Internet - Finctionality of Internet
Finctionality of Internet
Clint Server Architecture
Domain Name
Internet Resources
Internet Time
Internet Addressing
IP Addresses
InterNIC
Internet Society
ISP
Protocol
Search Engines
TCP/IP
Computer Viruses
Security
Finctionality of Internet
Clint Server Architecture
Client/server computing
Client/server computing is a common networking model which enables many users to access information in an efficient manner. Generally, the user's computer is called the client and the machine that contains the information being accessed is called the server.
Client/server computing is a phrase used to describe a model for computer networking. This model offers an efficient way to provide information and services to many users. A network connection is only made when information needs to be accessed by a user. This lack of a continuous network connection provides network efficiency.
In client/server computing, processes are divided between the client and the server. This relationship is based on a series of requests and responses.
Client: Requests services or information from another computer (the server computer).
Server: Responds to the client's request by sending the results of the request back to the client computer.
In a client/server setting, the server computer runs a software application called a server program. This software allows a computer to act as a server.
The server program:
Receives a request from a client and processes the request.
Responds by sending the requested information back to the client.;
The following diagram illustrates the relationship between client and server computers. The client requests information; the server processes the request and sends a response back to the client.
Most transactions that occur on the Internet are client/server based. Some examples include:
• FTP (file transfer protocol) - An FTP client program contacts an FTP server and requests the transfer of a file; the FTP server responds by transferring the file to the client.
WWW (World Wide Web) - In this case the client program is a browser. A browser requests the contents of a web page and displays the results on the user's computer.
E-MAIL - A mail client program enables the user to interact with a server in order to access, read and send electronic mail messages.
The client computer runs an application called a client program. A client program enables a user to send a request for information to the server and read the results that the server sends back.
The server computer runs a server program which processes requests and sends results back to the client. Most Internet transactions, such as FTP, e-mail and accessing web pages are based on client/server networking.
Domain Name
A domain name is a way to identify and locate computers connected to the Internet. A domain name must be unique; no two organizations on the Internet can have the same domain name.
A typical domain name consists of a second-level domain and a top-level domain, such as "bigco.com". In addition, hostname and subdomain information can be added, for example: "tiger.newyork.bigco.com".
The top-level domain name describes the type of organization or the country with the domain name (EDU, COM, GOV, UK, etc.).
• A way to identify computers
Hierarchical
Unique
A corresponding IP address
A domain name is a way to identify and locate computers connected to the Internet. No two organizations can have the same domain name. A domain name always contains two or more components separated by periods, called "dots".
Some examples of domain names are:
• java.net
• w3schools.com
• nasa.gov
• utexas.edu
• reston.va.us
Once a domain name has been established, "subdomains" can be created within the domain.
. For example, the domain name for a large company could be "bigco.com" and within this domain, subdomains can be created for each of the company's regional offices.
The structure for this is:
hostname.subdomain.second-level domain.top-level domain
For example, java.education.mkdtutorials.com
describes a single host computer named tiger, in the New York office of the Bigco Company. Not all domain names will have a hostname and subdomain. In addition, more than one subdomain can be assigned.
The top-level portion of a domain name describes the type of organization holding that name. The major categories for top-level domains are:
• COM - commercial entities
EDU - four year colleges and universities
NET - organizations directly involved in Internet operations, such as network providers and network information centers
ORG - miscellaneous organizations that don't fit any other category, such as non-profit groups
GOV - United States Federal Government entities
MIL - United States military
COUNTRY CODES - a two letter abbreviation for a particular country. For example, "UK" for United Kingdom or "FR" for France.
Each domain name corresponds to numeric IP (Internet Protocol) addresses. An IP address takes the form of 4 numbers, each one between 0 and 255, separated by periods.
The Internet uses the numeric IP address to send data. For instance, you may be connecting to a World Wide Web server with the domain name "rs.internic.net", but as far as the network is concerned, you are connecting to the Web server with the IP address associated with that domain name.
The Domain Name System completes the task of matching domain names to IP (Internet Protocol) addresses. Domain names, and their corresponding IP addresses, must be unique.
If more than one organization on the Internet had the same domain name, confusion would occur when the network tried to identify and communicate with the computers within those organizations.
For example, if there were two separate universitites, one in Maine and one in Arizona, they cannot both use the domain name "coolschool.edu", because the Domain Name System would not know which one of the universities' IP addresses were associated with that domain name.
The Domain Name System is a collection of databases that contain information about domain names and their corresponding IP addresses. Domain name servers are computers that translate domain names to IP addresses.
This system allows Internet users to deal with the more intuitive domain names, rather than having to remember a series of numbers.
Internet Resources
Internet Explorer enables you to access most Internet resources, including those available through FTP, Gopher and telnet. In addition, Internet Explorer comes with a newsreader and an e-mail interface so users can access Usenet newsgroups and send and read e-mail from within Internet Explorer. In order for telnet, newsreader and e-mail capabilities to work properly, certain configurations must be completed - such as indicating to Internet Explorer the name of the telnet client to invoke, or the name of the mail server being used.
Find people on the Internet
Locating a specific person on the Internet can be a challenging task. There is no single repository of information about Internet users. There is no single organization that is responsible for collecting and maintaining information about Internet users.
There are numerous tools that have been developed to find people on the Internet. However, it is likely that you will need to use a combination of these tools to be successful in your search.
Finding people on the Internet is a challenging task, because there is no single, centralized directory of Internet users.
Why?
• No one organization is in charge of collecting Internet user information.
It would be impossible for a single organization to manage, maintain and update information on every single Internet user.
However, there are a number of tools which can be used to find people on the Internet.
CWIS - Campus Wide Information Systems
Many universities make a wealth of information available through CWIS - for example, listings of campus events, class schedules and job opportunities. A CWIS also usually includes a directory of faculty and students.
To access this service, a user needs to be able to access the CWIS at the university where a student or faculty member can be reached. Here is a screen showing a link to the Campus Wide Information System at the University of Kansas:
CCSO/CSO
CCSO (often shortened to CSO) is another search tool found at many universities and large organizations. CCSO stands for Computing and Communications Services Office at the University of Illinois, Urbana- Champaign, which is where the directory and search tool was developed.
CSO allows the user to search for a person's name, e-mail address, department, etc. The CSO directory will return any information available for the person or department, and often includes phone numbers and e-mail addresses.
Finger
Finger is a program that displays information about users on a particular system.
Finger can be used two ways:
• Use the finger command to ask for information about a particular user. To do this, you need to provide the name of the machine that the person uses.
To find out who else is currently logged on to the same machine that you are logged on to.
In order for this to work, finger must be running on the remote machine (i.e., the machine used by the person you're interested in locating).
WHOIS
WHOIS is a searchable database of information about networks, networking organizations, domains, sites, and the contacts associated with them. WHOIS provides a way to find out e-mail addresses, postal addresses, and telephone numbers for those contacts.
The main WHOIS database is maintained by the InterNIC's Registration Services. An organization that registers a domain name is automatically added to the WHOIS database.
WHOIS is available through telnet, the World Wide Web, e-mail, or a local WHOIS client.
Netfind
Netfind is a simple Internet "white pages" directory that can be searched using keywords. Given the name of a user and a rough description of where the user works, Netfind attempts to locate information about that Internet user.
It is helpful to know the domain name of the computer used by the person that you are trying to locate. This is generally typed in as one of the key words. Netfind will present you with a list of possible domains based on the key words (perhaps all the domains at a particular university).
Once the domain has been narrowed down, Netfind uses finger to track down the person's name.
X.500
X.500 is an international standard that defines a type of directory service which can provide information about people, such as e-mail addresses and phone numbers. Many organizations throughout the world have made information available in X.500.
X.500 has two major components:
• DUA (Directory User Agent) - a client program, or interface, that enables the user to query the available information. DUAs differ, depending on the type of X.500 access.
DSAs (Directory System Agents) - which contain the information. X.500 consists of many DSAs, each of which holds part of the total information available. If necessary, several DSAs will be searched to answer a user's query, but this is invisible to the user.
X.500 can be accessed through the WWW, gopher, e-mail and telnet.
USENET archives
The Massachusetts Institute of Technology (MIT) maintains an archive that contains the e-mail addresses of most of the people who have posted articles to USENET newsgroups. USENET is the network which carries newsgroup articles.
If you believe that someone has posted an article to a USENET newsgroup, you can probably get their e-mail address by requesting it from the MIT archive via electronic mail.
Search Engines
Another way to locate people is to make use of one of the search engines or indexes available via the World Wide Web. By searching for a user's name, it may be possible to find their e-mail address, postal address, telephone number, or even their personal webpage.
The results will vary from one search engine or index to the next. Here is an example of a screen from the search tool called Internet Address Finder:
Internet Time
Internet Time is a "new" way to tell time, invented and marketed by the Swiss watch company Swatch. The current Internet Time is the same all over the World (no time zones or daylight saving time adjustments). The current Internet time can be found on the World Clock just below the long list of cities there. ("Internet time: @xxx .beats")
Simple Internet Time .beat converter
Theory
New time unit - the .beat
Instead of dividing the virtual and real day into 24 hours and 60 minutes per hour, the Internet Time system divides the day into 1000 ".beats". Each .beat is 1 minute and 26.4 seconds.
New meridian
Internet Time is based on a new Meridian (as opposed to the Greenwich Meridian). This new Meridian goes through Swatch's office in Biel, Switzerland and is called the BMT Meridian.
BMT - the reference for Internet Time
BMT, another invention of Swatch, Biel Mean Time, which is linked up to the Central European Winter/Standard time - which is UTC + 1 hour. When it is Midnight in BMT, the Internet Time is @000 beats, Noon is @500 beats.
Time unit conversions
Beat Unit
Conversion
Unit
Beat Conversion
1 .beat
= 0.001 day
1 day
= 1000 .beats
1 .beat
= 0.024 hours
1 hour
= 41.666 .beats
1 .beat
= 1.44 minutes
1 minute
= 0.6944 .beats
1 .beat
= 86.4 seconds
1 second
= 0.01157 .beats
Advantages of the Internet Time system
• It uses the normal decimal system, instead of the ancient 24 hour, 60 minute, 60 second system which makes time telling more complicated.
• .beat time calculations are easy, @345 + 456 .beats = @801, compared to e.g. 3:45:20 + 2 hours, 25 minutes, 45 seconds, where the seconds, minutes and hours must all be added.
• No need for time zone conversions - the Internet Time is the same everywhere.
Disadvantages of the Internet Time system
• The use of the Biel Meridian introduces an unwanted additional Meridian - the Greenwich Meridian is the standard Meridian of the world.
• Wrong use of mean time - The Biel Meridian is not at exactly 15 degrees east longitude, which it should have been if the BMT (Biel Mean Time) should be 1 hour ahead of UTC / GMT (Greenwich Mean Time)
• The second, and not the beat is the basic unit of time in the International System of Units (and using .beats instead, would complicate the system).
• The Internet Time system might seem like more of commercial marketing attempt, than a real system.
• Milliday would be a more accurate name than beat.
Internet Addressing
Internet addressing is used to identify people, computers, and Internet resources.
Using the Internet requires an understanding of different addressing schemes. People are identified with electronic mail addresses. Computers are identified with IP addresses and domain names. Resources and files available through the World Wide Web are identified using URLs.
• A way to locate people, computers, and Internet resources
IP (Internet Protocol) addresses and domain names
Electronic mail addresses
URLs
In general, Internet addressing is a systematic way to identify people, computers and Internet resources. On the Internet, the term "address" is used loosely. Address can mean many different things from an electronic mail address to a URL.
IP Address
An IP address is a unique number that identifies computers on the Internet; every computer directly connected to the Internet has one. An IP address consists of four numbers separated by periods. Each number must be between 0 and 255.
An example is: 204.81.205.32
Domain Name
Most computers on the Internet have a unique domain name. Special computers, called domain name servers, look up the domain name and match it to the corresponding IP address so that data can be properly routed to its destination on the Internet.
An example domain name is: healthyway.com Domain names are easier for most people to relate to than a numeric IP address.
Electronic Mail Address
An Internet electronic mail, or e-mail, address is used to identify a person (or persons) and a computer for purposes of exchanging electronic mail messages.
An example Internet e-mail address is: janedoe@xyz.edu
Internet e-mail addresses are read from left to right:
• "janedoe" is the name of the person receiving or sending the message; this is referred to as the username.
• "xyz" is part of the domain name of the organization
• "edu" is also part of the domain name and indicates that "xyz" is an educational institution.
Electronic Mail Address
Other networks may use different electronic mail addressing schemes within their own networks. To be used in Internet e-mail, these addresses often need to be modified.
For example, within CompuServe an e-mail address consists only of two numbers separated by a comma: 36547,891.
To convert this to an address that can be used on the Internet, the comma is changed to a period and the number serves as the username.
The domain name is compuserve.com, so the Internet address would be: 36547.891@compuserve.com
URLs
URL stands for Uniform Resource Locator. URLs are used to identify specific sites and files available on the World Wide Web. The structure of a URL is: protocol://server.subdomain.top-level-domain/directory/filename
Not all URLs will have the directory and filename.
Two examples:
• http://www.healthyway.com/exercise/mtbike.html
gopher://gopher.state.edu/
URLs
Similar to an e-mail address, a URL is read like a sentence.
For example the URL http://www.healthyway.com
is read as "http colon forward slash forward slash www dot healthyway dot com".
IP Addresses
An IP address is a unique, numeric identifier used to specify a particular host on a particular network, and is part of a global, standardized scheme for identifying machines that are connected to the Internet.
IP addresses consist of four numbers between 0 and 255, separated by periods, which represent both the network and the host machine.
The InterNIC, under the authority of the Internet Assigned Numbers Authority (IANA), allocates the network portions of IP addresses to Internet Service Providers (ISPs); ISPs are responsible for assigning the host portion of the IP address to machines within their local networks.
A way to identify machines on the Internet
A number
Unique
Global
Standardized
If you want to connect to another computer, transfer files to or from another computer, or send an e-mail message, you first need to know where the other computer is - you need the computer's "address."
An IP (Internet Protocol) address is an identifier for a particular machine on a particular network; it is part of a scheme to identify computers on the Internet.
IP addresses are also referred to as IP numbers and Internet addresses An IP address consists of four sections separated by periods. Each section contains a number ranging from 0 to 255.
Example = 198.41.0.52
Which sections of the IP address represent the network and which sections represent the machine will depend on what "class" of IP address is assigned to a network. There are 5 classes of IP addresses: Class A, Class B, Class C, Class D, and Class E.
Classes correspond either to the size of the network (the number of hosts that the network can support) or are reserved for specific purposes, such as multicasting and experimentation.
The diagram below compares Class A, Class B and Class C IP addresses. The blue numbers represent the network and the red numbers represent hosts on the network. Therefore, a Class A network can support many more hosts than a Class C network.
IP addresses are unique.
.No two machines can have the same IP number. .
IP addresses are also global and standardized. .
All machines connected to the Internet agree to use the same scheme for establishing an address.
InterNIC
The InterNIC (Internet Network Information Center) was formed in 1993 through a cooperative agreement issued by the National Science Foundation (NSF). The NSF provided initial funding for the project. In addition, the NSF provides guidelines and completes periodic reviews for adherence to project requirements
• NSF cooperative agreement
Registration Services
Information and Education Services
Directory and Database Services
Net Scout
The InterNIC consists of:
• Network Solutions, Inc. - operates the Registration Services and the Information and Education Services. The Information and Education Services includes the Net Scout, which is located at the Computer Sciences Department at the University of Wisconsin-Madison.
AT&T - operates the Directory and Database Services.
Registration Services (managed by Network Solutions, Inc.)
Under the delegation of the Internet Assigned Numbers Authority (IANA), the InterNIC manages registrations of second-level domain names under the following top-level domains: EDU, GOV, COM, NET and ORG.
The InterNIC also assigns blocks of IP addresses to various entities. For example, the InterNIC allocates blocks of IP addresses to Internet Service Providers, who then distribute these IP addresses to their customers.
Regional Network Information Centers such as APNIC (Asian-Pacific Network Information Center) and RIPE (Réseaux IP Européens) also receive blocks of IP addresses from the InterNIC for distribution in their regions.
Information and Education Services(managed by Network Solutions, Inc.)
Provides resources for the Internet community including:
• InterNIC News - an on-line, monthly newsletter that replaces the out-of-print "NSF Net News" newsletter.
Net Scout Services - Net Scout Services compiles current information about Internet resources and network tools. These services include The Scout Report, Net-Happenings and the Scout Toolkit.
Training Resources - for librarians, educators and others who support Internet users. Resources include the Roadmap '96, written by Patrick Crispen and sponsored by the InterNIC.
Directory and Database Services(managed by AT&T)
Provides links to Internet resources and information including:
• Directory of Directories
"White Pages": WHOIS, Netfind and x.500
Internet Documentation (RFC's, FYI's, etc.) and Internet Engineering Task Force (IETF) Information
Public databases, government information and search engines
Internet Society
Who is the Internet Society?
The Internet Society (ISOC) is an international organization that was founded in 1992. The ISOC is dedicated to the expansion, development and availability of the Internet.
Some of the Internet Society's goals:
• Development and maintenance of Internet standards
Evolution of Internet technologies
Internet related education and research
Assisting emerging countries with their Internet infrastru
To help facilitate the completion of its goals, the Internet Society coordinates and supports the Internet standards development process as carried out by the:
• Internet Engineering Task Force (IETF)
Internet Engineering Steering Group (IESG)
Internet Architecture Board (IAB)
Internet Assigned Numbers Authority (IANA)
• Internet Engineering Task Force (IETF) - develops solutions to technical and operational problems that arise on the Internet and develops Internet standards and protocols.
Internet Engineering Steering Group (IESG) - acts as the operational management arm of the IETF.
Internet Architecture Board (IAB) - oversees the development of Internet standards and protocols, and acts as a liason between the ISOC and other standards bodies.
Internet Assigned Numbers Authority (IANA) - chartered by the ISOC and the Federal Network Council (FNC). The IANA is the central coordinator for the assignment of the unique parameters that are used on the Internet, such as domain names and IP (Internet Protocol) addresses.
Membership in the Internet Society is open to anyone in the world. Membership is international and is as diverse as the Internet community itself, including corporations, non-profit organizations, educators, network specialists, individual users and others
ISP
Internet Service Provider?
An Internet Service Provider (ISP) is a company that provides access to the Internet. Their customers can be businesses, individuals or organizations. The advent of ISPs has made connecting to the Internet an affordable and convenient option for many people.
ISPs are also sometimes referred to as Internet Access Providers.
ISPsoffer different types of connections. Two common connectivity options are:
Dial-up shell accounts
SLIP/PPP (Serial Line Internet Protocol or Point-to-Point Protocol)
Dial-up shell accounts
The user connects with a modem and phone line to a host machine at the ISP. The host machine is connected to the Internet; therefore, the user can access the Internet via the host machine.
All software needed for Internet access, such as TCP/IP (Transmission Control Protocol/Internet Protocol) is on the host machine, not the user's computer.
Also, the user must use the client programs that reside on the host machine. For example, if the host uses a Lynx web browser and command line ftp, then the user must also use these tools.
Dial-up accounts provide access but cannot support graphical interfaces, as these must be run on the user's desktop computer.
SLIP/PPP
In this option, the user also uses a modem to connect to a remote computer (called a SLIP server) at the ISP. However, in a SLIP/PPP account, the user's computer has both SLIP/PPP and TCP/IP software installed directly on it.
This allows the user to choose whatever client programs (web browsers, ftp client, telnet client, etc.) he or she desires.
SLIP/PPP cont'd
Once a connection has been made to a SLIP server at the ISP, the SLIP/PPP software on the user's computer requests a SLIP/PPP connection. Then, the ISP assigns an IP (Internet Protocol) address to the user's computer.
Often, an ISP has a block of IP addresses that they assign to user's "on-the-fly" at the time the connection is made; a user may not always get the same IP address.
At this point, the TCP/IP software on the user's computer "takes over" and manages the flow of data between the Internet and the user's computer.
In addition to providing access to the Internet, ISPs usually offer additional services as well. These services can include:
• Web hosting - An individual or organization can place their web pages on a web server located at the ISP. These web pages can then be accessed by Internet users.
Domain Name Service - Provides domain name servers, which are computers dedicated to translating a customer's domain name into the actual numeric IP (Internet Protocol) address of the customer's computer. Domain name service is integral to the proper functioning of the Internet.
Proprietary Online Services - Such as the custom services offered by America Online, Inc. or CompuServe. These special options are available only to their subscribers.
ISPs charge a fee for the service of providing Internet access. Charges vary from region to region and can depend on variables such as:
• type of connection
modem speed
level of service
Some ISPs charge for each hour that a user is connected to the ISP. Other service providers allow unlimited connection time once the user has paid a flat fee - either by the month or by the year.
There are many sources of information about Internet Service Providers via the World Wide Web.
Two sources are:
In Summary:
An Internet Service Provider is a company that provides Internet access. Customers can be businesses, individuals and organizations. Two common types of Internet access are dial-up shell accounts and SLIP/PPP accounts.
In a shell account, the user connects to a host computer at the ISP and can then access the Internet through the host computer. All necessary software is on the host machine, not the user's machine.
In a SLIP/PPP account, the user has all necessary software installed on his or her computer and connects directly to the Internet through the ISP.
Additional services that can be offered by an ISP include web hosting, domain name service and proprietary online services. Fees charged by ISPs vary from region to region and depend on a number of variables such as type of connection and level of service.
Protocol
A protocol is a standard set of rules that governs how computers communicate with each other. Protocols describe both the format that a message must take and the way in which messages are exchanged between computers.
Different types of computers are able to communicate with each other - in spite of their differences - when they agree to use a protocol that offers a standard format and method for communication. Some of the protocols used on the Internet are TCP/IP, SMTP, FTP, HTTP, and NNTP.
A protocol is a standard set of rules that determines how computers communicate with each other across networks. A network is two or more computers that are physically connected to each other and able to share information.
When computers communicate with one another, they exchange a series of messages. To understand and act on these messages, computers must agree on what a message means.
Examples of messages include establishing a connection to a remote machine; sending or receiving e-mail; and transferring files and data.
A protocol describes:
• the format that a message must take, and
• the way in which computers must exchange a message
within the context of a particular activity, such as sending messages across networks, exchanging e-mail, establishing remote connections, or transferring files.
Think of an electronic mail message. Both the format of the electronic mail message and the way that it is transmitted across the network are described and governed by a protocol.
Protocols ensure that electronic mail messages are correctly formatted and transmitted from the originating computer to the destination computer.
A comparison can be made to the rules that govern how letters are handled by the post office:
There are different protocols for different types of network services. For example, the Internet is based on the TCP/IP suite, or family, of protocols.
Some of the protocols used on the Internet are:
• Simple Mail Transfer Protocol (SMTP) - to send and receive electronic mail
File Transfer Protocol (FTP) - to transfer files between computers
Hypertext Transfer Protocol (HTTP) - to transmit information on the World Wide Web
Network News Transfer Protocol (NNTP) - to transmit network news
Protocols enable different types of computers (Macintosh, PCs, UNIX, VMS, etc.) to communicate in spite of their differences. This is because they describe a standard format and method for communicating.
A very simple comparison can be made to Morse Code:
• People using Morse Code agree that a given combination of dots and dashes will always have the same meaning.
Someone who speaks only Russian and someone who speaks only Greek can exchange messages using Morse Code because they agree on the format and method for exchanging messages.
Search Engines
• A tool for locating Internet resources
Interactive
Database
Automated
Web search engine is an interactive tool to help people locate information available via the World Wide Web.
Web search engines are actually databases that contain references to thousands of resources. Users are able to interact with the database, submitting queries that "ask" the database if it contains resources that match specific criteria.
There are many search engines available on the web. A web search engine provides an interface between the user and the underlying database.
The interface presents the user with a place to type in a search string, which may be a word, a phrase, a date, or some other criterion, and a way to submit the request. The web search engine runs the search string against the database, returns a list of resources that match the criteria, and displays the results for the user.
Many web search engines use "fill-out" forms as an interface, and support complex queries. Many also include instructions and help in searching the database. Here is an example from the search engine AltaVistaTM:
Because web search engines can use hypertext, users are able to link directly to resources listed in the results display. For example, here are some of the results from the previous query "DNA and cancer".
How do resources end up in a web search engine's database?
Most web search engines use automated tools and programs to gather resources. These tools, often referred to as worms, spiders, crawlers, and robots, search thousands of websites worldwide, collect information, and store the information in the database.
Each web search engine provides its own database, interface, and special features. A search engine's database cannot possibly contain every piece of information that is on the WWW, therefore search results will not include every available web resource.
In addition, because each search engine collects resources differently, the same query typed into several search engines is likely to produce different results.
A web search engine is an interactive tool that enables users to locate information available via the World Wide Web. Search engines provide "fill-out" forms and other interfaces so the user can type in a query, submit the request, and retrieve a list of resources that match the search criteria.
The hypertext environment makes it possible to offer a link directly from the list of results to the resources themselves. A single search engine cannot cover every available web resource, but many do contain references to millions of resources. Results may vary from one search engine to the next.
TCP/IP
TCP/IP is a communications protocol used to transfer digital data around the internet. TCP and IP were developed by a Department of Defense (DOD) research project to connect different networks designed by different vendors into a network of networks (the "Internet"). TCP/IP is often referred to as the 'internet protocol'.
As with all communications protocols, TCP/IP is composed of layers:
IP - is responsible for moving packet of data from node to node. IP forwards each packet based on a four byte destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations.
The organizations assign groups of their numbers to departments. IP operates on gateway machines that move data from department to organization to region and then around the world.
TCP - is responsible for verifying the correct delivery of data from client to server. Data can be lost in the intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and completely received.
Sockets - is a name given to the package of subroutines that provide access to TCP/IP on most systems.
TCP/IP is a suite, or family, of protocols that govern the way data is transmitted across networks.
TCP/IP protocols work together to break the data into small pieces that can be efficiently handled by the network, communicate the destination of the data to the network, verify the receipt of the data on the other end of the transmission, and reconstruct the data in its original form.
TCP/IP stands for Transmission Control Protocol/Internet Protocol. TCP/IP is actually a collection of protocols, or rules, that govern the way data travels from one machine to another across networks.
<td