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MAIL SERVER

A mail server is an application that permit you to send messages from an

user to any other user regardless of the net where the users are. The mailserver also is named MTA (mail transport agent), it transports the mail tothe MTA of destination using SMTP (Simple Message Trasfer Protocol).

Then MTA receives the mail and sends it to a mail deliver agent (MDA)which puts the e-mail in storage while the user accepts the mail.

POP3 is a mail local client to get emails stored in a remote server to ourserver.

IMAP is an access protocol to stored messages in a server. You canaccess to your mail with imap from a anywhere.

The message is genereted in the client side by the MUA application, theMUA sends the message to its local MTA, the local MTA searches itsregisters, if the destination is registered, it sends the message immediatelyto its MDA, which stores the message until the user access it using POP3or IMAP protocols. For this reason the mail server is named pop server orimap server, according the used protocol.

The mail server uses ldap for user authentication and stored informationin it, also implements ssl /tls for traffic encryption to provide secure pagesfor the users.

The server uses anti-spam system to detect and delete all the mails thatthe user doesn't want and also uses an anti-virus system to find badprograms.

Security

There aren`t any security server 100% secure one form to secure the netagainst electronic attacks from out is to separate the net of other netsand systems.The security servers have an adequate level of security to connect thenet with other nets. a solid secure server has a limited value if there areweak points in the net, for this reason it is necessary use security in all the

components of the net and to plan a security policy that takes intoaccount the risks of each component.

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The principal features for the mail server

1 set and apply the adequate level to guarantee email servers install afirewall to avoid access non authorized in the net use security protocol

ip version 6 to avoid the mail traffic don't connect the mail server toInternet if there is no a firewall configured

2 set and apply the authentication method pop3 standardauthentication service of users send authentication information to mailserver in plain text, so the password to connect the mail server and clientis encrypted, this avoids access denied.

WEB APLICATION

The users can access to a web application thanks to a web server onInternet. A web server is a software that reply web pages when an user isusing a browser. A user generate a request when the user clicks in a link

or write a URL in a browser.

Previously, users can not interact with information found by browsersbecause the pages were static or just simple documents in html. A staticweb page doesn't change when you request it , the web server sendsthe page to a web browser without editing allowed.

the building of html documents had change from the first wrote page inhtml stored in a folder in the web server to dynamic pages. the dynamicpages ere edited before submit the page to the client browser

How does a web application really work?

when a web browser receives a request to show a static web page, theserver only sends the page to the client browser . when a web browsersends a request looking for a dynamic web page to a server, the serverfind the page and send it to the application server which passes the

page to the browser changing it according to the user actions.

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How does the web application access the database?

An application server can not access the database because the formatdoesn't let decrypt data. the application server only can connect withthe database thanks to controller that work between the database. thissoftware works as an interpreter between application server anddatabase the controller sets connections with the database and builds aseries of registers.

This series of registers are sets of data extracted from a database , it isreturned to the application server , it uses the data to complete the

page an application server let to work with resources of the sever , likedatabase , for example , a dynamic page can indicate to applicationserver to extract data from a database and insert it in code html of thepage the instruction to extract data from a database is nameddatabase query, a query requires a search expressed in a databaselanguage called SQL (structured query language) the sql query is writtenin scrips or tags in the server that has the page.

We can use practically any database with web application as long asthe database controller is installed right in the server , if we want to

develop applications for Enterprise client ,we can use a databasebased on servers as SQL server, oracle or MYSQL.

if the database is located in a web server we must secure a connectionavailable and fast between systems for looking a web application runfast and efficiently advantages of web applications

You can access from anywhere, we only need connection and a webbrowser if you open source tools , you don't pay to use the operative

system Linux , Apache web server ,the php language or mysql databaseengine, it is not necessary to pay for tools used by users easyauthentication .just make changes to the server onlineit is an multi platform application ,so , the user can use the program usingwindows Macintosh or other system, the most necessary is a webbrowser.

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SNMP

Simple Network Management Protocol, developed in august of 1988 bycase, MCcloghric, rose and waldbusser, as a solution to the problem ofcommunication of different networks. It gives the capacity to audit andcommunicate status communication among huge verify of hosts. It isuseful on large networks and where demands the vitality of the network.SNMP is as protocol of application layer that belongs to the TCP/IP familyand it serves for managing of data, Its based on packages, UDP, itmeans, its connectionless defining a server-client connection betweenthe networks manager (client) and the managed elements (servers,

active devices) called agents.

SNMP COMPONENTS:

Agents: Called the clients It means, are the equipments or devices,that make part of the network and when are monitored (Work station,routers, switches).

NMS: Network Management Station, Its the device where its located

the monitoring software, meaning the Server that allows us themonitoring of the network and where stores all collected information.

MIB`s: Management Information Base, Its the logical database that theNMS and networks device (Agents), keep, where we found theinformation of the components of each of these devices. This databasehierarchy structured and contains the OID (Object Identify)

There are 2 MIB versions, which are:

MIB1: Contains 8 levels that correspond to 8 different types of objectsand can be detailed on network:

System (Operating system Information, this level is optional)Interfaces (Show as the devices are connected to network, this level isobligatory when the SNMP version2 is used; and its optional on version3)Address Translation (Maps the networks address to the physicaladdresses)

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Internet Protocol (IP) (Packages controller, obligatory)Internet Control Message Protocol (ICMP), (Types of used massage,obligatory)Transport Control Protocol (TCP), (Open connections, obligatory on TCPconnections)

User Datagram Protocol (UDP), (Closed connections, obligatory on UDPconnections)

Exterior Gateway Protocol (EGP), (Used to exchange routing informationamong autonomal systems)

MIB2: Contains the same 8 before levels (ENHANCED): but with 3 newlevels which are: TRANSMITION, SNMP, CMOT.

The rules describe the MIB objects are implement by SMI that uses theASN.1, It is the descriptive language, the objects, description are

composed by the next components: description of the objects, syntax,definition, status.The SNMP uses two types of massages, the pooling whose objective isasking and answering , this effect to performance of the networks and itworks by the 161 port and the method of interruption (Traps) This onlyhandles the message of error or the network alarms , it works on 162 port.