Network Working Group
Request for Comments: 1316
B. Stewart, Editor
Xyplex, Inc.
April 1992

Definitions of Managed Objects

for Character Stream Devices

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.

1. Abstract

This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in TCP/IP based internets. In particular it defines objects for the management of character stream devices.

2. The Network Management Framework

The Internet-standard Network Management Framework consists of three components. They are:

RFC 1155 which defines the SMI, the mechanisms used for describing and naming objects for the purpose of management. RFC 1212 defines a more concise description mechanism, which is wholly consistent with the SMI.

RFC 1156 which defines MIB-I, the core set of managed objects for the Internet suite of protocols. RFC 1213, defines MIB-II, an evolution of MIB-I based on implementation experience and new operational requirements.

RFC 1157 which defines the SNMP, the protocol used for network access to managed objects.

The Framework permits new objects to be defined for the purpose of experimentation and evaluation.

3. Objects

Managed objects are accessed via a virtual information store, termed the Management Information Base or MIB. Objects in the MIB are defined using the subset of Abstract Syntax Notation One (ASN.1) [7] defined in the SMI. In particular, each object has a name, a syntax, and an encoding. The name is an object identifier, an administratively assigned name, which specifies an object type.

The object type together with an object instance serves to uniquely identify a specific instantiation of the object. For human convenience, we often use a textual string, termed the OBJECT DESCRIPTOR, to also refer to the object type.

The syntax of an object type defines the abstract data structure corresponding to that object type. The ASN.1 language is used for this purpose. However, the SMI [3] purposely restricts the ASN.1 constructs which may be used. These restrictions are explicitly made for simplicity.

The encoding of an object type is simply how that object type is represented using the object type's syntax. Implicitly tied to the notion of an object type's syntax and encoding is how the object type is represented when being transmitted on the network.

The SMI specifies the use of the basic encoding rules of ASN.1 [8], subject to the additional requirements imposed by the SNMP.

3.1. Format of Definitions

Section 5 contains the specification of all object types contained in this MIB module. The object types are defined using the conventions defined in the SMI, as amended by the extensions specified in [9,10].

4. Overview

The Character MIB applies to interface ports that carry a character stream, whether physical or virtual, serial or parallel, synchronous or asynchronous. The most common example of a character port is a hardware terminal port with an RS-232 interface. Another common hardware example is a parallel printer port, say with a Centronics interface. The concept also includes virtual terminal ports, such as a software connection point for a remote console.

The Character MIB is one of a set of MIBs designed for complementary use. At this writing, the set comprises:

        Character MIB
        PPP MIB
        RS-232-like MIB
        Parallel-printer-like MIB

The RS-232-like MIB and the Parallel-printer-like MIB represent the physical layer, providing service to higher layers such as the Character MIB or PPP MIB. Further MIBs may appear above these.

The following diagram shows two possible "MIB stacks", each using the RS-232-like MIB.

                                               .-----------------.
                    .-----------------.        |  Standard MIB   |
                    |   Telnet MIB    |        | Interface Group |
                    |-----------------|        |-----------------|
                    |  Character MIB  |        |     PPP MIB     |
                    |-----------------|        |-----------------|
                    | RS-232-like MIB |        | RS-232-like MIB |
                    `-----------------'        `-----------------'

The intent of the model is for the physical-level MIBs to represent the lowest level, regardless of the higher level that may be using it. In turn, separate higher level MIBs represent specific applications, such as a terminal (the Character MIB) or a network connection (the PPP MIB).

For the most part, character ports are distinct from network interfaces (which are already covered by the Interface group). In general, they are attachment points for non-network devices. The exception is a character port that can support a network protocol, such as SLIP or PPP. This implies the existence of a corresponding entry in the Interfaces table, with ifOperStatus of 'off' while the port is not running a network protocol and 'on' if it is. The intent is that such usage is exclusive of non-network character stream usage. That is, while switched to network use, charPortOperStatus would be 'down' and Character MIB operational values such as charPortInFlowState and charPortInCharacters would be inactive.

The Character MIB is mandatory for all systems that offer character ports. This includes, for example, terminal servers, general-purpose time-sharing hosts, and even such systems as a bridge with a (virtual) console port. It may or may not include character ports that do not support network sessions, depending on the system's needs.

The Character MIB's central abstraction is a port. Physical ports have a one-to-one correspondence with hardware ports. Virtual ports are software entities analogous to physical ports, but with no hardware connector.

Each port supports one or more sessions. A session represents a virtual connection that carries characters between the port and some partner. Sessions typically operate over a stack of network protocols. A typical session, for example, uses Telnet over TCP.

The MIB comprises one base object and two tables, detailed in the following sections. The tables contain objects for ports and sessions.

The MIB intentionally contains no distinction between what is often called permanent and operational or volatile data bases. For the purposes of this MIB, handling of such distinctions is implementation specific.

5. Definitions

RFC1316-MIB DEFINITIONS ::= BEGIN

IMPORTS

                            Counter, TimeTicks, Gauge
                                    FROM RFC1155-SMI
                            DisplayString
                                    FROM RFC1213-MIB
                            OBJECT-TYPE
                                    FROM RFC-1212;

-- this is the MIB module for character stream devices

char OBJECT IDENTIFIER ::= { mib-2 19 }

            -- Textual Conventions

AutonomousType ::= OBJECT IDENTIFIER

-- The object identifier is an independently extensible type -- identification value. It may, for example indicate a -- particular sub-tree with further MIB definitions, or -- define something like a protocol type or type of -- hardware.

InstancePointer ::= OBJECT IDENTIFIER

-- The object identifier is a pointer to a specific instance -- of a MIB object in this agent's implemented MIB. By -- convention, it is the first object in the conceptual row -- for the instance.

            -- the generic Character group

-- Implementation of this group is mandatory for all -- systems that offer character ports

charNumber OBJECT-TYPE

                SYNTAX INTEGER
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The number of entries in charPortTable, regardless
                    of their current state."
                ::= { char 1 }
            
            -- the Character Port table

charPortTable OBJECT-TYPE

                SYNTAX SEQUENCE OF CharPortEntry
                ACCESS not-accessible
                STATUS mandatory
                DESCRIPTION
                    "A list of port entries.  The number of entries is
                    given by the value of charNumber."
                ::= { char 2 }

charPortEntry OBJECT-TYPE

                SYNTAX CharPortEntry
                ACCESS not-accessible
                STATUS mandatory
                DESCRIPTION
                    "Status and parameter values for a character port."
                INDEX { charPortIndex }
                ::= { charPortTable 1 }

CharPortEntry ::=

SEQUENCE {

                    charPortIndex
                        INTEGER,
                    charPortName
                        DisplayString,
                    charPortType
                        INTEGER,
                    charPortHardware
                        AutonomousType,
                    charPortReset
                        INTEGER,
                    charPortAdminStatus
                        INTEGER,
                    charPortOperStatus
                        INTEGER,
                    charPortLastChange
                        TimeTicks,
                    charPortInFlowType
                        INTEGER,
                    charPortOutFlowType
                        INTEGER,
                    charPortInFlowState
                        INTEGER,
                    charPortOutFlowState
                        INTEGER,
                    charPortInCharacters
                        Counter,
                    charPortOutCharacters
                        Counter,
                    charPortAdminOrigin
                        INTEGER,
                    charPortSessionMaximum
                        INTEGER,
                    charPortSessionNumber
                        Gauge,
                    charPortSessionIndex
                        INTEGER
                }

charPortIndex OBJECT-TYPE

                SYNTAX INTEGER
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "A unique value for each character port.  Its value
                    ranges between 1 and the value of charNumber.  By
                    convention and if possible, hardware port numbers
                    come first, with a simple, direct mapping.  The
                    value for each port must remain constant at least
                    from one re-initialization of the network management
                    agent to the next."
                ::= { charPortEntry 1 }

charPortName OBJECT-TYPE

                SYNTAX DisplayString (SIZE (0..32))
                ACCESS read-write
                STATUS mandatory
                DESCRIPTION
                    "An administratively assigned name for the port,
                    typically with some local significance."
                
                ::= { charPortEntry 2 }

charPortType OBJECT-TYPE

                SYNTAX INTEGER { physical(1), virtual(2) }
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The port's type, 'physical' if the port represents
                    an external hardware connector, 'virtual' if it does
                    not."
                ::= { charPortEntry 3 }

charPortHardware OBJECT-TYPE

SYNTAX AutonomousType
ACCESS read-only
STATUS mandatory
DESCRIPTION

"A reference to hardware MIB definitions specific to a physical port's external connector. For example, if the connector is RS-232, then the value of this object refers to a MIB sub-tree defining objects specific to RS-232. If an agent is not configured to have such values, the agent returns the object identifier:

                        nullHardware OBJECT IDENTIFIER ::= { 0 0 }
                    "
                ::= { charPortEntry 4 }

charPortReset OBJECT-TYPE

                SYNTAX INTEGER { ready(1), execute(2) }
                ACCESS read-write
                STATUS mandatory
                DESCRIPTION
                    "A control to force the port into a clean, initial
                    state, both hardware and software, disconnecting all
                    the port's existing sessions.  In response to a
                    get-request or get-next-request, the agent always
                    returns 'ready' as the value.  Setting the value to
                    'execute' causes a reset."
                ::= { charPortEntry 5 }

charPortAdminStatus OBJECT-TYPE

                SYNTAX INTEGER { enabled(1), disabled(2), off(3),
                                 maintenance(4) }
                ACCESS read-write
                STATUS mandatory
                DESCRIPTION
                    "The port's desired state, independent of flow
                    control.  'enabled' indicates that the port is
                    allowed to pass characters and form new sessions.
                    'disabled' indicates that the port is allowed to
                    pass characters but not form new sessions.  'off'
                    indicates that the port is not allowed to pass
                    characters or have any sessions. 'maintenance'
                    indicates a maintenance mode, exclusive of normal
                    operation, such as running a test."
                ::= { charPortEntry 6 }

charPortOperStatus OBJECT-TYPE

                SYNTAX INTEGER { up(1), down(2),
                                 maintenance(3), absent(4), active(5) }
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The port's actual, operational state, independent
                    of flow control.  'up' indicates able to function
                    normally.  'down' indicates inability to function
                    for administrative or operational reasons.
                    'maintenance' indicates a maintenance mode,
                    exclusive of normal operation, such as running a
                    test.  'absent' indicates that port hardware is not
                    present.  'active' indicates up with a user present
                    (e.g. logged in)."
                ::= { charPortEntry 7 }

charPortLastChange OBJECT-TYPE

                SYNTAX TimeTicks
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The value of sysUpTime at the time the port entered
                    its current operational state.  If the current state
                    was entered prior to the last reinitialization of
                    the local network management subsystem, then this
                    object contains a zero value."
                ::= { charPortEntry 8 }

charPortInFlowType OBJECT-TYPE

                SYNTAX INTEGER { none(1), xonXoff(2), hardware(3),
                                 ctsRts(4), dsrDtr(5) }
                ACCESS read-write
                STATUS mandatory
                DESCRIPTION
                    "The port's type of input flow control.  'none'
                    indicates no flow control at this level or below.

'xonXoff' indicates software flow control by recognizing XON and XOFF characters. 'hardware' indicates flow control delegated to the lower level, for example a parallel port.

                    'ctsRts' and 'dsrDtr' are specific to RS-232-like
                    ports.  Although not architecturally pure, they are
                    included here for simplicity's sake."
                ::= { charPortEntry 9 }

charPortOutFlowType OBJECT-TYPE

                SYNTAX INTEGER { none(1), xonXoff(2), hardware(3),
                                 ctsRts(4), dsrDtr(5) }
                ACCESS read-write
                STATUS mandatory
                DESCRIPTION
                    "The port's type of output flow control.  'none'
                    indicates no flow control at this level or below.
                    'xonXoff' indicates software flow control by
                    recognizing XON and XOFF characters.  'hardware'
                    indicates flow control delegated to the lower level,
                    for example a parallel port.
                
                    'ctsRts' and 'dsrDtr' are specific to RS-232-like
                    ports.  Although not architecturally pure, they are
                    included here for simplicy's sake."
                ::= { charPortEntry 10 }

charPortInFlowState OBJECT-TYPE

                SYNTAX INTEGER { none(1), unknown(2), stop(3), go(4) }
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The current operational state of input flow control
                    on the port.  'none' indicates not applicable.
                    'unknown' indicates this level does not know.
                    'stop' indicates flow not allowed.  'go' indicates
                    flow allowed."
                ::= { charPortEntry 11 }

charPortOutFlowState OBJECT-TYPE

                SYNTAX INTEGER { none(1), unknown(2), stop(3), go(4) }
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The current operational state of output flow
                    control on the port.  'none' indicates not
                    applicable.  'unknown' indicates this level does not
                
                    know.  'stop' indicates flow not allowed.  'go'
                    indicates flow allowed."
                ::= { charPortEntry 12 }

charPortInCharacters OBJECT-TYPE

                SYNTAX Counter
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "Total number of characters detected as input from
                    the port since system re-initialization and while
                    the port operational state was 'up', 'active', or
                    'maintenance', including, for example, framing, flow
                    control (i.e. XON and XOFF), each occurrence of a
                    BREAK condition, locally-processed input, and input
                    sent to all sessions."
                ::= { charPortEntry 13 }

charPortOutCharacters OBJECT-TYPE

                SYNTAX Counter
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "Total number of characters detected as output to
                    the port since system re-initialization and while
                    the port operational state was 'up', 'active', or
                    'maintenance', including, for example, framing, flow
                    control (i.e. XON and XOFF), each occurrence of a
                    BREAK condition, locally-created output, and output
                    received from all sessions."
                ::= { charPortEntry 14 }

charPortAdminOrigin OBJECT-TYPE

                SYNTAX INTEGER { dynamic(1), network(2), local(3),
                                 none(4) }
                ACCESS read-write
                STATUS mandatory
                DESCRIPTION
                    "The administratively allowed origin for
                    establishing session on the port.  'dynamic' allows
                    'network' or 'local' session establishment. 'none'
                    disallows session establishment."
                ::= { charPortEntry 15 }

charPortSessionMaximum OBJECT-TYPE

SYNTAX INTEGER
ACCESS read-write
STATUS mandatory

                DESCRIPTION
                    "The maximum number of concurrent sessions allowed
                    on the port.  A value of -1 indicates no maximum.
                    Setting the maximum to less than the current number
                    of sessions has unspecified results."
                ::= { charPortEntry 16 }

charPortSessionNumber OBJECT-TYPE

                SYNTAX Gauge
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The number of open sessions on the port that are in
                    the connecting, connected, or disconnecting state."
                ::= { charPortEntry 17 }

charPortSessionIndex OBJECT-TYPE

                SYNTAX INTEGER
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The value of charSessIndex for the port's first or
                    only active session.  If the port has no active
                    session, the agent returns the value zero."
                ::= { charPortEntry 18 }
            
            -- the Character Session table

charSessTable OBJECT-TYPE

                SYNTAX SEQUENCE OF CharSessEntry
                ACCESS not-accessible
                STATUS mandatory
                DESCRIPTION
                    "A list of port session entries."
                ::= { char 3 }

charSessEntry OBJECT-TYPE

                SYNTAX CharSessEntry
                ACCESS not-accessible
                STATUS mandatory
                DESCRIPTION
                    "Status and parameter values for a character port
                    session."
                INDEX { charSessPortIndex, charSessIndex }
                ::= { charSessTable 1 }

CharSessEntry ::=

                SEQUENCE {
                    charSessPortIndex
                        INTEGER,
                    charSessIndex
                        INTEGER,
                    charSessKill
                        INTEGER,
                    charSessState
                        INTEGER,
                    charSessProtocol
                        AutonomousType,
                    charSessOperOrigin
                        INTEGER,
                    charSessInCharacters
                        Counter,
                    charSessOutCharacters
                        Counter,
                    charSessConnectionId
                        InstancePointer,
                    charSessStartTime
                        TimeTicks
                }

charSessPortIndex OBJECT-TYPE

                SYNTAX INTEGER
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The value of charPortIndex for the port to which
                    this session belongs."
                ::= { charSessEntry 1 }

charSessIndex OBJECT-TYPE

                SYNTAX INTEGER
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The session index in the context of the port, a
                    non-zero positive integer.  Session indexes within a
                    port need not be sequential.  Session indexes may be
                    reused for different ports.  For example, port 1 and
                    port 3 may both have a session 2 at the same time.
                    Session indexes may have any valid integer value,
                    with any meaning convenient to the agent
                    implementation."
                ::= { charSessEntry 2 }

charSessKill OBJECT-TYPE

                SYNTAX INTEGER { ready(1), execute(2) }
                ACCESS read-write
                STATUS mandatory
                DESCRIPTION
                    "A control to terminate the session.  In response to
                    a get-request or get-next-request, the agent always
                    returns 'ready' as the value.  Setting the value to
                    'execute' causes termination."
                ::= { charSessEntry 3 }

charSessState OBJECT-TYPE

                SYNTAX INTEGER { connecting(1), connected(2),
                                 disconnecting(3) }
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The current operational state of the session,
                    disregarding flow control.  'connected' indicates
                    that character data could flow on the network side
                    of session.  'connecting' indicates moving from
                    nonexistent toward 'connected'.  'disconnecting'
                    indicates moving from 'connected' or 'connecting' to
                    nonexistent."
                ::= { charSessEntry 4 }

charSessProtocol OBJECT-TYPE

                SYNTAX AutonomousType
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The network protocol over which the session is
                    running.  Other OBJECT IDENTIFIER values may be
                    defined elsewhere, in association with specific
                    protocols.  However, this document assigns those of
                    known interest as of this writing."
                ::= { charSessEntry 5 }

wellKnownProtocols OBJECT IDENTIFIER ::= { char 4 }

            protocolOther  OBJECT IDENTIFIER ::= {wellKnownProtocols 1}
            protocolTelnet OBJECT IDENTIFIER ::= {wellKnownProtocols 2}
            protocolRlogin OBJECT IDENTIFIER ::= {wellKnownProtocols 3}
            protocolLat    OBJECT IDENTIFIER ::= {wellKnownProtocols 4}
            protocolX29    OBJECT IDENTIFIER ::= {wellKnownProtocols 5}
            protocolVtp    OBJECT IDENTIFIER ::= {wellKnownProtocols 6}

charSessOperOrigin OBJECT-TYPE

                SYNTAX INTEGER { unknown(1), network(2), local(3) }
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "The session's source of establishment."
                ::= { charSessEntry 6 }

charSessInCharacters OBJECT-TYPE

                SYNTAX Counter
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "This session's subset of charPortInCharacters."
                ::= { charSessEntry 7 }

charSessOutCharacters OBJECT-TYPE

                SYNTAX Counter
                ACCESS read-only
                STATUS mandatory
                DESCRIPTION
                    "This session's subset of charPortOutCharacters."
                ::= { charSessEntry 8 }

charSessConnectionId OBJECT-TYPE

SYNTAX InstancePointer
ACCESS read-only
STATUS mandatory
DESCRIPTION

"A reference to additional local MIB information. This should be the highest available related MIB, corresponding to charSessProtocol, such as Telnet. For example, the value for a TCP connection (in the absence of a Telnet MIB) is the object identifier of tcpConnState. If an agent is not configured to have such values, the agent returns the object identifier:

                        nullConnectionId OBJECT IDENTIFIER ::= { 0 0 }
                    "
                ::= { charSessEntry 9 }

charSessStartTime OBJECT-TYPE

SYNTAX TimeTicks
ACCESS read-only
STATUS mandatory
DESCRIPTION

"The value of sysUpTime in MIB-2 when the session

                    entered connecting state."
                ::= { charSessEntry 10 }
            
            END

6. Acknowledgements

Based on several private MIBs, this document was produced by the Character MIB Working Group:

Anne Ambler, Spider
Charles Bazaar, Emulex
Christopher Bucci, Datability
Anthony Chung, Hughes LAN Systems
George Conant, Xyplex
John Cook, Chipcom
James Davin, MIT-LCS
Shawn Gallagher, DEC
Tom Grant, Xylogics
Frank Huang, Emulex
David Jordan, Emulex
Satish Joshi, SynOptics
Frank Kastenholz, Clearpoint
Ken Key, University of Tennessee
Jim Kinder, Fibercom
Rajeev Kochhar, 3Com
John LoVerso, Xylogics
Keith McCloghrie, Hughes LAN Systems Donald Merritt, BRL
David Perkins, 3Com
Jim Reinstedler, Ungerman-Bass
Marshall Rose, PSI
Ron Strich, SSDS
Dean Throop, DG
Bill Townsend, Xylogics
Jesse Walker, DEC
David Waitzman, BBN
Bill Westfield, cisco

7. References

   [1] Cerf, V., "IAB Recommendations for the Development of
   
       Internet  Network Management Standards", RFC 1052, NRI,
       April 1988.
   
   [2] Cerf, V., "Report of the Second Ad Hoc Network
       Management Review  Group", RFC 1109, NRI, August 1989.
   
   [3] 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.
   
   [4] McCloghrie K., and M. Rose, "Management Information Base
       for  Network Management of TCP/IP-based internets", RFC
       1156, Hughes  LAN Systems, Performance Systems
       International, May 1990.
   
   [5] Case, J., Fedor, M., Schoffstall, M., and J. Davin,
       "Simple  Network Management Protocol", RFC 1157, SNMP
       Research,  Performance Systems International, Performance
       Systems  International, MIT Laboratory for Computer Science,
       May 1990.
   
   [6] McCloghrie K., and M. Rose, Editors, "Management
       Information Base  for Network Management of TCP/IP-based
       internets", RFC 1213,  Performance Systems International,
       March 1991.
   
   [7] Information processing systems - Open Systems
       Interconnection -  Specification of Abstract Syntax Notation
       One (ASN.1),  International Organization for
       Standardization, International  Standard 8824, December
       1987.
   
   [8] Information processing systems - Open Systems
       Interconnection -  Specification of Basic Encoding Rules for
       Abstract Notation One  (ASN.1), International Organization
       for Standardization,  International Standard 8825, December
       1987.
   
   [9] Rose, M., and K. McCloghrie, Editors, "Concise MIB
       Definitions",  RFC 1212, Performance Systems International,
       Hughes LAN Systems,  March 1991.
  
  [10] Rose, M., Editor, "A Convention for Defining Traps for
       use with  the SNMP", RFC 1215, Performance Systems
       International, March 1991.

8. Security Considerations

Security issues are not discussed in this memo.

9. Author's Address

Bob Stewart
Xyplex, Inc.
330 Codman Hill Road
Boxborough, MA 01719

   Phone: (508) 264-9900
   EMail: rlstewart@eng.xyplex.com