IMP(4)		    UNIX Programmer's Manual		   IMP(4)


NAME
     imp - 1822 network interface

SYNOPSIS
     /sys/conf/SYSTEM:
	  NIMP count	 # ARPAnet IMP 1822 interface

DESCRIPTION
     The imp interface, as described in BBN Report 1822, provides
     access to an intelligent message processor normally used
     when participating in the Department of Defense ARPA net-
     work.  The network interface communicates through a device
     controller, usually an ACC LH/DH or HDH or a DEC IMP-11A,
     with the IMP.  The interface is "reliable" and "flow-
     controlled" by the host-IMP protocol.

     To configure IMP support, at least one of acc(4), css(4) or
     hdh(4) must be included.  The count specifies the total
     number of IMP connections.  The network number on which the
     interface resides is specified at boot time using the SIOC-
     SIFADDR ioctl.  The host number is discovered through
     receipt of NOOP messages from the IMP.

     The network interface is always in one of four states: up,
     down, initializing, or going down.  When the system is
     booted, the interface is marked down.  If the hardware con-
     troller is successfully probed, the interface enters the
     initializing state and transmits three NOOP messages to the
     IMP.  It then waits for the IMP to respond with two or more
     NOOP messages in reply.  When it receives these messages it
     enters the up state.  The ``going down'' state is entered
     only when notified by the IMP of an impending shutdown.
     Packets may be sent through the interface only while it is
     in the up state.  Outgoing packets are dropped with the
     error ENETDOWN returned to the caller if the interface is in
     any other state.

DIAGNOSTICS
     imp%d: not configured.  A hardware interface could not be
     attached during autoconfiguration because too few IMP
     pseudo-devices were configured.

     imp%d: leader error.  The IMP reported an error in a leader
     (1822 message header).  This causes the interface to be
     reset and any packets queued up for transmission to be
     purged.

     imp%d: going down in 30 seconds.
     imp%d: going down for hardware PM.
     imp%d: going down for reload software.
     imp%d: going down for emergency reset.  The Network Control
     Center (NCC) is manipulating the IMP.  By convention these


Printed 11/26/99	 August 2, 1987                         1


IMP(4)		    UNIX Programmer's Manual		   IMP(4)


     messages are reported to all hosts on an IMP.

     imp?: host %x, lost %d rfnms.  The IMP had messages out-
     standing to the host listed, but no RFNM (Request for Next
     Message) messages were received from the IMP in 127 seconds.
     The software state for that host is reinitialized.

     imp%d: interface reset.  The host has received an interface
     reset message from the IMP.

     imp%d: address reset to x%x (%d/%d).  The host has received
     a NOOP message which caused it to reset its notion of its
     current address.  The Internet address is printed in hexade-
     cimal, with the host and IMP numbers following.  This indi-
     cates that the address originally set by ifconfig(8) was
     incorrect, that the IMP has undergone an identity crisis, or
     that communication between the IMP and the host is being
     garbled.

     imp%d: data error.  The IMP noted an error in data transmit-
     ted.  The host-IMP interface is reset and the host enters
     the init state (awaiting NOOP messages).

     imp%d: interface reset.  The reset process has been com-
     pleted.

     imp%d: marked down.  After receiving a "going down in 30
     seconds" message, and waiting 30 seconds, the host has
     marked the IMP unavailable.  Before packets may be sent to
     the IMP again, the IMP must notify the host, through a
     series of NOOP messages, that it is back up.

     imp%d: can't handle af%d.	The interface was handed a mes-
     sage with addresses formatting in an unsuitable address fam-
     ily; the packet was dropped.

SEE ALSO
     intro(4N), inet(4F), acc(4), css(4), hdh(4), implog(8),
     implogd(8)


Printed 11/26/99	 August 2, 1987                         2


 
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