Absolute SLIP, PPP, DIP newbie needs serious HELP!

Absolute SLIP, PPP, DIP newbie needs serious HELP!

Post by Colin Fah » Fri, 17 Mar 1995 10:37:57



============================================================================

Hello,

  Let me begin by telling you what my objective is, and perhaps a few
solutions will come to mind:

        I am running a version of X-Windows on a Pentium PC with the
        Slackware distribution of Linux.  This PC has an internal 28800
        baud modem.

        I have a DEC 5000/240 workstation running Ultrix (very much like
        Berkeley UNIX), and it has a 28800 baud modem connected to it.
        This workstation is also connected to the INTERNET.

        I want to be able to dial up the workstation from the PC, and
        do the following:

                [1] Run Mosaic (or Netscape) on the PC and browse the
                        INTERNET just as I can when I am using the
                        workstation's console.
                [2] Open "xterm" windows on the PC, and have each window
                        actually be running shells on the workstation,
                        and thus give me a kind of remote console to
                        the workstation.
                [3] Do FTP and have files appear on the PC's local disk.

  I have read numerous articles posted to this newsgroup, and I have a vague
understanding of what is required.  But I would like a comprehensive
introduction, in the form of a step-by-step guide, to the mechanisms required
to achieve the goals I have listed.  I don't want to buy a book on the
subject, partly because books are inevitably a little behind the times in
this area.  I think the solution to my problem will be of wide interest,
and may merit a kind of FAQ posting in this group.

  Just to get the ball rolling, let me give you a snapshot of my current
understanding:

        [a] Ethernet is nothing more than a high-speed serial line on
            which specially structured data packets (group of bytes)
            are transmitted and received.

        [b] By using special hardware (an Ethernet board) and software
            (various drivers, etc), Linux can have an Ethernet connection
            to other PC's running Linux, and also the INTERNET.

        [c] A modem or direct RS-232 connection to a PC's serial port
            is another way the PC can send and recieve serial data.

        [d] In principle it is possible to use the PC's serial port
            in place of the Ethernet card as a way of transmitting
            and receiving serial data between machines in a
            "client"-"server" relationship.  So, anything that can
            be done with an Ethernet connection under Linux, could,
            in principle, be done with a modem or direct RS-232 connection,
            provided that the PC running Linux connects to a system
            that can act as a "server" to feed the PC the right kind
            of data.

        [e] Just as there is an Ethernet "protocol" defining the byte
            structure of the serial data packets sent on Ethernet cables,
            there are recently defined protocols for modem and RS-232 lines:
                PPP ("Point-To-Point Protocol"),
                SLIP ("Serial Line Interface Protocol"),
                CSLIP ("?????? Serial Line Interface Protocol").

Now my understanding of the situation grows even weaker, and so the following
is even more speculative [which is precisely what I want filled in and
corrected].  I know I am wrong when I write the following, but I am writing
it to draw feedback:

        [f] When connecting two or more computers using a PPP or SLIP
            method over a modem (or direct RS-232) it is necessary to
            have special software running on each of the computers
            involved.

            One part of the software required are executable programs:
            [1] a PPP or SLIP "server" daemon (like "pppd" or "slipd")
                that is constantly running in the background after
                bootup -- always ready to handle future PPP or SLIP
                connections.
            [2] a PPP or SLIP "client" program that is called by the
                system after connecting to a machine running the
                "server" program.  One of these "client" programs is
                called "slattach" ("SLIP attach").

            The other part of the software required for SLIP and PPP
            operation is a modification to the __operating_system__
            itself!!  This means that part of the "kernel" (the source
            code for the actual operating system, often written in C code)
            must be modified, and the system program must be re-compiled,
            and the system rebooted.  The kernel modification usually
            takes the form of a few pages of C code, and this code is
            often included among the various optional files distributed
            with your system's original source code (for example, the
            "Slackware" distribution of Linux).  Also, you may need to
            put some "include" and "library" files on the harddrive
            to before re-compiling the system (because such files define
            macro's, constants, and functions or function prototypes
            necessary for compiling the new PPP or SLIP system kernel
            modifications).

            There is a way to check if your operating system has SLIP
            or PPP capability in its kernel through "ifconfig" (a program).

        [g]  A typical SLIP session might transpire as follows:

                [0] There is a workstation or PC that is equiped
                    with a system that has the SLIP or PPP kernel
                    functions, and is running the corresponding
                    daemon ("slipd" or "pppd") in the background.
                    This workstation or PC also has a modem or
                    direct RS-232 line.

                [1] A person approaches a PC running Linux and some
                    form of X-Windows (the X-Windows part is not
                    really necessary, but I want to assume in the
                    following that it is running).  This person
                    has a modem (or RS-232 line), and somehow gains
                    a connection to the "server" (either by dialing
                    a telephone number with the modem, or just having
                    a direct physical RS-232 connection to the "server").

                [2] Once the person establishes the connection to the
                    "server", he can execute a "client" program to
                    get the SLIP or PPP operation going -- perhaps
                    by explicitly typing "slattach" (or whatever)
                    at a "sh"/"csh"/"tcsh" shell prompt.

                [3] Now (and this is the fuzziest part of my guesses
                    so far) the person's PC behaves just as if it
                    were on the Ethernet.  If a program like "Mosaic"
                    is executed on the PC, it can access the INTERNET
                    through the host "server", provided that the host
                    machine is connected to the INTERNET.

-----------------------------------------------------------------------------

Okay, almost everything I have written is speculative because it is difficult
to find an easy-to-understand description on the whole SLIP/PPP thing.
Most of the people posting to this newsgroup seem to know all about SLIP and
PPP, and their questions involve performance issues or freak problems;
but I am totally fresh to this game, and I need massive help.

I am willing to re-write my little outline above to help future SLIP/PPP
newbies, and so I would be grateful for any contributions you can make
concerning each of my many vague impressions.  Again, it can be turned in
to an evolving FAQ.

People sometimes refer to NET2-HOWTO as a source of information.  I thought
I was reading that file one day, but I was either reading something else or
I was completely bewildered.  In any case, I would like to know where copies
of this file can be found.

 
 
 

Absolute SLIP, PPP, DIP newbie needs serious HELP!

Post by Jesse Dougher » Tue, 21 Mar 1995 08:45:40


Every question you have can be answered by reading the Linux Network
Adminin Guide.  You can buy it or ftp it from
ftp.cdrom.com://pub/linux/sunsite/docs
probably in the LDP dir

Please before posting an essay on what you don't know, maybe rtfm.

 
 
 

1. linux newbie needs help with dip and dynamic slip

Hmm...

This might sound awfully stupid but as a linux newbie I think this newsgroup
is a good way to ask questions about linux and stuff. :)

I have a dynamic slip acct and a Linux Slackware, but after days reading the HOWTO I still
can't figure out these problems below:

I tried to use dip but the modem doesn't connect. It doesn't even make a sound.
If you have a dip configuration for dynamic slip, could you send me the file,
please? :)

Also, how to test the slip connection once I get connected? I tried to email myself from elm
but it bounced back to me with some error messages. Do I have to setup something for this email thing
so it can go outside my computer? And same thing goes with ftp and telnet; I can't connect to
outside world.

Thanks for the info. :)

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