( 1 ) Mail Servers

 

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There are a number of servers performing different roles on the Internet. ( 1 ) MAIL SERVERS • Are servers that transmit transmit the E-mail sent from the the mailer (mail software) Installed in the user’s machine to the mail server of the destination. • Mail servers controls the e-mail in accordance with with the following two protocols: SMTP (Simple Mail Transfer Protocol) POP3 (Post Office Protocol Version 3)

Mail delivery program

SMTP Transfer to other mail server

Mail delivery program memory

memory

Some mail Servers are Divided into SMTP and POP server

POP 3 Delivery the mail to client client

( 2 ) WWW Server

( 3 ) PROXY Server

• Are also called HTTP (Hy (Hyper per Text Text Transfer Protocol) servers or Web Servers. • These consist of programs used to transfer hyperlinked text, video, audio, etc. (also called hypertext information) and HTML (Hyper Text Text Markup Langu age files.

• is a server that allows lows access to the in nternet ternet for computers that are forbidden to access the interne t directly. • Also has the functionality to temporarily store (caching) accessed information, designated to reduce the traffic load a nd faster access. servers

HTML file transfer program

HTTP

client

PROXY servers

firewall

internet router

HTML file transfer HTML file transfer (hypertext information)

Direct access To the internet Is forbidden. (In place of the Client, the proxy Server access the Internet.

router

clients

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( 5 ) News Server

( 4 ) ftp (File Transfer Protocol) Server

• Also called NNTP (Network (Network News Transfer Transfer Protocol) servers, transfer news from other news servers and control the readout of news and news contribution from users.

• Deli Deliver ver files, files, etc., to the user over the Inter Internet. net.

program

program

client FTP server, transfers Programs and other files.

terminal

Network transfer program

contribution

tansfer NTTP

Network transfer program

tansfer internet

NTTP Readout News file

News file

( 6 ) Name Server • Also called DNS (D (Domain omain Name System) servers, that can answer domain name inquiries from users with IP address. • This function is one of those that have facilitated use of the Internet. • To ensure high reliability, name servers usually have the following owing redundant configuration. a . P ririm ar ary Na Na m me e Se err ve ve r b. Sec Second ondar ary y Name Name Ser Server ver -

A se err v ve e r th a att ha ha s t he he m ma an na ag ge em me en ntt rights for a specialized zone. Se Serv rver er that that hol holds ds the the iinf nfor ormat matio ion n of the primary server.

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