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      |d|i|g|i|t|a|l|                   INTEROFFICE MEMORANDUM

      TO: DECnet SWSkit                 DATE: 1-APR-82
                                        FROM: NCSS
                                        EXT: HOTLINE (8-231-5911)
                                        LOC/MAIL STOP: MR1-2/H22

      SUBJ:  Self-Study Program for Learning DECnet

      This memo attempts to describe a scheme  for  learning  DECnet  if
      you've had no experience with networks before.

      The best way, and the quickest, to pick up DECnet is to attend the
      courses  offered  by  Educational  Services.   There  are  several
      appropriate courses offered.  If you do  end  up  in  Bedford  for
      training,  try  to  setup  a  visit with NCSS for a couple of days
      afterwards.  We can get to know each other and you can see what we

      Unfortunately, we know that many times specialists don't get  sent
      to  courses  in  a timely way and it becomes necessary for them to
      pick things up on their own.  If this happens, the general outline
      given  below  may be of help.  Feel free to adapt this to your own
      particular needs.

      This memo makes many references to documents.  For  more  detailed
      information      including     order     numbers,     refer     to
      DECNET-DOCUMENTATION.MEM elsewhere on this SWSkit.


      First  get  an  idea  of  what  DECnet  is  all   about   from   a
      product/program point of view.  The following materials might be a

      1.  Introduction to Minicomputer Networks (a Digital handbook)

      2.  Introduction to DECnet self-paced course

      3.  DECnet Marketing Guide
                                                                  Page 2

      4.  Any available Customer Support Plans and Network Profiles  for
          sites in your district


      This part of the learning process will help you a lot in  presales
      situations.   Find the appropriate SPDs for the current release of
      DECnet and learn them!  In addition, take a look  at  the  current
      DECnet-20  Programmer's  Guide  and Operations Manual -- this will
      tell you what programs and features are available  and  supported.
      A  look  through this SWSkit may give you an idea of what kinds of
      applications can be written, but remember  that  any  programs  on
      this SWSkit are not supported.


      For this step it will be almost essential  to  have  access  to  a
      DECnet-20  system  to  experiment with.  Read the DECnet-20 manual
      and try experimenting with the information given.  Learn what  can
      be  done  with  NFT/FAL.  A very important part of this step is to
      write a simple DECnet application program.  This may be as  simple
      or  as  complex  as  you  desire;   the purpose is simply to get a
      handle on the JSYS's which are used to implement DECnet programs.

      One simple example of what can be done is a program which opens  a
      link  as  a server and then waits for input.  When text is sent to
      it over a logical link it  types  it  on  the  terminal.   Such  a
      program can be easily tested, because the EXEC COPY command can be
      used to send text to the program, and the  accuracy  of  the  data
      transfer  can  be  quickly determined.  In addition, if the server
      program is written first and the EXEC is used to communicate  with
      it,  you  have  only  one  program to write and debug at any given
      time.  Once your server program is written you can  write  another
      application  which  might  communicate  with  the server in a more
      elaborate fashion.


      You don't have to double as a field  service  person,  but  it  is
      useful  to  know  about  the  modem  signals  involved  in  DECnet
      communications and to have a fairly good  idea  of  how  the  line
      drivers  work.  A very good reference for this is McNamara's book,
      Technical  Aspects  of  Data  Communications.   This   should   be
      available  through the Digital Press.  Don't worry about trying to
      understand all the electronics details in this book,  but  try  to
      get  a handle on what the various modem signals, like DTR and DSR,
      are used for.  At this point it's also a good idea to take a  look
      at   the   PDP11  Terminals  and  Communications  Handbook.   This
                                                                  Page 3

      describes all the line drivers used by DECnet  (plus  many  others
      not  used  by  DECnet).   A very good course to take at this point
      would be the Communications Interfaces and Modems Workshop.


      Unfortunately, this is probably the step most specialists will end
      up  doing  first,  whether  they're prepared or not.  Try to get a
      handle on the "big picture" that each step is a  part  of,  rather
      than  just  following  the  steps  by  rote.   An  installation is
      probably your best chance  to  learn  the  operator  commands  for
      DECnet, which are provided by the NCP subset of OPR.


      If you've managed to get this far  through  the  learning  process
      without  losing interest or running out of time, it's time to take
      a serious look at the protocol specifications.  The  protocols  of
      greatest  interest  are  DDCMP, NSP, DAP, and MOP.  Specifications
      are  available  from  the  SDC.   Once  you  think  you  have   an
      understanding  of the specs, it can be instructive to try to write
      down, on paper, what a particular DDCMP or NSP message  will  look
      like.   Then  verify  your prediction with a Datascope, if you can
      get one.  DNSR can be used to dump NSP  messages  passing  between
      the DN20 and the KL for learning purposes.

      The reason the protocols have been ignored until this point in the
      learning  process  is  because the protocol details can get in the
      way of learning more useful things.  Most of the questions we have
      seen  from  the  Hotline  have been basic questions about what the
      product can do.  It is our feeling that, once the  product  is  in
      the  field,  most  of  our  problems  will  come with installation
      procedures or questions about the basic functions provided.  It is
      not  necessary  or  even  desirable  to  get  deeply involved with
      protocol details until these other things are understood.

      7.0  LEARN THE CODE

      This is strictly optional for field specialists.  The sources  are
      either  supplied on the release tape, or listings are available on
      the DECnet SWSkit.  It would probably be easier to start with  the
      -10  code  --  NSPSRV,  NSPPAR, NSPINT and KDPSRV monitor modules,
      NETCON   sources,    and    network    file    transfer    sources

      Before attempting to tackle the MCB code, it  might  be  advisable
      for the specialist to learn something about -11M, since the DECnet
      front end is based on a system similar to  RSX11M.   If  possible,
      find  an  -11M system and play with it as a user, and learn enough
                                                                  Page 4

      of -11M macro and the task builder and utilities to write a simple
      assembly language program.  The -11M support course offered by Ed.
      Services would be a good choice here, if you can get to it.   Then
      you  could tackle the MCB listings supplied on the SWSkit, placing
      emphasis on the NETACP code, the NSP modules  and  the  Comm  Exec
      subroutines.  The file


      If you plan to repeat this whole process for  future  releases  of
      DECnet,  it  would  be  advisable  for you to become familiar with
      BLISS while DECnet release 2 is in the field.  Future releases  of
      the DECnet code will use BLISS extensively.