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COMPUTER NETWORKS UNIT 5
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- 2. ARCHITECTURE The WWW todayis a distributed client/server service, in which a client using a browser can access a service using a server. However, the service provided is distributed over many locations called sites. Client (Browser) Server Uniform Resource Locator Cookies Topics discussed in this section:
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- 5. WEB DOCUMENTS: The documentsin the WWW can be grouped into three broad categories: static, dynamic, and active. The category is based on the time at which the contents of the document are determined. Static Documents Dynamic Documents Active Documents Topics discussed in this section:
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- 11. Dynamic document usingserver-site script
- 12. Dynamic documents aresometimes referred to as server-site dynamic documents. SERVER-SITE DYNAMIC:
- 13. Active document usingJava applet
- 14. Active document usingclient-site script
- 15. Active documents aresometimes referred to as client-site dynamic documents. CLIENT-SITE DYNAMIC:
- 16. HTTP: The Hypertext TransferProtocol (HTTP) is a protocol used mainly to access data on the World Wide Web. HTTP functions as a combination of FTP and SMTP. HTTP Transaction Persistent Versus Nonpersistent Connection Topics discussed in this section:
- 17. HTTP uses theservices of TCP on well- known port 80.
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- 19. Request and responsemessages
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- 32. DOMAIN NAME SPACE Tohave a hierarchical name space, a domain name space was designed. In this design the names are defined in an inverted-tree structure with the root at the top. The tree can have only 128 levels: level 0 (root) to level 127. Label Domain Name Domain Topics discussed in this section:
- 33. Example of usingthe DNS service
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- 35. Domain names andlabels
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- 38. DISTRIBUTION OF NAMESPACE The information contained in the domain name space must be stored. However, it is very inefficient and also unreliable to have just one computer store such a huge amount of information. In this section, we discuss the distribution of the domain name space. Hierarchy of Name Servers Zone Root Server Primary and Secondary Servers Topics discussed in this section:
- 39. Hierarchy of nameservers
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- 41. A primary serverloads all information from the disk file; the secondary server loads all information from the primary server. When the secondary downloads information from the primary, it is called zone transfer.
- 42. DNS IN THEINTERNET DNS is a protocol that can be used in different platforms. In the Internet, the domain name space (tree) is divided into three different sections: generic domains, country domains, and the inverse domain. Generic Domains Country Domains Inverse Domain Topics discussed in this section:
- 43. DNS IN THEINTERNET
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- 48. RESOLUTION Mapping a nameto an address or an address to a name is called name-address resolution. Resolver Mapping Names to Addresses Mapping Addresses to Names Recursive Resolution Caching Topics discussed in this section:
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- 51. DNS MESSAGES DNS hastwo types of messages: query and response. Both types have the same format. The query message consists of a header and question records; the response message consists of a header, question records, answer records, authoritative records, and additional records. Header Topics discussed in this section:
- 52. Query and responsemessages
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