6.4. The Interfaces Group

          -- the Interfaces group

          -- Implementation of the Interfaces group is mandatory for
          -- all systems.

          ifNumber OBJECT-TYPE
              SYNTAX  INTEGER
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of network interfaces (regardless of
                      their current state) present on this system."
              ::= { interfaces 1 }

          -- the Interfaces table

          -- The Interfaces table contains information on the entity's
          -- interfaces.  Each interface is thought of as being
          -- attached to a `subnetwork'.  Note that this term should
          -- not be confused with `subnet' which refers to an
          -- addressing partitioning scheme used in the Internet suite
          -- of protocols.

          ifTable OBJECT-TYPE
              SYNTAX  SEQUENCE OF IfEntry
              ACCESS  not-accessible
              STATUS  mandatory
              DESCRIPTION
                      "A list of interface entries.  The number of
                      entries is given by the value of ifNumber."
              ::= { interfaces 2 }

          ifEntry OBJECT-TYPE
              SYNTAX  IfEntry
              ACCESS  not-accessible
              STATUS  mandatory
              DESCRIPTION
                      "An interface entry containing objects at the
                      subnetwork layer and below for a particular
                      interface."
              INDEX   { ifIndex }
              ::= { ifTable 1 }

          IfEntry ::=
              SEQUENCE {
                  ifIndex
                      INTEGER,
                  ifDescr
                      DisplayString,
                  ifType
                      INTEGER,
                  ifMtu
                      INTEGER,
                  ifSpeed
                      Gauge,
                  ifPhysAddress
                      PhysAddress,
                  ifAdminStatus
                      INTEGER,
                  ifOperStatus
                      INTEGER,
                  ifLastChange
                      TimeTicks,
                  ifInOctets
                      Counter,
                  ifInUcastPkts
                      Counter,
                  ifInNUcastPkts
                      Counter,
                  ifInDiscards
                      Counter,
                  ifInErrors
                      Counter,
                  ifInUnknownProtos
                      Counter,
                  ifOutOctets
                      Counter,
                  ifOutUcastPkts
                      Counter,
                  ifOutNUcastPkts
                      Counter,
                  ifOutDiscards
                      Counter,
                  ifOutErrors
                      Counter,
                  ifOutQLen
                      Gauge,
                  ifSpecific
                      OBJECT IDENTIFIER
              }

          ifIndex OBJECT-TYPE
              SYNTAX  INTEGER
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "A unique value for each interface.  Its value
                      ranges between 1 and the value of ifNumber.  The
                      value for each interface must remain constant at
                      least from one re-initialization of the entity's
                      network management system to the next re-
                      initialization."
              ::= { ifEntry 1 }

          ifDescr OBJECT-TYPE
              SYNTAX  DisplayString (SIZE (0..255))
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "A textual string containing information about the
                      interface.  This string should include the name of
                      the manufacturer, the product name and the version
                      of the hardware interface."
              ::= { ifEntry 2 }

          ifType OBJECT-TYPE
              SYNTAX  INTEGER {
                          other(1),          -- none of the following
                          regular1822(2),
                          hdh1822(3),
                          ddn-x25(4),
                          rfc877-x25(5),
                          ethernet-csmacd(6),
                          iso88023-csmacd(7),
                          iso88024-tokenBus(8),
                          iso88025-tokenRing(9),
                          iso88026-man(10),
                          starLan(11),
                          proteon-10Mbit(12),
                          proteon-80Mbit(13),
                          hyperchannel(14),
                          fddi(15),
                          lapb(16),
                          sdlc(17),
                          ds1(18),           -- T-1
                          e1(19),            -- european equiv. of T-1
                          basicISDN(20),
                          primaryISDN(21),   -- proprietary serial
                          propPointToPointSerial(22),
                          ppp(23),
                          softwareLoopback(24),
                          eon(25),            -- CLNP over IP [11]
                          ethernet-3Mbit(26),
                          nsip(27),           -- XNS over IP
                          slip(28),           -- generic SLIP
                          ultra(29),          -- ULTRA technologies
                          ds3(30),            -- T-3
                          sip(31),            -- SMDS
                          frame-relay(32)
                      }
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The type of interface, distinguished according to
                      the physical/link protocol(s) immediately `below'
                      the network layer in the protocol stack."
              ::= { ifEntry 3 }

          ifMtu OBJECT-TYPE
              SYNTAX  INTEGER
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The size of the largest datagram which can be
                      sent/received on the interface, specified in
                      octets.  For interfaces that are used for
                      transmitting network datagrams, this is the size
                      of the largest network datagram that can be sent
                      on the interface."
              ::= { ifEntry 4 }

          ifSpeed OBJECT-TYPE
              SYNTAX  Gauge
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "An estimate of the interface's current bandwidth
                      in bits per second.  For interfaces which do not
                      vary in bandwidth or for those where no accurate
                      estimation can be made, this object should contain
                      the nominal bandwidth."
              ::= { ifEntry 5 }

          ifPhysAddress OBJECT-TYPE
              SYNTAX  PhysAddress
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The interface's address at the protocol layer
                      immediately `below' the network layer in the
                      protocol stack.  For interfaces which do not have
                      such an address (e.g., a serial line), this object
                      should contain an octet string of zero length."
              ::= { ifEntry 6 }

          ifAdminStatus OBJECT-TYPE
              SYNTAX  INTEGER {
                          up(1),       -- ready to pass packets
                          down(2),
                          testing(3)   -- in some test mode
                      }
              ACCESS  read-write
              STATUS  mandatory
              DESCRIPTION
                      "The desired state of the interface.  The
                      testing(3) state indicates that no operational
                      packets can be passed."
              ::= { ifEntry 7 }

          ifOperStatus OBJECT-TYPE
              SYNTAX  INTEGER {
                          up(1),       -- ready to pass packets
                          down(2),
                          testing(3)   -- in some test mode
                      }
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The current operational state of the interface.
                      The testing(3) state indicates that no operational
                      packets can be passed."
              ::= { ifEntry 8 }

          ifLastChange OBJECT-TYPE
              SYNTAX  TimeTicks
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The value of sysUpTime at the time the interface
                      entered its current operational state.  If the
                      current state was entered prior to the last re-
                      initialization of the local network management
                      subsystem, then this object contains a zero
                      value."
              ::= { ifEntry 9 }

          ifInOctets OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The total number of octets received on the
                      interface, including framing characters."
              ::= { ifEntry 10 }

          ifInUcastPkts OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of subnetwork-unicast packets
                      delivered to a higher-layer protocol."
              ::= { ifEntry 11 }

          ifInNUcastPkts OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of non-unicast (i.e., subnetwork-
                      broadcast or subnetwork-multicast) packets
                      delivered to a higher-layer protocol."
              ::= { ifEntry 12 }

          ifInDiscards OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of inbound packets which were chosen
                      to be discarded even though no errors had been
                      detected to prevent their being deliverable to a
                      higher-layer protocol.  One possible reason for
                      discarding such a packet could be to free up
                      buffer space."
              ::= { ifEntry 13 }

          ifInErrors OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of inbound packets that contained
                      errors preventing them from being deliverable to a
                      higher-layer protocol."
              ::= { ifEntry 14 }

          ifInUnknownProtos OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of packets received via the interface
                      which were discarded because of an unknown or
                      unsupported protocol."
              ::= { ifEntry 15 }

          ifOutOctets OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The total number of octets transmitted out of the
                      interface, including framing characters."
              ::= { ifEntry 16 }

          ifOutUcastPkts OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The total number of packets that higher-level
                      protocols requested be transmitted to a
                      subnetwork-unicast address, including those that
                      were discarded or not sent."
              ::= { ifEntry 17 }

          ifOutNUcastPkts OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The total number of packets that higher-level
                      protocols requested be transmitted to a non-
                      unicast (i.e., a subnetwork-broadcast or
                      subnetwork-multicast) address, including those
                      that were discarded or not sent."
              ::= { ifEntry 18 }

          ifOutDiscards OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of outbound packets which were chosen
                      to be discarded even though no errors had been
                      detected to prevent their being transmitted.  One
                      possible reason for discarding such a packet could
                      be to free up buffer space."
              ::= { ifEntry 19 }

          ifOutErrors OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of outbound packets that could not be
                      transmitted because of errors."
              ::= { ifEntry 20 }

          ifOutQLen OBJECT-TYPE
              SYNTAX  Gauge
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The length of the output packet queue (in
                      packets)."
              ::= { ifEntry 21 }

          ifSpecific OBJECT-TYPE
              SYNTAX  OBJECT IDENTIFIER
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "A reference to MIB definitions specific to the
                      particular media being used to realize the
                      interface.  For example, if the interface is
                      realized by an ethernet, then the value of this
                      object refers to a document defining objects
                      specific to ethernet.  If this information is not
                      present, its value should be set to the OBJECT
                      IDENTIFIER { 0 0 }, which is a syntatically valid
                      object identifier, and any conformant
                      implementation of ASN.1 and BER must be able to
                      generate and recognize this value."
              ::= { ifEntry 22 }