Basic Network Concepts

Introduction:
-A network can be defined as a group of computers and other devices connected in some ways so as to be able to exchange data.
-Each of the devices on the network can be thought of as a node; each node has a unique address.
-Addresses are numeric quantities that are easy for computers to work with, but not for humans to remember.
Example: 204.160.241.98
-Some networks also provide names that humans can more easily remember than numbers.
Example: http://www.javasoft.com, corresponding to the above numeric address.
Port Numbers
HTTP 80
FTP 20 & 21
SMTP(e-mail) 25
POP3(e-mail) 110
TELNET 23
Data Transmission:
-In modern networks, data are transferred using packet switching.
-Messages are broken into units called packets, and sent from one computer to the other.
-At the destination, data are extracted from one or more packets and used to reconstruct the original message.
-Each packet has a maximum size, and consists of a header and a data area.
-The header contains the addresses of the source and destination computers and sequencing information necessary to reassemble the message at the destination.
Types of Networks:
There are two principle kinds of networks:
Wide Area Networks (WANs)
Local Area Networks (LANs).
WANs
-Cover cities, countries, and continents.
-Based on packet switching technology
-Examples of WAN technology:
Asynchronous Transfer Mode (ATM),
Integrated Services Digital Network (ISDN)
LANs
-Cover buildings or a set of closely related buildings.
-Examples of LAN technology: Ethernet, Token Ring, and Fibber Distributed Data Interconnect (FDDI).
Ethernet LANs: based on a bus topology and broadcast communication
Token ring LANs: based on ring topology
FDDI LANs: use optical fibbers and an improved token ring mechanism based on two rings flowing in opposite directions.
Interconnection:
According to the protocols involved, networks interconnection is achieved using one or several of the following devices:
→Bridge: a computer or device that links two similar LANs based on the same protocol.
→ Router: a communication computer that connects different types of networks using different protocols.
→ B-router or Bridge/Router: a single device that combines both the functions of bridge and router.
→ Gateway: a network device that connects two different systems, using direct and systematic translation between protocols.
Protocols
-Define the rules that govern the communications between two computers connected to the network.
-Roles: addressing and routing of messages, error detection and recovery, sequence and flow controls etc.

Networks Interconnection/Internet
Posted by surfingall on May 6, 2010
– Requires the definition of a common interconnection protocol on top
the local protocols.
– The Internet Protocol (IP) plays this role, by defining unique addresses
for a network and a host machine.
Internet Protocol (IP)
The IP protocol provides
→ Decomposition of the initial information flow into packets of
standardized size, and reassembling at the destination.
→ Routing of a packet through successive networks, from the source
machine to the destination identified by its IP address.
The IP protocol does not request for connection (connectionless) before sending data and does not make any error detection.
Functions
– Decompose the initial data (to be sent) into datagrams.
– Each datagram will have a header including, the IP address and the port number of the destination.
– Datagrams are then sent to selected gateways, e.g IP routers, connected at the same time to the local network and to an IP service provider network.
– IP packet can be a maximum of 64Kb long.
Transmission Control Protocol (TCP)
– TCP provides by using IP packets a basic service that does guarantee safe delivery:
→ error detection
→ safe data transmission
→ assurance that data are received in the correct order
– Before sending data, TCP requires that the computers communicating
establish a connection (connection-oriented protocol).
– TCP provides support for sending and receiving arbitrary amounts of data as one big stream of byte data (IP is limited to 64Kb).
– TCP does so by breaking up the data stream into separate IP packets.
– Packets are numbered, and reassembled on arrival, using sequence and sequence acknowledge numbers.
– TCP also improves the capability of IP by specifying port numbers.
→ There are 65,536 different TCP ports (sockets) through which every TCP/IP machine can talk.
User Datagram Protocol (UDP)
– Has the same packet-size limit (64Kb) as IP, but allows for port number specification.
– Provides also 65,536 different ports.
– Hence, every machine has two sets of 65,536 ports: one for TCP and the other for UDP.
– Connectionless protocol, without any error detection facility.
– Provides only support for data transmission from one end to the other, without any further verification.
– The main interest of UDP is that since it does not make further verification, it is very fast.
– Useful for sending small size data in a repetitive way such as time information.
Posted in Networking | Tagged: datagrams, gateways, Internet Protocol (IP), IP address, ports, protocol, TCP, UDP | Leave a Comment »
Protocol Layers
Posted by surfingall on May 6, 2010
OSI (Open Systems Interconnection) Data Model
-Involves at least 7 layers
Physical layer: ensures a safe and efficient travel of data; consists of electronic circuits for data transmission etc.
Data link layer: in charge of data encapsulation under the form of packets and their interpretation at the physical layer.
Network layer: in charge of packets transmission from a source A to a destination B.
Transport layer: in charge of the delivery of packets from a source A to a destination B
Session layer: in charge of the management of network access.
Presentation layer: determines the format of the data transmitted to applications, data compressing/decompressing, encrypting etc.
Application layer: contains the applications which are used by the end-user, such as Java, Word etc.
TCP/IP Model
Network layer:
-Provides the same functionality as the physical, the data link and network layers in the OSI model.
-Mapping between IP addresses and network physical addresses.
-Encapsulation of IP datagrams, e.g packets, in format understandable by the network.
Internet layer:
-Lies at the heart of TCP/IP.
-Based on the Internet Protocol (IP), which provides the frame for transmitting data from place A to place B.
Transport layer:
-Based on two main protocols: TCP (Transmission Control Protocol) and UDP (User Datagram protocol)
Application layer
-Combines the functions of the OSI application, presentation, and session layers.
-Protocols involved in this layer: HTTP, FTP, SMTP etc.

Tirupathi Perumal image /Good Luck Quotes

 

 

https://rgkumaran.files.wordpress.com/2011/06/bc3a4lc3a4ji.gif

Good Luck Quotes & SayingsBelow listed Good Luck Quotes are collected from different sources around the world. No claims are made! We would love to hear from you in case your favorite Good Luck quote isn’t listed yet. Luck does not favor hesitation. (Roman words of wisdom) It is better to be born lucky than rich. (unknown) All of us have bad luck and good luck. The man who persists through the bad luck — who keeps right on going — is the man who is there when the good luck comes — and is ready to receive it. (Robert Collier) Men of action are favored by the Goddess of luck. (George S. Clason) Better an ounce of luck than a pound of gold. (Yiddish proverb) I find that the harder I work, the more luck I seem to have. (John Heywood) Luck is the residue of design. (John Milton) If one is lucky, a solitary fantasy can totally transform one million realities. (M. Angelou) Luck is a dividend of sweat. The more you sweat, the luckier you get. (Ray A. Kroc) Good luck is a lazy man’s estimate of a worker’s success. The only sure thing about luck is that it will change. (Wilson Mizner) Each misfortune you encounter will carry in it the seed of tomorrow’s good luck. (Mandino) Good luck is often with the man who doesn’t include it in his plans. (Unknown) Luck is when opportunity knocks and you answer. (Unknown) It’s hard to detect good luck – it looks so much like something you’ve earned. (Frank Clark) Luck never gives; it only lends. (Swedish proverb) I am a great believer in luck, and I find the harder I work the more I have of it. (T. Jefferson) May good luck be your friend in whatever you do and may trouble be always a stranger to you. (Irish blessing) For each petal on the shamrock this brings a wish your way. Good health, good luck, and happiness for today and every day. (Irish blessing) Being deeply learned and skilled, being well trained and using well spoken words; This is good luck. (Buddha quote) May your pockets be heavy and your heart be light. May good luck pursue you each morning and night. (Irish blessing) Good luck happens when preparedness meets opportunity. Good luck comes in slender currents, misfortune in a rolling tides. (Irish saying) The amount of good luck coming your way depends on your willingness to act. (B. Sher) For a long time now I have tried simply to write the best I can. Sometimes I have good luck and write better than I can. (Ernest Hemingway) Diligence is the mother of good luck. (Benjamin Franklin) The luck of having talent is not enough; one must also have a talent for luck. (H. Berlioz ) They say you have to be good to be lucky, but I think you have to be lucky to be good. (Rico Carty) Depend on the rabbit’s foot if you will, but remember it didn’t work for the rabbit. (R. Shay) Everything in life is luck. (Donald Trump) Go and wake up your luck. (Persian saying) Luck is what you have left over after you give 100 percent. (L. Coleman) Those who have succeeded at anything and don’t mention luck are kidding themselves. (Larry King) Shallow men believe in luck. Strong men believe in cause and effect. (Ralph Emerson) I don’t know anything about luck. I’ve never banked on it, and I’m afraid of people who do. Luck to me is something else; hard work and realizing what is opportunity and what isn’t. (Lucille Ball) Men have made an idol of luck as an excuse for their own thoughtlessness. (Democritus) Winners believe that they create their own luck by their actions; losers believe in good and bad luck. (Unknown) We must believe in luck. For how else can we explain the success of those we don’t like? (Jean Costeau) Success is just a matter of luck, all you need to do is ask a failure. History may be written by academics but it’s rarely created by them. (Unknown) Nobody gets justice. People only get good luck or bad luck. (Orson Welles) If it weren’t for bad luck, I’d have no luck at all. (Country Western Song) It is the mark of an inexperienced man not to believe in luck. (Joseph Conrad) Throw a lucky man in the sea, and he will come up with a fish in his mouth. (Arab proverb) If your are lucky enough to be Irish, you are lucky enough. (unknown) One-half of life is luck; the other half is discipline – and that’s the important half, for without discipline you would not know what to do with luck. (Carl Zuckmeyer) Don’t believe in miracles – depend on them. (Laurence Peter) Fortune brings in some boats that are not steered. (W. Shakespeare) I never knew an early-rising, hard-working, prudent man, careful of his earnings, and strictly honest who complained of bad luck. (Henry Ward Beecher) Reverence, humility, contentment, gratitude and hearing the good Dhamma, this is the best good luck.(Hindu Prince Gautama Siddharta, the founder of Buddhism, 563-483 B.C.) Luck take a second look at what appears to be someone’s Good Luck. You’ll find not luck but preparation, planning, and success-producing thinking. (D. J. Schwartz) Good luck seldom comes in pairs but bad things never walk (occur) alone. (Chinese proverb) As good luck would have it. (W. Shakespeare)

Router

http://rgkumaran.blogspot.com/2011_06_01_archive.html

http://gkstech.hpage.com

http://gkmtech.hpage.com

http://techrgk.hpage.com

http://rgkgoal.webs.com

Definition: Routers are physical devices that join multiple wired or wireless networks together. Technically, a wired or wireless router is a Layer 3 gateway, meaning that the wired/wireless router connects networks (as gateways do), and that the router operates at the network layer of the OSI model. Home networkers often use an Internet Protocol (IP) wired or wireless router, IP being the most common OSI network layer protocol. An IP router such as a DSL or cable modem broadband router joins the home’s local area network (LAN) to the wide-area network (WAN) of the Internet. By maintaining configuration information in a piece of storage called the routing table, wired or wireless routers also have the ability to filter traffic, either incoming or outgoing, based on the IP addresses of senders and receivers. Some routers allow the home networker to update the routing table from a Web browser interface. Broadband routers combine the functions of a router with those of a network switch and a firewall in a single unit. A network router is a small electronic device that allows you build a home network simply. The home router serves as the core or “centerpiece” of the network to which computers, printers and other devices can be connected. Networking with a router helps you to (for example): •share files between computers •share an Internet connection between computers •share a printer •connect your game console or other home entertainment equipment to the Internet Routers are not necessarily required to build a network. For example, you can connect two computers directly to each other with just a cable (or without wires in some cases). Home routers offer convenience and easier maintenance as your network grows. Choosing a Network Router You can choose from among several different types of home network router products. The two most common types in popular usage are the 802.11b and 802.11g WiFi models. 802.11g is the newer technology, but 802.11b routers often can do the job for an even lower cost. •More – Choosing a Wireless Router •Gear – Top 802.11g Wireless Routers •Gear – Top 802.11b Wireless Routers Installing a Network Router Network routers receive their power from an ordinary home electrical socket. When powered on, lights (LEDs) signify the unit is operating. Network routers must be carefully configured when they are first installed. Like computers and other devices on the home network, routers must be set up with IP addresses. Routers also offer optional (but strongly recommended) security features. Routers contain built-in software to enable setup. You access this software through your Web browser on any computer connected to the router.

Net Terms

 

 

Bookmark : A browser feature that places selected URLs in a file for quick access, allowing you to automatically return to the website by clicking on the site’s name.Domain Name : The portion of an Internet address that identifies the host and indicates the type of organization.Extranet : Similar to an internet, but extending the network to select people outside the organization.

Homepage : The primary website for an organization or individual; the first hypertext
document displayed on a website.

Internet : A world wide collection of interconnected networks that enables users to share information electronically and provides digital access to a wide variety of services.

Internet Service Provider (lSP) : A company that provides access to the Internet, usually for a monthly fee, via telephone lines or cable; ISPs can be local companies or specialists such as America Online.

Internet Telephony : Using the Internet to converse vocally.

Intranet : A private network, set up within a corporation or organization, that operates over the internet and may be used to link geographically remote sites.

Multimedia : The combination of two or more of the following elements : graphics, text, sound, video, or computer programs.
Pagers : Small radio receivers that signal users to call someone

Personal Digital Assistant (PDA) : Handheld computer that store and organize contract information, calendars, task lists, and other organizational and travel information.

Telecommute : To work from home and communicate with company’s main office via computer and communication devices.

Telnet : A way to access someone else’s computer (the host computer) and to use it as if it were right at your desk.

Uniform Resource Locator (URL) : Web address that gives the exact location of an Internet resource.

Upload : To send a file from your computer to a server or host system.

Usenet Newsgroups : One or more discussion groups on the Internet where people with similar interests can post articles and reply to messages.

Viruses : From the computer sabotage embedded in software or passed from one computer to the next that change or delete computer files or programs.

Voice Mail : A computerized telephone message recording system; an e-mail system that supports audio.

Webpages : Related files containing multimedia data that are made available on a website.

Website : A related collection of files on the World Wide Web and accessing Internet resources such as text, graphics, sound, and other multimedia resources.

rgkumaran group

Dear All,

I am Gnanakumaranr ,have maintain more number of blogs,you come and share with me .

i wish you every success my friends and all.

i hope and  maintain a site here and there.

Thanks

Warm Regards,

RGnanaKumaran.,MCA,M.Tech.,MISTE.,

Hello world!

Welcome to WordPress.com. After you read this, you should delete and write your own post, with a new title above. Or hit Add New on the left (of the admin dashboard) to start a fresh post.

Here are some suggestions for your first post.

1. You can find new ideas for what to blog about by reading the Daily Post.
2. Add PressThis to your browser. It creates a new blog post for you about any interesting  page you read on the web.
3. Make some changes to this page, and then hit preview on the right. You can alway preview any post or edit you before you share it to the world.