TCP (G)

The TCP objects (Transmission Control Protocol) are the data transmission statistics and connection data for the TCP layer. The (G) indicates that graphs are available. Objects that represent information about a particular TCP connection are transient; the objects exist only as long as the specified connection is in use. It provides information on retransmissions, opens, connections, and segments.

Figure 79. SNMP Browser - TCP Group

The fields on the TCP MIB Information screen are:

RTO Algorithm

TCP Retrans. Timeout Algorithm. The algorithm used to determine the timeout value for retransmitting unacknowledged octets.

RTO Minimum

TCP Retrans. Timeout Minimum. 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.

RTO Maximum

TCP Retrans. Timeout Maximum. 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.

Max Connections

TCP Maximum Connections. The limit on the total number of TCP connections the entity supports. In entities where the maximum number of connections is dynamic, this object should contain the value -1.

Segments In

TCP In Segments. The total number of segments received, including those received in error. This count includes segments received on currently established connections.

Segments Out

TCP Out Segments. The total number of segments sent, including those on current connections but excluding those containing only retransmitted octets.

Curr Established

TCP Current Established. The number of TCP connections for which the current state is either ESTABLISHED or CLOSE-WAIT.

Retrans Segments

TCP Retransmit Segments. The total number of segments retransmitted, that is, the number of TCP segments transmitted containing one or more previously transmitted octets.

Active Open

TCP Active Open. The number of times TCP connections have made a direct transition to the SYN-SENT state from the CLOSED state.

Passive Open

TCP Passive Open. The number of times TCP connections have made a direct transition to the SYN-RCVD state from the LISTEN state.

Attempt Fails

TCP Attempt Fails. 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.

Errors In

TCP In Errors. The total number of segments received in error, for example, bad TCP checksums.

Estab Resets

TCP Established Resets. 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.

Out Resets

TCP Out Resets. The number of TCP segments sent containing the RST flag.

 

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