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Network Working Group                                           M. RoseRequest for Comments: 1283                 Dover Beach Consulting, Inc.Obsoletes: RFC1161                                       December 1991SNMP over OSIStatus of this Memo   This memo defines 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 Contents1. Background ............................................11.1 A Digression on User Interfaces ......................21.1.1 Addressing Conventions for UDP-based service .......31.2 A Digression of Layering .............................32. Mapping onto CLTS .....................................32.1 Addressing Conventions ...............................42.1.1 Conventions for CLNP-based service .................43. Mapping onto COTS .....................................43.1 Addressing Conventions ...............................53.1.1 Conventions for TP4/CLNP-based service .............53.1.2 Conventions for TP0/X.25-based service .............64. Trap PDU ..............................................65. Acknowledgements ......................................76. References ............................................77. Security Considerations................................88. Author's Address.......................................81.  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], and   the Management Information Base (MIB) [3], 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 SNMPRose                                                            [Page 1]

RFC 1283                     SNMP over OSI                 December 1991   in an environment which supports the OSI transport services.   In OSI, there are two such services, a connection-oriented transport   services (COTS) as defined in [4], and a connectionless-mode   transport service (CLTS) as defined in [5].  Although the primary   deployment of the SNMP is over the connectionless-mode transport   service provided by the Internet suite of protocols (i.e., the User   Datagram Protocol or UDP [6]), a design goal of the SNMP was to be   able to use either a CO-mode or CL-mode transport service.  As such,   this memo describes mappings from the SNMP onto both the COTS and the   CLTS.1.1.  A Digression on User Interfaces   It is likely that user-interfaces to the SNMP will be developed that   support multiple transport backings.  In an environment such as this,   it is often important to maintain a consistent addressing scheme for   users.  Since the mappings described in this memo are onto the OSI   transport services, use of the textual scheme described in [7], which   describes a string encoding for OSI presentation addresses, is   recommended.  The syntax defined in [7] is equally applicable towards   transport addresses.   In this context, a string encoding usually appears as:      [<t-selector>/]<n-provider><n-address>[+<n-info>]      where:      (1)  <t-selector> is usually either an ASCII string enclosed           in double-quotes (e.g., "snmp"), or a hexadecimal number           (e.g., '736e6d70'H);      (2)  <n-provider> is one of several well-known providers of a           connectivity-service, one of: "Internet=" for a           transport-service from the Internet suite of protocols,           "Int-X25=" for the 1980 CCITT X.25 recommendation, or           "NS+" for the OSI network service;      (3)  <n-address> is an address in a format specific to the           <n-provider>; and,      (4)  <n-info> is any additional addressing information in a           format specific to the <n-provider>.   It is not the purpose of this memo to provide an exhaustive   description of string encodings such as these.  Readers should   consult [7] for detailed information on the syntax.  However, thisRose                                                            [Page 2]

RFC 1283                     SNMP over OSI                 December 1991   memo recommends that, as an implementation option, user-interfaces to   the SNMP that support multiple transport backings SHOULD implement   this syntax.1.1.1.  Addressing Conventions for UDP-based service   In the context of a UDP-based transport backing, addresses would be   encoded as:                           Internet=<host>+161+2   which says that the transport service is from the Internet suite of   protocols, residing at <host>, on port 161, using the UDP (2).  The   token <host> may be either a domain name or a dotted-quad, e.g., both                     Internet=cheetah.nyser.net+161+2   and                        Internet=192.52.180.1+161+2   are both valid.  Note however that if domain name "cheetah.nyser.net"   maps to multiple IP addresses, then this implies multiple transport   addresses.  The number of addresses examined by the application (and   the order of examination) are specific to each application.   Of course, this memo does not require that other interface schemes   not be used.  Clearly, use of a simple hostname is preferable to the   string encoding above.  However, for the sake of uniformity, for   those user-interfaces to the SNMP that support multiple transport   backings, it is strongly RECOMMENDED that the syntax in [7] be   adopted and even the mapping for UDP-based transport be valid.1.2.  A Digression of Layering   Although other frameworks view network management as an application,   extensive experience with the SNMP suggests otherwise.  In essense,   network management is a function unlike any other user of a transport   service.  The citation [8] develops this argument in full.  As such,   it is inappropriate to map the SNMP onto the OSI application layer.   Rather, it is mapped to OSI transport services, in order to build on   the proven success of the Internet network management framework.2.  Mapping onto CLTS   Mapping the SNMP onto the CLTS is straight-forward.  The elements of   procedure are identical to that of using the UDP, with one exception:   a slightly different Trap PDU is used.  Further, note that the CLTSRose                                                            [Page 3]

RFC 1283                     SNMP over OSI                 December 1991   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.2.1.  Addressing Conventions   Unlike the Internet suite of protocols, OSI does not use well-known   ports.  Rather demultiplexing occurs on the basis of "selectors",   which are opaque strings of octets, which have meaning only at the   destination.  In order to foster interoperable implementations of the   SNMP over the CLTS, it is necessary define a selector for this   purpose.2.1.1.  Conventions for CLNP-based service   When the CLTS is used to provide the transport backing for the SNMP,   demultiplexing will occur on the basis of transport selector.  The   transport selector used shall be the four ASCII characters                                   snmp   Thus, using the string encoding of [7], such addresses may be   textual, described as:                             "snmp"/NS+<nsap>   where:   (1)  <nsap> is a hex string defining the nsap, e.g.,                     "snmp"/NS+4900590800200038bafe00   Similarly, SNMP traps are, by convention, sent to a manager listening   on the transport selector                                 snmp-trap   which consists of nine ASCII characters.3.  Mapping onto COTS   Mapping the SNMP onto the COTS is more difficult as the SNMP does not   specifically require an existing connection.  Thus, the mapping   consists of establishing a transport connection, sending one or more   SNMP messages on that connection, and then releasing the transport   connection.  Further, a slightly different Trap PDU is used.Rose                                                            [Page 4]

RFC 1283                     SNMP over OSI                 December 1991   Consistent with the SNMP model, the initiator of a connection should   not require that responses to a request be returned on that   connection.  However, if a responder to a connection sends SNMP   messages on a connection, then these MUST be in response to requests   received on that connection.   Ideally, the transport connection SHOULD be released by the   initiator, however, note that the responder may release the   connection due to resource limitations.  Further note, that the   amount of time a connection remains established is implementation-   specific.  Implementors should take care to choose an appropriate   dynamic algorithm.   Also consistent with the SNMP model, the initiator should not   associate any reliability characteristics with the use of a   connection.  Issues such as retransmission of SNMP messages, etc.,   always remain with the SNMP application, not with the transport   service.3.1.  Addressing Conventions   Unlike the Internet suite of protocols, OSI does not use well-known   ports.  Rather demultiplexing occurs on the basis of "selectors",   which are opaque strings of octets, which have meaning only at the   destination.  In order to foster interoperable implementations of the   SNMP over the COTS, it is necessary define a selector for this   purpose.  However, to be consistent with the various connectivity-   services, different conventions, based on the actual underlying   service, will be used.3.1.1.  Conventions for TP4/CLNP-based service   When a COTS based on the TP4/CLNP is used to provide the transport   backing for the SNMP, demultiplexing will occur on the basis of   transport selector.  The transport selector used shall be the four   ASCII characters                                   snmp   Thus, using the string encoding of [7], such addresses may be   textual, described as:                             "snmp"/NS+<nsap>   where:   (1)  <nsap> is a hex string defining the nsap, e.g.,                     "snmp"/NS+4900590800200038bafe00Rose                                                            [Page 5]

RFC 1283                     SNMP over OSI                 December 1991   Similarly, SNMP traps are, by convention, sent to a manager listening   on the transport selector                                 snmp-trap   which consists of nine ASCII characters.3.1.2.  Conventions for TP0/X.25-based service   When a COTS based on the TP0/X.25 is used to provide the transport   backing for the SNMP, demultiplexing will occur on the basis of X.25   protocol-ID.  The protocol-ID used shall be the four octets                                 03018200   This is the X.25 protocol-ID assigned for local management purposes.   Thus, using the string encoding of [7], such addresses may be textual   described as:                        Int-X25=<dte>+PID+03018200   where:   (1)  <dte> is the X.121 DTE, e.g.,                    Int-X25=23421920030013+PID+03018200   Similarly, SNMP traps are, by convention, sent to a manager listening   on the protocol-ID                                 03019000   This is an X.25 protocol-ID assigned for local purposes.4. Trap PDU   The Trap-PDU defined in [1] is designed to represent traps generated   on IP networks.  As such, a slightly different PDU must be used when   representing traps generated on OSI networks.RFC1283 DEFINTIONS ::= BEGIN   IMPORTS        TimeTicks            FROMRFC1155-SMI  -- [2] --        VarBindList            FROMRFC1157-SNMP -- [1] --        ClnpAddressRose                                                            [Page 6]

RFC 1283                     SNMP over OSI                 December 1991            FROM CLNS-MIB     -- [9] --;   Trap-PDU ::=        [4]            IMPLICT SEQUENCE {                enterprise              -- type of object generating                    OBJECT IDENTIFIER,  -- trap, see sysObjectID                agent-addr              -- address of object generating                    ClnpAddress,        -- trap                generic-trap            -- generic trap type                    INTEGER {                        coldStart(0),                        warmStart(1),                        linkDown(2),                        linkUp(3),                        authenticationFailure(4),                        egpNeighborLoss(5),                        enterpriseSpecific(6)                    },                specific-trap           -- specific code, present even                    INTEGER,            -- if generic-trap is not                                        -- enterpriseSpecific                time-stamp              -- time elapsed between the last                    TimeTicks,          -- (re)initialization of the                                        -- network entity and the                                        -- generation of the trap                variable-bindings       -- "interesting" information                    VarBindList        }   END5.  Acknowledgements   The predecessor of this document (RFC 1161) was produced by the SNMP   Working Group, and subsequently modified by the editor to reflect   operational experience gained since the original publication.6.  References   [1] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "A Simple       Network Management Protocol (SNMP)",RFC 1157, SNMP Research,       Performance Systems International, Performance SystemsRose                                                            [Page 7]

RFC 1283                     SNMP over OSI                 December 1991       International, and MIT Laboratory for Computer Science, May 1990.   [2] Rose M., and K. McCloghrie, "Structure and Identification of       Management Information for TCP/IP-based internets",RFC 1155,       Performance Systems International, Hughes LAN Systems, May 1990.   [3] McCloghrie K., and M. Rose, Editors, "Management Information Base       for Network Management of TCP/IP-based internets",RFC 1213,       Hughes LAN Systems, Performance Systems International, March       1991.   [4] Information Processing Systems - Open Systems Interconnection,       "Transport Service Definition", International Organization for       Standardization, International Standard 8072, June 1986.   [5] Information Processing Systems - Open Systems Interconnection,       "Transport Service Definition - Addendum 1: Connectionless-mode       Transmission", International Organization for Standardization,       International Standard 8072/AD 1, December 1986.   [6] Postel, J., "User Datagram Protocol",RFC 768, USC/Information       Sciences Institute, November 1980.   [7] Kille, S., "A String Encoding of Presentation Address",RFC 1278,       Department of Computer Science, University College London,       November 1991.   [8] Case, J., Davin, J., Fedor, M., and M. Schoffstall, "Network       Management and the Design of SNMP", ConneXions (ISSN 0894-5926),       Volume 3, Number 3, March 1989.   [9] Satz, G., "CLNS MIB for use with CLNP and ES-IS",RFC 1238, cisco       Systems, June 1991.7.  Security Considerations   Security issues are not discussed in this memo.8.  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   X.500: mrose, dbc, usRose                                                            [Page 8]