NETWORK APPLICATION

Network Application

·         DNS – Domain Name Server

DNS be created to will overcome name conflict host that often will happen when name host will along with address ip- will not be regulated according to centralization. problem DNS is nomenclature pattern invention based on domain has hierarchy and database system invention that distributing for this nomenclature pattern implementation.

Use DNS implementation :

·         Application program calls literature procedure that called resolver, devolve name as the parameter.

·         Resolver send package UDP to server DNS local

·         DNS local then searching name and return IP to resolver

·         Resolver return IP to caller

Two kinds domain high level :

1.    Generic domain is com( commercial ), org( nirlaba organization ), edu( education institution ), mil( AS armed forces ), gov( government ).

2.    Country domain  covers one entry to every country. every domain given name based on track to on aim root.

·         Electronic Mail

email system there are two sub system: user agent and message user agent.

User agent is give permission somebody reads and send email. Message user agent is move message from source to aim

§  Five functions base email :

1.    Composition

2.    Transfer

3.    Reporting

4.    Show

5.    Disposition

§  Problem email delivery :

Ø  Message that use language with certain access

Ø  Message with alphabet not roman script

Ø  Message with language without alphabet

Ø  Message not text

Pop3 is simple protocol that used to take email from letter remote box, and has command for user can do to log-in, take message,  and delete message.

·         World Wide Web

WWW is architecture to enter documents mutual connected widespread at thousands engine in all internet.

from client side, web consists of document collection widespread throughout world, usually called page.

From server side, every site has server process that watch connection enter from client in TCP port 80. After connection appointed, client sending the request and server sending the answer (reply).

For example :

http://www.arvands.blogspot.com/networkconcept.html

1.    http is protocol name

2.    www.arvands.blogspot.com is DNS host name

3.    networkaconcept.html is file name

Not all servers understand http. Old server use FTP, Gopher, or other protocol. And solution for this problem, use proxy server. Proxy server is a kind of gateway that talk with gateway by using http, but use ftp, gopher,  or another protocol with server.