SNMP over OSI
How to carry SNMP over the OSI connectionless-mode transport service instead of UDP.
Rose, M., "SNMP over OSI", RFC 1418, DOI 10.17487/RFC1418, March 1993, <https://www.rfc-editor.org/info/rfc1418>.
@misc{rfc1418,
series = {Request for Comments},
number = 1418,
howpublished = {RFC 1418},
publisher = {RFC Editor},
doi = {10.17487/RFC1418},
url = {https://www.rfc-editor.org/info/rfc1418},
author = {M. Rose},
title = {{SNMP over OSI}},
pagetotal = 4,
year = 1993,
month = mar,
} RFC text
Contents
Network Working Group M. Rose
Request for Comments: 1418 Dover Beach Consulting, Inc.
Obsoletes: 1161, 1283 March 1993
SNMP over OSI
Status of this Memo
This RFC specifies an IAB standards track protocol for the Internet
community, and requests discussion and suggestions for improvements.
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. Background ................................................. 1
2. Mapping onto the CLTS ...................................... 2
2.1 Well-known Addresses ...................................... 2
2.2 Traps ..................................................... 2
2.3 Maximum Message Size ...................................... 3
3. Acknowledgements ........................................... 3
4. References ................................................. 3
5. Security Considerations .................................... 4
6. Author's Address ........................................... 4
1. Background
The Simple Network Management Protocol (SNMP) as defined in [1] is
now used as an integral part of the network management framework for
TCP/IP-based internets. Together with its companions standards,
which define the Structure of Management Information (SMI) [2,3], and
the Management Information Base (MIB) [4], the SNMP has received
widespread deployment in many operational networks running the
Internet suite of protocols.
It should not be surprising that many of these sites might acquire
OSI capabilities and may wish to leverage their investment in SNMP
technology towards managing those OSI components. This memo
addresses these concerns by defining a framework for running the SNMP
in an environment which supports the OSI connectionless-mode
transport service.
However, as noted in [5], the preferred mapping for SNMP is onto the
UDP [6]. This specification is intended for use in environments
where UDP transport is not available. No aspect of this
specification should be construed as a suggestion that, in a
heterogeneous transport environment, a managed agent should support
more than one mapping.
2. Mapping onto the CLTS
Mapping the SNMP onto the CLTS [7,8] is straight-forward. The
elements of procedure are identical to that of using the UDP. Note
that the CLTS and the service offered by the UDP both transmit
packets of information which contain full addressing information.
Thus, mapping the SNMP onto the CLTS, a "transport address" in the
context of [1], is simply a transport-selector and network address.
It should be noted that the mapping of SNMP onto a connectionless-
mode transport service is wholly consistent with SNMP's architectural
principles, as described in [1,5]. However, the CLTS itself can be
realized using either a connectionless-mode or a connection-oriented
network service. The mapping described in this mapping allows for
either realization. (When both network services are available, the
CLNS should be used as the basis of realization.)
2.1. Well-known Addresses
Unlike the Internet suite of protocols, OSI does not use well-known
ports. Rather,
demultiplexing occurs on the basis of "selectors", opaque strings of
octets which have local significance. In order to foster
interoperable implementations of the SNMP over the CLTS, it is
necessary define four selectors for this purpose.
When the CLTS is used to provide the transport backing for the SNMP,
and the CLTS uses a connectionless-mode network service, then
transport selector used shall be "snmp-l" which consists of six ASCII
characters; and, SNMP traps are, by convention, sent to an SNMP
manager listening on the transport selector "snmpt-l" which consists
of seven ASCII characters.
When the CLTS is used to provide the transport backing for the SNMP,
and the CLTS uses a connection-oriented network service, then
transport selector used shall be "snmp-o" which consists of six ASCII
characters; and, SNMP traps are, by convention, sent to an SNMP
manager listening on the transport selector "snmpt-o" which consists
of seven ASCII characters.
2.2. Traps
When SNMP traps are sent over the CLTS, the agent-addr field in the
Trap-PDU contains the IP-address "0.0.0.0" An SNMP manager may
ascertain the source of the trap based on information provided by the
transport service (i.e., from the T-UNIT-DATA.INDICATION primitive).
2.3. Maximum Message Size
An entity implementing SNMP over OSI must be prepared to accept
messages whose size is at least 484 octets. Implementation of larger
values is encouraged whenever possible.
3. Acknowledgements
This specification was derived from RFC 1283, based on discussions in
the IETF's "SNMP in a Multi-Protocol Internet" working group.
4. References
[1] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple
Network Management Protocol", STD 15, RFC 1157, SNMP Research,
Performance Systems International, Performance Systems
International, MIT Laboratory for Computer Science, May 1990.
[2] Rose M., and K. McCloghrie, "Structure and Identification of
Management Information for TCP/IP-based internets", STD 16, RFC
1155, Performance Systems International, Hughes LAN Systems, May
1990.
[3] Rose, M., and K. McCloghrie, Editors, "Concise MIB Definitions",
STD 16, RFC 1212, Performance Systems International, Hughes LAN
Systems, March 1991.
[4] Rose M., and K. McCloghrie, Editors, "Management Information Base
for Network Management of TCP/IP-based Internets", STD 17, RFC
1213, Hughes LAN Systems, Inc., Performance Systems
International, March 1991.
[5] Kastenholz, F., "SNMP Communications Services", RFC 1270,
Clearpoint Research Corporation, October 1991.
[6] Postel J., "User Datagram Protocol", STD 6, RFC 768,
USC/Information Sciences Institute, August 1980.
[7] Information processing systems - Open Systems Interconnection -
Transport Service Definition - Addendum 1: Connectionless-mode
Transmission, International Organization for Standardization.
International Standard 8072/AD 1, June 1986.
[8] Information processing systems - Open Systems Interconnection -
Protocol Specification for Providing the Connectionless-mode
Transport Service, International Organization for
Standardization. International Standard 8602, December 1987.
5. Security Considerations
Security issues are not discussed in this memo.
6. Author's Address
Marshall T. Rose
Dover Beach Consulting, Inc.
420 Whisman Court
Mountain View, CA 94043-2112
Phone: (415) 968-1052
EMail: mrose@dbc.mtview.ca.us
AI ELI5
On this page
§1Why SNMP Over OSI
The Simple Network Management Protocol (SNMP) is used as part of the network management framework for TCP/IP-based internets, alongside the Structure of Management Information (SMI) and the Management Information Base (MIB). Sites that acquire OSI capabilities may want to reuse that investment to manage OSI components.
This memo defines a framework for running SNMP over the OSI connectionless-mode transport service (CLTS). It is clear that UDP remains the preferred mapping for SNMP: the specification is meant for environments where UDP is not available. It also says a managed agent in a heterogeneous transport environment should not be taken to support more than one mapping.
SNMP normally travels on one kind of road. This memo builds a second road for places that use a different kind of network, but says the first road is still the better one.
§2Mapping Onto the CLTS
The mapping is described as straightforward: the elements of procedure are identical to using UDP. Both the CLTS and UDP send packets that carry full addressing information, so a "transport address" is simply a transport-selector plus a network address.
The CLTS itself can run over either a connectionless-mode or a connection-oriented network service, and the mapping allows both. When both are available, the connectionless network service (CLNS) should be used as the basis.
OSI has no well-known ports. Demultiplexing uses selectors, opaque strings of octets with local significance, so the memo defines four so that implementations interoperate.
Mail still needs a full address, so the rules stay the same as before. Only the street names are different.
§2.1Selectors, Traps and Message Size
Over a connectionless network service the transport selector is snmp-l, and traps go by convention to a manager listening on snmpt-l. Over a connection-oriented network service the selectors are snmp-o and snmpt-o. All are ASCII strings.
When traps are sent over the CLTS, the agent-addr field in the Trap-PDU contains the IP address 0.0.0.0, and the manager works out the source from information supplied by the transport service. An entity must be prepared to accept messages of at least 484 octets, and larger sizes are encouraged.
The Security Considerations section says only that security issues are not discussed in the memo.
Each kind of message gets a short name tag so the right program picks it up. Every receiver must be able to handle messages of a minimum size.
| Network service | SNMP selector | Trap selector |
|---|---|---|
| Connectionless-mode | snmp-l | snmpt-l |
| Connection-oriented | snmp-o | snmpt-o |