The Defense Switched Network
    By: DataStorm <havok@tfs.net>

    This is an extremely shortened tutorial on the DSN.  More information
is available through the DoD themselves and various places on the Internet.  If
you have any comments or suggestions, feel free to e-mail me.


***THE BASICS OF THE DSN***


    Despite popular belief, the AUTOVON is gone, and a new DCS
communication standard is in place, the DSN, or Defense Switched Network.

    The DSN is used for the communication of data and voice between various
DoD installations in six world theaters: Canada, the Caribbean, the
Continental United States (CONUS), Europe, the Pacific and Alaska, and
Southwest Asia.  The DSN is used for everything from video-teleconferencing,
secure and insecure data and voice, and any other form of communication that
can be transmitted over wiring.  It is made up of the old AUTOVON system, the
European telephone system, the Japanese and Korean telephone upgrades, the
Oahu system, the DCTN, the DRSN, the Video Teleconferencing Network, and more.

    This makes the DSN incredibly large, which in turn makes it very useful.
(See the section TRICKS in this article for more information.)

    The DSN is extremely isolated.  It is designed to function even when
outside communication lines have been destroyed and is not dependent on any
outside equipment.  It uses its own switching equipment, lines, phones, and
other components.  It has very little link to the outside world, since in a
bombing/war, civilian telephone may be destroyed.  This aspect, of course,
also means that all regulation of the DSN is done by the government itself.
When you enter the DSN network, you are messing with the big boys.
	
    To place a call to someone in the DSN, you must first dial the DSN access
number, which lets you into the network itself.  From there you can dial any
number within the DSN, as long as it is not restricted from your calling area
or hone. (Numbers both inside and outside the DSN can be restricted from calling
certain numbers). 

    If you are part of the DSN, you may periodically get a call from an
operator, wanting to connect you with another person in or out of the network.
To accept, you must tell her your name and local base telephone extension,
your precedence, and any other information the operator feels she must have
from you at that time. (I'm not sure of the operators abilities or
technologies. They may have ANI in all or some areas.)

    The DSN uses signaling techniques similar to Bell, with a few differences.
The dial tone is the same on both networks; the network is open and ready.
When you call or are being called, a DSN phone will ring just like a Bell
phone, with one difference.  If the phone rings at a fairly normal rate, the
call is of average precedence, or "Routine." If the ringing is fast, it is of
higher precedence and importance.  A busy signal indicates that the line is
either busy, or DSN equipment is busy.  Occasionally you may hear a tone
called the "preempt" tone, which indicates that your call was booted off
because one of higher precedence needed the line you were connected with.  If
you pick up the phone and hear an odd fluctuating tone, this means that a
conference call is being conducted and you are to be included.

    As on many other large networks, the DSN uses different user classes to
distinguish who is better than who, who gets precedence and more calls and who
does not.  The most powerful user class is the "Special C2" user.  This
fortunate military employee (or hacker?) has virtually unrestricted access to
the system.  The Special C2 user identifies himself as that through a
validation process.

    The next class of user is the regular "C2" user.  To qualify, you must
have the requirements for C2 communications, but do not have to meet the
requirements for the Special C2 user advantages.  (These are users who
coordinate military operations, forces, and important orders.)  The last type
of user is insensitively called the "Other User."  This user has no need for
Specail C2 or C2 communications, so he is not given them.  A good comparison
would be "root" for Special C2, "bin" for C2, and "guest" for other.

    The network is fairly secure and technologically advanced.  Secure voice
is encrypted with the STU-III.  This is the third generation in a line of
devices used to make encrypted voice, which is NOT considered data over the
DSN.  Networking through the DSN is done with regular IP version 4, unless
classified, in which case Secret IP Routing Network(SIPRNET) protocol is
used.  Teleconferencing can be set up by the installation operator, and video
teleconferencing is a common occurrence.

    The DSN is better than the old AUTOVON system in speed and quality, which
allows it to take more advantage of these technologies.  I'm sure that as we
progress into faster transmission rates and higher technology, we will begin
to see the DSN use more and more of what we see the good guys using on
television.

    Precedence on the DSN fits the standard NCS requirements, so I will not
talk about it in great detail in this article.  All I think I have to clear up
is that DSN phones do NOT use A, B, C, and D buttons as the phones in the
AUTOVON did for precedence.  Precedence is done completely with standard DTMF
for efficiency.

    A DSN telephone directory is not distributed to the outside, mainly
because of the cost and lack of interest.  However, I have listed the NPA's
for the different theaters.  Notice that the DSN only covers major ally areas.
You won't be able to connect to Russia with this system, sorry.  Keep in mind
that each base has their own operator, who for the intra-DSN circuit, is
reachable by dialing "0."  Here is a word of advice: there ARE people who sit
around all day and monitor these lines.  Further, you can be assured these are
specialized teams that work special projects at the echelons above reality.
This means that if you do something dumb on the DSN from a location they can
trace back to you, you WILL be imprisoned.

AREA		DSN NPA

Canada		312
CONUS		312
Caribbean	313
Europe		314
Pacific/Alaska	315/317
S.W. Asia	318

    The format for a DSN number is NPA-XXX-YYYY, where XXX is the installation
prefix (each installation has at least one of their own) and YYYY is the
unique number assigned to each internal pair, which eventually leads to a
phone.  I'm not even going to bother with a list of numbers; there are just
too many.  Check http://www.tfs.net/~havok (my home page) for the official DSN
directory and more information.

    DSN physical equipment is maintained and operated by a team of military
specialists designed specifically for this task, (you won't see many Bell
trucks around DSN areas).

    Through even my deepest research, I was unable to find any technical
specifications on the hardware of the actual switch, although I suppose they
run a commercial brand such as ESS 5.  My resources were obscure in this area,
to say the least.


***TRICKS***

    Just like any other system in existence, the DSN has security holes and
toys we all can have fun with.  Here are a few. (If you find any more, drop me
an e-mail.)

    * Operators are located on different pairs in each base; one can never
tell before dialing exactly who is behind the other line.  My best luck has
been with XXX-0110 and XXX-0000.

    * To get their number in the DSN directory, DoD installations write to:

        HQ DISA, Code D322
        11440 Isaac Newton Square
        Reston, VA 20190-5006

    * Another interesting address: It seems that

        GTE Government Systems Corporation
        Information Systems Division
        15000 Conference Center Drive
        Chantilly, VA 22021-3808

    has quite a bit of involvement with the DSN and its documentation projects.


***IN CONCLUSION***

    As the DSN grows, so does my fascination with the system.  Watch for more
articles about it.  I would like to say a BIG thanks to someone who wishes to
remain unknown, a special english teacher, and the DoD for making their
information easy to get a hold of.