SNMP MUX protocol and MIB
RFC 1227
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RFC - Historic
(May 1991; No errata)
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Marshall Rose
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2020-07-29
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RFC 1227 (Historic)
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Network Working Group M. Rose
Request for Comments: 1227 Performance Systems International, Inc.
May 1991
SNMP MUX Protocol and MIB
Status of this Memo
This memo suggests a mechanism by which a user process may associate
itself with the local SNMP agent on a host, in order to implement
portions of the MIB. This mechanism would be local to the host.
This is an Experimental Protocol for the Internet community.
Discussion and suggestions for improvement are requested. Please
refer to the current edition of the "IAB Official Protocol Standards"
for the standardization state and status of this protocol.
Distribution of this memo is unlimited.
Table of Contents
1. Introduction .......................................... 1
2. Architecture .......................................... 2
3. Protocol .............................................. 3
3.1 Tricky Things ........................................ 3
3.1.1 Registration ....................................... 4
3.1.2 Removing Registration .............................. 4
3.1.3 Atomic Sets ........................................ 4
3.1.4 Variables in Requests .............................. 5
3.1.5 Request-ID ......................................... 5
3.1.6 The powerful get-next operator ..................... 5
3.2 Protocol Data Units .................................. 6
3.3 Mappings on Transport Service ........................ 8
3.3.1 Mapping onto the TCP ............................... 8
4. MIB for the SMUX ...................................... 9
5. Acknowledgements ...................................... 12
6. References ............................................ 12
7. Security Considerations................................ 13
8. Author's Address....................................... 13
1. Introduction
On typical kernel/user systems, an agent speaking the SNMP [1] is
often implemented as a user-process, that reads kernel variables in
order to realize the Internet-standard MIB [2]. This approach works
fine as long as all of the information needed by the SNMP agent
resides in either the kernel or in stable storage (i.e., files).
However, when other user-processes are employed to implement other
Rose [Page 1]
RFC 1227 SMUX May 1991
network services, such as routing protocols, communication between
the SNMP agent and other processes is problematic.
In order to solve this problem, a new protocol, the SNMP multiplexing
(SMUX) protocol is introduced. When a user-process, termed a SMUX
peer, wishes to export a MIB module, it initiates a SMUX association
to the local SNMP agent, registers itself, and (later) fields
management operations for objects in the MIB module.
Carrying this approach to its fullest, it is possible to generalize
the SNMP agent so that it knows about only the SNMP group of the
Internet-standard MIB. All other portions of the Internet-standard
MIB can be implemented by another process. This is quite useful, for
example, when a computer manufacturer wishes to provide SNMP access
for its operating system in binary form.
In addition to defining the SMUX protocol, this document defines a
MIB for the SMUX. Obviously, this MIB module must also be
implemented in the local SNMP agent.
2. Architecture
There are two approaches that can be taken when trying to integrate
arbitrary MIB modules with the SNMP agent: request-response and
cache-ahead.
The request-response model simply propagates the SNMP requests
received by the SNMP agent to the user process which exported the MIB
module. The SMUX peer then performs the operation and returns a
response. In turn, the SNMP agent propagates this response back to
the network management station. The request-response model is said
to be agent-driven since, after registration, the SNMP agent
initiates all transactions.
The cache-ahead model requires that the SMUX peer, after
registration, periodically updates the SNMP agent with the subtree
for the MIB module which has been registered. The SNMP agent, upon
receiving an SNMP request for information retrieval, locally performs
the operation, and returns a response to the network management
station. (SNMP set requests are given immediately to the SMUX peer.)
The cache-ahead model is said to be peer-driven since, after
registration, the SMUX peer initiates all transactions.
There are advantages and disadvantages to both approaches. As such,
the architecture envisioned supports both models in the following
fashion: the protocol between the SNMP agent and the SMUX peer is
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