Networking Concepts

Cloud Computing in Simple Terms

2011-12-31T03:20:00.001-08:00

Cloud computing is a technology that uses the internet and central remote servers to maintain data and applications. Cloud computing allows consumers and businesses to use applications without installation and access their personal files at any computer with internet access. This technology allows for much more efficient computing by centralizing storage, memory, processing and bandwidth.

A simple example of cloud computing is Yahoo email, Gmail, or Hotmail etc. You dont need a software or a server to use them. All a consumer would need is just an internet connection and you can start sending emails. The server and email management software is all on the cloud ( internet) and is totally managed by the cloud service provider Yaho , Google etc. The consumer gets to use the software alone and enjoy the benefits.

The analogy is , 'If you need milk , would you buy a cow ?' All the users or consumers need is to get the benefits of using the software or hardware of the computer like sending emails etc. Just to get this benefit (milk) why should a consumer buy a (cow) software /hardware ?Cloud computing is broken down into three segments: "application" "storage" and "connectivity." Each segment serves a different purpose and offers different products for businesses and individuals around the world.

Actuators

2011-12-20T01:57:00.000-08:00

An Actuator is something that converts energy into motion. It also can be used to apply a force. An actuator typically is a mechanical device that takes energy, usually energy that is created by air, electricity or liquid, and converts it into some kind of motion. That motion can be in virtually any form, such as blocking, clamping, ejecting or many other types of motion.

In simple words, an actuator that generates linear motion or movement is called Linear Actuator. Most of these actuators are operated using hydraulic or mechanical actuation techniques and they are using non-linear motion as their input.Electric Linear Actuators are most suitable for the movement of final control elements which require linear movement. The rotary to linear conversion is done without any wear and thrust rod can transfer force directly to the final element.

Many actuators are designed to be used in hazardous areas. They are operated by standard electronic units.Literally hundreds of actuators are available in the market. One needs to understand the required force, rated speed, maximum stroke range, and whether explosion protection is needed or not. Then one can select appropriate linear actuator for their needs.A standard linear actuator commonly has the motor as a separate cylinder attached to the side of the actuator, It is attached either in parallel way with the actuator or it sticks out to the side 90 degrees to the actuator. Motion control also plays an important role in the working of this device.The motor may also be attached to the back of the actuator. The drive motor has a solid drive shaft. This shaft is geared to the drive nut or drive screw.

Google+ was never a comptetior to Facebook

2011-11-26T00:45:00.001-08:00

The social web is a well reported topic within the media today, and for good reason. We are in a transitional change with how we communicate with each other online, how brands reach consumers and how organisations market to their audience. We are undoubtedly immersed in the technology age, and our lives, the way we

interact with others, is changing totally.

The monumental success of Facebook, Mark Zuckerberg's world leading social platform, has enticed brands, consumers, investors alike, and the world is continually awaiting for that 'next big thing'. A likely reason therefore that the majority of news stories, magazine articles and blog posts on Google's latest foray into the social web repeatedly draw up comparisons to Zuckerberg's global giant.

Predicting the next big thing is often easier than some might think. You simply have to look at what is already out there, not at who's focusing on doing something different, but rather someone who's doing it better.

Take the iPod for example. Certainly not the first digital music player on the market, but Apple's cult status products have led the way in both design and function. Google was certainly not the first search engine. Remember the likes of Lycos, Hotbot and AltaVista? Google simply developed a product that was faster, cleaner, and easier to use than its rivals, and they now command a dominating portion of the search market.

Skype too was not the first online video chat service, but with successful brand building and fantastic integration with offline communication, it continues to be the world's favourite online audio/video communication tool.

Contrary to popular belief, Google+ was never created to directly compete for people's time on the internet. A simple, ad free system, Google+ was launched to compete for users' personal data. Becoming the primary platform for social networking would simply be a bonus.

Speaking at the Monaco Media Forum recently, Nikesh Arora, Google's chief business officer said that Google+ is a platform that allows the bringing together of all the services and products that they currently offer. It was never 'just about getting people together on one site and calling it a social network'.

The real power behind what Google has created comes down to the integration of Google's products, meaning that as people are using the search engine, they are also logged into Google+. The combination of that user data and knowing when people are actively searching for something opens up the possibility of the most targeted advertising platform in history, and Google are very aware of the fact.

Little over a week into taking the reigns as CEO, Larry Page prioritised the company's social media strategy, by directly linking the annual bonuses of over 25% of Google employees to the success or failure of their social products.

What is Subnet and Subnet Mask?

2011-08-12T08:35:00.000-07:00

Subnet:A subnet (short for "subnetwork") is an identifiably separate part of an organization's network. Typically, a subnet may represent all the machines at one geographic location, in one building, or on the same local area network (LAN). Having an organization's network divided into subnets allows it to be connected to the Internet with a single shared network address. Without subnets, an organization could get multiple connections to the Internet, one for each of its physically separate subnetworks, but this would require an unnecessary use of the limited number of network numbers the Internet has to assign. It would also require that Internet routing tables on gateways outside the organization would need to know about and have to manage routing that could and should be handled within an organization.

A subnet is a also logical grouping of connected network devices. Nodes on a subnet tend to be located in close physical proximity to each other on a LAN. Network designers employ subnets as a way to partition networks into logical segments for greater ease of administration. When subnets are properly implemented, both the performance and security of networks can be improved.

Subnet Mask:
A mask used to determine what subnet an IP address belongs to. An IP address has two components, the network address and the host address. For example, consider the IP address 150.215.017.009. Assuming this is part of a Class B network, the first two numbers (150.215) represent the Class B network address, and the second two numbers (017.009) identify a particular host on this network.

Subnetting enables the network administrator to further divide the host part of the address into two or more subnets. In this case, a part of the host address is reserved to identify the particular subnet. This is easier to see if we show the IP address in binary format. The full address is:

10010110.11010111.00010001.00001001

The Class B network part is:

10010110.11010111

and the host address is

00010001.00001001

If this network is divided into 14 subnets, however, then the first 4 bits of the host address (0001) are reserved for identifying the subnet.

The subnet mask is the network address plus the bits reserved for identifying the subnetwork. (By convention, the bits for the network address are all set to 1, though it would also work if the bits were set exactly as in the network address.) In this case, therefore, the subnet mask would be 11111111.11111111.11110000.00000000. It's called a mask because it can be used to identify the subnet to which an IP address belongs by performing a bitwise AND operation on the mask and the IP address. The result is the subnetwork address:
Subnet Mask 255.255.240.000 11111111.11111111.11110000.00000000
IP Address 150.215.017.009 10010110.11010111.00010001.00001001
Subnet Address 150.215.016.000 10010110.11010111.00010000.00000000

The subnet address, therefore, is 150.215.016.000.

Hope you enjoyed !!!

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Hina Rabbani Khar

Unicast,Multicast,Broadcast

2011-08-03T07:41:00.000-07:00

Unicast:Unicast traffic is traffic addressed to a single device on the network.Unicast packets are sent from host to host. The communication is from a single host to another single host. There is one device transmitting a message destined for one reciever.Unicast uses IP delivery methods such as Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), which are session-based protocols. When a Windows Media Player client connects using unicast to a Windows Media server, that client has a direct relationship to the server.

Multicast:Multicast is a special protocol for use with IP. Multicast enables a single device to communicate with a specific set of hosts, not defined by any standard IP address and mask combination. This allows for communication that resembles a conference call.Multicast is a true broadcast. The multicast source relies on multicast-enabled routers to forward the packets to all client subnets that have clients listening. There is no direct relationship between the clients and Windows Media server. The Windows Media server generates an .nsc (NetShow channel) file when the multicast station is first created. Typically, the .nsc file is delivered to the client from a Web server.

Broadcast:Broadcast is when a single device is transmitting a message to all other devices in a given address range. This broadcast could reach all hosts on the subnet, all subnets, or all hosts on all subnets. Broadcast packets have the host (and/or subnet) portion of the address set to all ones. By design, most modern routers will block IP broadcast traffic and restrict it to the local subnet.

IEEE Standards

2011-07-29T10:27:00.000-07:00

IEEE 802.1 Bridging (networking) and Network Management
IEEE 802.2 Logical link control (upper part of data link layer)
IEEE 802.3 Ethernet (CSMA/CD)
IEEE 802.4 Token bus (disbanded)
IEEE 802.5 Defines the MAC layer for a Token Ring (inactive)
IEEE 802.6 Metropolitan Area Networks (disbanded)
IEEE 802.7 Broadband LAN using Coaxial Cable (disbanded)
IEEE 802.8 Fiber Optic TAG (disbanded)
IEEE 802.9 Integrated Services LAN (disbanded)
IEEE 802.10 Interoperable LAN Security (disbanded)
IEEE 802.11 Wireless LAN & Mesh (Wi-Fi certification)
IEEE 802.12 demand priority (disbanded)
IEEE 802.13 Not Used
IEEE 802.14 Cable modems (disbanded)
IEEE 802.15 Wireless PAN
IEEE 802.15.1 (Bluetooth certification)
IEEE 802.15.4 (ZigBee certification)
IEEE 802.16 Broadband Wireless Access (WiMAX certification)
IEEE 802.16e (Mobile) Broadband Wireless Access
IEEE 802.17 Resilient packet ring
IEEE 802.18 Radio Regulatory TAG
IEEE 802.19 Coexistence TAG
IEEE 802.20 Mobile Broadband Wireless Access
IEEE 802.21 Media Independent Handoff
IEEE 802.22 Wireless Regional Area Network

Ethernet

2011-07-26T05:13:00.000-07:00

The ethernet is a system for connecting computers within a building using hardware running from machine to machine. It differs from the Internet, which connects remotely located computers by telephone line, software protocol and some hardware. Ethernet uses some software (borrowed from Internet Protocol), but the connecting hardware was the basis of the patent (#4,063,220) involving newly designed chips and wiring. The patent* describes ethernet as a "multipoint data communication system with collision detection".

In simple terms ethernet is the most common LAN (Local Area Network) technology in use today.Ethernet was developed by Xerox in the 1970s, and became popular after Digital Equipment Corporation and Intel joined Xerox in developing the Ethernet standard in 1980.Ethernet was officially accepted as IEEE standard 802.3 in 1985.
The original Xerox Ethernet operated at 3Mbps. Ethernet networks up to 10Gbps now exist.

Ethernet uses CSMA/CD when transmitting packets. The Carrier Sense Multiple Access with Collision Detection (CSMA/CD) is an algorithm, for transmitting and receiving packets over a common network hardware medium, by aiding in avoiding transmission collisions. The network is checked for other transmissions; when the way is clear, the computer transmissions can begin. If a collision is detected the packet is retransmitted later.

Routing Tables

2011-07-23T03:52:00.000-07:00

A routing table is an electronic document that stores the routes to the various nodes in a computer network. The nodes may be any kind of electronic device connected to the network. The Routing Table is usually stored in a router or networked computer in the form of a database or file. When data needs to be sent from one node to another on the network, the routing table is referred to in order to find the best possible route for the transfer of information.

Almost all computers and network devices connected to Internet use routing tables to compute the next hop for a packet. It is electronic table that is stored in a router or a networked computer. The routing table stores the routes (and in some cases, metrics associated with those routes) to particular network destinations. This information contains the topology of the network immediately around it. The construction of routing table is the primary goal of routing protocols and static routes.

Routing tables can generally be maintained manually when the network is small and static. The routing tables for all static network devices never change unless and until the administrator of the network changes them manually. In dynamic routing, the devices themselves automatically build and maintain their own routing tables. They do this by exchanging information regarding the network topology using routing protocols. This enables the devices in the network to automatically adapt to the changes in the network like device failures and network congestion as and when they occur.

Network Topologies

2011-07-21T01:51:00.000-07:00

In this post we are going to discuss about the type of network topologies that are available to a network administrator.Based on the requirement he can select any of them.In this post we will also see for which type of network which type of topology suited most.

A network topology is like a framework, although purely in virtual terms. A topology is a layout of how computers should connect, not how they are physically arranged in a space.

Bus Topology:
The most common network topologies include the bus topology, which connects all the computers with a single cable. The computers are all able to see when a machines taps into the wire to connect to another machine, however privacy is assured as only the connecting units can access the data. This arrangement work well with less devices, it’s easy enough to set up (10Base-2 ("ThinNet") and 10Base-5 ("ThickNet") cables work well). However the downside is that if the connecting cable fails all the units attached cannot interact.

Ring Topology:
The second one is the ring topology, typically used in schools; the arrangement is such that each unit is connected to two other units, hence like a ring. If one of the units crashes however the whole network ceases to function properly (FDDI, SONET, or Token Ring technology are good for implementing this topology).

Star Topology:
Next, the star topology typically has a hub (hub, router or switch) to which all units are connecting using a unshielded twisted pair cable. The benefits of this type are that if a unit crashes, the network still continues to function. The downside is that more cable is required.

Tree Topology:
The tree topology consists of a number of star topologies connected through a bus topology. Confusing? It’s actually quite simple; we simple connect the central hubs of the star networks in the form of a bus topology. This type of network is easy to expand.

Mesh Topology:
The mesh topology uses routes, therefore any messages transferred can take a number of routes to get to their destination, in a full mesh network, every device connects to every other device.

The type of topology you choose to implement really depends on you requirements, so look carefully at the number of units involved and how complicated your network is expected to be.

Golf Platzreife

2011-07-19T12:12:00.000-07:00

Golf is now the emerging game that is popularized among all the people. Earlier only the rich and educated people played it. Now the popularity of the game is wide spread, so that every one has interest in playing the game. This particular game attracts all the types of crowds regardless of their age. Many people are now interested in learning this game. Mainly students involve themselves in this game so much and are very eager to learn the game. They are interested in learning in all the nuances, rules and regulations of the game. Since many people are interested in learning the game, there are many golf academies newly erecting in and around the city. Golf academies bear the responsibility to teach the young generation about the game. The rules of the golf etiquette are the first and fore most things, the golf academies teach their students. The rules of the game mainly aim at the safety of the golfers and to the pace of the play, which helps in keeping the game enjoyable. The golf etiquette is an essential part of the game. This is something very vital that all the new comers and the new beginners should learn on the course. For any game to be played successfully, the instruments used for the play should be manufactured or prepared with utmost care and you can found all these instruments at their Golf shop. A standard set of a golf club mainly consists of three woods, eight irons and a putter. Actually according to the rules and regulations of the play a golfer is allowed to carry 14 clubs in the bag. The more clubs the player carries the easier is his victory. To know more about golf academies, please visit Golfkurse.
The above site explains you all the details about the game. They are one of the largest German golf shops with a full range of all brand names. You can also visit Golf Platzreife it will be useful for you.

Ideal Destination for Golf Lovers

2011-07-14T22:29:00.000-07:00

A truly exciting sport that requires patience and skill. The sport of men. The Sport of sophisticates. The sport of men with way too much money. Jokes aside but, no gaming console is really complete without its own golf game.

Yesterday I was visiting some sites on golf club house locations and in those the one that i really found interesting is Whisper Rock Golf Course Homes.They provides you such a wonderful location in Scottsdale area that is ideal for any golf course home.

The whisper rock country club is nestled in amongst meandering hillsides and is laid out in a jungle setting. This golf course has some of the most beautifully designed holes on the Eastern side. The 18-hole course is carved through a virgin forest of full-grown trees that make for excellent playing under mature conditions.

Fairways and greens are kept in excellent condition. Utilizing water hazards, dog-legs and four island greens to good effect, the relatively short 18-hole course is well suited for golfers of all levels.

Greens are fast and generally have large undulations making reading the correct line especially important. The narrow palm tree lined fairways make it a challenge to recover from errant tee shots. Adding to the difficulty is also the relative long distance between the tees and the fairways. Shorter tee shots often wind up in the difficult to hit out of semi rough.

If you have any doubt or queries regarding buying or selling the club house in the space you can always contact to Holm Group that will help you in exploring more.

More Ideas On Business Gifts

2011-07-11T06:35:00.000-07:00

As all we know christmas is on its way and like always we want to gift something to our specials.In this post i am going to majorly concentrate on business gifts ideas that you can gift to your loving ones.If you are tired of always gifting the same type of thing always then here this post can help you in selecting the ideal business gift for your lovable.You can gift the same old type of items like umbrella,pens,mugs,briefcase and etc but in little bit different fashion.

Lets assume that you want to gift a Mug to your dear one.A lovely coffee mug designed with your business name and logo on it is a great way to give your business a leg up. It may seem like a small item but it is one that is extremely significant because it is an item that is used in homes and offices all around the world. It is used on the go and in the public eye on many occasions and it is also the type of item that can be given out alone for a business referral or to a special customer or one that can serve a variety of other purposes can be jazzed up to make a nice gift or even an incredible centerpiece.

You can also consider umbrellas as an option for business gifts because wherever it goes it will promote your business.Logo umbrellas can will help you to make your business stand out at a tradeshow or community event and what you will find is that colorful umbrella will make people take notice and come in for a closer look of what is being offered under the umbrella. Because these items are so large and eye catching they really do help to attract customers to your booth or table and help to get you more attention than others when at such a large event.

If you are interested in knowing more,please leave a comment or you can visit yourcoworkers.blogspot.com.

Format FAT32 Drive

2011-07-10T22:59:00.000-07:00

There are many cases where you need a FAT32 drive. For example, I had to reformat my HDD in FAT32 for transferring files to my PS3.

You can format your drive (HDD, usb etc) easily by using the mkfs utility. But before you issue the mkfs command you need to verify that your system supports FAT32. Open your terminal and type:

cat /proc/filesystem

If the output contains vfat, you can proceed. Now issue the following command:

sudo mkfs.vfat -n

Once again Ticket America Rocks

2010-11-27T04:09:00.000-08:00

If you plan to attend any kind of ticketed event on your travels to the USA, then I can give a big thumbs up to Ticketamerica.com, the biggest provider around, and in my experience, also the best. I've used this service several times when attending sporting events in the USA, and it works quite smoothly, so I have no real complaints at all about the service. The biggest point for Ticketamerica is that they are far from unique in applying these extra costs, and it is symptomatic of the ticketing industry in general, rather than this one individual supplier. With ticket america can get a chance to visit all the best stadiums across whole america which includes Bank of America Stadium,Lucas Oil Stadium,Lambeau Field,FedEx Field,Invesco Field and may more in the same list.

Assuming there are tickets remaining to your show, the tickets you have selected will be presented to you. Once they are in your 'basket', you have a limited amount of time to complete the transaction before the tickets are released for other people to buy. This is normally a few minutes worth, but it's often best to have all of your card details at hand to avoid any wasted time. Another alternative is to create an account on the site, whereby all of your personal information is stored, thus making the checkout process a lot quicker.

Take Expertise adavantage on Ticket America

2010-10-15T06:25:00.000-07:00

If you enjoy going to see live music then you should check out TicketAmerica.com. They have a huge list of arenas and stadiums all over the country. For example, they offer tickets to events at Green Bay Packers,Philadelphia,New York Yankees,Detroit Lions,San Fransisco Giants, Arco Arena, Chicago Bears,Staples Center, Texas rangers,Carolina Panthers and many, many others.

The website is easy to navigate and contains all of the information you need to choose the perfect seat and area. They also have phone numbers, layouts and maps. The maps open up into a Google Map page so you can see the entire area (in case you need driving directions or just want to see if there's a restaurant or hotel nearby.)

They're touted as having the most comprehensive inventory of tickets online, and tickets are sent via FedEx. Some of the current list of shows are Kelly Clarkson, John Mayer, Leonard Cohen, No Doubt, and Neil Diamond (yes, he's still performing!) There are many, many other tickets available for other shows as well. And you can order from the comfort of your own home.

My Favorite Ticket America

2010-10-15T06:23:00.000-07:00

If you enjoy going to see live music then you should check out TicketAmerica.com. They have a huge list of arenas and stadiums all over the country. For example, they offer tickets to events at Philadelphia, New York Yankees,San Fransisco Giants, Arco Arena, Staples Center, Texas rangers, and many, many others.

The website is easy to navigate and contains all of the information you need to choose the perfect seat and area. They also have phone numbers, layouts and maps. The maps open up into a Google Map page so you can see the entire area (in case you need driving directions or just want to see if there's a restaurant or hotel nearby.)

They're touted as having the most comprehensive inventory of tickets online, and tickets are sent via FedEx. Some of the current list of shows are Kelly Clarkson, John Mayer, Leonard Cohen, No Doubt, and Neil Diamond (yes, he's still performing!) There are many, many other tickets available for other shows as well. And you can order from the comfort of your own home.

Fight against anti aging with Oxis

2010-06-24T10:50:00.000-07:00

Antioxidants are intimately involved in the prevention of cellular damage -- the common pathway for cancer, aging, and a variety of diseases. The scientific community has begun to unveil some of the mysteries surrounding this topic, and the media has begun whetting our thirst for knowledge. Athletes have a keen interest because of health concerns and the prospect of enhanced performance and/or recovery from exercise. The purpose of this article is to serve as a beginners guide to what antioxidants are and to briefly review their role in exercise and general health. What follows is only the tip of the iceberg in this dynamic and interesting subject.

Endurance exercise can increase oxygen utilization from 10 to 20 times over the resting state. This greatly increases the generation of free radicals, prompting concern about enhanced damage to muscles and other tissues. The question that arises is, how effectively can athletes defend against the increased free radicals resulting from exercise? Do athletes need to take extra antioxidants?

Because it is not possible to directly measure free radicals in the body, scientists have approached this question by measuring the by-products that result from free radical reactions. If the generation of free radicals exceeds the antioxidant defenses then one would expect to see more of these by-products. These measurements have been performed in athletes under a variety of conditions.

Glutathione (gamma-glutamyl-cysteinyl-glycine; GSH) is the most abundant low-molecular-weight thiol, and GSH/glutathione disulfide is the major redox couple in animal cells. The synthesis of GSH from glutamate, cysteine, and glycine is catalyzed sequentially by two cytosolic enzymes, gamma-glutamylcysteine synthetase and GSH synthetase. Compelling evidence shows that GSH synthesis is regulated primarily by gamma-glutamylcysteine synthetase activity, cysteine availability, and GSH feedback inhibition. Animal and human studies demonstrate that adequate protein nutrition is crucial for the maintenance of GSH homeostasis. In addition, enteral or parenteral cystine, methionine, N-acetyl-cysteine, and L-2-oxothiazolidine-4-carboxylate are effective precursors of cysteine for tissue GSH synthesis.

These initial products position OXIS for a feasible entry into the wellness market with a lot of room for expansion. This paves the way for solid partnerships with leaders in the industry with an established customer base or those with the capacity to build one. The ultimate goal is to be regarded as a health partner. For now, it may be penny stocks for OXIS, but with more nutraceutical products lined up (including functional foods like nutrition bars and energy beverages sold over the Internet and through multi-level marketing, infomercials, direct mail, and retail outlets), the future of OXIS is secure and will benefit people all over, allowing them to be healthy and young.

http://www.oxis.com

Oxis on Twitter

Oxis on facebook

Netware

2010-06-17T05:44:00.000-07:00

The NetWare operating system was one of the first software products built for the networking of personal computers (PCs). NetWare emphasizes file and print serving capabilities, and the predominant use of NetWare is as a LAN server. Early version of NetWare appeared in the late 1980s, and today NetWare enjoys an installed base of millions of computers.NetWare is just one of many networking software products and services developed by Novell, Inc. Despite stiff competition from Microsoft and various other companies, Novell continues to offer strong network technology.The netware operating system is also known as Novell NetWare.

Know more about USB

2010-05-14T07:14:00.000-07:00

USB is a high-performance serial bus communication technology. Most new computers and associated peripheral devices like printers and scanners contain built-in support for this technology. USB hubs for file and printer sharing also exist. USB and FireWire are the most popular, competing standards for networking computer peripherals.

Multiple versions of USB have been developed by the computer industry:

* USB 1.0 and 1.1: the first commercial versions supported a maximum data rate of 12 Mbps
* USB 2.0: the current version supports a much faster theoretical maximum rate of 480 Mbps
* USB 3.0: the future standard is expected to support up to 4.8 Gbps

Using USB for Local Networking
To build a USB network, simply connect USB cables to the USB ports on those devices. USB is plug and play compatible, meaning the operating system USB driver software automatically detects and configures device connections. One USB network supports up to 127 devices.

USB interfaces are backward compatible; for example, a USB 2.0 and a USB 1.1 can be networked. When two ends of a connection support different versions of USB, the link automatically runs at the lower speed of the older version.

Hotspot in WiFi Network

2010-04-27T06:17:00.000-07:00

A hotspot is any location where Wi-Fi network access (usually Internet access) is made publicly available. You can often find hotspots in airports, hotels, coffee shops, and other places where business people tend to congregate. Hotspots are considered a valuable productivity tool for business travelers and other frequent users of network services.Technically speaking, hotspots consist of one or several wireless access points installed inside buildngs and/or adjoining outdoor areas. These APs are typically networked to printers and/or a shared high-speed Internet connection. Some hotspots require special application software be installed on the Wi-Fi client, primarily for billing and security purposes, but others require no configuration other than knowledge of the network name (SSID).

TraceRoute command

2010-04-13T07:10:00.000-07:00

Traceroute is a utility program that monitors the network path of test data sent to a remote computer. On Unix and Linux computers, the "traceroute" application is available in the shell, while on Windows computers, the "tracert" program can be accessed from DOS.Traceroute programs take the name or IP address of a remote computer on the command line. When run, traceroute sends a series test messages over the network (using ICMP) to each intermediate router progressing until the last message finally reaches its destination. When finished, traceroute displays the ordered list of routers that represent the path from that computer to the destination.

Concept of Aircards

2010-04-07T06:49:00.000-07:00

An aircard is a type of wireless broadband modem used for connecting to cellular networks. Aircards provide roaming access to the Internet from mobile computers outside the range of Wi-Fi hotspots. They may also be used as an alternative to home dial up Internet service in rural areas.

Types of Aircards
Several manufacturers produce wireless network modems including Kyocera, Novatel, Option and Pantech. In recent years, however, the term "aircard" has become associated most closely with the Sierra Wireless AirCard brand of wireless modem products.

Cellular network service providers typically bundle (and sometimes rebrand) compatible wireless modems together with their service contracts. In the U.S., for example, both AT&T and Verizon utilize Sierra Wireless products even though these may be called "AT&T AirCard" and "Verizon AirCard."

Understand Broadband Router

2010-04-01T07:14:00.000-07:00

A broadband router combines the features of a traditional network switch, a firewall, and a DHCP server. Broadband routers are designed for convenience in setting up home networks, particularly for homes with high-speed cable modem or DSL Internet service. A broadband router supports file sharing, Internet connection sharing, and home LAN gaming.

A broadband router follow the Ethernet standard for home networking. Traditional broadband routers required Ethernet cables be run between the router, the broadband modem, and each computer on the home LAN. The newer wireless routers also support broadband Internet access and the Ethernet standard without the need for cabling.

Several manufacturers offer broadband router products to the consumer. Features that differentiate broadband router products include the number and type of ports available on the unit for cabling computers, external modems, or other network devices.

Note: Image reference is taken from the answers.com.

Understand ASP in field of Computer Networks

2010-03-31T06:32:00.000-07:00

An Application Service Provider (ASP) is a business that offers software services to customers, using computer networks and the Internet as the mechanism to deliver and manage the service. Among the most well-known Application Service Providers are Clickability, Salesforce.com and WebEx.

The goal of an ASP business is to reduce the cost of software distribution and maintenance. Using a client/server model (often Web-based), network software can be installed in a centrally-controlled place and hosted - accessed by the customers over remote links. This method to providing software solutions is sometimes called the software as a service (SaaS) approach.

Apache Web Servers

2010-03-30T06:14:00.000-07:00

Apache is generally recognized as the world's most popular Web server (HTTP server). Originally designed for Unix servers, the Apache Web server has been ported to Windows and other network operating systems (NOS). The name "Apache" derives from the word "patchy" that the Apache developers used to describe early versions of their software.The Apache Web server provides a full range of Web server features, including CGI, SSL, and virtual domains. Apache also supports plug-in modules for extensibility. Apache is reliable, free, and relatively easy to configure.Apache is free software distributed by the Apache Software Foundation. The Apache Software Foundation promotes various free and open source advanced Web technologies.

Cisco launches super fast router.....

2010-03-29T06:39:00.000-07:00

NETWORKING HARDWARE VENDOR Cisco announced a router that it thinks could change the world wide web for evermore.The company said its glorious CRS-3 carrier-grade router is designed to serve as the foundation of the next-generation Internet, as it can manage speeds of up to 322 Terabits per second.

Just so the great unwashed know, that is fast enough to transmit the entire printed collection of the US Library of Congress in one second, or the bandwidth required for every man, woman and child in China to make a video call, simultaneously. Every movie ever created could be streamed in less than four minutes, Cisco claims.

Of course it is just a router and not the entire world wide web infrastructure, but it has more than 12 times the traffic capacity of anything else out there.Cisco says that it will make Internet and cloud services much more efficient. It mentions that AT&T recently tested the Cisco CRS-3 during the world's first field trial of 100-Gigabit backbone network technology, which took place over AT&T's live network between New Orleans and Miami recently.

The CRS-3 machine will replace the firm's CRS-1 router, which is still one of the most popular and fastest available commercial routers. The CRS-3 is three times faster than the CRS-1.The firm says its latest top of the line carrier-grade router is powered by its Quantumflow Array Processor, which unifies the combined power of six communications processor chips to work as one. This apparently will deliver high service capabilities and processing power. It also will require only a fraction of the power.

Cloud security weaknesses prompt call for global data protection law

2010-03-26T07:47:00.000-07:00

European leaders have called for a worldwide agreement on data protection to address the data security weaknesses of cloud computing.The call was made today before an international audience of 300 cyber law experts who had assembled at the Council of Europe to discuss the harmonisation of cybercrime regulations.

Francesco Pizetti, president of the data protection authority of Italy, warned that cloud computing had challenged the legal basis on which personal data was handled by corporations."It is not possible to continue to guarantee the protection of citizens' data without very strong international rules accepted by all countries around the world," he said.

Udo Helmbrecht, executive director of the European Network and Information Security Agency (ENISA), said the agency was examining cloud computing because of the risks it held for data security.ENISA will push for European regulation to oblige cloud providers to notify customers about security breaches, said Helmbrecht.

"We need to build trust into the cloud," he said. "If we don't build trust into this environment, the business model will not run."

Jim Reavis, executive director of the Cloud Security Alliance, said the regulatory environment needed clarifying for cloud providers. One uncertainty was how to deal with government requests to access the data they held. Cloud providers might want to make it difficult for "adverse" governments from getting at their data, but should assist governments who had the legal authority to make requests."We don't have a lot of good rules and structures for doing that sort of thing," he said. "There's a lot dealing with the legal domains, there's a lot dealing with incident response, there's a lot with the technology of cloud that we need to secure."

Yves Poullet, director of the Research Centre of IT and Law at the University of Namur, warned that "cloud computing is challenging the definitions of privacy" and foreign police might seize data contained in cloud datacentres hosted in their country.Pizetti said an EU desire for better cloud regulation had been prompted by the US seizure of European banking data held by Swift - a move that caused the firm to close its US datacentres.He said the Council of Europe's Convention on Cyber Crime would help create an international system of regulation that would make cloud computing safer.

The Council of Europe's annual Octopus conference was a focus for efforts to harmonise cyber laws around the world, mostly to give law enforcers the legal basis on which to gather cross-border evidence and bring prosecutions for cybercrimes such as hacking and fraud.Alexander Seger, head of economic crime at the Council of Europe, warned that European businesses did not want to use cloud providers who hosted datacentres in countries that did not have adequate legal protections.

Jorg Polakiewicz, head of law reform at the Council of Europe, said both the Convention of Cyber Crime and the Council of Europe's Data Protection Convention were being updated to take account of new technologies such as cloud computing.

Holiday glasses from Zenni

2009-11-27T05:26:00.000-08:00

As if you are planning holiday somewhere then don't forget to take your's eye partner,yes you understand right,I am talking about glasses.Now Zenni opticals bring you their special collection of Holiday Fun Eyeglasses where you can find a huge collection of these holiday eyeglasses.You can select eyeglasses as per your vacation like if your going at some beach or sea resort then their are some special eyeglasses for you.You can check all these eyeglasses in their New Arrivals section and best thing about these Holiday Fun Eyeglasses is that all these are available at only $8 also more popularly known as $8 Prescription Zenni Glasses.

Review on GolfKurse

2009-08-22T07:01:00.000-07:00

Golf is now the emerging game that is popularized among all the people. Earlier only the rich and educated people played it. Now the popularity of the game is wide spread, so that every one has interest in playing the game. This particular game attracts all the types of crowds regardless of their age. Many people are now interested in learning this game. Mainly students involve themselves in this game so much and are very eager to learn the game. They are interested in learning in all the nuances, rules and regulations of the game. Since many people are interested in learning the game, there are many golf academies newly erecting in and around the city. Golf academies bear the responsibility to teach the young generation about the game. The rules of the golf etiquette are the first and fore most things, the golf academies teach their students. The rules of the game mainly aim at the safety of the golfers and to the pace of the play, which helps in keeping the game enjoyable. The golf etiquette is an essential part of the game. This is something very vital that all the new comers and the new beginners should learn on the course. For any game to be played successfully, the instruments used for the play should be manufactured or prepared with utmost care and you can found all these instruments at their Golfshop. A standard set of a golf club mainly consists of three woods, eight irons and a putter. Actually according to the rules and regulations of the play a golfer is allowed to carry 14 clubs in the bag. The more clubs the player carries the easier is his victory. To know more about golf academies, please visit Golfreisen.
The above site explains you all the details about the game. They are one of the largest German golf shops with a full range of all brand names. You can also visit golfkurse it will be useful for you.

LocalTalk

2009-06-14T10:47:00.000-07:00

LocalTalk is a network protocol that was developed by Apple Computer, Inc. for Macintosh computers. The method used by LocalTalk is called CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance). It is similar to CSMA/CD except that a computer signals its intent to transmit before it actually does so. LocalTalk adapters and special twisted pair cable can be used to connect a series of computers through the serial port. The Macintosh operating system allows the establishment of a peer-to-peer network without the need for additional software. With the addition of the server version of AppleShare software, a client/server network can be established. The LocalTalk protocol allows for linear bus, star, or tree topologies using twisted pair cable. A primary disadvantage of LocalTalk is speed. Its speed of transmission is only 230 Kbps.

Wireless LAN

2009-06-08T10:42:00.000-07:00

Not all networks are connected with cabling; some networks are wireless. Wireless LANs use high frequency radio signals, infrared light beams, or lasers to communicate between the workstations and the file server or hubs. Each workstation and file server on a wireless network has some sort of transceiver/antenna to send and receive the data. Information is relayed between transceivers as if they were physically connected. For longer distance, wireless communications can also take place through cellular telephone technology, microwave transmission, or by satellite.Wireless networks are great for allowing laptop computers or remote computers to connect to the LAN. Wireless networks are also beneficial in older buildings where it may be difficult or impossible to install cables.

The two most common types of infrared communications used in schools are line-of-sight and scattered broadcast. Line-of-sight communication means that there must be an unblocked direct line between the workstation and the transceiver. If a person walks within the line-of-sight while there is a transmission, the information would need to be sent again. This kind of obstruction can slow down the wireless network.

Scattered infrared communication is a broadcast of infrared transmissions sent out in multiple directions that bounces off walls and ceilings until it eventually hits the receiver. Networking communications with laser are virtually the same as line-of-sight infrared networks.
Wireless LANs have several disadvantages. They provide poor security, and are susceptible to interference from lights and electronic devices. They are also slower than LANs using cabling.

Bluetooth Technology

2009-06-03T04:41:00.000-07:00

First of all, I want to told you from where word “Bluetooth” came, it put on the name of a great Denmark king whose name was “Harald Bluetooth” a thousand years of ago. Now the question is, what is bluetooth technology, actually it is a technology which is used for low-power radio communications to wirelessly link phones, computers and other network devices over short distances. Initially it was developed for support of personal wireless devices including cell phones, PDAs, and wireless headsets.The signals that are transmitted through “Bluetooth” devices are short distance in nature, They diminishes after 10m(30 feet).The data transferred through Bluetooth devices is at a rate of less than 1Mbps.As I already told you “Bluetooth” devices works on the principle of radio communication systems, so it is not required that the two Bluetooth devices must be in line of sight of each other, they can be either in different rooms, as long as the received transmission is powerful enough.

Today,there are many bluetooth enabled devices exists such as phones, printers, modems and headsets etc. This technology is useful only when the Bluetooth enabled devices are present in low- bandwidth position. Today Bluetooth is mainly used in cell phones to transfer sound data, or text data with laptops, and from Bluetooth enabled devices.From the security point of view, the data transferred between blue tooth devices is encrypted through some custom algorithms so that it can be safely transmitted. Hence, we can say that data transferred through Bluetooth devices is secure.As, the work is going on the development of Bluetooth so that it can be made more faster,simpler in comparison to other wireless technology.

Understsnding FDDI topology

2009-05-30T04:56:00.000-07:00

FDDI stands for Fiber Distributed Data Interface. The FDDI standard is ANSI X3T9.5 . The FDDI topology is ring with two counter rotating rings for reliability with no hubs. Cable type is fiber-optic. Connectors are specialized. The media access method is token passing. Multiple tokens may be used by the system. The maximum length is 100 kilometers. The maximum number of nodes on the network is 500. Speed is 100 Mbps. FDDI is normally used as a backbone to link other networks. A typical FDDI network can include servers, concentrators, and links to other networks. CDDI is a copper version of FDDI which uses category 5 cable. Obviously the distance is more limited than FDDI.

Devices called concentrators provide functions similar to hubs. Most concentrators use dual attachment station network cards but single attachment concentrators may be used to attach more workstations to the network.

FDDI token passing allows multiple frames to circulate around the ring at the same time. Priority levels of a data frame and token can be set to allow servers to send more data frames. Time sensitive data may also be given higher priority. The second ring in a FDDI network is a method of adjusting when there are breaks in the cable. The primary ring is normally used, but if the nearest downstream neighbor stops responding the data is sent on the secondary ring in attempt to reach the computer. Therefore a break in the cable will result in the secondary ring being used. There are two network cards which are:

1. Dual attachment stations (DAS) used for servers and concentrators are attached to both rings.
2. Single Attachment stations (SAS) attached to one ring and used to attach workstations to concentrators.
A router or switch can link an FDDI network to a local area network (LAN). Normally FDDI is used to link LANs together since it covers long distances.

Deal on business loans

2009-05-27T00:31:00.000-07:00

Today you see a lot of people whose business is deeply suffered by recession and now they are in great need of financial support from some external sources.For availing these financial support the only option to them is to contact some banks or organization that can provide financial aid to them.But as all we very well known that these banks have a very tedious process of issuing business loans.But now here is the solution of your problem at ezunsecured.com,because they provide you their financial help without any personal guarantee,that means they can sanctioned you loan upto $400,000 without any guarantee.

If you need amount much larger than this then also you can apply here and with some easy documentation your application is approved.But generally many people are in need of small business loans for recovering their business needs,hence this is the right place for your business loans.If you are worried about your past bad credit personal history then also they can issue easy unsecured loans within 7 days of your application.If you want more proof on how this company helped other people in recovering their business then you can watch the success stories of the people that already taken benefit from them.For availing all these facilities you had to just sign up with them,and once you sign up a prosper and secure future is waiting for you.

Destination and Next Hop Addresses

2009-02-27T07:45:00.000-08:00

What is the relationship between the destination address in a datagram header and the address of the next hop to which the datagram is forwarded?The Destination IP address field in a datagram contains the address of the Ultimate destination.When a router receives a datagram,the router extracts the destination address D,and uses it to compute the address of the next router to which datagram should be sent,N.Although the datagram is sent directly to address N,the header in the datagram retains destination address D.All routes are computed using IP address.After computing the address of a next hop,N,IP software uses the address binding to translate N to an equivalent hardware address for transmission.

Physical Network Connection With Routers

2009-02-22T04:41:00.000-08:00

The basic hardware component used to connect heterogeneous networks is a Router.Physically,routers resembles bridges that means each router is a special purpose hardware system dedicated to the task of interconnecting networks.Like a bridge,a contains a processor and memory as well as a separate I/O interface for each network to which it connects.The network treats a connection to a router, the same as the connection to any other computer.

The most important that you have to kept in your mind about router is that it is not only used to connect two similar technology,it can also be used to connect two different types of network technology. Router can connect two LAN's,a LAN and a WAN,or two WAN's.Furthermore,when a router connects two network in the same general category,the networks do not need to use the same technology.For ex:- A router can connect an Ethernet LAN to a frame relay network.Thus,each cloud represents an arbitrary network technology.On summarizing this whole,we can say that a router is a special purpose system dedicated to the task of interconnecting networks.A router can interconnect networks that use different technologies,including different media,physical addressing schemes or frame formats.

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Goal of Internet

2009-02-21T04:53:00.000-08:00

The main goal of internetworking is to provide a universal service across heterogeneous networks.To provide universal service among all computers on an internet,routers must agree to forward information from a source on one network to the specified destination on the other network.The task is complex because as all we know that different frame formats and different addressing schemes are used by different networks.Hence,to overcome this problem protocol software is needed on computers and routers to make universal service possible.The main task of these internet protocols is to overcome the differences in frame formats and physical addresses to make communication possible among networks that use different technologies.
For knowing more about protocols for internetworking you can visit:
http://networkingconcepts4u.blogspot.com/2009/02/protocol-for-internetworking.html

Internet Architecture

2009-02-20T05:31:00.000-08:00

With the help of routers it is possible for an organization to choose network technologies appropriate for each need,and to use routers to connect all networks into a single network.As all we know that router is used exactly two connections but commercial routers can connect more than two networks.Thus,a single router could connect any number of networks.However,an organization seldom uses single router to connect all of its networks.There are two main reasons behind it:

1.As all we know that router must forwarded each packet,the processor in given router is insufficient to handle the traffic passing among an arbitrary number of networks.

2.The second reason behind this is redundancy,because redundancy improves reliability.To avoid a single point of failure,protocol software continuously monitors internet connection,and instructs the routers to send traffic long alternative paths when a network or router fails.

Thus,when planning an internet,an organization must choose a design that meet's the organization's need for reliability,capacity and cost.In particular,the exact details of internet topology often depends on the bandwidth of the physical networks,the expected traffic,the organization's reliability requirements,and the cost and performance of available router hardware.

Connection between a NIC and a network

2009-02-19T03:59:00.000-08:00

The type of connection used between a NIC and a network depends on that network technology.In some technologies,the NIC contains most of the necessary hardware,and attaches directly to the network medium using a single cable or optical fiber.In many other technologies,the NIC does not contain all the electronic circuitry needed to attach directly to the network.Instead,the cable from a NIC attaches to an additional electronic component that then attaches to the network.Surprisingly,the exact details of the connection between a NIC and a network are not determined by the technology that means a given network technology can support multiple wiring schemes.Let take the example of Ethernet technology in which technology i.e Ethernet remains same while the wiring scheme changes.Wiring scheme can be Thick Ethernet Wiring,Thin Ethernet Wiring and Twisted pair Ethernet Wiring.

Thin Ethernet Wiring

2009-02-18T11:27:00.000-08:00

A second generation of Ethernet wiring uses a thinner,more flexible cable than the original thick wiring.Formally named as a 10 Base2 and informally named as thin wire Ethernet or Thinnet.This wiring scheme differs from Thicknet wiring scheme in three important ways.First,Thinnet generally costs less to install and operate than Thicknet.Second,because the hardware that performs the transceiver function is built into the NIC,no external transceivers are needed.Third,Thinnet does not use an AUI cable to attach the NIC to a communication medium.Instead,Thinnet attachs directly to the back of each computer using BNC connector.In a Thinnet installation,a coaxial cable stretches between each pair of machines.The cable doesn't need to follow a straight line-it may lie loosely on the tabletop between computers,run under floor,or run in a conduit.Although,wiring for a thin Ethernet appears to be completely different than the wiring for a thick Ethernet,the two schemes share several important properties.Both thick and thin cables are coaxial,meaning that they shield signals from outer interference.Both thick and thin cables requires termination,and both use the bus topology.Most important,because two wiring systems have similar electrical characteristics,that means signals propagate along the cable is in the same way.

Twisted Pair Ethernet

2009-02-16T01:39:00.000-08:00

This type of Ethernet wiring is known as Third Generation of Ethernet wiring.This generation is completely differ from its previous two generation that are thick and thin Ethernet because it does not use a coaxial cable.This generation Ethernet typically known as twisted pair Ethernet or TP Ethernet and its first version was formally known as 10BaseT.The wiring for Fast Ethernet is known as 100BaseT,and wiring for Gigabit Ethernet is known as 1000BaseT.Instead of shared medium,the new technology extends the idea used with connection multiplexing in which an electronic device serves as the center of the network.
The basic electronic device is known as an Ethernet Hub.Like the other wiring schemes,twisted pair requires each computer to have a network interface card and a direct connection from NIC to the network.The connection uses unshielded twisted pair wiring with RJ-45 connectors which are the largest versions of the modular connectors used with the telephones.The connector on one end of a twisted pair cable plugs into the network interface on a computer and the connector on the other end plugs into the hub.
Thus,each computer has a dedicated connection to the hub device.Electronic components in hub emulate a physical cable,making the entire system operate like a conventional Ethernet.For ex:A computer attached to a hub must have a physical Ethernet Address that means each computer must use the CSMA/CD to access the network and the standard Ethernet Frame Format.In fact,software does not distinguish between thick Ethernet,thin Ethernet and twisted pair Ethernet because the network interface handles the details and hides any differences.

The Berkeley Broadcast Address Form

2009-02-08T09:21:00.000-08:00

The University of California at Berkeley developed and distributed an early implementation of TCP/IP protocols as a part of BSD UNIX.The BSD implementation contained a non-standard feature that has affected many subsequent implementations.Instead of using a host suffix of all ones to represent a directed broadcast address,the Berkeley implementation used a host suffix that contained all zeros.The address form is informally known as Berkeley Broadcast.Unfortunately,many computer manufacturers derived their early TCP/IP software from the Berkeley implementation,and a few sites still use Berkeley broadcast.Some implementations include a configuration parameter that can select between the TCP/IPTCP/IP standard and Berkeley form;many implementations are built to accept both standard and Berkeley broadcast address forms.

Directed Broadcast Address

2009-02-07T05:28:00.000-08:00

Sometimes,it is convenient to send a copy of a packet to all hosts on a physical network.To make broadcast easy,IP defines a directed broadcast address for each physical network.When a packet is sent to network's broadcast address,a single copy of the packet travels across the internet until it reaches the specified network.The packet is then delivered to all the hosts on the network.The directed broadcast address for a network is formed by adding a suffix that consists of all 1 bits to the network prefix.

To ensure that each network can have directed broadcast address,IP reserves the host address that contains all 1 bits.An administrator must not assign the all ones host address to a specific computer or the software may malfunction.If a network hardware supports broadcast,a directed broadcast will be delivered using the hardware broadcast capability.In such cases,transmission of the packet will reach all computers on the network.When a directed broadcast is sent to a network that does not have hardware support for broadcast,software must send a separate copy of the packet to each host on the network.

Authority for Addresses

2009-02-06T09:09:00.000-08:00

Throughout an internet,each network prefix must be unique.For networks connected to the global internet,an organization obtains network numbers from the communication company that supplies internet connections.Such companies are called Internet Service Providers(ISPs).Internet Service Providers coordinate with a central organization,the Internet Assigned Number Authority,to ensure that each network prefix is unique throughout the entire Internet.For a private internet,the choice of the network prefix can be made by organization.To ensure that each prefix is unique, group that builds a private internet must decide how to coordinate network number assignments.Often,a single network administrator assign prefixes to all networks in the company's internet to ensure that numbers are not duplicated.

Loopback Address

2009-02-05T11:35:00.000-08:00

IP defines a loopback address used to test network applications.Programmers often use loopback testing for preliminary debugging after a network application has been created.To perform a loopback test,a programmer must have two application programs that are intended to communicate across a network.Each application includes the code needed to interact with TCP/IP protocol software.Instead of executing each program on a separate computer,the programmer runs both program on a single computer and instructs them to use a loopback IP address when communicating.

When one application sends data to another,data travels from the protocol stack to the IP software,which forwards it back up through the protocol stack to the second program.Thus,the programmer can test the program logic quickly without needing two computers and without sending packets across a network.IP reserves the network prefix 127/8 for use with loopback.The host address used with 127 is irrelevant that means all host addresses are treated the same.By convention.programmers often use host number 1,making 127.0.0.1 the most popular form of loopback.During loopback testing no packets ever leave a computer that means the IP software forwards packets from one application program to another.Consequently,the loopback address never appears in packet traveling across a network.

Subnet and Classless Addressing

2009-02-04T06:21:00.000-08:00

As the Internet grew,the original classful addressing scheme became a limitation.On one hand,the IP address space was being exhausted.On the other hand,because all networks had to choose one of the three possible sizes,that means many addresses were unused.Two new mechanisms were invented to overcome the limitations,known as subnet addressing and classless addressing.These two addressing schemes are so closely related that they can be considered to be a part of single abstraction.The generalization is straight forward that means instead of having three distinct address classes,allow the division between prefix and suffix to occur on an arbitrary bit boundary.Let understand this situation with the help of an example,Consider a network that contains 9 hosts.Only four bits of host suffix are needed to represent all possible host values.However,a class C address,which has the fewest address hosts possible,devote eight bits to the host suffix.Classless addressing solves the problem by allowing an ISP(Internet Service Provider) to assign a prefix that is 28 bits long that means network can have up to 14 hosts.

Protocol for Internetworking

2009-02-03T11:27:00.000-08:00

As all we know that may protocols have been adapted for use in an internet,one suite stnds out as the most widely used for internetworking.The suite is formally known as The TCP/IP Internet Protocols.TCP/IP was the first set of protocols develop for use in an internet.Indeed,researchers who devised TCP/IP also developed the internet architecture.Work on TCP/IP began in 1970s,approximately the same time that Local Area Networks were being developed.The U.S military funded much of the research on the TCP/IP and internetworking through the Advanced Research Projects Agency.The military was among the first organizations to have multiple physical networks.Cosequently,the military was among the first to realize the need for universal service.By the mid-1980s,the National Science Foundation and the other U.S government agencies were funding development of TCP/IP and a large internet that was used to test the protocols.

Art of Protocol Design

2009-02-02T05:16:00.000-08:00

Although the techniques needed to solve specific problems are well known,protocol design is on-trivial for two reasons.First to make communication efficient,details must be chosen carefully that means small design errors can result in incorrect operation,unnecessary packets or delays.For example:sequence numbers are usually stored in a fixed field in a packet header.The field must be large enough so sequence numbers are not reused frequently,but small enough to avoid wasting unnecessary bandwidth.Similarly,a higher level protocol can cause excessive overhead if the protocol chooses a non-optimal message size.

Second,protocol mechanism can interact in unexpected ways.For example:Consider the interaction between flow control and congestion control mechanism.A sliding window scheme aggressively use more of the underlying network bandwidth to improve throughput.A congestion control mechanism does,the opposite by reducing the number of packets being inserted to prevent the networking from collapsing.

The balance between sliding window and congestion control can be tricky,and a design that does both well is difficult.A protocol that is too aggressive about using bandwidth can adjust the underlying network and a protocol that is too conservative can result in lower throughput then necessary.More important,designs that attempts to switch from aggressive to conservative whenever congestion occurs tend to oscillate - then slowly increase their use of bandwidth until the network begins to experience congestion,decrease use until the network becomes stable and then begin to increase again.

Understanding Protocol Suites

2009-01-31T05:12:00.000-08:00

After knowing the importance of protocol in communication,designers have chosen to divide the communication problem into sub pieces and to design a protocol for each of the sub piece instead of having a single giant protocol that specifies complete details for all possible forms of communications.Doing so makes each protocol easier to design,analyze,implement and test.The main advantage of dividing communication software into multiple protocols increases flexibility because it allows subsets of protocols to be used as added.The division into separate protocols must be chosen carefully to ensure the resulting communication system is efficient and effective.To avoid duplication of effort,each protocol should handle part of the communication problem not handled by other protocols.

To make efficient implementation possible,protocols should be designed so that,they can share data structures and information.Finally,the combination of protocols should handle all possible hardware failures or other exceptional conditions.Now the main question that arises in front of us is that how can one guarantee that protocols will work together.The answer of this question lies in an overall design plan that means instead of developing each protocol in isolation,protocols are designed and developed in complete,cooperative sets called suites or families.Each protocol in a suite solves one part of the communication problem;together they solve the entire communication problem.Furthermore,the entire suite is designed to make interactions among protocol efficient.

Need for Protocols

2009-01-30T04:20:00.000-08:00

As all we know that basic communication hardware consists of mechanisms that can transfer bits from one point to another.However,using raw hardware to communicate is analogous to programming by entering 1s and 0s but it is cumbersome and inconvenient.To aid programmers,computers attached to a network use complex software that provides a convenient,high level interface for applications.The software handles most low level communication details and problems automatically,making it possible for applications to communicate easily.Thus,most application programs rely on network software to communicate that means hey do not interact with network hardware directly.All parties involved in a communication must agree on a set of rules to be used when exchanging messages and such type of agreement is known as protocol.This term is also applied to computer communications meaning of which "a set of rules that specify the format of messages and the appropriate action required for each message is known as a network protocol or a computer communication protocol."The software that implement such rules is called as protocol software.

Significance of Internetworking and TCP/IP

2009-01-28T08:57:00.000-08:00

Internetworking has become one of the most important ideas in modern networking.In fact,Internet Technology has revolutionized computer communication.Most large organizations already use internetworking as the primary computer communication mechanism.Smaller organizations and individuals are beginning to do so well.More important,in addition to private internet,the TCP/IP technology has made possible a global internet that reaches schools,commercial organizations,and government and military sites in all populated countries around the world.The worldwide demand for internetworking products has affected most companies that sell networking technologies.

Competition has increased because new companies have been formed to sell hardware and software need for internetworking.In addition may companies have modified their protocol designs to accommodate internetworking.In particular,most network protocols were originally designed to work with one network technology and one physical network at a time.To provide internetworking capabilities,companies have extended the designs in two ways:the protocols have been adapted to work with many network technologies and new features have been added that allows the protocols to transfer data across internet.

Public and Private Networks

2009-01-27T08:16:00.000-08:00

When applied to a network,the term public refers to the availability of the service,not to the data transferred.In particular,most public networks provide private communications i.e when a computer sends a message across a public network,only the intended recipient receives the copy.Some public networks permit a group of computers to communicate analogous to a telephone conference hall.However,the public network doesn't use the broadcast technology.That is,the public network doesn't have a broadcast address nor it does forward broadcast packets.

The chief advantage of a private network is that owner has full control over both the technical decisions and policies.In addition to this it also have some disadvantages like a large private network can be expensive to install and maintain.In addition to purchasing the network hardware,a corporation must hire and train a staff to install,manage and operate the network.

On the other hand the chief advantage of a public network are flexibility and the ability to use state of the art networking without maintaining the technical expertise. public network is flexible because an arbitrary subscriber at a arbitrary location can connect to the network at any time.Furthermore,connections between a computer owned by one organization and a computer owned by another can be made broken the same way a public telephone system allows voice connections to be made or broken

Concept of ISDN

2009-01-23T07:59:00.000-08:00

Integrated Services Digital Network(ISDN) is launched by telephone companies and used to provide large scale digital services to subscribers.ISDN provides digitized voice and data to subscribers over conventional local wiring.ISDN uses the same type of twisted pair copper wiring as the analog telephone system.If we discuss from the subscribers point of view then ISDN offers three separate digital channels designated B,B and D(usually written 2B+D).The two B channels operates at a speed of 64 Kbps,are intended to carry digitized voice and data or compresses videos, on the other hand the D channel which operates at 16 Kbps,is intended as a control channel.In general,a subscriber uses the D channel to request services which are then supplied over the B channels.The subscriber can also use the D channel to manage a session that is in progress or to terminate a session.Finally,both the B channels can be combined or bonded together to produce a single channel with effective data rate at 128 Kbps.The 2B+D channels are known as ISDN Basic Rate Interface(BRI).Infact,ISDN uses a form of time division multiplexing to provide the illusion of multiple channels of data to travel over a single pair of wires.

Understanding Bridges

2009-01-20T10:04:00.000-08:00

A bridge is an electronic device that is used to connects two LAN segments.Unlike a repeater,however a bridge is a digital device that uses the same network interface as a conventional computer and handles frames.The bridge listen to traffic on each segment in promiscuous mode.When it receives a frame from one segment,the bridge verifies that the frame arrived intact i.e there was no electrical interference on LAN during transmission and after that it forwards a copy of the frame to the other segment if necessary.Thus,two LAN segments behave connected by a bridge behave like a single LAN.A computer connected to either segment can send a frame to any of the other computers connected to the two segments.Because each segment supports standard network connections and uses the standard frame format that means computers do not know whether they are connected to a LAN or a bridged LAN.

When we compare bridges with LAN it is found that bridges are more useful and popular than repeaters because they help isolate problems.If two segments are connected by a repeater and lightning causes electrical interference on one of them,the repeater will propagate the interference to the other segment.In contrast if interference occurs on one of the two segments connected by a bridge,the bridge will receive an incorrectly formed frame,which the bridges simply discards the same way a conventional computer discards a frame that contains an error.Similarly,a bridge will not forward a collision from one segment to another.Thus,the bridge keeps problems on one segment from affecting the other.

Combining Switches and Hubs

2009-01-16T12:14:00.000-08:00

From the last post it is clear that switching provides higher aggregate data rates in comparison to a hub,but the main drawback that occurred with the switched networks is the higher cost in comparison to hub.To overcome all these problems network administrator choose a compromise between the hub and the switched networks that means instead of connecting one computer to each port on a switch,the administrator connects the hub to each of the port of the switch and then connect each computer to one of the hubs.This result is very much closer to the conventional bridged LAN where each hub appears to be a single LAN segment, and the switch makes it appear that bridges connect all segments.The system also performs like a conventional bridged LAN where a computer must share a bandwidth with other computers connected to the same hub,communication can occur in parallel between a pair of computers attached to one hub and a pair of computers attached to another.

Concept of Switching

2009-01-15T09:57:00.000-08:00

In general,a network technology is called switched if the hardware includes an electronic device that connects to one or more computers and allows them to send and receive data from each other.More specifically,a switched LAN consisted of a single electronic device that transfers frames among many computers.As all we know that a switch resembles a hub,like a hub, a switch consists of a single box with multiple ports that each attach to a single computer.The main difference between a switch and a hub arises from the way the devices operates,a hub simulates a single shared medium while in the case of a switch it simulates a bridged LAN with one computer per segment.

If we talk about the chief advantage of using a switched LAN instead of a hub then the reason is same as that of using bridged LAN instead of a single segment.In the case of a hub a single segment is shared by all computers,that means at most two computers can communicate through hub at a time.Thus the maximum possible throughput of a hub system is R,the rate at which single computer can send data across a LAN segment.In the case of a switched LAN,each computer has a simulated LAN segment to itself that means the segment is busy only when a frame is being transferred to or from the computer.As a result,as many as one half of the computers connected to a switch can send the data at the same time(if they send to one of the computers that is not busy in sending).Thus,in this case the maximum throughput of a switch is RN/2 where R is the rate at which data transmits,and N is total number of computers that are connected to the switch.

Understanding Baud Rate and Framing Errors

2009-01-13T21:22:00.000-08:00

As all we know that sending and receiving hardware are agreed on the length of the time the voltage will be held for each bit.Instead of specifying the time per bit,which is a small fraction of second,communication systems specify the number of bits that can be transferred in a second.For ex:some early RS-232 connections operated at 300 bits per second,19200 bits per second and 33600 bits per second are more common.Technically ,transmission hardware is rated in baud,the number of changes in the signal per second that the hardware generated.For the simple RS-232 scheme presented, the baud rate is exactly equal to the number of bits per second.Thus,9600 baud means 9600 bits per second.

To make RS-232 hardware more general,manufacturers usually design each piece of hardware to operate at variety of baud rates.The baud rate can be configured either manually by physically setting switches on the hardware when it is installed in a computer or automatically by device driver software in a computer.If the sending and receiving hardware are not configured to use the same baud rate,errors will occur because the receiver's timer will not wait an appropriate length of time for each bit.To detect errors,a receiver's measure the voltage for each bit multiple times and compares the measurements.If the voltage do not all agree or if the stop bit does not occur exactly at the time expected,the receiver reports an error.Such errors are known as framing errors.

Concept of Parity Bits

2008-12-23T06:19:00.000-08:00

Fortunately,few communication systems experience frequent experience.More important,the interference on a long distance communication circuit may be so small that modems can handle all problem automatically.Despite the low probability of error,scientists and engineers who design networks understand that transmission errors do occur,and provide hardware and software mechanisms to detect and correct such problems.But now a days most RS-232 circuits use the different mechanism to ensure that each character arrives intact.This mechanism is known as Parity Check mechanism,this mechanism requires the sender to compute an additional bit,called a parity bit,and to attach it to each character before sending.After all bits of a character arrives,the receiver removes the parity bit,performs the same computation as the sender,and verifies that result agrees with the value of the parity bits.The parity computation chosen is such that if one of the bits in the character is damaged in transit,the receiver's computation will not agree with the parity bit and the receiver will report that an error occurred.

There are two forms of parity,even or odd.Both the sender and receiver must agree on which form is being used.In either form,the computation of the parity bit for a given character is straightforward.To achieve even parity,the sender sets the parity bit to 0 or 1 whichever will make the total number of 1 bits(including parity bit)an even number.Thus,when using even parity ,the parity bit for 0100101 is 1 because the character contains an odd number of 1 bits,and the parity bit for 0101101 is 0 because the character already contains an even number of 1 bits.Similarly to achieve odd parity,the sender chooses a parity bit such that it makes the total number of one in the character is odd.If all bits from the character arrive intact,the receiver's computation of parity will agree with the sender's.If interference changes one of the bits during transmission,the receiver's computation will not agree with the sender's and the receiver will report a parity error.

Transmission errors in Computer Networks

2008-12-21T06:58:00.000-08:00

Lightning,Power Surges,and other electro-magnetic interference can introduce unwanted electrical currents in the electronic components or wires used for communication.Interference that is severe especially lightning can cause permanent damage to network equipment.More often,however interference merely changes the signal used for transmission without damaging the equipment.A small change in the electrical signal can cause the receiver to misinterpret one or more bits of the data.In fact,interference can completely destroy a signal,meaning that although the sender transmits,the receiver does not detect that any data has arrived.Surprisingly,interference on a completely idle transmission circuit can create the opposite effect that means the sender does not transmit any thing,a receiver might interpret the incoming interference as a valid sequence of bits or characters.All these types of errors are known as transmission errors.In the last we can summarize the whole thing in this way that much of the complexity in the computer networks arises because digital transmission system are susceptible to interference that can cause random data to appear or transmitted data to be lost or changed.

Concept of Packets

2008-12-20T00:21:00.000-08:00

Most computer networks do not transfer data as an arbitrary string of continuous bits.Instead the network system divides the data into small blocks called packets,which it sends individually.Computer networks are often called packet networks or packet switching networks because they use packet technology.The concept of using data packets for data transmission is supported by two facts,first a sender and receiver need to coordinate transmission to ensure that data arrives correctly.Dividing the whole data into small blocks helps a sender and receiver to determine which blocks arrive correctly and which blocks do not.

The second fact that supports packet technique is as all we know that communication circuits and modem hardware are expensive,multiple computers often shares underlying connection and hardware.To ensure that all computers receive fair,prompts access to a shared communication facility,a network system cannot allow one computer to access deny to other computers.Using small packets helps ensure fairness.Let understand this more clearly.The networks that do not packet technology allows an application program(computer) to hold a shared communication resource arbitrarily long that means an application was permitted to finish before another application could begin using the resource.But now the networks that uses packet technology have a solution of this problem.Here the networks permits one computer to send a packet of data and then blocks that computer from sending another packet.Meanwhile the network permits another computer to send a packet and so on.A single computer can hold a shared resource only long enough to send single packet,and must wait until other computers have a turn before sending a second packet.

Understanding Proxy Server

2008-10-17T03:27:00.000-07:00

Proxy Server:A proxy server is a kind of buffer between your computer and the Internet resources you are accessing. The data you request come to the proxy first, and only then it transmits the data to you.Proxy servers accumulate and save files that are most often requested by thousands of Internet users in a special database, called “cache”. Therefore, proxy servers are able to increase the speed of your connection to the Internet. The cache of a proxy server may already contain information you need by the time of your request, making it possible for the proxy to deliver it immediately.Security and privacy. Anonymous proxy servers that hide your IP address thereby saving you from vulnerabilities concerned with it. Sometimes you may encounter problems while accessing to web server when server administrator restricted access from your IP or even from wide IP range (for example restricting access from certain countries or geographical regions). So you try to access those pages using an anonymous proxy server.

Public Proxy Server:It is a proxy server which is free and open for everybody on the Internet. Unfortunately most of them are not anonymous.Free service trying to provide list of public HTTP proxy servers. Usually provide small list of proxies with low percent of functioning servers due to hosting restrictions on CPU time (they simply can't allow themselves to check many proxies every second especially in parallel).

Address Binding Technique Part-3

2008-10-13T11:18:00.000-07:00

Now as all we aware of the first and second technique of address binding, now its high time to tell you the third and last technique of address binding.In this technique the address resolution takes place through message exchange.

Address Resolution with message exchange: In this approach the computer that needs to resolve an address sends a message across network and receives reply.The message carries a request that specifies the protocol address,and the reply carries the corresponding hardware address.Now the main question that came in front of us is that where all these requests be sent.Generally there are two designs that are used for this.In the first design a network includes one or more servers that are assigned the task of answering address resolution requests.

Whenever,address resolution is needed a message must be sent to any of these servers which will send a reply.In the second design no special address resolution servers are needed.Instead,each computer on the network participates in address resolution by agreeing to answer resolution requests for its address.When a computer needs to resolve an address,it broadcasts a request on the network.All machine receive the request and examine the requested address.If an incoming request matches a computer’s address, the computer responds.Now discuss the advantages of both the designs.

The chief advantage of the first scheme arise from centralization because a few address resolution servers handle all resolution tasks on the network,address resolution is easier to configure,manage and control.Now the advantage of second design arise from distributed computation.Address resolution servers may be expensive.In addition to the expense of additional hardwares like extra memory.In addition to this servers are expensive to maintain because address binding information stored in servers must be updated whenever new computers are added to the network or hardware address changes.Furthermore ,address resolution servers can become a bottleneck on a large busy network.If each computer is able to resolve its own address ,then there is no need of servers.

Address Binding Technique 2

2008-10-08T13:08:00.000-07:00

Hello friends in the last post I told you about the first technique through which address binding takes place.Now in this post I am going to tell you second technique through which address binding takes place.

Address Resolution with closed form computation: As all we know that many network technologies use static physical addresses, some technologies use configurable addressing in which a network interface can be assigned a specific hardware address. For such type of networks it is possible that we can choose addresses that make closed form address resolution possible.A resolver that uses a closed form method computes a mathematical function that maps an IP address to its equivalent hardware address. If the relationship between the IP address and its coprresponding hardware address is straightforward, the computation requires only a few arithmetic operations.Infact,the host portion of a computer’s IP address can be chosen such that it is identical to the computer’s hardware address.

Let’s understand this situation with the help of a example, suppose a configurable network has been assigned the network address 220.123.152.xxx and its suffix ranging from 0-24. As computers are added to the network, each computer is assigned an IP address from this range and a matching hardware address.The first host is assigned an IP address 220.123.152.1 and hardware address 1. The second host is assigned an IP address 220.123.152.2 and hardware address 2. The suffixes need not be sequential, if a router attached to a network assigned IP address202.123.152.101,then the router is assigned an IP address of 121.Given the IP address of any computer on the network, the computer’s hardware address can be computed by a single Boolean ‘and’ operation.

Hardware Address=IP Address & 0xff

As I think it is clear from the example that why closed form resolution is often used with configurable networks.

Address Binding Technique 1

2008-10-07T11:25:00.000-07:00

Hello friends in this post I am going to tell you all the first way through which address binding takes place.

1.Address resolution with table lookup: This technique of address resolution requires a data structure that contains information about address binding. The table consists of an array. Each entry in the array contains a pair (P,H),where P is the protocol address and H is its corresponding hardware address. The main advantage of table lookup approach is generality- a table can store the address bindings for an arbitrary set of computers on a given network. In particular a particular protocol address can map to an arbitrary hardware address.

Furthermore, the table lookup algorithm is straight forward and easies among all the approaches. Suppose we have given a next-hop address, N, the software searches the table until it finds an entry where the IP address matches N. The software then extracts the hardware address from the entry.For a network that contains a less then dozen of hosts, a sequential search is sufficient ,the resolution software begins at first entry and searches each entry in table until a match is found. But for large networks this sequential search is not possible because it consumes excessive CPU time. In these type of situations to improve computational efficiency we can use Hashing or Direct Indexing.

As all we know that Hashing is a general purpose data structure and is well known to all the programmers, so, here I am not going to discuss it. Let’s take a look at the other technique that is of Direct Indexing. Direct Indexing is slightly more efficient but less general technique. In particular Direct Indexing is possible only in those cases where protocol addresses are assigned from a compact range.

For ex: Direct Indexing can be used with IP addresses that are arranged in sequential order. In these type of cases the software maintains a one dimensional array of hardware addresses, and uses the host suffix from an IP address as an index to an array.

In the next post I will tell you the second technique of Address Binding.

Address Resolution Protocol

2008-10-05T06:40:00.000-07:00

Hello friends in this post I am going to discuss one of the most interesting topics in computer networks that is of Binding Protocol Addresses or Address Resolution Protocol.

As all we know that IP addresses are virtual because they are maintained by software. Neither Local Area network nor Wide Area Network hardware understands the relationship between an IP address prefix and a network or the relationship between an IP address suffix and a particular computer. I am telling you all these things because we have to know all these things before understanding Binding Address Protocol. Now let’s come to our main issue of Binding Protocol Addresses, the first point that came into the mind of any one that is new to networking is what Binding Protocol Address is and what its requirement is.

Now before giving answer of first question I would like to give the answer of our second question. Let’s consider an application program that generates data to be sent across an internet, for this software places the data in the packet, which contains the protocol address (IP address) of the destination. Software in each host or router uses the protocol destination address to select the next hop for the packet. Once a next hop has been selected, software transfers the packet across one physical network to the selected host or router. To provide the illusion of a single, large network, software works with the IP addresses when forwarding the packets. Both the next hop and destination addresses are the IP addresses.

Now the main problem arises here, when we want to transmit frames across physical network hardware we need hardware address of the destination because the hardware does not understand the IP addressing. So, when a frame is set across a physical network it must use the hardware’s frame format and all the addresses in the frame must be hardware addresses. Consequently, the protocol address of the next hop must be translated to an equivalent hardware address before a frame can be sent. The process of converting IP address to its equivalent hardware address is known as Address Resolution and a protocol address is said to be resolved to the correct hardware address. Address Resolution is local to network that means one computer can resolve the address of another computer only if both computers attach to the same physical network. A computer never resolves the address of a computer on a remote network.

After this explanation I hope you understand a little bit about the Address Resolution Protocol. In the next post I will tell about the various techniques through which Address Resolution takes place. Hope you like this post.If you have any doubts in any of the topics of Computer Networks then post your problem in the comment. I will try to sort it out.

Types of Viruses

2008-10-01T22:57:00.000-07:00

Hello friends in this post i am going to give you a whole detail of almost all of the virus types in which trojan is the most common one.

Trojan:Remember the Trojan Horse? Bad guys hid inside it until they could get into the city to do their evil deed. A trojan computer program is similar. It is a program hitch does an unauthorized function, hidden inside an authorized program. It does something other than what it claims to do, usually something malicious (although not necessarily!),and it is intended by the author to do whatever it does. If it's not intentional, its called a 'bug' or, in some cases, a feature :) Some virus scanning programs detect some trojans. Some virus scanning programs don't detect any trojans. No virus scanners detect all trojans.

Virus: A virus is an independent program which reproduces itself. It may attach to other programs, it may create copies of itself (as in companion viruses). It may damage or corrupt data, change data, or degrade the performance of your system by utilizing resources such as memory or disk space. Some virus scanners detect some viruses. No virus scanners detect all viruses. No virus scanner can protect against "any and all viruses, known and unknown, now and forevermore".

Worm:Made famous by Robert Morris, Jr. , worms are programs which reproduce by copying themselves over and over, system to system, using up resources and sometimes slowing down the systems. They are self contained and use the networks to spread, in much the same way viruses use files to spread. Some people say the solution to viruses and worms is to just not have any files or networks. They are probably correct.We would include computers.
Logic Bomb:Code which will trigger a particular form of 'attack' when a designated condition is met. For instance, a logic bomb could delete all files on Dec. 5th. Unlike a virus, a logic bomb does not make copies of itself.

Hope you found this post useful.Waiting for your responses.

DHCP Server

2008-10-01T03:37:00.000-07:00

Hello friends in this post i am giving answer to one of the most common question from the field of networking,that is how an IP address is assigned to any computer or any device like switch,hub,bridge.

DHCP is the only responsible to assign IP address to any device.Dynamic Host Configuration Protocol (DHCP) is a network protocol that enables a server to automatically assign an IP address to an individual computer's TCP/IP stack software. DHCP assigns a number dynamically from a defined range of numbers configured for a given network.Today you found almost all wireless access points, many wired Ethernet routers, and computers running Internet Connection Sharing have built-in DHCP servers.Due to this reason DHCP servers are mainly preffered for the small networks in comparison to large networks.DHCP assigns a TCP/IP address when a system is started. Typically, it works like this:
1. A user turns on a computer with a DHCP client.

2. The client computer sends a broadcast request (called a DISCOVER or DHCPDISCOVER), looking for a DHCP server to answer.

3. The router directs the DISCOVER packet to the correct DHCP server.

4. The server receives the DISCOVER packet. Based on availability and usage policies set on the server, the server determines an appropriate address (if any) to give to the client. The server then temporarily reserves that address for the client and sends back to the client an OFFER (or DHCPOFFER) packet, with that address information. The server also configures the client's DNS servers, WINS servers, NTP servers, and sometimes other services as well.

5. The client sends a REQUEST (or DHCPREQUEST) packet, letting the server know that it intends to use the address.

6. The server sends an ACK (or DHCPACK) packet, confirming that the client has a been given a lease on the address for a server-specified period of time.

When we assign IP address statically to any computer then there is always a probability that two computers are configured with the same IP address. This creates a conflict that results in loss of service. Using DHCP to dynamically assign IP addresses minimizes these conflicts.

Classful Vs Classless Address

2008-09-30T05:17:00.000-07:00

Hello friends in this post i am again going to tell you some more interesting concepts of networking.In this post i am going to tell you what is the difference between classfull and classless address.
Classful addressing:In the classful addressing system all the IP addresses that are available are divided into the five classes A,B,C,D and E, in which class A,B and C address are frequently used because class D is for Multicast and is rarely used and class E is reserved and is not currently used.Each of the IP address belongs to a particular class that's why they are classful addresses.Earlier this addressing system did not have any name,but when classless addressing system came into existence then it is named as Classful addressing system.The main disadvantage of classful addressing is that it limited the flexibility and number of addresses that can be assigned to any device.One of the major disadvantage of classful addressing is that it does not send subnet information but it will send the complete network address. The router will supply its own subnet mask based on its locally configured subnets. As long as you have the same subnet mask and the network is contiguous, you can use subnets of a classful network address.

Classless Addressing:Classless addressing system is also known as CIDR(Classless Inter-Domain Routing).Classless addressing is a way to allocate and specify the Internet addresses used in inter-domain routing more flexibly than with the original system of Internet Protocol (IP) address classes.What happened in classful addressing is that if any company needs more than 254 host machines but far fewer than the 65,533 host addresses then the only option for the company is to take the class B address.Now suppose company needs only 1000 IP addresses for its host computers then in this (65533-1000=64533) IP addresses get wasted.For this reason, the Internet was, until the arrival of CIDR, running out of address space much more quickly than necessary. CIDR effectively solved the problem by providing a new and more flexible way to specify network addresses in routers.A CIDR network address looks like this:

192.30.250.00/15

The "192.30.250.00" is the network address itself and the "15" says that the first 15 bits are the network part of the address, leaving the last 17 bits for specific host addresses.One more advantage of classless addressing is that classless protocol sends subnet information. This allows you to create discontiguous networks with any given classful network address.

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Operating System Concepts
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Hina Rabbani Khar

Repeater Vs Switch Vs Hub

2008-09-28T21:56:00.000-07:00

Hello friends this is my post and i this post i am going to give you a brief description and difference between various networking devices.

As all we know various types of devices like repeaters,hub, routers, switch are used very frequently in the setup of any computer network.Here in this post we see all these devices one by one.

Repeater: A repeater is an electronic device that is used to receive a signal and after receiving, it transmit signal to the higher level so that it can move to long distance without any destruction in its value.In other words we can also say that repeater is a device that is designed to overcome signal attenuation means to recover signal degradation.All repeaters has two ports one for receiving the signal and other for its transmission. Repeaters can be used for carrying electrical signals in the form of copper wire or to carry light in the form of fiber optics.It is a layer 1 device that means Physical layer device.

Hub: In simple words we can say that a hub is a multi port repeater.It means it allows multiple machines to connect to the same network, by broadcasting traffic to all of its ports.The most practical implication of this is that only one device can send data at a time, otherwise a collision occurs. Hubs implement a collision detection multiple access method to detect when two machines attempt to send data at the same time. A hub supports broadcasting of any signal.It is also layer 1 device.

Switch:In general switch is very much different from the repeater and the hub , both of them works on IP address while the switch works on the MAC address. A switch works by keeping track of which MAC addresses are attached to each port. It inspects traffic and only sends it to the port that the destination device is on (based on the destination MAC address). A switch had a finite amount of memory in which it can store MAC addresses, smaller switches such as ones intended for desktop use have less memory then larger ones that may form part of an enterprise networks backbone. When a switches memory becomes full of active MAC addresses it will often revert to functioning like a hub and broadcast traffic to all ports.A switch is a layer 2 device(Data link Layer).

Introducing Blog

2008-09-28T21:52:00.000-07:00

Hello friends this is my first blog and in this blog i am going to explore all the important concepts of Computer Networks in which students find themselves in difficulty.Here you will find a complete description of all the topics that will really help you in understanding these concepts.In this blog you will also found some latest hacking technologies in Windows XP,UNIX and Linux that will definitely a fun stuff for you.In addition to this i also give you latest news from the field of technology and also some reviews.