<sect1 id="configurations-ppp-intro">

    <title>Introduction</title>

    <para>

        This chapter describes how to configure &TC;; to provide some

        Internet services through the telephone line. In this chapter,

        the computer holding the Internet services is named the

        <quote>server</quote> and the computer that want to make use

        of such services is named the <quote>client</quote>. We assume

        that both server and client computers have been installed with

        &TC;; (release 5.5).

    </para>

    <para>

        In this configuration, both client and server computers use

        modems to transmit data in form of sound through the telephone

        lines system. The dial-up connection described in this chapter

        could be a choise when the only communication medium you have

        access to is the telephone lines system.

    </para>

    <para>

        This configuration emerged from the need of sharing

        information with my friends in a country where Internet access

        is limitted to statal organizations and controlled there with

        an increasing crazy obsession. However, in this environment,

        the telephone lines system provides an alternative platform to

        interchange information in a point-to-point fashion. It can be

        used to create small social groups and organize ideas safetly

        (e.g., by using TLS to encrypt connections). To be more

        specific, the goal would be to provide public access to an

        Internet Service Provider (ISP) where people can express

        themselves freely (e.g., through a mailing list with open

        subscriptions).

    </para>

    <para>

        Even this configuration tries to reduce the lack of

        communication, there are limitations around it that we cannot

        take away, yet. The following list shows what these

        limitations are:

    </para>

    <itemizedlist>

    <listitem>

    <para>

        Only one connection (of 15 minutes) is possible at a time.

    </para>

    </listitem>

    <listitem>

    <para>

        More than 3 consecutive connections from the same phone number

        in a time range of 60 minutes means that that number is

        attacking the ISP to provoke a <quote>Denying of Service

        (DoS)</quote> attach. In such cases the phone number

        originating the call will be permantly banished from

        realizing further calls to the ISP.  Fourtunly, such controls

        can be automated so I hope they achieve an acceptable degree

        of efficiency.

    </para>

    </listitem>

    <listitem>

    <para>

        The ISP is isolated from Internet, so it is not possible to

        provide Internet access through the ISP.

    </para>

    </listitem>

    <listitem>

    <para>

        The information generated inside the ISP is jailed to it. This

        way, it will be available to people registered inside the ISP

        only (e.g., through the web internface).

    </para>

    </listitem>

    <listitem>

    <para>

        The implementation of services that required persistent

        connections (e.g., <application>chats</application>) will not

        be considered as a practical offer.  Instead, only

        asynchronous services (e.g.,

        <application>e-mail</application>) will be supported. This

        restriction is required to reduce the connection effective

        times. For example, consider an environment where you connect

        the ISP to send/receive e-mails only and then disconnect.  In

        fact, to force this behaivour the ISP will be configured to

        close connections after 15 minutes passed the connection

        establishment.  

    </para>

    </listitem>

    <listitem>

    <para>

        Your user profile will be removed from ISP when no effective

        point-to-point connection is established by you in a period of

        7 days since the last effective point-to-point connection you

        established to the ISP. When your user profile is removed, you

        will need to register yourself again inside the ISP, to access

        its services.

    </para>

    </listitem>

    </itemizedlist>

    <para>

        I'm very sorry about these limitations, but this is the best I

        can offer with one PC, one modem, and one single telephone

        line. If you think this configuration can be improved somehow,

        please send me an e-mail to <email>al@example.com</email>.

        Notice that, for any mail to reach me, you should be

        registered inside the ISP first; I don't answer phone calls

        personally, the phone is very busy answering point-to-point

        connections ;).

    </para>

    <para>

        In order for you to share information with others, it is

        required that both you and the person you want to share

        information with, have an e-mail address registered inside

        ISP. This registration process is realized through a secured

        web interface accessable through an encrypted connection as

        the following url illustrates:

    </para>

    <itemizedlist>

    <listitem>

    <para>

        <ulink url="https://example.com/users?action=register" />

    </para>

    </listitem>

    </itemizedlist>

    <para>

        The web interface should permit everyone to update or delete

        their personal profiles without compromising personal

        information. Notice that all actions realized through this web

        interface must be simple enough to be achieved in less than 15

        minutes (the time the point-to-point connection reamins active

        from its first establishment on).

    </para>

    <para>

        User information is stored inside an LDAP server. The web

        application manipulates LDAP records and all related files

        inside the operating system that make possible a user to

        establish a poit-to-point connection to the ISP, as well as

        register, update or delate its profile inside the ISP. Care

        should be taken to prevent one user to modify/delete profiles

        from other users. The user's profile administration is

        individual to each user based on its identity. Notice that,

        all related subsystems (e.g., Postix, Cyrus-Imapd and

        Saslauthd) must use the user information from LDAP server.

        Likewise, the mailbox administration must be automated based

        on the users in the LDAP server. The web application must be

        able to be aware of all files related inside the

        infrastructure in a way that administration tasks can be

        automated and presented friendly to end users (this will

        required the web application to run some program that needs

        root privileges =:-|). The whole proces would be, establish a

        point-to-point connection to the ISP, register a new user

        through the web application and start using the e-mail client

        with your new address. The LDAP server will be available for

        everyone to consult from their mail clients. Inside the web

        application, verifications must be included to avoid

        duplicated values, invalid characters and similar stuff.

    </para>

    <para>

        In case some kind of force intend to confiscate me the

        computer where the ISP is installed in, I am plaing to encrypt

        the whole filesystem in a way that it would be very difficult

        to get any valid data from it. The encryption feature is

        applied before the operating system starts. In this

        configuration a password is required to decrypt the operating

        system filesystem in order to be able of booting up the

        operating system as expected. If the password is not provided,

        the only thing you get is a prompt to enter a password :).

    </para>

    <para>

        Another important matter to be aware of is about the ISP's

        policy.  In order to keep freedom, it is required to define

        the boundaries of that freedom so you can determine and judge

        it.  Absolute freedom (anarchism) will not be permitted (it

        would end up in total destruction) and communism will be

        avoided (it would suppress the natural freedom of human

        beings). So a middle point will be used. For example, if you

        think you have the freedom to abuse the ISP I provide (e.g.,

        by spamming it, or by provoking denying of service attaks) you

        probably have it, but consider that I am free to banish you

        immediatly for trying to destroy my work. On the other hand,

        if you show yourself to be an educated person with solid ideas

        and reasons to share, you'll be totaly welcome to stay. The

        general idea behind this work is improving Cuban communication

        to make ourselves better persons, understand our nature and

        environment either social, economical or polital. 

    </para>

</sect1>