OS/2 Shareware BBS: 35 Internet/35-Internet.zip/fsp2-10a.zip/info

Text File | 1993-04-22 | 6KB | 124 lines

                         Interested party please email
                           [e-mail]
    What is the purpose of FSP (V2.7):

    FSP is a set of programs that implements a public-access archive
    similar to an anonymous-FTP archive.  It is not meant to be a
    replacement for ftp; it is only meant to do what anonymous-ftp
    does, but in a manner more acceptible to the provider of the
    service and more friendly to the clients.

    Providing anonymous-FTP service can be costly --- each active
    session consumes one process slot in the OS and one stream socket
    entry in the network sub-system.  The servers can also run
    concurrently, adding to the system load.  A popular archive site
    can easily be overwhelmed as a result.  Some were forced to
    shutdown and some impose inconvenient access restrictions.

    Unlike FTP, FSP is connection-less and virtually state-less.  One
    server handles requests from all clients machines.  Each active
    client machine takes up 16-bytes in a dynamically extensible
    table.  Since only one server exists on a server machine at any
    time, the load added to the server machine is no more than one.

    In exchange for allowing site operators to keep their sites open
    and do away with cumbersome access restrictions, this is what the
    clients accept with FSP:

     1) Lower transfer rate.  The maximum rate is 1 kbyte per UDP
        message round-trip time between the client and the server.

    In addition to the potential for more abundant sites and more
    accessible sites, this is what the clients gain with FSP:

     1) Robustness.  Since FSP is connectionless, flucturations in
        the network will not abort a FSP transaction.  Furthermore,
        the 16-bytes of data for each client can be regenerated at
        any point during any transaction.  Thus, if the server goes
        down at any point during a transaction, the transaction will
        resume when the server is restarted.  (like NFS)

     2) Friendlier user interface.  FSP does not have its own command
        interpretor like FTP.  Since it is connectionless, there is
        no reason to carry much information from one command to the
        next, and the commands can all be made into individual unix
        programs.  For instance, there is one program you run to list
        the directory and another you run to download a file.

     3) Client protection.  FSP oversees a directory structure similar
        to that of an anonymous-FTP.  However, a directory created
        via FSP transaction is owned by the client machine that issued
        the creation request.  The client can create and delete files
        and subdirectories in that directory.  In addition, the client
        can enable any of the four attributes for that directory:

        A) Give all other clients the permission to create files.

        B) Give all other clients the permission to delete files
           or subdirectories.

        C) Give all other clients the permission to read files.
           (this is true by default)

        D) Give all other clients the permission to create sub-
           directories.

        Note: A subdirectory can be deleted if it is empty and the
          client owns the subdirectory.

     4) Server protection.  FSP server does not spawn sub-programs.
        It will accept only paths that are downward relative to its
        designated working directory.  On systems with symbolic links,
        the server will follow symbolic links, but it does not follow
        uplinks ("..").  Clients cannot create symbolic links and
        care should be taken so that other users on the server machine
        cannot create symbolic links in the server's work space.

        It is also fairly difficult to formuate an attack to force a
        shutdown of a FSP site by actions of a rogue site.  About the
        only way to distrupt a FSP service is to flood the FSP site
        with network packets.  FSP server prevents itself from
        'counter-flooding' by filtering for legitimate requests using
        the following method:

        A) Each request message contains a key.  For each client,
           server database contains the keys to be used for the
           next client request and for the previous client request.

        B) If the next request does not contain a key that matches
           either of the two keys, it is accepted only if at least
           one minute has elapsed since the last time a request
           is accepted.  If the key does match the old key
           (retransmit by client) it is accepted if the elapse time
           is greater than 3 seconds.

        C) Every request message accepted is acknowledged with
           one reply message.  The reply message contains a new
           key to used for the next request.  The new key is
           computed by the server with a pseudo-random number
           generator.

        Flooding is a blatant violation of network etiquette because
        a site can be subjected to flooding attack whether it has FSP
        running or not, and flooding congests every link and gateway
        between the rogue client and the server.  As a further measure
        of protection, the server loads a table of rogue clients on
        startup.  The server will not respond to requests from any of
        those clients.

    ***********************************************************************

    This is a free software.  Be creative; make your own macros and tools
    and let me know of any bugs and suggestions.

    A mailing list for the discussion of the FSP software is now available
    (started Oct 2, 1992.)  To get on the list, send an email stating
    that you want to be on the FSP list to the following address:

        [e-mail]

    Articles to be distributed to the subscribers should be sent to the
    following email address:

        [e-mail]