RFC 1592 (rfc1592) - Page 3 of 54

Simple Network Management Protocol Distributed Protocol Interface Version 2

RFC 1592                        SNMP-DPI                      March 1994


   since 1989 and is included in the SNMP agents for VM, MVS and OS/2.
   Version 1.2 of this protocol has been in use within BNR since 1992.

1.1  MOTIVATION

   The Simple Network Management Protocol [1] defines a protocol that
   permits operations on a collection of variables.  This set of
   variables is called the Management Information Base (MIB) and a core
   set of variables has previously been defined [4, 5]; however, the
   design of the MIB makes provision for extension of this core set.
   Thus, an enterprise or individual can define variables of their own
   which represent information of use to them.  An example of a
   potentially interesting variable which is not in the core MIB would
   be CPU utilization (percent busy).  Unfortunately, conventional SNMP
   agent implementations provide no means for an end-user to make
   available new variables.

   Besides this, today there are many MIBs that people want to implement
   on a system.  Without a capability for sub-agents, this requires all
   the MIBs to be implemented in one big monolithic agent, which is in
   many cases undesirable.

   The SNMP DPI addresses these issues by providing a light-weight
   mechanism by which a process can register the existence of a MIB
   variable or a MIB sub-tree with the SNMP agent.  Requests for the
   variable(s) that are received by the SNMP agent are passed to the
   process acting as a sub-agent.  The sub-agent then returns an
   appropriate answer to the SNMP agent.  The SNMP agent eventually
   packages an SNMP response packet and sends the answer back to the
   remote network management station that initiated the request.

   Remote network management stations have no knowledge that the SNMP
   agent calls on other processes to obtain an answer.  As far as they
   can tell, there is only one network management application (agent)
   running on the host.

   At the San Diego IETF (March 1992) a BOF was held on multiplexing
   SNMP agent's requirements.  Both the SMUX [6] and DPI [7] protocols
   were discussed, as well as other unpublished approaches.  There was
   also discussion regarding a need for a standard for multiplexing SNMP
   agents or sub-agent support.  At the end of the BOF, however, there
   was not enough support for defining a standard.  This was due, at
   least partially, to a few well known SNMP authors who stated that the
   proxy and party support for SNMPv2 (SMP at the time) would solve the
   problem.






Wijnen, Carpenter, Curran, Sehgal & Waters