6.8. The TCP Group

          -- the TCP group

          -- Implementation of the TCP group is mandatory for all
          -- systems that implement the TCP.

          -- Note that instances of object types that represent
          -- information about a particular TCP connection are
          -- transient; they persist only as long as the connection
          -- in question.

          tcpRtoAlgorithm OBJECT-TYPE
              SYNTAX  INTEGER {
                          other(1),    -- none of the following

                          constant(2), -- a constant rto
                          rsre(3),     -- MIL-STD-1778, Appendix B
                          vanj(4)      -- Van Jacobson's algorithm [10]
                      }
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The algorithm used to determine the timeout value
                      used for retransmitting unacknowledged octets."
              ::= { tcp 1 }

          tcpRtoMin OBJECT-TYPE
              SYNTAX  INTEGER
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The minimum value permitted by a TCP
                      implementation for the retransmission timeout,
                      measured in milliseconds.  More refined semantics
                      for objects of this type depend upon the algorithm
                      used to determine the retransmission timeout.  In
                      particular, when the timeout algorithm is rsre(3),
                      an object of this type has the semantics of the
                      LBOUND quantity described in RFC 793."
              ::= { tcp 2 }

          tcpRtoMax OBJECT-TYPE
              SYNTAX  INTEGER
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The maximum value permitted by a TCP
                      implementation for the retransmission timeout,
                      measured in milliseconds.  More refined semantics
                      for objects of this type depend upon the algorithm
                      used to determine the retransmission timeout.  In
                      particular, when the timeout algorithm is rsre(3),
                      an object of this type has the semantics of the
                      UBOUND quantity described in RFC 793."
              ::= { tcp 3 }

          tcpMaxConn OBJECT-TYPE
              SYNTAX  INTEGER
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The limit on the total number of TCP connections
                      the entity can support.  In entities where the
                      maximum number of connections is dynamic, this
                      object should contain the value -1."
              ::= { tcp 4 }

          tcpActiveOpens OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of times TCP connections have made a
                      direct transition to the SYN-SENT state from the
                      CLOSED state."
              ::= { tcp 5 }

          tcpPassiveOpens OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of times TCP connections have made a
                      direct transition to the SYN-RCVD state from the
                      LISTEN state."
              ::= { tcp 6 }
          tcpAttemptFails OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of times TCP connections have made a
                      direct transition to the CLOSED state from either
                      the SYN-SENT state or the SYN-RCVD state, plus the
                      number of times TCP connections have made a direct
                      transition to the LISTEN state from the SYN-RCVD
                      state."
              ::= { tcp 7 }

          tcpEstabResets OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of times TCP connections have made a
                      direct transition to the CLOSED state from either
                      the ESTABLISHED state or the CLOSE-WAIT state."
              ::= { tcp 8 }

          tcpCurrEstab OBJECT-TYPE
              SYNTAX  Gauge
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of TCP connections for which the
                      current state is either ESTABLISHED or CLOSE-
                      WAIT."
              ::= { tcp 9 }

          tcpInSegs OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The total number of segments received, including
                      those received in error.  This count includes
                      segments received on currently established
                      connections."
              ::= { tcp 10 }

          tcpOutSegs OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The total number of segments sent, including
                      those on current connections but excluding those
                      containing only retransmitted octets."
              ::= { tcp 11 }

          tcpRetransSegs OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The total number of segments retransmitted - that
                      is, the number of TCP segments transmitted
                      containing one or more previously transmitted
                      octets."
              ::= { tcp 12 }

          -- the TCP Connection table

          -- The TCP connection table contains information about this
          -- entity's existing TCP connections.

          tcpConnTable OBJECT-TYPE
              SYNTAX  SEQUENCE OF TcpConnEntry
              ACCESS  not-accessible
              STATUS  mandatory
              DESCRIPTION
                      "A table containing TCP connection-specific
                      information."
              ::= { tcp 13 }

          tcpConnEntry OBJECT-TYPE
              SYNTAX  TcpConnEntry
              ACCESS  not-accessible
              STATUS  mandatory
              DESCRIPTION
                      "Information about a particular current TCP
                      connection.  An object of this type is transient,
                      in that it ceases to exist when (or soon after)
                      the connection makes the transition to the CLOSED
                      state."
              INDEX   { tcpConnLocalAddress,
                        tcpConnLocalPort,
                        tcpConnRemAddress,
                        tcpConnRemPort }
              ::= { tcpConnTable 1 }

          TcpConnEntry ::=
              SEQUENCE {
                  tcpConnState
                      INTEGER,
                  tcpConnLocalAddress
                      IpAddress,
                  tcpConnLocalPort
                      INTEGER (0..65535),
                  tcpConnRemAddress
                      IpAddress,
                  tcpConnRemPort
                      INTEGER (0..65535)
              }

          tcpConnState OBJECT-TYPE
              SYNTAX  INTEGER {
                          closed(1),
                          listen(2),
                          synSent(3),
                          synReceived(4),
                          established(5),
                          finWait1(6),
                          finWait2(7),
                          closeWait(8),
                          lastAck(9),
                          closing(10),
                          timeWait(11),
                          deleteTCB(12)
                      }
              ACCESS  read-write
              STATUS  mandatory
              DESCRIPTION
                      "The state of this TCP connection.

                      The only value which may be set by a management
                      station is deleteTCB(12).  Accordingly, it is
                      appropriate for an agent to return a `badValue'
                      response if a management station attempts to set
                      this object to any other value.

                      If a management station sets this object to the
                      value deleteTCB(12), then this has the effect of
                      deleting the TCB (as defined in RFC 793) of the
                      corresponding connection on the managed node,
                      resulting in immediate termination of the
                      connection.

                      As an implementation-specific option, a RST
                      segment may be sent from the managed node to the
                      other TCP endpoint (note however that RST segments
                      are not sent reliably)."
              ::= { tcpConnEntry 1 }

          tcpConnLocalAddress OBJECT-TYPE
              SYNTAX  IpAddress
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The local IP address for this TCP connection.  In
                      the case of a connection in the listen state which
                      is willing to accept connections for any IP
                      interface associated with the node, the value
                      0.0.0.0 is used."
              ::= { tcpConnEntry 2 }

          tcpConnLocalPort OBJECT-TYPE
              SYNTAX  INTEGER (0..65535)
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The local port number for this TCP connection."
              ::= { tcpConnEntry 3 }

          tcpConnRemAddress OBJECT-TYPE
              SYNTAX  IpAddress
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The remote IP address for this TCP connection."
              ::= { tcpConnEntry 4 }

          tcpConnRemPort OBJECT-TYPE
              SYNTAX  INTEGER (0..65535)
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The remote port number for this TCP connection."
              ::= { tcpConnEntry 5 }

          -- additional TCP objects

          tcpInErrs OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The total number of segments received in error
                      (e.g., bad TCP checksums)."
              ::= { tcp 14 }

          tcpOutRsts OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The number of TCP segments sent containing the
                      RST flag."
              ::= { tcp 15 }