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Network topologies and types

Network topology

• Computer networks may be classified according to the network topology upon which the network is based, such as Bus network, Star network, Ring network, Mesh network, Star-bus network, Tree or Hierarchical topology network, etc.
• Network Topology signifies the way in which intelligent devices in the network see their logical relations to one another.

Mesh Topology

• The value of fully meshed networks is proportional to the exponent of the number of subscribers, assuming that communicating groups of any two endpoints, up to and including all the end points.

Star Topology

• A star network consists of one central switch, hub or computer, which acts as a conduit to transmit messages. This consists of a central node, to which all other nodes are connected; this central node provides a common connection point for all nodes through a hub. In star topology, every node (computer workstation or any other peripheral) is connected to a central node called a hub or switch.

Bus Topology

• Bus Topology is the simplest of network topologies. In this type of topology, all the nodes (computers as well as servers) are connected to the single cable (called bus), by the help of interface connectors. This central cable is the backbone of the network and is known as Bus (thus the name). Every workstation communicates with the other device through this Bus.

Ring Topology

• The type of network topology in which each of the nodes of the network is connected to two other nodes in the network and with the first and last nodes being connected to each other, forming a ring – all data that is transmitted between nodes in the network travels from one node to the next node in a circular manner and the data generally flows in a single direction only

Computer Networks

A communications network is two or more computers connected to share data and resources are “networked.” The simple idea behind computer networking is to allow users to access more information and give them access to devices not directly attached to their “local” system, such as printers or storage devices

Personal Area Network (PAN)

A personal area network (PAN) is the interconnection of information technology devices within the range of an individual person, typically within a range of 10 meters. For example, a person traveling with a laptop, a personal digital assistant (PDA), and a portable printer could interconnect them without having to plug anything in, using some form of wireless technology.

Local Area Network (LAN)

A network covering a small geographic area, like a home, office, or building. Current LANs are most likely to be based on Ethernet technology. The simple idea behind computer networking is to allow users to access more information and give them access to devices not directly attached to their “local” system, such as printers or storage devices.

Metropolitan Area Network (MAN)

A metropolitan area network (MAN) is a computer network larger than a local area network, covering an area of a few city blocks to the area of an entire city, possibly also including the surrounding areas.

wide area network (wan)

A computer network that spans a relatively large geographical area. Typically, a WAN consists of two or more local-area networks (LANs).Computers connected to a wide-area network are often connected through public networks, such as the telephone system. They can also be connected through leased lines or satellites. The largest WAN in existence is the Internet.

Network Protocols

Protocols

• A protocol means the rules that are applicable for a network.
• It defines the standardized format for data packets, techniques for detecting and correcting errors and so on.
• A protocol is a formal description of message formats and the rules that two or more machines must follow to exchange those messages.

Types of protocols are:

1. HTTP
2. FTP
3. TCP/IP
4. SLIP/PPP

Hypertext Transfer Protocol (HTTP) HTTP (Hypertext Transfer Protocol) is the set of rules for transferring files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. As soon as a Web user opens their Web browser, the user is indirectly making use of HTTP. HTTP is an application protocol that runs on top of the TCP/IP suite of protocols (the foundation protocols for the Internet).

FTP (File Transfer Protocol) is the simplest and most secure way to exchange files over the Internet. The objectives of FTP are:
• To promote sharing of files (computer programs and/or data).
• To encourage indirect or implicit use of remote computers.
• To transfer data reliably, and efficiently.

TCP/IP (Transmission Control Protocol / Internet Protocol)
TCP - is responsible for verifying the correct delivery of data from client to server. Data can be lost in the intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and completely received.
IP - is responsible for moving packet of data from node to node. IP forwards each packet based on a four byte destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations. The organizations assign groups of their numbers to departments. IP operates on gateway machines that move data from department to organization to region and then around the world.

SLIP (Serial Line Internet Protocol)
The Serial Line Internet Protocol (also SLIP) is an encapsulation of the Internet Protocol designed to work over serial ports and modem connections. SLIP is a TCP/IP protocol used for communication between two machines that are previously configured for communication with each other.

Point to Point Protocol (PPP)
In computer networking, Point-to-Point Protocol (PPP) is a data link protocol used to establish a direct connection between two nodes. It can provide connection authentication, transmission encryption and compression.

Telnet-
It is an older internet utility that lets us log on to remote computer system. It also facilitates for terminal emulation purpose. Terminal emulation means using a pc like a mainframe computer through networking.
(i) Run telnet client- Type telnet in run dialog box.
(ii) Connect to telnet site -specify the host name, port and terminal type.
(iii) Start browsing- surf the shown site with provided instruction.
(iv) Finally disconnect-press Alt+F4.

Mailing Protocols:-

IMAP (Internet Message Access Protocol) – Is a standard protocol for accessing e-mail from your local server. IMAP is a client/server protocol in which e-mail is received and held for you by your Internet server. As this requires only a small data transfer this works well even over a slow connection such as a modem. Only if you request to read a specific email message will it be downloaded from the server. You can also create and manipulate folders or mailboxes on the server, delete messages etc.

POP3 Protocol:
The POP (Post Office Protocol 3) protocol provides a simple, standardized way for users to access mailboxes and download messages to their computers. When using the POP protocol all your eMail messages will be downloaded from the mail server to your local computer. You can choose to leave copies of your eMails on the server as well. The advantage is that once your messages are downloaded you can cut the internet connection and read your eMail at your leisure without incuring further communication costs. On the other hand you might have transferred a lot of message (including spam or viruses) in which you are not at all interested at this point.

SMTP
The SMTP (Simple Mail Transfer Protocol) protocol is used by the Mail Transfer Agent (MTA) to deliver your eMail to the recipient's mail server. The SMTP protocol can only be used to send emails, not to receive them. Depending on your network / ISP settings, you may only be able to use the SMTP protocol under certain conditions

MAPI
MAPI is Microsoft's proprietary email protocol. It provides greater functionality than IMAP for Outlook email clients interacting with an Exchange email server. It doesn't work for anything else.

Wireless/Mobile Computing

Wireless communication is simply data communication without the use of landlines. Mobile computing means that the computing device is not continuously connected to the base or central network.

1. GSM(Global System for Mobile communication): it is leading digital cellular system. In covered areas, cell phone users can buy one phone that will work anywhere the standard is supported. It uses narrowband TDMA, which allows eight simultaneous calls on the same radio frequency.
2. CDMA(Code Division Multiple Access): it is a digital cellular technology that uses spread-spectrum techniques. CDMA does not assign a specific frequency to each user. Instead ,every channel uses the full available spectrum.
3. WLL(Wireless in Local Loop) : WLL is a system that connects subscribers to the public switched telephone network using radio signals as a substitute for other connecting media.
4. Email(Electronic Mail): Email is sending and receiving messages by computer.
5. Chat: Online textual talk in real time , is called Chatting.
6. Video Conferencing: a two way videophone conversation among multiple participants is called video conferencing.
7. SMS (Short Message Service): SMS is the transmission of short text messages to and from a mobile phone, fax machine and or IP address.
8. 3G and EDGE: 3G is a specification for the third generation of mobile communication of mobile communication technology. 3G promises increased bandwidth, up to 384 Kbps when a device is stationary. EDGE (Enhanced Data rates for Global Evolution) is a radio based high speed mobile data standard.




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