Web Hosting Services

Free Web Hosting Service:

A free web hosting service is a web hosting service that is free, usually advertisement-supported. Free web hosts will usually provide a subdomain (yoursite.example.com) or a directory (www.example.com/yourname). In contrast, paid web hosts will usually provide a second-level domain along with the hosting (www.yourname.com). Many free hosts do allow use of separately-purchased domains. Rarely, a free host may also operate as a domain name registrar.

Example : www.Orgfree.com

Monetizing Free Web Hosting:

The majority of the hosting companies use free hosting to introduce their services, and as an entry point to their more expensive offerings. Generally they recoup their costs in one of a few ways:

* Advertising - Selling online advertising on the customer sites is generally considered a fair trade - the reasoning is that high traffic sites are more expensive to host, but the additional traffic allows for additional ad impressions therefore covering the cost. For the web master, it can be a good trade if the advertising is of good quality and non-competitive. This is one of the main reasons that businesses do not use free hosting for their website. The majority of free hosting companies use this method.

* Referrals - Using a simple form of viral marketing, these providers rely on the users to spread the offer. The ratio of free to paid accounts is known, and by having each free user refer a number of friends, the hosting provider is able to get enough paid accounts to cover the cost.

* Resell Hosting - This is where someone starts up a hosting company, attracts lots of visitors, then sells the hosting company to someone else once it can no longer support itself. Once sold, this individual uses the money to start up multiple hosting ventures and sells each in turn.

Some hosting companies are using hybrid approaches that mix these tactics.

Methods of giving out web hosting:

A few methods of giving out Free Webhosting to people by Webhosts.

Instant Activation:

Due to the risks of illegal, inappropriate, and abusive website, hosts with instant activation usually give very little storage space and monthly bandwidth. Other restrictions will likely also be in effect. The webhosts usually either require the users' web pages to display their banner ads, textlink ads, or popups; or else the users' files to be uploaded through a web-based file manager that display ads to the user uploading files.

Hosts with instant activation are often abused, such as link spamming.

Post for Hosting:

Some free hosts require posting in a forum. Forum-based free hosting requires users to either reach a certain amount of posts before getting a free hosting account, or be an active contributor in the forum. Forum-based free hosting often work on a system of points where posts give points to a user and can be used as credits toward getting a hosting account or more resources. Typically, the forum where users have to post contains advertising as the hosts way of making a profit.

Forum applications:

This method is popular, as the hosts can decide which applications to deny and allow. This is common when a popular forum has free hosting as an add-on service, rather than the other way around.

Facial Recognition Software

The technology within facial recognition software has the potential for an extensive range of uses, far beyond just matching the facial features of people in a crowd to those of crooks in a database. Several airports have experimented with it to identify “people of interest” attempting to cross U.S. borders, but given that it’s a new technology that often provides false positives, facial recognition software hasn’t yet been widely adopted as a means toward that end. Even so, the United Kingdom reportedly has plans to electronically include facial biometrics in passports by 2009 to help curb identity theft. In addition, some manufacturers of portable devices, such as mobile phones, laptops, and PDAs (personal digital assistants), have been working on bundling facial recognition software with their products—the thought being that if your phone doesn’t recognize a user, it won’t work. That would increase the security of the device itself and make it a less attractive target for thieves. Facial recognition software also can be used instead of a pass code or security card to grant access to high-security facilities, such as nuclear reactors and bank vaults.

Protect E mail Account from Spam & Spyware !!

A year after she bought Spyware Doctor using a debit card, Price received e-mail stating that the annual renewal fee had been debited from her checking account. “I was not asked if I wanted a yearly renewal,” she says. “I did not authorize any renewal, and I definitely did not authorize the company to access my checking account.” Welcome to Subscription Hell. A growing number of programs, utilities, and even games charge yearly or monthly fees for software, updates, or support. Major antivirus packages have long charged annual fees for virus signature and other updates (and also nag you to buy upgrades), but other types of software are moving to subscription pricing. For example, Cerulean Studios’ Trillian Pro cross-platform instant messaging client costs $25 a year for tech support, forum access, and updates. For many users the problem lies not in paying a few bucks every year, but in managing subscriptions or canceling them, which isn’t always easy. Here’s how to avoid subscription surprises and deal with common problems.

While no one likes plowing through legalese, it’s the best way to see what you will be getting into. With Spyware Doctor, for example, you must click through to its checkout page to find the terms of service; near the top of the terms of service, the agreement states clearly that the company will renew your subscription automatically “by directly charging your credit card or debiting your debit card prior to each anniversary of the date of purchase…” PC Tools does not provide the option of limiting the subscription to a single period, either. Price admits that she never read the agreement, instead assuming that “any renewal would follow other subscriptions I’ve had: advance notice by e-mail and the option to renew or not.” Don’t assume that one company’s policies will emulate another’s. Take the time to read the license agreement so you don’t get an unwelcome surprise 365 days later.Much subscription grief arises from changes to your contact information or your credit card. For example, if you change your e-mail address and don’t update subscription accounts, you won’t receive notices of upcoming renewals. Th at could lead to unwanted automatic re - newals or service cancellation (which in the case of antivirus soft ware might leave you exposed to viruses whose signatures you haven’t downloaded). Similarly, if you cancel a credit card or it expires, notify companies that bill you automatically so that your account won’t be suspended or canceled.

Address Resolution Protocol (ARP)

IP (logical) addresses are assigned independently from physical (hardware) addresses. The logical address is called a 32-bit IP address, and the physical address is a 48-bit MAC address in Ethernet and token ring protocols. The delivery of a packet to a host or a router requires two levels of addressing, such as logical (IP) address and physical (MAC) addresses. When a host or a router has an IP datagram forwarding to another host or router, it must know the logical IP address of the receiver. Since the IP datagram is encapsulated in a form to be passed through the physical network (such as a LAN), the sender needs the physical MAC address of the receiver.

Mapping of an IP address to a physical address can be done by either static or dynamic mapping. Static mapping means creating a table that associates an IP address with a physical address. But static mapping has some limitations because table lookups are inefficient. As a consequence, static mapping creates a huge overhead on the network. Dynamic mapping can employ a protocol to find the other. Two protocols (ARP and RARP) have been designed to perform dynamic mapping. When a host needs to find the physical address of another host or router on its network, it sends an ARP query packet. The intended recipient recognises its IP address and sends back an ARP response which contains the recipient IP and physical addresses. An ARP request is broadcast to all devices on the network, while an ARP reply is unicast to the host requesting the mapping.

mapping. Let a host or router call a machine. A machine uses ARP to find the physical address of another machine by broadcasting an ARP request. The request contains the IP address of the machine for which a physical address is needed. All machines (M1, M2, M3, . . .) on the network receive an ARP request. If the request matches a M2 machine’s IP address, the machine responds by sending a reply that contains the requested physical address. Note that Ethernet uses the 48-bit address of all 1’s (FFFFFFFFFFFF) as the broadcast address.

A proxy ARP is an ARP that acts on behalf of a set of hosts. Proxy ARP can be used to create a subnetting effect. In proxy ARP, a router represents a set of hosts. When an ARP request seeks the physical address of any host in this set, the router sends its own physical address. This creates a subnetting effect. Whenever looking for the IP address of one of these hosts, the router sends an ARP reply announcing its own physical address. To make address resolution easy, choose both IP and physical addresses the same length. Address resolution is difficult for Ethernet-like networks because the physical address of the Ethernet interface is 48 bits long and the high-level IP address is 32 bits long. In order for the 48-bit physical address to encode a 32-bit IP address, the next generation of IP is being designed to allow 48-bit physical (hardware) addresses P to be encoded in IP addresses I by the functional relationship of P = f (I).

Addressing schemes

Each IP address is made of two parts in such a way that the netid defines a network and the hostid identifies a host on that network. An IP address is usually written as four decimal integers separated by decimal points i.e. 239.247.135.93. If this IP address changes from decimal-point notation to binary form, it becomes 11101111 11110111 10000111 01011101. Thus, we see that each integer gives the value of one octet (byte) of the IP address. IP addresses are divided into five different classes: A, B, C, D and E. Classes A, B and C differ in the number of hosts allowed per network. Class D is used for multicasting and class E is reserved for future use. Table 2.3 shows the number of networks and hosts in five different IP address classes. Note that the binary numbers in brackets denote class prefixes. The relationship between IP address classes and dotted decimal numbers is summarised in Table 2.4, which shows the range of values for each class. The use of leading bits as class prefixes means that the class of a computer’s network can be determined by the numerical value of its address. A number of IP addresses have specific meanings. The address 0.0.0.0 is reserved and 224.0.0.0 is left unused. Addresses in the range 10.0.0.0 through to 10.255.255.255 are available for use in private intranets. Addresses in the range 240.0.0.0 through to 255.255.255.255 are class E addresses and are reserved for future use when new protocols are developed. Address 255.255.255.255 is the broadcast address,

Network Access Layer

The network access layer contains protocols that provide access to a communication network. At this layer, systems are interfaced to a variety of networks. One function of this layer is to route data between hosts attached to the same network. The services to be provided are flow control and error control between hosts. The network access layer is invoked either by the Internet layer or the application layer. This layer provides the device drivers that support interactions with communications hardware such as the token ring or Ethernet. The IEEE token ring, referred to as the Newhall ring, is probably the oldest ring control technique and has become the most popular ring access technique in the USA. The Fiber Distributed Data Interface (FDDI) is a standard for a high-speed ring LAN. Like the IEEE 802 standard, FDDI employs the token ring algorithm.

What is the OSI Model ?

The Ethernet, originally called the Alto Aloha network, was designed by the Xerox Palo Alto Research Center in 1973 to provide communication for research and development CP/M computers. When in 1976 Xerox started to develop the Ethernet as a 20Mbps product, the network prototype was called the Xerox Wire. In 1980, when the Digital, Intel and Xerox standard was published to make it a LAN standard at 10 Mbps, Xerox Wire changed its name back to Ethernet. Ethernet became a commercial product in 1980 at 10 Mbps. The IEEE called its Ethernet 802.3 standard CSMA/CD (or carrier sense multiple access with collision detection). As the 802.3 standard evolved, it has acquired such names as Thicknet (IEEE 10Base-5), Thinnet or Cheapernet (10Base-2), Twisted Ethernet (10Base-T) and Fast Ethernet (100Base-T).

The design of Ethernet preceded the development of the seven-layer OSI model. The Open System Interconnect (OSI) model was developed and published in 1982 by the International Organisation for Standardisation (ISO) as a generic model for data communication. The OSI model is useful because it is a broadly based document, widely available and often referenced. Since modularity of communication functions is a key design criterion in the OSI model, vendors who adhere to the standards and guidelines of this model can supply Ethernet-compatible devices, alternative Ethernet channels, higherperformance Ethernet networks and bridging protocols that easily and reliably connect other types of data network to Ethernet.

Since the OSI model was developed after Ethernet and Signaling System #7 (SS7), there are obviously some discrepancies between these three protocols. Yet the functions and processes outlined in the OSI model were already in practice when Ethernet or SS7 was developed. In fact, SS7 networks use point-to-point configurations between signalling points. Due to the point-to-point configurations and the nature of the transmissions, the simple data link layer does not require much complexity.

The OSI reference model specifies the seven layers of functionality, as shown in Figure 1.2. It defines the seven layers from the physical layer (which includes the network adapters), up to the application layer, where application programs can access network services. However, the OSI model does not define the protocols that implement the functions at each layer.

Implementations of the OSI model stipulate communication between layers on two processors and an interface for interlayer communication on one processor. Physical communication occurs only at layer 1. All other layers communicate downward (or upward) to lower (or higher) levels in steps through protocol stacks.

The following briefly describes the seven layers of the OSI model:

1. Physical layer. The physical layer provides the interface with physical media. The interface itself is a mechanical connection from the device to the physical medium used to transmit the digital bit stream. The mechanical specifications do not specify the electrical characteristics of the interface, which will depend on the medium being used and the type of interface. This layer is responsible for converting the digitaldata into a bit stream for transmission over the network. The physical layer includes the method of connection used between the network cable and the network adapter, as well as the basic communication stream of data bits over the network cable. The physical layer is responsible for the conversion of the digital data into a bit stream for transmission when using a device such as a modem, and even light, as in fibre optics. For example, when using a modem, digital signals are converted into analogue audible tones which are then transmitted at varying frequencies over the telephone line. The OSI model does not specify the medium, only the operative functionality for a standardised communication protocol. The transmission media layer specifies the physical medium used in constructing the network, including size, thickness and other characteristics.

2. Data link layer. The data link layer represents the basic communication link that exists between computers and is responsible for sending frames or packets of data without errors. The software in this layer manages transmissions, error acknowledgement and recovery. The transceivers are mapped data units to data units to provide physical error detection and notification and link activation/deactivation of a logical communication connection. Error control refers to mechanisms to detect and correct errors that occur in the transmission of data frames. Therefore, this layer includes error correction, so when a packet of data is received incorrectly, the data link layer makes system send the data again. The data link layer is also defined in the IEEE 802.2 logical link control specifications.

Data link control protocols are designed to satisfy a wide variety of data link requirements: – High-level Data Link Control (HDLC) developed by the International Organisation for Standardisation (ISO 3309, ISO 4335);

– Advanced Data Communication Control Procedures (ADCCP) developed by the American National Standards Institute (ANSI X3.66);

– Link Access Procedure, Balanced (LAP-B) adopted by the CCITT as part of its X.25 packet-switched network standard;

– Synchronous Data Link Control (SDLC) is not a standard, but is in widespread use. There is practically no difference between HDLC and ADCCP. Both LAP-B and SDLC are subsets of HDLC, but they include several additional features.

3. Network layer. The network layer is responsible for data transmission across networks. This layer handles the routing of data between computers. Routing requires some complex and crucial techniques for a packet-switched network design. To accomplish the routing of packets sending from a source and delivering to a destination, a path or route through the network must be selected. This layer translates logical network addressing into physical addresses and manages issues such as frame fragmentation and traffic control. The network layer examines the destination address and determines the link to be used to reach that destination. It is the borderline between hardware and software. At this layer, protocol mechanisms activate data routing by providing network address resolution, flow control in terms of segmentation and blocking and collision control (Ethernet). The network layer also provides service selection,

What are Routers?

Routers operate in the physical, data link and network layers of the OSI model. The Internet is a combination of networks connected by routers. When a datagram goes from a source to a destination, it will probably pass through many routers until it reaches the router attached to the destination network. Routers determine the path a packet should take. Routers relay packets among multiple interconnected networks. In particular, an IP router forwards IP datagrams among the networks to which it connects. A router uses the destination address on a datagram to choose a next-hop to which it forwards the datagram. A packet sent from a station on one network to a station on a neighbouring network goes first to a jointly held router, which switches it over the destination network. In fact, the easiest way to build the Internet is to connect two or more networks with a router. Routers provide connections to many different types of physical networks: Ethernet, token ring, point-to-point links, FDDI and so on.

• The routing module receives an IP packet from the processing module. If the packet is to be forwarded, it should be passed to the routing module. It finds the IP address of the next station along with the interface number from which the packet should be sent. It then sends the packet with information to the fragmentation module. The fragmentation module consults the MTU table to find the maximum transfer unit (MTU) for the specific interface number.

• The routing table is used by the routing module to determine the next-hop address of the packet. Every router keeps a routing table that has one entry for each destination network. The entry consists of the destination network IP address, the shortest distance to reach the destination in hop count, and the next router (next hop) to which the packet should be delivered to reach its final destination. The hop count is the number of networks a packet enters to reach its final destination. A router should have a routing table to consult when a packet is ready to be forwarded. The routing table should specify the optimum path for the packet. The table can be either static or dynamic. A static table is one that is not changed frequently, but a dynamic table is one that is updated automatically when there is a change somewhere in the Internet. Today, the Internet needs dynamic routing tables.

• A metric is a cost assigned for passing through a network. The total metric of a particular router is equal to the sum of the metrics of networks that comprise the route. A router chooses the route with the shortest (smallest value) metric. The metric assigned to each network depends on the type of protocol. The Routing Information Protocol (RIP) treats each network as one hop count. So if a packet passes through 10 networks to reach the destination, the total cost is 10 hop counts. The Open Shortest Path First protocol (OSPF) allows the administrator to assign a cost for passing through a network based on the type of service required. A route through a network can have different metrics (costs). OSPF allows each router to have several routing tables based on the required type of service.

what are Repeaters?

A repeater is an electronic device that operates on the physical layer only of the OSI model. A repeater boosts the transmission signal from one segment and continues the signal to another segment. Thus, a repeater allows us to extend the physical length of a network. Signals that carry information can travel a limited distance within a network before degradation of the data integrity due to noise. A repeater receives the signal before attenuation, regenerates the original bit pattern and puts the restored copy back on to the link.

what is Frame Relay?

Frame relay is a WAN protocol designed in response to X.25 deficiencies. X.25 provides extensive error-checking and flow control. Packets are checked for accuracy at each station to which they are routed. Each station keeps a copy of the original frame until it receives confirmation from the next station that the frame has arrived intact. Such station-to-station checking is implemented at the data link layer of the OSI model, but X.25 only checks for errors from source to receiver at the network layer. The source keeps a copy of the original packet until it receives confirmation from the final destination. Much of the traffic on an X.25 network is devoted to error-checking to ensure reliability of service. Frame relay does not provide error-checking or require acknowledgement in the data link layer. Instead, all error-checking is left to the protocols at the network and transport layers, which use the frame relay service. Frame relay only operates at the physical and data link layer.

Fiber Distributed Data Interface (FDDI)

FDDI is a LAN protocol standardised by ANSI and ITU-T. It supports data rates of 100 Mbps and provides a high-speed alternative to Ethernet and token ring. When FDDI was designed, the data rate of 100 Mbps required fibre-optic cable. The access method in FDDI is also called token passing. In a token ring network, a station can send only one frame each time it captures the token. In FDDI, the token passing mechanism is slightly different in that access is limited by time. Each station keeps a timer which shows when the token should leave the station. If a station receives the token earlier than the designated time, it can keep the token and send data until the scheduled leaving time. On the other hand, if a station receives the token at the designated time or later than this time, it should let the token pass to the next station and wait for its next turn.

FDDI is implemented as a dual ring. In most cases, data transmission is confined to the primary ring. The secondary ring is provided in case of the primary ring’s failure. When a problem occurs on the primary ring, the secondary ring can be activated to complete data circuits and maintain service.

Ethernet LAN

Ethernet is a LAN standard originally developed by Xerox and later extended by a joint venture between Digital Equipment Corporation (DEC), Intel Corporation and Xerox. The access mechanism used in an Ethernet is called Carrier Sense Multiple Access with Collision Detection (CSMA/CD). In CSMA/CD, before a station transmits data, it must check the medium where any other station is currently using the medium. If no other station is transmitting, the station can send its data. If two or more stations send data at the same time, it may result in a collision. Therefore, all stations should continuously check the medium to detect any collision. If a collision occurs, all stations ignore the data received. The sending stations wait for a period of time before resending the data. To reduce the possibility of a second collision, the sending stations individually generate a random number that determinates how long the station should wait before resending data.

As an access method, the token is passed from station to station in sequence until it encounters a station with data to send. The station to be sent data waits for the token. The station then captures the token and sends its data frame. This data frame proceeds around the ring and each station regenerates the frame. Each intermediate station examines the destination address, finds that the frame is addressed to another station, and relays it to its neighbouring station. The intended recipient recognises its own address, copies the message, checks for errors and changes four bits in the last byte of the frame to indicate that the address has been recognised and the frame copied. The full packet then continues around the ring until it returns to the station that sent it.

Internetworking and Layered Models

The Internet today is a widespread information infrastructure, but it is inherently an insecure channel for sending messages. When a message (or packet) is sent from one Website to another, the data contained in the message are routed through a number of intermediate sites before reaching its destination. The Internet was designed to accommodate heterogeneous platforms so that people who are using different computers and operating systems can communicate. The history of the Internet is complex and involves many aspects – technological, organisational and community. The Internet concept has been a big step along the path towards electronic commerce, information acquisition and community operations.

Early ARPANET researchers accomplished the initial demonstrations of packetswitching technology. In the late 1970s, the growth of the Internet was recognised and subsequently a growth in the size of the interested research community was accompanied by an increased need for a coordination mechanism. The Defense Advanced Research Projects Agency (DARPA) then formed an International Cooperation Board (ICB) to coordinate activities with some European countries centered on packet satellite research, while the Internet Configuration Control Board (ICCB) assisted DARPA in managing Internet activity. In 1983, DARPA recognised that the continuing growth of the Internet community demanded a restructuring of coordination mechanisms. The ICCB was disbanded and in its place the Internet Activities Board (IAB) was formed from the chairs of the Task Forces. The IAB revitalised the Internet Engineering Task Force (IETF) as a member of the IAB. By 1985, there was a tremendous growth in the more practical engineering side of the Internet. This growth resulted in the creation of a substructure to the IETF in the form of working groups. DARPA was no longer the major player in the funding of the Internet. Since then, there has been a significant decrease in Internet activity at DARPA. The IAB recognised the increasing importance of IETF, and restructured to recognise the Internet Engineering Steering Group (IESG) as the major standards review body. The IAB also restructured to create the Internet Research Task Force (IRTF) along with the IETF.