RFC 98 (rfc98) - Page 3 of 10

Logger Protocol Proposal

RFC 98                  Logger Protcol Proposal                 Feb 1971


      3. The admission phase occurs after the user has successfully
         completed the login dialog. It consists of switching his
         network typewriter connections from the logger to an entity
         providing a command processor of some sort. In some hosts
         this switching may be totally conceptual; in others there
         may be a real internal switching between entities.


The Connection Phase

        The issues involved in specifying a  protocol  for  implementing
login  can  be  separatedintop  two  major  parts:  how to establish and
maintain the network connection between the typewriter and  the  logger,
and how to conduct a dialog after the connection is made. The first part
is called the Initial Connection Protocol by Harlem and Heafner  in  RFC
80.  It  in turn consists of two subparts: how to establish a connection
and how and when to destroy it.

        We endorse the proposal for establishing a  connection  made  in
RFC  80,  which  we  summarize briefly for convenience. It is a two-step
process utilizing the  NCP  control  messages  to  effect  a  connection
between  the logger and the console of a potential user. First, the user
causes the hosts NCP to send out  a  "request  for  connection"  control
message  destined  for the serving hosts loggers contact socket. The two
purposes of this message are to indicate to the logger  that  this  user
wishes  to initiate a login dialog and to communicate the identifiers of
the and send socket he wishes to operate for this  purpose.  The  logger
rejects  this request to free its contact socket. As the second step the
logger choses  two  sockets  to  connect  to  the  user's  sockets,  and
dispatches  connection  requests  for  these.  If  the  user accepts the
connection within a reasonable period, the connection phase is over, and
the  dialog  phase can begin. If the user does not respond, the requests
are aborted and the logger abandons this login attempt.

        There is another part to an NCP: when  and  how  to  disconnect.
There  are  two  basic  situations  when a logger should disconnect. The
first situation may arise of the serving host's volition. The logger may
decide  to abandon a login attempt or a logged-in user may decide to log
out. The second situation may be due to the  using  host's  volition  or
network  difficulties.  This  situation  occurs  when  the  serving host
receives a "close connection" control message  or  one  of  the  network
error  messages signifying that further transmission is impossible. This
may  happen  for  either  the  "read"   or   the   "write"   connection,
Disconnecting  involves both the deletion of the network connections and
the stoppage of any activity at the serving host related to  that  user.
If  the  login  is  in  progress, it should be abandoned. If the user is
already logged in, his process should be stopped, since he no longer has
control over what it is doing. This is not intended to restrict absentee