TCP Tab

The TCP Tab displays various TCP statistics and the TCP connection table.

Statistics

RtoAlgorithm: The algorithm used to determine the timeout value used for retransmitting unacknowledged octets. Valid algorithms are: other - none of the following; constant - a constant rto; rsre - MIL-STD-1778, Appendix B; vanj - Van Jacobson's algorithm.

RtoMin: 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, an object of this type has the semantics of the LBOUND quantity described in RFC 793.

RtoMax: 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, an object of this type has the semantics of the UBOUND quantity described in RFC 793.

MaxConn: The limit on the total number of TCP connections the router can support.

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

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

AttemptFails: 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.

EstabResets: 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.

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

InSegs: The total number of segments received, including those received in error. This count includes segments received on currently established connections.

OutSegs: The total number of segments sent, including those on current connections but excluding those containing only retransmitted octets.

ReTransSegs: The total number of segments retransmitted - that is, the number of TCP segments transmitted containing one or more previously transmitted octets.

InErrs: The total number of segments received in error (eg, bad TCP checksums).

OutErrs: The number of TCP segments sent containing the RST flag.

Connection Table

The TCP connection table contains information about the router's existing TCP connections. Each entry comprises:

State: Information about the state of a particular current TCP connection. This state is transient, in that it ceases to exist when (or soon after) the connection makes the transition to the CLOSED state. The valid states are: closed, listen, synSent, synReceived, established, finWait1, finWait2, closeWait, lastAck, closing, timeWait, and deleteTCB.

Local IP: 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 router, the value 0.0.0.0 is used.

Local Port: The local port number for this TCP connection.

Remote IP: The remote IP address for this TCP connection.

Remote Port: The remote port number for this TCP connection.

The "Copy table" button will copy the contents of this table to the clipboard. The "Save table" button allows you to save the contents of the table to a file.

Help

The "Help" button will display the context-sensitive help file for this tab. Pressing F1 at any time will also display the context-sensitive help file.

Update

The "Update" button will update the information displayed in this tab.