Network fundamentals

HTTP

• Stores and delivers Hyper Text Documents as requested by the client.
• It operates at application layer called Hyper Text Transfer Protocol.

Proxy Servers

• Acts as an intermediate between the LAN and the Internet.
• Web page information browsed by the cooperate user will be cached (copied) by proxy server. When the user browses the same page next time the proxy server serves these pages making the access time less and also reduces the Internet traffic.
• A proxy server can be configured to deny access of particular URL and also prohibit an user to access Internet.
• Supports transaction logging which helps to monitor user activities like URL accessed, dates, amount of bits download ete..
• It secures the hosts from accessing from Internet.
• All application such as web browsers are to be configured properly to work with the proxy server.

Mail Servers

• Mail server stores and delivers e-mail using SMTP,POP and IMAP Protocols.
• SMTP server sends mails only.
• POP servers stores and forward the e-mail to the host.
• IMAP allows the user to brows and files before download.
• Common mail servers are
  • Netscape messaging server - UNIX & Windows NT
  • Microsoft Exchange server - Only Windows NT

Mailing list Servers

• A standard SMTP server send copies of e-mails to all members included in the distribution list
• Another name of mailing list server - REFLECTOR.
• Autoresponder is not a mail server.
• The Interface used to manage the mailing list is called as Mail List Manager (MLM)

Media Server

• Offers a streaming audio and video over a network.

DNS Server

• Translates the domain address to IP address.
• DNS Servers contain the application supports this translation.

FTP Servers

• FTP servers allow user to transfer files in real time.
• Large files of the order of MB FTP is the option because it is faster than e-mail or HTTP.

News Servers

• News Servers use NNTP protocol to transfer news group postings.

Certificate Servers

• Generates and manage digital certificates by using Cryptography.

Directory Servers

• Allows a company to provide instantaneous worldwide access to employ-related database such as e-mail address.
• Uses LDAP (Lightweight Directory Access Protocol) to access the directory.
• The users e-mail program is configured to query the directory.

Catalog Servers