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DDN - The Defense Data Network

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                  DDN - The Defense Data Network

    The Department of Defense started the major networking scene in the US in
    the late '70s and early 80s.  Their first baby was ARPANET (Advanced
    Research Projects Agency NETwork).  It was just a development system to see
    how feasible a national computer network would be and to help facillitate
    information transfer between defense researchers (and some university
    projects).  The world of InterNET has grown up around that existing
    foundation to become one of the most (THE most?) used network in the world
    as researchers in other nations found they also needed access to
    counterparts around the nation to exchange knowledge and ideas.  Well to end
    this simple history I will get back to the DDN and its workings (what little
    I do really know of them) and it structure.

    The DoD  (Dept of Defense) has been maintaining its own separate networks
    ever since ARPANET became a success and was "gobbled up" by the growing
    InterNET structure.  The DoD wanted to be able to secure its important work
    and research and to do so it needed to be isolated from the existing
    infrastructure.  They decided that a somewhat free flow of information would
    be necessary between constituents and that some kind of framework similar to
    Internet would be beneficial but that access to their systems would have to
    be limited by means more secure than anything available on the public
    Internet system.  They developed MILNET for this specific purpose (to carry
    unclassified data traffic between defense contractors and researchers).

    Beyond MILNET there were also been establish three other military nets under
    the auspices of the Defense Secure NETwork (DSNET).  The three were DSNET1
    for Secret data, DSNET2 for Top Secret data, and DSNET3 for special Top
    Secret data (probably weapons systems and plans, and ELINT/SIGINT systems --
    but that is only a guess).  These three each had a separate communications
    hub including local and widearea nets.  The 3 DSNETS have been combined (are
    being combined) in a unified DISNET (Defense Integrated Security NETwork).

    The Defense Communication Agency (DCA) was put in charge of maintaining the
    backbones of the defense networks (except ARPANET which is primarily used by
    the R&D community and is maintained by DARPA and is not really associated
    with DDN) as part of the Defense Communication System (DCS).  All DDN Nets
    are not part (officially) of InterNET because of the security risks

    The restructuring of DDN into DISNET is a continually evolving project
    (especially in the area of Defense Messaging System - which I know little
    about at this time and WOULD LIKE TO SEE MORE INFO about if anyone knows
    about it ), but I will explain its structure as presently laid out...

    "(1) Security architecture should include a well-defined set of network
    security services offered to subscribers"
         1.Mandatory Confidentiality - protects classified data using DDN
                                       rule based security
         2.Discretionary Confid. - identity based (Need-to-Know) security
         3.Traffic Flow Confid. - protects against disclosure by observing
            \                     characteristics of data flow
              \_____See the encrypthion and communities descriptions below for
                    more on this.

    DATA INTEGRITY - protects against (OR ATLEAST TRYS TO DETECT) unauthorized
                     changes of data

         1.Identification- standard name for each system entity (just like
                           every net.
         2.Authentication- ensures that a stated identity is correct (HOW???)
         3.Access Control- limits system resources to a correctly identified

    "(2) Subscribers should not pay for or be hampered by unneedded security"
      ^\______ Interesting...who does pay for un-needed security then?!?

    ""(4) Subscribers should share responsibility for security where appro-
       priate"  <----<<<< COULD THIS BE A MAJOR DOWNFALL?? Hmm...
         * - As for I,A, and AC(above) These services are subscriber respons-
             ibility except for major communities and subcommunities.

                        STRUCTURE OF THE DDN :
    The primary elements are computers called switches which communicate
    via inter-switch trunks.(DCA owns the switches and leases most trunks)

    Each subscriber connects to DDN as a HOST or a TERMINAL.  DDN serves hosts
    at the OSI (Open Systems Interconnect) network level; the Host - Switch
    interface is the standard X.25 (CCITT). Many of the hosts are gateways to
    other nets (mainly LANs) and the number of gateways is increasing.

    Special Hosts:
         Montitor Centers (MC) : they manage the switches, trunks, and other
                   special hosts.
         Name Server hosts - they translate the addresses of the other hosts

         Terminal Access Controllers (TACs) - more limited DDN service. Instead
                   of a direct Host-to-Switch connection you can connect to a
                   TAC (via dial-up) and be addressed as a terminal by DDN
                   through TAC. TAC uses TELNET protocol so terminal can
                   communicate with a second DDN Host as if directly connected.

         TAC Access Control Systems (TACACS) - prompt user to login at a TAC

    Priority Access:
    All DDN switches can handle data packets according to 4 level hierarchy
    system.  precedence lavels are assigned to hosts and terminals by the Joint
    Chiefs of Staff.  To my knowledge this hasn't been implemented yet.

    Host to Host Encryption:
    DISNET uses a end-to-end encryption system (E3) called BLACKER. These are
    installed on each host-to-switch path of all hosts including TACs .  These
    BLACKER front end devices (BFEs) encrypt all data packets but leave the X.25
    header unencrypted for the backbone to use.  The BLACKER system includes a
    Key Distribut-ion Center (KDC) and Access Control Center (ACC) hosts.
    BLACKER is a Class A1 System (under the Trusted Computer System Evaluation
    Criteria / "Orange Book"), and it will be able to prevent a community MC
    from communicating with other MCs in other communities; this will not happen
    for a while and the MC sites will still have a terminal through a TAC
    directly to a switch without going through BFE.

    Bridges between Nets:
    The plan calls for limited gateways between MILNET and DISNET to allow
    unclassified data traffic (in the form of store-and-forward electronic mail
    in both directions).  Data entering DISNET from MILNET will be identified as
    such by the bridge.
    The DDN plans forbid a subscriber from connecting to both MILNET and DISNET
    and also forbids DoD system to connect both to a DDN segment and to a
    segment that does not conform to DDN security structure.

    Other Stuff:
    To insure that every subscriber system can exercise discretionary access
    control over its resources through DDN, and of DDN resources via the
    subscriber system, DDN requires that all subscribers be TCSEC Class C2
    secure.  By september '92 any non-complying system will need OSD and JCS
    waivers or DCA can remove them from the Net.

    DDN plans to segregate subscribers according to whether or not they meet the
    TCSEC C2 requirement.  Conforming systems comprise a Trusted Subcommunity
    within each security level.  Within this subcommunity hosts can freely
    communicate.  NonConforming systems with waivers will form Closed
    Communities within each  level.  Direct net communications between
    subcommunities will be prevented by switching logic in MILNET and by BLACKER
    in DISNET except over trusted bridges.

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