancing loads between access points. The idea behind using a wireless network is that the client is not controlled to being stationary.

As the client gets closer to another access point, the signal strength from the first drops where the signal strength from the other increases. At one point the signal strenghts of the two will be equal but the other will have the strongest signal and the client should roam to the next access point.

The channels should be spaced properly to avoid interference. The graphics illustrates reusability of a channel and still avoid interference. The client will effortlessly roam between these access points.

For the client to be able to roam effortlessly , it is necessary for the access points to:

* Be connected to the same IP subnet, the client don't have to change IP address

* Have the same SSID to identify the wireless network

* Have the same encryption and authentication schemes so that the client knows how to authenticate and encrypt.

If one or more of these requirements are not met, communication for the client will halt. The client will not regain communication before it configures until it reaches another access point with the same configuration as the first or new access point.

The client does not have to move physically to roam. Roaming could be happened as the result of the access points negotiating load balancing or sharing. Wireless network is a shared medium and the resources for each decrease with the increase of clients. The rational thing would be for the access points to share the load. The decision to roam a client is a result of the access points evaluating factors like the number of associated clients on the different access points, the traffic, quality and the signal strength of the client. http://forskningsnett.uninett.no/wlan/pictures/roaming_loadbalancing.jpg

LOAD OF DIFFERENT ACCCESS POINTS

The client roams between the access points on channels 1 and 6 in this illustration depending on the other clients in the network.

Part 3: General Review on Wi-Fi.

a.) What is Wi-Fi? Describe their types.

Wi-Fi, short form of Wireless Fidelity, and it is used to describe high speed wireless connection over short distances between mobile computing devices such as laptops and the internet.

Wi-Fi is a type of wireless network. It is also increasingly used for communication between consumer electronic devices such as televisions, DVD players, digital cameras and mobile phones. Ref. Link [9]

Mainly the Wi-Fi networks come under three types categories.

1. Enterprise Wi-Fi networks

An enterprise Wi-Fi network has multiple wireless access points to provide hotspot coverage, ubiquitous coverage, hotspot or ubiquitous coverage. Wi-Fi devices can be enabled in any coverage area and can be configured by using layer 2 authentications.

An organization may consider an enterprise Wi-Fi network to be un trusted and require that all Wi-Fi connections to the organization's network occur through a VPN concentrator. You must configure Wi-Fi enabled devices to support the authentication type that your organization uses.

An enterprise Wi-Fi network permits optimized access to the Wi-Fi Enterprise Server over a direct IP connection to the Router.

2. Home Wi-Fi networks

Home WI-Fi network is use only a single access point to supply Internet access through a broadband gateway. The broadband gateway can implement NAT and permit VPN connections through the firewall. You can configure a home Wi-Fi network with layer 2 securities and password authentication. You must configure devices to support the authentication that the home Wi-Fi network requires.

A home Wi-Fi network permits users to access all BlackBerry services from Wi-Fi enabled devices.

3. Hotspots

A hotspot is offered by a property owner in public areas or an Internet Service Provider or a mobile network provider. The network uses a captive portal for authentication and can be an open network without layer 2 security and blocks the traffic that uses and redirects the HTTP request to a login page.

After a user logs in to the hotspot, the captive portal permits the user to access wireless network services.

Hotspots permits VPN connections and can be used as firewall and permits users to access services from their Wi-Fi devices using the infrastructure. Ref.Link[14]

b.) Explain how the 802.11g differs from 802.11b and 802.11a?

SUMMERY OF IEEE 802.11 SATNDARDS

Standard

Frequency Range

(united States)

Data Rate

802.11b

2.4 – 2.485 GHZ

Up to 11 mbps

802.11a

5.1 -5.8 GHZ

Up to 54 Mbps

802.11g

2.4 -2.485 GHZ

Up to 54 Mbps

Ref.Link[20]

802.11g wireless LAN operates in a frequency between 2.4 -2.485 GHZ and has a data rate of 54 Mbps and 802.11b also operates with the same frequency with a different data rate of 11 Mbps.

802.11a has a Data rate of 54 Mbps like 802.11g. It operates in different Frequency range (5.1 GHZ – 5.8 GHZ) almost double frequency range of 802.11g.

It means that 802.11a provides data rates up to 54Mbps over short distances, while 802.11b provides data rates up to 11 Mbps over longer distances up to 500 feet. 802.11g is designed to overcome both of these by providing 54 Mbps over long distances.

c.) How does Wi-Fi differ from shared Ethernet in terms of topology, media access control,

And error control?

The Wi-Fi's physical and logical topologies are the same as those of shared Ethernet. Detecting collisions in radio transmission is more difficult than in over wired networks, so Wi-Fi attempts to avoid collisions to a greater extent than the traditional Ethernet. Ref. Link [12]

REFERENCE

1. ictlab.tyict.vtc.edu.hk/~kenhui/.../ch06_suggested_answer.doc

2. http://www.os-monitor.com/lan-monitoring.htm

3. http://www.real-time.com/linuxsolutions/fileserver.html

4. http://voip.about.com/od/voipbasics/g/whatisEthernet.html

6. http://www.selu.edu/admin/technology/resources/wireless/index.html

7. http://www.ecst.csuchico.edu/~pc/What%20is%20a%20Wireless%20LAN.htm

8. www.student.nvcc.edu/home/vkodali/assignment07.docx

9. http://www.emfexplained.info/?Page=24502

11. http://www.filesaveas.com/wifi.html

12. www.student.nvcc.edu/home/vkodali/assignment07.docx

13. http://computer.howstuffworks.com/ethernet5.htm

14. http://docs.blackberry.com/en/admin/deliverables/7335/Types_of_WiFi_networks_604796_11.jsp

15. http://www.wisegeek.com/what-is-a-print-server.htm

16. http://www.wisegeek.com/what-is-an-application-server.htm

BOOK REFERENCE:

20.Kurose, J & Keith, W (2007, 4th edition, p.526) Computer Networking, Boston: Pearson Education

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