Sunday, November 22, 2009
Tuesday, November 3, 2009
ANSWERS TO SELECTED QUESTION
1. What are the two types of transmission technology available? Explain in detail.
There are basically two types of transmission technologies available :
1. Broadcast: In this type every host sends the packet/message to all the hosts. The message has a source address and a destination address. Destination address helps the host to identify whether the message is indeed for them or somebody else. The source address allows them to identify from whom the message has come.
2. Point to Point: Point-to-point networks consist of many connections between individual pairs of machines. To go from the source to the destination, a packet on this type of network may have to first visit one or more intermediate machines. Often multiple routes, of different lengths are possible, so routing algorithms play an important role in point-to-point networks.
2. What Is a MAC Address? Explain in detail.
MAC address
The Media Access Control address (MAC address) is a unique identifier assigned to most network adapters or network interface cards (NICs) by the manufacturer for identification, and used in the Media Access Control protocol sublayer. If assigned by the manufacturer, a MAC address usually encodes the manufacturer's registered identification number. It may also be known as an Ethernet Hardware Address (EHA), hardware address, adapter address, or physical address.
They uniquely identify an adapter on a LAN. MAC addresses are 12-digit hexadecimal numbers (48 bits in length). By convention, MAC addresses are usually written in one of the following two formats:
MM:MM:MM:SS:SS:SS
MM-MM-MM-SS-SS-SS
The first half of a MAC address contains the ID number of the adapter manufacturer. These IDs are regulated by an Internet standards body (see sidebar). The second half of a MAC address represents the serial number assigned to the adapter by the manufacturer. In the example,
00:A0:C9:14:C8:29
The prefix 00A0C9 indicates the manufacturer is Intel Corporation.
Why MAC Addresses?
Recall that TCP/IP and other mainstream networking architectures generally adopt the OSI model. In this model, network functionality is subdivided into layers. MAC addresses function at the data link layer (layer 2 in the OSI model). They allow computers to uniquely identify themselves on a network at this relatively low level.
3. What is the difference between bit rate and baud rate?
The bit rate and baud rate are dependent and inter-related. But the simplest explanation is that a Bit Rate is how many data bits are transmitted per second. A baud Rate is the measurement of the number of times per second a signal in a communications channel changes.
Bit rates measure of the number of data bits (that's 0's and 1's) transmitted in one second in a communication channel. A figure of 2400 bits per second means 2400 zeros or ones can be transmitted in one second, hence the abbreviation "bps". Individual characters (for example letters or numbers) which are also referred to as bytes are composed of several bits.
A baud rate, by definition, means the number of times a signal in a communications channel changes state or varies. For example, a 2400 baud rate means that the channel can change states up to 2400 times per second. The term "change state", means that it can change from 0 to 1 or from 1 to 0 up to X (in this case, 2400) times per second. It also refers to the actual state of the connection, such as voltage, frequency or phase level).
The main difference of the two is that one change of state can transmit one bit - or slightly more or less than one bit, that depends on the modulation technique used. So the bit bate (bps) and baud rate (baud per second) have this connection:
bps = baud per second x the number of bit per baud.
4. What is the difference between baseband and broadband transmission?
In a baseband transmission, the entire bandwidth of the cable is consumed by a single signal.
In broadband transmission, signals are sent on multiple frequencies, allowing multiple signals to be sent simultaneously.
Baseband transmission
1) Uses digital signaling
2) No frequency-division multiplexing
3) Bi-directional transmission
4) Signal travels over short distances
Broadband transmission
1) Uses analog signaling
2) Unidirectional transmission
3) Frequency-division multiplexing is possible
4) Signal can travel over long distances before being attenuated
5.What is the difference between node, host, terminal, system and hub?
Hub: A network hub or repeater hub is a networking device that is used to connect several devices for a single network segment.
Fig. A HUB
It is a device for connecting multiple twisted pair or fiber optic Ethernet devices together and thus making them act as a single network segment. Hubs work at the physical layer (layer 1) of the OSI model. The device is thus a form of multiport repeater. Repeater hubs also participate in collision detection, forwarding a jam signal to all ports if it detects acollision.
Node: It can be any device connected to a network for example in a LAN, computers and printers can be called as nodes.
Host: It can be any end system connected to a network, for example it may be a computer, home security system, cell phone, printer, etc.,
Terminal: A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying data from, a computer or a computing system.
System: The system includes not only the computer, but also any software and peripheral devices that are necessary to make the computer function. Every computer system, for example, requires an operating system.
6. What are the major types of networks? Explain.
Different types of (private) networks are distinguished based on their size (in terms of the number of machines), their data transfer speed, and their reach. Private networks are networks that belong to a single organisation. There are usually said to be three categories of networks:
LAN (local area network)
MAN (metropolitan area network)
WAN (wide area network)
LAN
LAN stands for Local Area Network. It's a group of computers which all belong to the same organization, and which are linked within a small geographic area using a network, and often the same technology (the most widespread being Ethernet).
A local area network is a network in its simplest form. Data transfer speeds over a local area network can reach up to 10 Mbps (such as for an Ethernet network) and 1 Gbps (as with FDDI or Gigabit Ethernet). A local area network can reach as many as 100, or even 1000, users.
By expanding the definition of a LAN to the services that it provides, two different operating modes can be defined:
In a "peer-to-peer" network, in which communication is carried out from one computer to another, without a central computer, and where each computer has the same role.
in a "client/server" environment, in which a central computer provides network services to users.
MAN
MANs (Metropolitan Area Networks) connect multiple geographically nearby LANs to one another (over an area of up to a few dozen kilometres) at high speeds. Thus, a MAN lets two remote nodes communicate as if they were part of the same local area network.
A MAN is made from switches or routers connected to one another with high-speed links (usually fibre optic cables).
WANs
WAN
A WAN (Wide Area Network or extended network) connects multiple LANs to one another over great geographic distances.
The speed available on a WAN varies depending on the cost of the connections (which increases with distance) and may be low.
WANs operate using routers, which can "choose" the most appropriate path for data to take to reach a network node. The most well-known WAN is the Internet.
7. Why should we care about the OSI Reference Model? What is the main purpose for creating this OSI model? Why it is a layered model?
We should care about this model because this was the 1st model to be created for internet standard. So this is an internet standard model and all the standards made after this model follow all the rules of this model too.
Main purpose for creating this model was to send data from one terminal to another terminal without any loss in the transmitted data.
It is a layered model because every layer is used for some specific work and it is not possible for one layer to handle all the tasks of transmitting data.
8. What is an email client? What is difference between email client and web mail?
Email Client:
Email clients download your emails onto your computer. Using a specialized email program such as Outlook Express or Apple Mail has the advantage of giving you complete control over your email; every email you receive is placed on your computer and you can keep as many large file attachments as you want.
Webmail:
If you host with Needmore Designs you have a limited amount of space available for your web mailbox. For daily use you will want to use an email client. Nevertheless you might find that you want to check your email while traveling.
Checking your email through our webmail is similar to using Hotmail or YAHOO! Mail. You never actually copy your messages to your computer; in fact you are looking at them through your web browser on somebody else's computer. When you are not online you are not able to see your email.
9. If a person is accessing his corporate network from home. How is the connection established and how does the data flow from internet to intranet?
| If aperson wants to access his corporate network from home he have to establish a VPN (virtual private network): He will require the following in case if want to connect by wireless technology: · A notebook PC, Pocket PCs, or Tablet PC equipped with wireless WAN access cards or with built-in support for wireless WANs · A wireless WAN card and WAN connectivity provider |
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10. What is difference between dial-up internet connection and broadband connection?
The fundamental difference between dialup and broadband connections is the manner in which the connection is made from PC to the Internet.
A dialup service connects to the Internet through a phone line with a maximum speed of 56kbps.
Broadband refers to a connection that has capacity to transmit large amount of data at high speed. Presently a connection having download speeds of 256kbps or more is classified as broadband.
Broadband comes in a number of forms - depending how the data is delivered - for example via cable, satellite and most commonly using a telephone line where as a dialup service always connects to the Internet through a phone line.
While using a dialup connection, we need to pay for a local call every time we dial the Internet. In addition phone line is engaged while we are on the Internet. With a broadband connection, phone line (if existing phone line is used) can still be used while using the Internet and both the phone and the Internet work simultaneously and no dialup costs are incurred. Telecommunication systems were originally built to carry analogue signals. In a dial up connection, modems are used to translate digital into analogue signals and communicating with Internet.
Dialup connection speeds make it more difficult to view certain types of media, such as video, and it can take much longer to download and open emial attachments, play online games and so on.
In an broadband system, digital data does not have to be converted into analogue. it uses a different part of the line's frequency spectrum, offers much wider bandwidth 9more lanes) and does not interfere with the use of the line for voice transmission. When connected to the Internet, such a connection allows surfing or downloading much faster than a dial-up connection. Dialup connection users a built-in modem to connect and does not require a special router, whereas broadband requires a special router or modem.
In terms of security for attack, dialup is more secured then broadband, Broadband users need to use a firewall to keep the computer "invisible" to the outside.
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