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INTRODUCTION TO INFORMATION TECHNOLOGY

I.B.COM CA SUBCODE : 19CCU02

UNIT 3

Communication Technology: Communication Technology – WWW – Intranets – Extranets – Voice Networks Data Communication Networks – Last Mile – Wireless System – Web Hosting – Application Service Providers

Communication Technology:

In Data Communications, data generally are defined as information that is stored in digital form. Data communications is the process of transferring digital information between two or more points. Information is defined as the knowledge or intelligence. Data communications can be summarized as the transmission, reception, and processing of digital information. For data communications to occur, the communicating devices must be part of a communication system made up of a combination of hardware (physical equipment) and software (programs). The effectiveness of a data communications system depends on four fundamental characteristics: delivery, accuracy, timeliness, and jitter. A data communications system has five components: 1. Message: The message is the information (data) to be communicated. Popular forms of information include text, numbers, pictures, audio, and video. 2. Sender: The sender is the device that sends the data message. It can be a computer, workstation, telephone handset, video camera, and so on. 3. Receiver: The receiver is the device that receives the message. It can be a computer, workstation, telephone handset, television, and so on. 4. Transmission medium: The transmission medium is the physical path by which a message travels from sender to receiver. Some examples of transmission media include twisted-pair wire, coaxial cable, fiber-optic cable, and radio waves. 5. Protocol: A protocol is a set of rules that govern data communications. It represents an agreement between the communicating devices.

COMPUTER NETWORK:

Interconnection of two or more computers in order for sharing resources and information.

Types of Communication Networks

Communication Networks can be of following 5 types:

1. Local Area Network (LAN)2. Metropolitan Area Network (MAN)3. Wide Area Network (WAN)4. Wireless5. Inter Network (Internet)

Prepared by Dr. S.SHANKARII, Assistant Professor, PG & Research Department Of Commerce CA



Local Area Network (LAN)

It is also called LAN and designed for small physical areas such as an office, group of buildings or a factory. LANs are used widely as it is easy to design and to troubleshoot. Personal computers and workstations are connected to each other through LANs. We can use different types of topologies through LAN, these are Star, Ring, Bus, Tree etc.

LAN can be a simple network like connecting two computers, to share files and network among each other while it can also be as complex as interconnecting an entire building.

LAN networks are also widely used to share resources like printers, shared hard-drive etc.

Characteristics of LAN

LAN's are private networks, not subject to tariffs or other regulatory controls. LAN's operate at relatively high speed when compared to the typical WAN. There are different types of Media Access Control methods in a LAN, the prominent

ones are Ethernet, Token ring. It connects computers in a single building, block or campus, i.e. they work in a

restricted geographical area.

Applications of LAN

One of the computer in a network can become a server serving all the remaining computers called clients. Software can be stored on the server and it can be used by the remaining clients.

Connecting Locally all the workstations in a building to let them communicate with each other locally without any internet access.




Sharing common resources like printers etc are some common applications of LAN.

Advantages of LAN

Resource Sharing: Computer resources like printers, modems, DVD-ROM drives and hard disks can be shared with the help of local area networks. This reduces cost and hardware purchases.

Software Applications Sharing: It is cheaper to use same software over network instead of purchasing separate licensed software for each client a network.

Easy and Cheap Communication: Data and messages can easily be transferred over networked computers.

Centralized Data: The data of all network users can be saved on hard disk of the server computer. This will help users to use any workstation in a network to access their data. Because data is not stored on workstations locally.

Data Security: Since, data is stored on server computer centrally, it will be easy to manage data at only one place and the data will be more secure too.

Internet Sharing: Local Area Network provides the facility to share a single internet connection among all the LAN users. In Net Cafes, single internet connection sharing system keeps the internet expenses cheaper.

Disadvantages of LAN

High Setup Cost: Although the LAN will save cost over time due to shared computer resources, but the initial setup costs of installing Local Area Networks is high.

Privacy Violations: The LAN administrator has the rights to check personal data files of each and every LAN user. Moreover he can check the internet history and computer use history of the LAN user.

Data Security Threat: Unauthorised users can access important data of an organization if centralized data repository is not secured properly by the LAN administrator.

LAN Maintenance Job: Local Area Network requires a LAN Administrator because, there are problems of software installations or hardware failures or cable disturbances in Local Area Network. A LAN Administrator is needed at this full time job.

Covers Limited Area: Local Area Network covers a small area like one office, one building or a group of nearby buildings.

Metropolitan Area Network (MAN)

It was developed in 1980s.It is basically a bigger version of LAN. It is also called MAN and uses the similar technology as LAN. It is designed to extend over the entire city. It can be




means to connecting a number of LANs into a larger network or it can be a single cable. It is mainly hold and operated by single private company or a public company.

Characteristics of MAN

It generally covers towns and cities (50 km) Communication medium used for MAN are optical fibers, cables etc. Data rates adequate for distributed computing applications.

Advantages of MAN

Extremely efficient and provide fast communication via high-speed carriers, such as fibre optic cables.

It provides a good back bone for large network and provides greater access to WANs. The dual bus used in MAN helps the transmission of data in both directions

simultaneously. A MAN usually encompasses several blocks of a city or an entire city.

Disadvantages of MAN

More cable required for a MAN connection from one place to another. It is difficult to make the system secure from hackers and industrial espionage(spying)

graphical regions.

Wide Area Network (WAN)

It is also called WAN. WAN can be private or it can be public leased network. It is used for the network that covers large distance such as cover states of a country. It is not easy to design and maintain. Communication medium used by WAN are PSTN or Satellite links. WAN operates on low data rates.

Characteristics of WAN

It generally covers large distances(states, countries, continents). Communication medium used are satellite, public telephone networks which are

connected by routers.




Advantages of WAN

Covers a large geographical area so long distance business can connect on the one network.

Shares software and resources with connecting workstations. Messages can be sent very quickly to anyone else on the network. These messages

can have picture, sounds or data included with them(called attachments). Expensive things(such as printers or phone lines to the internet) can be shared by all

the computers on the network without having to buy a different peripheral for each computer.

Everyone on the network can use the same data. This avoids problems where some users may have older information than others.

Disadvantages of WAN

Need a good firewall to restrict outsiders from entering and disrupting the network. Setting up a network can be an expensive, slow and complicated. The bigger the

network the more expensive it is. Once set up, maintaining a network is a full-time job which requires network

supervisors and technicians to be employed. Security is a real issue when many different people have the ability to use information

from other computers. Protection against hackers and viruses adds more complexity and expense.

Wireless Network

Digital wireless communication is not a new idea. Earlier, Morse code was used to implement wireless networks. Modern digital wireless systems have better performance, but the basic idea is the same.

Wireless Networks can be divided into three main categories:

1. System interconnection2. Wireless LANs3. Wireless WANs

System Interconnection

System interconnection is all about interconnecting the components of a computer using short-range radio. Some companies got together to design a short-range wireless network called Bluetooth to connect various components such as monitor, keyboard, mouse and Prepared by Dr. S.SHANKARII, Assistant Professor, PG & Research Department Of Commerce CA



printer, to the main unit, without wires. Bluetooth also allows digital cameras, headsets, scanners and other devices to connect to a computer by merely being brought within range.

In simplest form, system interconnection networks use the master-slave concept. The system unit is normally the master, talking to the mouse, keyboard, etc. as slaves.

Wireless LANs

These are the systems in which every computer has a radio modem and antenna with which it can communicate with other systems. Wireless LANs are becoming increasingly common in small offices and homes, where installing Ethernet is considered too much trouble. There is a standard for wireless LANs called IEEE 802.11, which most systems implement and which is becoming very widespread.

Wireless WANs

The radio network used for cellular telephones is an example of a low-bandwidth wireless WAN. This system has already gone through three generations.

The first generation was analog and for voice only. The second generation was digital and for voice only. The third generation is digital and is for both voice and data.




Inter Network

Inter Network or Internet is a combination of two or more networks. Inter network can be formed by joining two or more individual networks by means of various devices such as routers, gateways and bridges.

INTERNET:

Is the Worldwide collection of networks that connects millions of computers. OR Is a global network in which million of computers are connected together worldwide to facilitate communication among users. E.g. sending and receiving e-mails, online talking, instant message, teleconferencing, video conferencing etc. OR Is the network of the networks that connect government, people, business etc all over the world Internet can also be defined as World wide network of computer making information available to everyone.

These Computers are connected through

1. Telephone lines: telephone lines internet signals from one place to another and the signals are translated by modems.

2. Cables in the ground: the use of optical cables which are laid in the ground then they connect different devices. optical cables transmit signals with a speed of light.(3x108m/s).

3. Satellite in space: satellite dishes

Modem through telephone lines or cable and from satellite dishes. The term stands for modulate and demodulate which changes the signal from digital, which computers use, to analog, which telephones use and then back again. A high speed connection also requires a modem but because the information is transferred digitally it isn't required to change the signal from digital to analog but is used to create the connection between your computer and the computer you are connecting with.

Protocol Set of rules that determine how data are exchanged between different computers.

Advantages of using Internet

1.Sharing files

2. Improving customer service

3. Communication Exchange e-mail Chat

4. Shopping

5. Learning




6. Entertainment

7. Sharing other devices (printers)

8. Central administration of all devices

9. Supporting network applications like:Email,Database services

Disadvantages of using Internet:

1. Viruses threat Today, Internet is the most popular source of spreading viruses. Most of the viruses transfer from one computer to another through e-mail or when information is downloaded on the Internet. These viruses create different problems in your computer. For example, they can affect the performance of your computer and damage valuable data and software stored in your computer.

2. Security Problems The valuable websites can be damaged by hackers and your valuable data may be deleted. Similarly, confidential data may be accessed by unauthorized Immorality

3. Some websites contains immoral materials in the form of text, pictures or movies etc. These websites damage the character of new generation.

4. Filtration of Information When a keyword is given to a search engine to search information of a specific topic, a large number of related links a displayed. In this case, it becomes difficult to filter out the required information.

5. Accuracy of Information A lot of information about a particular topic is stored on the websites. Some information may be incorrect or not authentic. So, it becomes difficult to select the correct information. Sometimes you may be confused.

6. Wastage of times A lot of time is wasted to collect the information on the Internet. Some people waste a lot of time in chatting or to play games. At home and offices, most of the people use Internet without any positive purpose.

7. English language problems Most of the information on the Internet is available in English language. So, some people cannot avail the

Designed to permit access by users who have access Privileges to the internal LAN of the organization, Private network (LAN) used to share resources in secure environment

Networking Devices

Repeater




Hub Bridge Switch Router Gateway

Network topology

Network topology is the arrangement of the various elements (links, nodes, etc.) of a computer network. Essentially, it is the topological structure of a network and may be depicted physically or logically.

Types of Network topologies:

1 The Bus topology

2 Hub/Tree topology

3 Star topology

4 Ring topology

5 Mesh topology

Bus topology:

Single cable connects all network nodes without intervening connectivity devices Devices share responsibility for getting data from one point to another Terminators stop signals after reaching end of wire Prevent signal bounce Inexpensive, not very scalable Difficult to troubleshoot, not fault-tolerant

Advantages and Disadvantages of Bus Topology Advantages

This network can still function if one of the computers malfunctions Works well for small networks Relatively inexpensive to implement Easy to add to it Disadvantages

The main disadvantage is bad connection to the cable can bring down the entire network Management costs can be high

Potential for congestion with network traffic

RING TOPOLOGY:

Ring topology Each node is connected to the two nearest nodes so the entire network forms a circle One method for passing data on ring networks is token passing Active topology Each workstation transmits data




Advantages and Disadvantages of Ring Topology Advantages :

This network can still function if one of the computers malfunctions Easier to manage; easier to locate a defective node or cable problem

Well-suited for transmitting signals over long distances on a LAN Handles high-volume network traffic Enables reliable communication

Disadvantages Expensive Requires more cable and network equipment at the start Not used as widely as bus

topology Fewer equipment options Fewer options for expansion to high-speed communication

Star topology

Star topology Every node on the network is connected through a central device Any single cable connects only two devices Cabling problems affect two nodes at most Requires more cabling than ring or bus networks More fault-tolerant Easily moved, isolated, or interconnected with other networks Scalable Supports max of 1024 addressable nodes on logical network

Advantages and disadvantages of Star Topology

Advantages

Good option for modern networks Low start-up costs Easy to manage Offers opportunities for expansion Most popular topology in use; wide variety of equipment available

Disadvantages

Hub is a single point of failure The communications in the network will stop if the host computer stops

functioning Requires more cable than the bus

Tree Network :

In hub or tree network, the wires that are used to connect different nodes are collapsed into a central unit, called hub. Hub does not perform switching function. It consists of repeaters that retransmitted all the signals from nodes to all other nodes in the same way. The multipoint nature of tree topology gives rise to several problems.




1. The access control is fairly difficult to determine the time slot for each node.

2. Another problem with multipoint is signal balancing.

WWW

World Wide Web (WWW) is a system of Internet servers that supports hypertext to access several Internet protocols on a single interface. The World Wide Web has its own protocol called Hypertext Transfer Protocol (HTTP). Is a system of interlinked hypertext documents accessed via the Internet. With a web browser, one can view web pages that may contain text, images, videos, and other multimedia and navigate between them via hyperlinks.

A Web site is a collection of related Web pages

A Web page contains text, graphics, sound, video, and links to other Web pages

You can share information by creating Web pages or posting photos on a photo community 2

Internet resources:

Apart from the www, the internet ca be used to send electronic mail ( e-mail) and to transfer files between computers. File transfer Protocol( FTP) is a program the allow you to transfer files between computers on the internet as distinct from transferring files for immediate viewing Download--To copy data from a remote computer (internet) to a local computer. Or Transferring a file from a remote computer to your own computer Upload—To send data from a local computer to a remote computer (internet).or Sending a file to a remote computer Other facilities available on the internet include NEWS GROUPS for the dissemination of information to interested groups, and Internet Relay Chat which allows people to communicate with each other instantly by typing text keyboard rather than by talking on the telephone.

Web Browser

is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. A web browser is a software that allows you to view, navigate and interact with the World Wide Web. A Browser is a program that allows a person to view pages over the Internet and to navigate/move from one page to another by the use of links found in the Web Pages Examples of browsers are such as:

1. Mozilla Firefox 2. Opera 3. Safari 4. Netscape Navigator 5. Microsoft Internet Explorer




Intranet and ExtranetsIntranetAn intranet is a network based on TCP/IP protocols (an internet) belonging to an organization, usually a corporation, accessible only by the organization’s members, employees, or others with authorization. An intranet’s Web sites look and act just like any other Web sites, but the firewall surrounding an intranet fends off unauthorized access.

Benefits1. Workforce productivityIntranets can help users to locate and view information faster and use applications relevant to their roles and responsibilities. With the help of a web browser interface, users can access data held in any database the organization wants to make available, anytime and — subject to security provisions — from anywhere within the company workstations, increasing employees’ ability to perform their jobs faster, more accurately, and with confidence that they have the right information. It also helps to improve the services provided to the users.

2. TimeIntranet allows organizations to distribute information to employees as-needed by the employees. Employees may link to relevant information at their convenience, rather than being distracted indiscriminately by email.3. CommunicationIntranets can serve as powerful tools for communication within an organization, vertically strategic initiatives that have a global reach throughout the organization. The type of information that can easily be conveyed is the purpose of the initiative and what the initiative is aiming to achieve, who is driving the initiative, results achieved to date, and who to speak to for more information. By providing this information on the intranet, staff have the opportunity to keep up-to-date with the strategic focus of the organization. Some examples of communication would be chat, email, and/or blogs. A great real-world example of where an intranet helped a company communicate is when Nestle had a number of food processing plants in Scandinavia. Their central support system had to deal with a number of queries every day. When Nestle decided to invest in an intranet, they quickly realized the savings. McGovern says the savings from the reduction in query calls was substantially greater than the investment in the intranet.

4. Web publishingWeb publishing allows cumbersome corporate knowledge to be maintained and easily accessed throughout the company using hypermedia and Web technologies. Examples include: employee manuals, benefits documents, company policies, business standards, news feeds, and even training, can be accessed using common Internet standards (Acrobat files, Flash files, CGI applications). Because each business unit can update the online copy of a document, the most recent version is usually available to employees using the intranet.5. Business operations and managementIntranets are also being used as a platform for developing and deploying applications to support business operations and decisions across the internetworked enterprise.




6. Cost-effectiveUsers can view information and data via web-browser rather than maintaining physical documents such as procedure manuals, internal phone list and requisition forms. This can potentially save the business money on printing, duplicating documents, and the environment as well as document maintenance overhead.

7. Enhance collaborationInformation is easily accessible by all authorised users, which enables teamwork.

8. Cross-platform capabilityStandards-compliant web browsers are available for Windows, Mac, and UNIX.

9. Built for one audienceMany companies dictate computer specifications which, in turn, may allow Intranet developers to write applications that only have to work on one browser (no cross-browser compatibility issues). Being able to specifically address your “viewer” is a great advantage. Since Intranets are user-specific (requiring database/network authentication prior to access), you know exactly who you are interfacing with and can personalize your Intranet based on role (job title, department) or individual (“Congratulations Jane, on your 3rd year with our company!”).

10. Promote common corporate cultureEvery user has the ability to view the same information within the Intranet.

11. Immediate updatesWhen dealing with the public in any capacity, laws, specifications, and parameters can change. Intranets make it possible to provide your audience with “live” changes so they are kept up-to-date, which can limit a company’s liability.

12. Supports a distributed computing architectureThe intranet can also be linked to a company’s management information system, for example a time keeping system.

ExtranetAn Extranet is actually an Intranet that is partially accessible to authorised outsiders. The actual server (the computer that serves up the web pages) will reside behind a firewall. The firewall helps to control access between the Intranet and Internet permitting access to the Intranet only to people who are suitably authorised. The level of access can be set to different levels for individuals or groups of outside users. The access can be based on a username and password or an IP address (a unique set of numbers such as 209.33.27.100 that defines the computer that the user is on).

The Benefits of Implementing an ExtranetPrepared by Dr. S.SHANKARII, Assistant Professor, PG & Research Department Of Commerce CA



1. Exchange large volumes of data using Electronic Data Interchange (EDI)

2. Share product catalogs exclusively with trade partners

3. Collaborate with other companies on joint development efforts

4. Jointly develop and use training programs with other companies

5. Provide or access services provided by one company to a group of other companies, such as an online banking application managed by one company on behalf of affiliated banks.

An application service provider (ASP) is a business providing computer-based services to customers over a network; such as access to a particular software application (such as customer relationship management) using a standard protocol (such as HTTP).

The need for ASPs has evolved from the increasing costs of specialized software that have far exceeded the price range of small to medium-sized businesses. As well, the growing complexities of software have led to huge costs in distributing the software to end-users. Through ASPs, the complexities and costs of such software can be cut down. In addition, the issues of upgrading have been eliminated from the end-firm by placing the onus on the ASP to maintain up-to-date services, 24 x 7 technical support, physical and electronic security and in-built support for business continuity and flexible working.

The importance of this marketplace is reflected by its size. As of early 2003, estimates of the United States market ranged from 1.5 to 4 billion dollars.Clients for ASP services include businesses, government organizations, non-profits, and membership organizations.

There are several forms of ASP business. These are:

A specialist or functional ASP delivers a single application, such as credit card payment processing or timesheet services;

A vertical market ASP delivers a solution package for a specific customer type, such as a dental practice;

An enterprise ASP delivers broad spectrum solutions; A local ASP delivers small business services within a limited area.

Some analysts identify a volume ASP as a fifth type. This is basically a specialist ASP that offers a low cost packaged solution via their own website. PayPal was an instance of this type, and their volume was one way to lower the unit cost of each transaction.

In addition to these types, some large multi-line companies (such as HP and IBM), use ASP concepts as a particular business model that supports some specific customers.


https://en.wikipedia.org/wiki/United_States

https://en.wikipedia.org/wiki/Business_continuity

https://en.wikipedia.org/wiki/HTTP

https://en.wikipedia.org/wiki/Customer_relationship_management



The ASP model:

The application software resides on the vendor's system and is accessed by users through a web browser using HTML or by special purpose client software provided by the vendor. Custom client software can also interface to these systems through XML APIs. These APIs can also be used where integration with in-house systems is required. ASPs may or may not use multitenancy in the deployment of software to clients; some ASPs offer an instance or license to each customer (for example using Virtualization), some deploy in a single instance multi-tenant access mode, now more frequently referred to as "SaaS".

Common features associated with ASPs include:

ASP fully owns and operates the software application(s) ASP owns, operates and maintains the servers that support the software ASP makes information available to customers via the Internet or a "thin client" ASP bills on a "per-use" basis or on a monthly/annual fee

The advantages to this approach include:

Software integration issues are eliminated from the client site Software costs for the application are spread over a number of clients Vendors can build more application experience than the in-house staff Low-code development platforms permit limited customization of pre-built applications Key software systems are kept up to date, available, and managed for performance by

experts Improved reliability, availability, scalability and security of internal IT systems A provider's service level agreement guarantees a certain level of service Access to product and technology experts dedicated to available products Reduction of internal IT costs to a predictable monthly fee Redeploying IT staff and tools to focus on strategic technology projects that impact the

enterprise's bottom line

Some inherent disadvantages include:

The client must generally accept the application as provided since ASPs can only afford a customized solution for the largest clients.

The client may rely on the provider to provide a critical business function, thus limiting their control of that function and instead relying on the provider

Changes in the ASP market may result in changes in the type or level of service available to clients

Integration with the client's non-ASP systems may be problematic

Evaluating an Application Service Provider security when moving to an ASP infrastructure can come at a high cost, as such a firm must assess the level of risk associated with the ASP itself. Failure to properly account for such risk can lead to:

Loss of control of corporate dataPrepared by Dr. S.SHANKARII, Assistant Professor, PG & Research Department Of Commerce CA

https://en.wikipedia.org/wiki/Service_level_agreement

https://en.wikipedia.org/wiki/Low-code_development_platforms

https://en.wikipedia.org/wiki/Thin_client

https://en.wikipedia.org/wiki/Internet

https://en.wikipedia.org/wiki/SaaS

https://en.wikipedia.org/wiki/Multitenancy

https://en.wikipedia.org/w/index.php?title=Saas_integration&action=edit&redlink=1

https://en.wikipedia.org/wiki/API

https://en.wikipedia.org/wiki/API

https://en.wikipedia.org/wiki/XML

https://en.wikipedia.org/wiki/HTML



Loss of control of corporate image Insufficient ASP security to counter risks Exposure of corporate data to other ASP customers Compromise of corporate data

Some other risks include failure to account for the financial future of the ASP in general, i.e. how stable a company is and if it has the resources to continue business into the foreseeable future. For these reasons Cisco Systems has developed a comprehensive evaluation guideline. This guideline includes evaluating the scope of the ASP's service, the security of the program and the ASP's maturity with regard to security awareness. Finally, the guidelines indicate the importance of performing audits on the ASP with respect to:

Port/Network service Application vulnerability ASP Personnel

Physical visits to the ASP to assess the formality of the organization will provide invaluable insight into the awareness of the firm.

Web hosting service

Web hosting deals with putting the contents of your website on a Web server. Hosting your website on your own server could be an option. But this will become very much expensive unless you are hosting a site like yahoo.com or google.com. So this tutorials does not cover how to set up your own hosting server.

Buying a server space or renting a complete server from an Internet Service Provider (ISP) is the most widely used option. This section guides you to choose a hosting type and makes you aware of other related concepts.

Hosting Platforms

You can go for any of the following two most widely used hosting platforms −

Windows Hosting Servers − If you are a Windows lover then you will find many hosting servers running different flavors of Windows and you can buy space from these servers. Normally Windows hostingservers are more expensive because of lot of software licensing costs are involved with these servers.

Linux Hosting Servers − If you want to go for Linux then opportunities are unlimited and they will have to pay less then what you will pay for Windows Hosting Server. There are many ISP who provides Hosting Servers with different flavors of Unix.


http://www.webhostgear.com/windows-hosting.php

https://en.wikipedia.org/wiki/Cisco_Systems



Hosting Types

There are many options available and you can select any hosting type based on your requirement and budget. Following are most widely used hosting types −

Free Hosting

Yes, this is true there are many service providers who will give you free space on their web server with a condition that you will allow them to run their advertisement at your web pages. So if you are OK with this option, then you have nothing to pay for a space. There are some websites like geocities.com, lycos.com, myspace.com, etc. that give you space to build your web pages.

Shared Hosting

With shared hosting, your website is hosted on a powerful server along with other websites. On a shared host, you will have your own user ID and password to login to the shared host and you will be allowed to work in your work area. You would not be able to touch any file or directory belonging to other host partner. Even you would not know how many sites are hosted on your shared host. This type of hosting is very cost effective and good for small websites where your space and speed are not very important. Here traffic on one site will affect the speed of all other hosted sites.

Virtual Dedicated Hosting

This type of hosting is better for medium size business. With virtual dedicated hosting, you will have a dedicated bandwidth and dedicated RAM for your site. You will be given a root ID and password to maintain your Web server. You will be the complete owner of your virtual dedicated server and will be able to install or de-install any software. This type of hosting is created on a single server, but it is managed in such a way that every user will have dedicated speed and bandwidth. This is bit more expensive but really good one for medium size business.

Dedicated Hosting

This type of hosting is very similar to virtual dedicated hosting, but here, a complete machine will be allotted for you. They are more expensive than virtual dedicated hosting and should be considered when you have a very high traffic requirement.

Collocated Hosting

It is very difficult to set dedicated resources such as high-security against fire and vandalism, regulated backup power, dedicated Internet connections and more. Collocation is the option which allows you to put your machine in a service provider's premises to avail all Prepared by Dr. S.SHANKARII, Assistant Professor, PG & Research Department Of Commerce CA

http://www.webhostgear.com/shared-hosting.php



the available facilities. This is also a very expensive option and should be opted when you have very high traffic requirement.

Hosting Components

When you buy a Web server space, then you should be clear about the follows. You should do a price comparison between different service providers based on the following components −

Disc Space

A small or medium website will require between 10 and 100MB of disk space. If you plan to keep a lot of audio and video on your website, then you need plan to buy more space. Before buying server space, you should check the options available to expand your disc space if you need it in future.

Monthly Traffic

A small or medium website will need between 1GB and 10GB of data transfer on a monthly basis. If you plan to keep a lot of audio and video on your website, then you need a plan with more data transfer capacity. Check different options based on your requirements. What are the other options available in case you cross the given data transfer limit. Your site should not be stopped in case you exceed given limit.

Processing Speed

If you are buying space on a shared machine, then you cannot guess how much speed will be given to you. In that case, only way is to see other hosted sites with the same service provider to know about their hosting quality. But if you are buying virtual dedicated server or dedicated server, then you should consider how much RAM is being allocated to you. Your pricing will depend on the given processing power to you.

Connection Speed

Nowadays, most service providers allow very fast connection speed. So choose a service provider who is giving better connection speed in terms of bits per second. You can have a connection speed ranging from 64Kb per second to 2.488Gb per second.

Email Accounts

Make sure you are going to get sufficient number of e-mail accounts. There are many other options available which come along with your e-mail account. Like, will you get IMAP, POP and E-mail Forwarding options available along with your e-mail facilities.

Emailing SupportPrepared by Dr. S.SHANKARII, Assistant Professor, PG & Research Department Of Commerce CA



Apart form having email accounts, it is also very important that your web server should have a facility to send emails from back-end. In case your site visitors want to contact to you using a form, then you will be able to use that emailing facility to send emails to your designated account. In simple terms, you should make sure that the SMTP Server is setup and working on your Web server.

Latest Technologies

You should make sure that your web server is equipped with all the latest technologies. It should have the latest version support for PHP, PERL, ASP and JAVA, etc.

Databases

There are many databases available MySQL, Oracle, SQL Server, etc. You should choose your server based on your database requirement. If you are buying space on a shared server, then you need to verify how much space will be allocated for your database. Many ISPs do not give more than a limited space for databases. If your site needs a lot of database size, then you should go for a virtual dedicated server.

Server Uptime

It is important that you buy a web server from a reliable and reputed ISP. You should make sure your ISP is giving you 99.99% server uptime. If the is server down, then there are many service providers who gives you compensation in case your sites goes down more than a limited number of time.

Backup & FTP

Make sure your Service Provider is giving you more ways of taking regular backup of your website. If your site is changing everyday, then it becomes very important that you should take regular backup of your website. Many service providers do it on your behalf by charging a small cost for this service.

Control Panel

Just make sure what type of facilities you will get to maintain your hosting account. Check if your service provider is providing you an easy-to-use Control Panel or some other similar tool. Using a Control Panel, you should be able to maintain basic operations related to your website such as logging your service request, your reboot request, or any other problem.

Customer Support

Before finalizing a deal with your service provider, you should make sure they provide you the required support. You can get this information using Internet forums or from your




friends. There are many service providers who give you 24x7 support for any technical or non-technical problem.

Voice Networks Data Communication Networks:

INTRODUCTION : Voice over Internet Protocol (VoIP) is the enabling technology for thisservice integration. In short, 64Kbps voice is converted into data packetsand transferred over the data backbone. The savings of voice and dataover a single corporate network can be considerable and the technologyexists. But where does a company begin? This article reviews the enabling technologies and presents a viable private network evolution strategy that takes advantage of current technologies and standards. Savingsare realized almost immediately.

VOICE AND DATA NETWORKS: Companies with private voice networks own one or more private branchexchanges (PBX)s to deliver the service. A PBX is the switching elementthat link two users together in a voice connection. PBXs can be brokendone into the following basic functional components:•Wiring: PBXs require dedicatedwiring to each telephone in thecompany. This allows employeesto call other employees connected to the PBX.

To gain access tothe public service telephone network (PSTN), PBXs require outside lines purchased from thelocal public telephone company.Hardware: PBX hardware includes line cards terminating the localwiring, a switch network that makes the connection between twotelephones, and servers for PBX software.•Software: PBX software controls the call setup and features such ascall forwarding, call transfer, and call hold; software also providesoperation and maintenance support as well as per-call statistics.

Companies with multiple locations require dedicated PBXs at each siteand public leased lines connecting the multiple PBXs into a single logicalnetwork.Private data networks are delivered using equipment known as routers and hubs. Similar to voice networks, data networks also require dedicated wiring between the different network elements and to eachdesktop. PCs, servers, printers, and scanners are some of the data devicesthat can be connected to the network to deliver specific services. Oncenetworked, these devices communicate with each other, passing information in the form of data packets.

VOICE OVER INTERNET PROTOCOL :

When a user picks up and dials the telephone, the PBX provides dialtone, collects digits, and routes the call based on entered digits. In routing the call, the PBX sets up a dedicated connection between the two users. As the users speak into their phones, the PBX converts the analogvoice into digital signals and sends the digitized voice across the connection at a rate of 64Kbps. The PBX converts the analog signal to digital format by sampling the analog voice every 125 microseconds andconverting the voice sample to an 8-Prepared by Dr. S.SHANKARII, Assistant Professor, PG & Research Department Of Commerce CA



bit digital representation. Digitizedvoice is converted back to an analog signal at the terminating end of theconnection.

IP data networks, on the other hand, handle device communication bypackaging information into logical envelopes known as packets, addressing the packets with destination information, and routing the packetsthrough the network. Each network node looks at the addressing information and passes the packet onto the next network node until the packet arrives at its final destination. This routing method is connectionlessbecause there is no dedicated connection between origination and termination as there is with a voice connection. A side benefit of connectionless communication is the fact that bandwidth is only required whenthere is information to send.

VoIP merges voice and data technologies into one ubiquitous voiceservice. Analog voice signals are sampled and digitized the same as thesteps performed by the voice network. However, rather than send the64Kbps digitized signals over dedicated voice channels, the digitizedvoice is packetized and sent over the IP data network. Furthermore,bandwidth efficiencies can be realized if the voice signal is compressedprior to packetization. Voice compression can lower bandwidth demandsas low as 4Kbps while maintaining near toll-quality voice. This meansthat a single 64Kbps channel that normally carries a single voice conversation in the voice network can carry up to 16 voice conversations in thedata network.

To support call control, the International Telecommunication Union(ITU-T) has standardized the H.323 protocol. H.323 describes terminals, equipment, and services for multimedia communication over a local areanetwork (LAN), voice being just one service supported. Taken as a whole, these recommendations provide the standards to which many backbone, access, andcustomer premise equipment vendors are developing VoIP componentsand guaranteeing interoperability.

LAST MILE

The last mile is typically the speed bottleneck in communication networks; its bandwidth effectively limits the bandwidth of data that can be delivered to the customer. This is because retail telecommunication networks have the topology of "trees", with relatively few high capacity "trunk" communication channels branching out to feed many final mile "twigs". The final mile links, being the most numerous and thus the most expensive part of the system, as well as having to interface with a wide variety of user equipment, are the most difficult to upgrade to new technology. For example, telephone trunk lines that carry phone calls between switching centres are made of modern optical fibre, but the last mile is typically twisted pair wires, a technology which has essentially remained unchanged for over a century since the original laying of copper phone cables.

To resolve, or at least mitigate, the problems involved with attempting to provide enhanced services over the last mile, some firms have been mixing networks for decades.


https://en.wikipedia.org/wiki/Twisted_pair

https://en.wikipedia.org/wiki/Optical_fiber

https://en.wikipedia.org/wiki/Telecommunications_link

https://en.wikipedia.org/wiki/Bandwidth_(signal_processing)



One example is fixed wireless access, where a wireless network is used instead of wires to connect a stationary terminal to the wireline network. Various solutions are being developed which are seen as an alternative to the last mile of standard incumbent local exchange carriers. These include WiMAX and broadband over power lines.

In recent years, usage of the term "last mile" has expanded outside the communications industries, to include other distribution networks that deliver goods to customers, such as the pipes that deliver water and natural gas to customer premises, and the final legs of mail and package delivery services.The term has also been used to describe education and training providers that more tightly link individuals with job opportunities.

Existing delivery system problems

Schematic representation of the tree topology of retail distribution networks. The "last mile" links are represented by the fine lines at the bottom.

The increasing worldwide demand for rapid, low-latency and high-volume communication of information to homes and businesses has made economical information distribution and delivery increasingly important. As demand has escalated, particularly fueled by the widespread adoption of the Internet, the need for economical high-speed access by end-users located at millions of locations has ballooned as well.

As requirements have changed, the existing systems and networks that were initially pressed into service for this purpose have proven to be inadequate. To date, although a number of approaches have been tried, no single clear solution to the 'last mile problem' has emerged.

As expressed by Shannon's equation for channel information capacity, the omnipresence of noise in information systems sets a minimum signal-to-noise ratio (shortened as S/N) requirement in a channel, even when adequate spectral bandwidth is available. Since the integral of the rate of information transfer with respect to time is information quantity, this requirement leads to a corresponding minimum energy per bit. The problem of sending any given amount of information across a channel can therefore be viewed in terms of sending sufficient Information-Carrying Energy (ICE).[citation needed] For this reason the concept of an ICE 'pipe' or 'conduit' is relevant and useful for examining existing systems.

The distribution of information to a great number of widely separated end-users can be compared to the distribution of many other resources. Some familiar analogies are:

Blood distribution to a large number of cells over a system of veins, arteries and capillaries

Water distribution by a drip irrigation system to individual plants, including rivers, aqueducts, water mains, etc.

Nourishment to a plant's leaves through roots, trunk and branches.


https://en.wikipedia.org/wiki/Branches

https://en.wikipedia.org/wiki/Trunk_(botany)

https://en.wikipedia.org/wiki/Root

https://en.wikipedia.org/wiki/Water_mains

https://en.wikipedia.org/wiki/Aqueduct_(watercourse)

https://en.wikipedia.org/wiki/River

https://en.wikipedia.org/wiki/Plants

https://en.wikipedia.org/wiki/Drip_irrigation

https://en.wikipedia.org/wiki/Capillaries

https://en.wikipedia.org/wiki/Arteries

https://en.wikipedia.org/wiki/Veins

https://en.wikipedia.org/wiki/Cell_(biology)

https://en.wikipedia.org/wiki/Wikipedia:Citation_needed

https://en.wikipedia.org/wiki/Eb/N0


https://en.wikipedia.org/wiki/Signal-to-noise_ratio

https://en.wikipedia.org/wiki/Noise

https://en.wikipedia.org/wiki/Channel_capacity

https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem

https://en.wikipedia.org/wiki/Internet

https://en.wikipedia.org/wiki/Information

https://en.wikipedia.org/wiki/Latency_(engineering)

https://en.wikipedia.org/wiki/Tree_(graph_theory)

https://en.wikipedia.org/wiki/Package_delivery

https://en.wikipedia.org/wiki/Mail

https://en.wikipedia.org/wiki/Natural_gas

https://en.wikipedia.org/wiki/Broadband_over_power_lines

https://en.wikipedia.org/wiki/WiMAX

https://en.wikipedia.org/wiki/Incumbent_local_exchange_carrier

https://en.wikipedia.org/wiki/Incumbent_local_exchange_carrier

https://en.wikipedia.org/w/index.php?title=Wireline_(networking)&action=edit&redlink=1

https://en.wikipedia.org/wiki/Terminal_(telecommunication)

https://en.wikipedia.org/wiki/Wireless_local_loop



All of these have in common conduits that carry a relatively small amount of a resource a short distance to a very large number of physically separated endpoints. Also common are conduits supporting more voluminous flow, which combine and carry many individual portions over much greater distances. The shorter, lower-volume conduits, which individually serve only one or a small fraction of the endpoints, may have far greater combined length than the larger capacity ones. These common attributes are shown to the right.

Costs and efficiency

The high-capacity conduits in these systems tend to also have in common the ability to efficiently transfer the resource over a long distance. Only a small fraction of the resource being transferred is wasted, lost, or misdirected. The same cannot necessarily be said of lower-capacity conduits.

One reason has to do with the efficiency of scale. Conduits that are located closer to the endpoint, or end-user, do not individually have as many users supporting them. Even though they are smaller, each has the overhead of an "installation" obtaining and maintaining a suitable path over which the resource can flow. The funding and resources supporting these smaller conduits tend to come from the immediate locale.

This can have the advantage of a "small-government model". That is, the management and resources for these conduits is provided by local entities and therefore can be optimized to achieve the best solutions in the immediate environment and also to make best use of local resources. However, the lower operating efficiencies and relatively greater installation expenses, compared with the transfer capacities, can cause these smaller conduits, as a whole, to be the most expensive and difficult part of the complete distribution system.

These characteristics have been displayed in the birth, growth, and funding of the Internet. The earliest inter-computer communication tended to be accomplished with direct wireline connections between individual computers. These grew into clusters of small local area networks (LAN). The TCP/IP suite of protocols was born out of the need to connect several of these LANs together, particularly as related to common projects among the United States Department of Defense, industry and some academic institutions.

ARPANET came into being to further these interests. In addition to providing a way for multiple computers and users to share a common inter-LAN connection, the TCP/IP protocols provided a standardized way for dissimilar computers and operating systems to exchange information over this inter-network. The funding and support for the connections among LANs could be spread over one or even several LANs.

As each new LAN, or subnet, was added, the new subnet's constituents enjoyed access to the greater network. At the same time the new subnet enabled access to any network or networks with which it was already networked. Thus the growth became a mutually inclusive or "win-win" event.


https://en.wikipedia.org/wiki/ARPANET

https://en.wikipedia.org/wiki/United_States_Department_of_Defense

https://en.wikipedia.org/wiki/United_States_Department_of_Defense

https://en.wikipedia.org/wiki/Internet_protocol_suite

https://en.wikipedia.org/wiki/TCP/IP

https://en.wikipedia.org/wiki/Local_area_network


https://en.wikipedia.org/wiki/Economies_of_scale



Economies of scale

In general, economy of scale makes an increase in capacity of a conduit less expensive as the capacity is increased. There is an overhead associated with the creation of any conduit. This overhead is not repeated as capacity is increased within the potential of the technology being utilized.

As the Internet has grown in size, by some estimates doubling in the number of users every eighteen months, economy of scale has resulted in increasingly large information conduits providing the longest distance and highest capacity backbone connections. In recent years, the capacity of fiber-optic communication, aided by a supporting industry, has resulted in an expansion of raw capacity, so much so that in the United States a large amount of installed fiber infrastructure is not being used because it is currently excess capacity "dark fiber".

This excess backbone capacity exists in spite of the trend of increasing per-user data rates and overall quantity of data. Initially, only the inter-LAN connections were high speed. End-users used existing telephone lines and modems, which were capable of data rates of only a few hundred bit/s. Now almost all end users enjoy access at 100 or more times those early rates.

Economical information transfer

Before considering the characteristics of existing last-mile information delivery mechanisms, it is important to further examine what makes information conduits effective. As the Shannon-Hartley theorem shows, it is the combination of bandwidth and signal-to-noise ratio which determines the maximum information rate of a channel. The product of the average information rate and time yields total information transfer. In the presence of noise, this corresponds to some amount of transferred information-carrying energy (ICE). Therefore, the economics of information transfer may be viewed in terms of the economics of the transfer of ICE.

Effective last-mile conduits must:

1. Deliver signal power, S — (must have adequate signal power capacity).2. Experience low loss (low occurrence of conversion to unusable energy forms).3. Support wide transmission bandwidth.4. Deliver high signal-to-noise ratio (SNR) — low unwanted-signal (Noise) power, N.5. Provide nomadic connectivity.

In addition to these factors, a good solution to the last-mile problem must provide each user:

1. High availability and reliability.2. Low latency; latency must be small compared with required interaction times.3. High per-user capacity.

1. A conduit which is shared among multiple end-users must provide a correspondingly higher capacity in order to properly support each individual user. This must be true for information transfer in each direction.


https://en.wikipedia.org/wiki/Latency_(engineering)

https://en.wikipedia.org/wiki/Reliability_engineering

https://en.wikipedia.org/wiki/Availability

https://en.wikipedia.org/wiki/Roaming

https://en.wikipedia.org/wiki/Noise



https://en.wikipedia.org/wiki/Signal_noise


https://en.wikipedia.org/wiki/Shannon-Hartley_theorem

https://en.wikipedia.org/wiki/Bit_rate

https://en.wikipedia.org/wiki/Dark_fiber

https://en.wikipedia.org/wiki/Fiber-optic_communication



2. Affordability; suitable capacity must be financially viable.

Existing last mile delivery systems

Wired systems (including optical fiber)

Wired systems provide guided conduits for Information-Carrying Energy (ICE). They all have some degree of shielding, which limits their susceptibility to external noise sources. These transmission lines have losses which are proportional to length. Without the addition of periodic amplification, there is some maximum length beyond which all of these systems fail to deliver an adequate S/N ratio to support information flow. Dielectric optical fiber systems support heavier flow at higher cost.

Local area networks (LAN)

Traditional wired local area networking systems require copper coaxial cable or a twisted pair to be run between or among two or more of the nodes in the network. Common systems operate at 100 Mbit/s, and newer ones also support 1000 Mbit/s or more. While length may be limited by collision detection and avoidance requirements, signal loss and reflections over these lines also define a maximum distance. The decrease in information capacity made available to an individual user is roughly proportional to the number of users sharing a LAN.

Telephone

In the late 20th century, improvements in the use of existing copper telephone lines increased their capabilities if maximum line length is controlled. With support for higher transmission bandwidth and improved modulation, these digital subscriber line schemes have increased capability 20-50 times as compared to the previous voiceband systems. These methods are not based on altering the fundamental physical properties and limitations of the medium, which, apart from the introduction of twisted pairs, are no different today than when the first telephone exchange was opened in 1877 by the Bell Telephone Company.

The history and long life of copper-based communications infrastructure is both a testament to the ability to derive new value from simple concepts through technological innovation – and a warning that copper communications infrastructure is beginning to offer diminishing returns for continued investment. However one of the largest costs associated with maintaining an ageing copper infrastructure is that of truck roll - sending engineers to physically test, repair, replace and provide new copper connections, and this cost is particularly prevalent in providing rural broadband service over copper. New technologies such as G.Fast and VDSL2 offer viable high speed solutions to rural broadband provision over existing copper. In light of this many companies have developed automated cross connects (cabinet based automated distribution frames) to eliminate the uncertainty and cost associated with maintaining broadband services over existing copper, these systems usually incorporate some form of automated switching and some include test functionality allowing an ISP representative to complete operations previously requiring a site visit (truck roll) from Prepared by Dr. S.SHANKARII, Assistant Professor, PG & Research Department Of Commerce CA

https://en.wikipedia.org/wiki/Diminishing_returns

https://en.wikipedia.org/wiki/Twisted_pair

https://en.wikipedia.org/wiki/Voiceband

https://en.wikipedia.org/wiki/Digital_subscriber_line

https://en.wikipedia.org/wiki/Collision_detection


https://en.wikipedia.org/wiki/Fiber_to_the_x



the central office via a web interface. In many countries the last mile link which connects landline business telephone customers to the local telephone exchange is often an ISDN30 which can carry 30 simultaneous telephone calls.

Wireless delivery systems

Mobile CDN coined the term the 'mobile mile' to categorize the last mile connection when a wireless system is used to reach the customer. In contrast to wired delivery systems, wireless systems use unguided waves to transmit ICE. They all tend to be unshielded and have a greater degree of susceptibility to unwanted signal and noise sources.

Because these waves are not guided but diverge, in free space these systems are attenuated following an inverse-square law, inversely proportional to distance squared. Losses thus increase more slowly with increasing length than for wired systems, whose loss increases exponentially. In a free space environment, beyond a given length, the losses in a wireless system are lower than those in a wired system.

In practice, the presence of atmosphere, and especially obstructions caused by terrain, buildings and foliage can greatly increase the loss above the free space value. Reflection, refraction and diffraction of waves can also alter their transmission characteristics and require specialized systems to accommodate the accompanying distortions.

Wireless systems have an advantage over wired systems in last mile applications in not requiring lines to be installed. However, they also have a disadvantage in that their unguided nature makes them more susceptible to unwanted noise and signals. Spectral reuse can therefore be limited.

Lightwaves and free-space optics

Visible and infrared light waves are much shorter than radio frequency waves. Their use to transmit data is referred to as free-space optical communication. Being short, light waves can be focused or collimated with a small lens/antenna, and to a much higher degree than radio waves. Thus, a receiving device can recover a greater portion of the transmitted signal.

Also, because of the high frequency, a high data transfer rate may be available. However, in practical last mile environments, obstructions and de-steering of these beams, and absorption by elements of the atmosphere including fog and rain, particularly over longer paths, can greatly restrict their use for last-mile wireless communications. Longer (redder) waves suffer less obstruction but may carry lower data rates.

Radio waves

Radio frequencies (RF), from low frequencies through the microwave region, have wavelengths much longer than visible light. Although this means that it is not possible to focus the beams nearly as tightly as for light, it also means that the aperture or "capture area"


https://en.wikipedia.org/wiki/Bit_rate

https://en.wikipedia.org/wiki/Free-space_optical_communication

https://en.wikipedia.org/wiki/Exponential_decay

https://en.wikipedia.org/wiki/Inverse-square_law

https://en.wikipedia.org/wiki/Attenuation

https://en.wikipedia.org/wiki/Mobile_CDN

https://en.wikipedia.org/wiki/ISDN30

https://en.wikipedia.org/wiki/Telephone_exchange



of even the simplest, omnidirectional antenna is significantly larger than that of a lens in any feasible optical system. This characteristic results in greatly increased attenuation or "path loss" for systems that are not highly directional.

Actually, the term path loss is something of a misnomer because no energy is lost on a free-space path. Rather, it is merely not received by the receiving antenna. The apparent reduction in transmission, as frequency is increased, is an artifact of the change in the aperture of a given type of antenna.

Relative to the last-mile problem, these longer wavelengths have an advantage over light waves when omnidirectional or sectored transmissions are considered. The larger aperture of radio antennas results in much greater signal levels for a given path length and therefore higher information capacity. On the other hand, the lower carrier frequencies are not able to support the high information bandwidths, which are required by Shannon's equation when the practical limits of S/N have been reached.

For the above reasons, wireless radio systems are optimal for lower-information-capacity broadcast communications delivered over longer paths. For high-information capacity, highly-directive point-to-point over short ranges, wireless light-wave systems are the most useful.

One-way (broadcast) radio and television communications

Historically, most high-information-capacity broadcast has used lower frequencies, generally no higher than the UHF television region, with television itself being a prime example. Terrestrial television has generally been limited to the region above 50 MHz where sufficient information bandwidth is available, and below 1,000 MHz, due to problems associated with increased path loss, as mentioned above.

Two-way wireless communications

Two-way communication systems have primarily been limited to lower-information-capacity applications, such as audio, facsimile, or radioteletype. For the most part, higher-capacity systems, such as two-way video communications or terrestrial microwave telephone and data trunks, have been limited and confined to UHF or microwave and to point-point paths.

Higher capacity systems such as third-generation cellular telephone systems require a large infrastructure of more closely spaced cell sites in order to maintain communications within typical environments, where path losses are much greater than in free space and which also require omnidirectional access by the users.

Satellite communications

For information delivery to end users, satellite systems, by nature, have relatively long path lengths, even for low earth-orbiting satellites. They are also very expensive to Prepared by Dr. S.SHANKARII, Assistant Professor, PG & Research Department Of Commerce CA

https://en.wikipedia.org/wiki/Radioteletype

https://en.wikipedia.org/wiki/Point-to-point_(telecommunications)

https://en.wikipedia.org/wiki/Path_loss

https://en.wikipedia.org/wiki/Attenuation



deploy and therefore each satellite must serve many users. Additionally, the very long paths of geostationary satellites cause information latency that makes many real-time applications unfeasible.

As a solution to the last-mile problem, satellite systems have application and sharing limitations. The ICE which they transmit must be spread over a relatively large geographical area. This causes the received signal to be relatively small, unless very large or directional terrestrial antennas are used. A parallel problem exists when a satellite is receiving.

In that case, the satellite system must have a very great information capacity in order to accommodate a multitude of sharing users and each user must have large antenna, with attendant directivity and pointing requirements, in order to obtain even modest information-rate transfer. These requirements render high-information-capacity, bi-directional information systems uneconomical. This is one reason why the Iridium satellite system was not more successful.

Broadcast versus point-to-point

For terrestrial and satellite systems, economical, high-capacity, last-mile communications requires point-to-point transmission systems. Except for extremely small geographic areas, broadcast systems are only able to deliver high S/N ratios at low frequencies where there is not sufficient spectrum to support the large information capacity needed by a large number of users. Although complete "flooding" of a region can be accomplished, such systems have the fundamental characteristic that most of the radiated ICE never reaches a user and is wasted.

As information requirements increase, broadcast wireless mesh systems (also sometimes referred to as microcells or nano-cells) which are small enough to provide adequate information distribution to and from a relatively small number of local users require a prohibitively large number of broadcast locations or points of presence along with a large amount of excess capacity to make up for the wasted energy.

Intermediate system

Recently a new type of information transport midway between wired and wireless systems has been discovered. Called E-Line, it uses a single central conductor but no outer conductor or shield. The energy is transported in a plane wave which, unlike radio does not diverge, whereas like radio it has no outer guiding structure.

This system exhibits a combination of the attributes of wired and wireless systems and can support high information capacity utilizing existing power lines over a broad range of frequencies from RF through microwave.

Line aggregation


https://en.wikipedia.org/wiki/Microwave

https://en.wikipedia.org/wiki/Radio_frequency

https://en.wikipedia.org/wiki/Broadband_over_power_lines

https://en.wikipedia.org/wiki/Single-wire_transmission_line#E-Line

https://en.wikipedia.org/wiki/Microcell

https://en.wikipedia.org/wiki/Wireless_mesh

https://en.wikipedia.org/wiki/Point-to-point_(telecommunications)

https://en.wikipedia.org/wiki/Iridium_Satellite_LLC



Aggregation is a method of bonding multiple lines to achieve a faster, more reliable connection. Some companies believe that ADSL aggregation (or "bonding") is the solution to the UK's last mile problem.


https://en.wikipedia.org/wiki/Link_aggregation

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