Protocols Used in World Wide Web - Essay Example

World Wide Web Introduction: World Wide Web (www) or ‘the web’ was embarked in1989 at CERN- the European center for nuclear research, and was developed by Tim Berners-Lee. WWW, a universe of knowledge, is the collection of linked documents or files. The web attained rapid popularity due to the vast publicity of internet and its ease of use. The web and internet are not synonymous. The internet is a world wide network that provides electronic connection among computers and the web is distributed system that runs on top of it. Basic operations of WWW: Internet consents to exchange of information among computers in various networks on a distributed environment. In a distributed system, interconnections between the systems are in a client-server model. The client uses a web browser, which is the tool that provides universal access to the large collection of materials made available in the WWW and internet to connect with a server. The internet, the network of networks, has a network of connections between computers containing hypertext/hypermedia files or documents. Web documents contain information and are also linked to other related sources in the web. Another important reason for the use of WWW Browsers is that they have the capability to handle all other forms of internet protocols (Gopher, WAIS, FTP, Telnet etc.). Protocols Used in WWW – an Overview: The transferring of hypertext/hypermedia materials from web server to browser is based on certain network architectures. There are two types of computer network architectures used in Internet - The OSI Reference Model and the TCP/IP Reference Model. Each model has its own protocols. After the implementation of satellite and radio networks TCP/IP Reference Model became popular. The main ability of TCP/IP is to connect networks in a faultless manner. Different layers of TCP/IP Reference Model (Application layer, Transport layer, Network layer etc.) comprise different protocols, to control and coordinate the format of packets and messages that are exchanged among different computers within a layer. These protocols are used by the entities to implement service definitions. The application layer contains various purpose protocols as shown below: (Tanenbaum, p.43). TELNET is a program that allows login to a remote computer on the internet, by using Telnet command. And it performs operations permitted by the host computers. FTP (File Transfer Protocol) is used to transfer files between different computers. It is possible to upload or download data from or to server, delete a file, rename a file, change access permission of a file and all operations on a block of files and so on. SMTP (Simple Mail Transfer Protocol) is the protocol that helps electronic mailing among different computers. It listen the port number 25 of server machine. HTTP: In internet computers communicate each other via certain protocols like HTTP. Client (Web browser) sends requests to the Server (Web Server) and Server responds to client requests. The Client-Server transaction, may be Client request or Server response, consists of three main parts: 1. A response or request line. 2. Message header information. 3. Message Body. The Client or the web browser contacts a server through the establishment of connection to port 80 on the server’s machine. Each request from client consists of one or more lines of ASCII text. The first word on the first line is the method name. (Tanenbaum, p.653). The method names are case sensitive. Additional object specific methods are available to access general objects. GET: The GET method is used to make a request to the server for send a page and this page is suitably encoded by MIME. Majority of requests from web browsers to web server are GET. The usual form of GET is “GET filename HTTP/1.1” where ‘filename’ indicates name of resource to be fetched and 1.1 indicates the version of protocol being used. HEAD: The HEAD method just asks for message header, without the actual page. This method can be used to get the last modification time of page, information for indexing purposes and validation test of URLs. PUT: The PUT method writes the page. This method builds a collection of web pages on a remote server. The body of request contains page and it is suitably encoded by MIME. The lines following the method name contain the content type and authentication headers to prove that the caller indeed has permission to perform the requested operation. POST: This method is same as PUT method, it also bears URLs. But instead of replacing existing file, the new data is appended to it. But in practice both PUT and POST methods are rarely used. DELETE: This method removes a page. The method name includes authentication headers and permissions to perform the request. TRACE: This method is for debugging. It instructs the server to send back the request and it is possible to the client to check the request that the server actually got. CONNECT: This method is reserved for the future use. OPTIONS: This method provides the way in which the client makes query to server about its properties or those of particular file. (Fielding, et al). Each request from the client gets a response from the server. This response consists of a status line and some additional information. The status line contains three digit status code indicating the status of the request from the client. The first digit is used to divide the response into five major groups. (Tanenbaum, p.654). Message Headers: Request line may be followed by additional lines with more information. These lines are called request header. Responses also have response headers. (Tanenbaum, p.655). DNS-Domain Name System: DNS is naming method used to identify each host or domain in internet. To identify a system on internet, a naming system is required. This naming is handled by DNS. It is an application layer service. The aim of DNS is the creation of a hierarchical domain based naming scheme. In DNS, internet is divided into several top level domains and each top level domain includes several hosts or hierarchy of sub-domains or hosts. Top level domains are two types; they are generic and country domains. Examples of generic domains are com (commercial), org (nonprofit organization), gov (US federal government), edu (educational institution), and net (network providers). Country domain comprises one unique entry for each country. The top level domain can be added in future with reference to requirements. The internet domain name space tree is shown blow: (The DNS Name Space). Naming of domain is done by the path upward from it to root, for example, cs.yale.edu. Domain name can be absolute or relative. Absolute domain always ends with a period (or‘.’) while relative doesn’t. It is noted that domain names are case insensitive, and full path name must not exceed 255 characters. Permission of higher domain is required for the creation of a new domain within that domain. In this way the name conflicts are removed. After creating a new domain, we can create number of sub-domain within that domain without permission. Functioning of DNS can be described as follows, “to map a name onto an IP address, an application program calls a library procedure called the resolver, passing it the name as a parameter. The ‘resolver’ sends a UDP packet to a local DNS server, which then looks up the name and returns the IP address to the resolver, which then returns it to the caller. Armed with the IP address, the program can then establish a TCP connection with destination or send it UDP packets.” (Setting Up DNS Servers, p.2). Resource records: A set of resource records should be linked with each domain or even a single host. DNS gives resource records associated with a domain name, when it gets domain name from a resolver. Hence it is obvious that primary function of a Domain Name System is to map domain names to resource records. Generally the resource records associated with a single host is its IP address; however many other types of resource records are also there. A resource record has five parts. Those are domain name, time to live, class, type, value. ‘Domain name’ represents domain where this record exists. ‘Time to live’ tells the stability of record. In practice, ‘class’ field is always ‘IN’ for internet information. The ‘type’ indicates the type of the record. Name servers: Name server is employed for storing whole DNS database and responding to all queries about it. But in practice it is not possible to handle this on a single server. So the DNS name space is divided into different zones without overlapping as in fig. (Name Servers). Conclusion: World Wide Web shows a phenomenal growth in the last decade. The web became a world of human knowledge. There are more than one billion users for the www, which shows its popularity. The people can’t imagine a world without web because it influenced profoundly the daily process of people. HTTP and other protocols provide means for the data transfer in internet. Domain Name System, which uses central management of the domain name and resource mapping, helps to avoid IP conflicts. There are new trends in the web such as web2. Works Cited Tanenbaum, Andrew S. Protocols and Networks in the TCP/IP Model Initially. Computer Network. 2002. 07 Feb. 2009. . Tanenbaum, Andrew S. The Built in HTTP Request Methods. Computer Network. 2002. 07 Feb. 2009. . Fielding, R., et al. Network Working Group. 2009. 07 Feb. 2009. Read More