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TCP_INFO_v1 structure (mstcpip.h)

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Contains the Transmission Control Protocol (TCP) statistics that were collected for a socket. Version 1.0 of this structure provides additional fields.

Syntax

typedef struct _TCP_INFO_v1 {
  TCPSTATE State;
  ULONG    Mss;
  ULONG64  ConnectionTimeMs;
  BOOLEAN  TimestampsEnabled;
  ULONG    RttUs;
  ULONG    MinRttUs;
  ULONG    BytesInFlight;
  ULONG    Cwnd;
  ULONG    SndWnd;
  ULONG    RcvWnd;
  ULONG    RcvBuf;
  ULONG64  BytesOut;
  ULONG64  BytesIn;
  ULONG    BytesReordered;
  ULONG    BytesRetrans;
  ULONG    FastRetrans;
  ULONG    DupAcksIn;
  ULONG    TimeoutEpisodes;
  UCHAR    SynRetrans;
  ULONG    SndLimTransRwin;
  ULONG    SndLimTimeRwin;
  ULONG64  SndLimBytesRwin;
  ULONG    SndLimTransCwnd;
  ULONG    SndLimTimeCwnd;
  ULONG64  SndLimBytesCwnd;
  ULONG    SndLimTransSnd;
  ULONG    SndLimTimeSnd;
  ULONG64  SndLimBytesSnd;
} TCP_INFO_v1, *PTCP_INFO_v1;

Members

State

Contains the Transmission Control Protocol (TCP) statistics that were collected for a socket.

Mss

The current maximum segment size (MSS) for the connection, in bytes.

ConnectionTimeMs

The lifetime of the connection, in milliseconds.

TimestampsEnabled

TRUE if TCP time stamps are turned on for the connection; otherwise FALSE.

RttUs

The current estimated round-trip time for the connection, in microseconds.

MinRttUs

The minimum sampled round trip time, in microseconds.

BytesInFlight

The current number of sent bytes that are unacknowledged.

Cwnd

The size of the current congestion window, in bytes.

SndWnd

The size of the send window (SND.WND in RFC 793), in bytes.

RcvWnd

The size of the receive window (RCV.WND in RFC 793), in bytes.

RcvBuf

The size of the current receive buffer, in bytes. The size of the receive buffer changes dynamically when autotuning is turned on for the receive window.

BytesOut

The total number of bytes sent.

BytesIn

The total number of bytes received.

BytesReordered

The total number of bytes reordered.

BytesRetrans

The total number of bytes retransmitted.

FastRetrans

The number of calls of the Fast Retransmit algorithm.

DupAcksIn

The total number of duplicate acknowledgments received.

TimeoutEpisodes

The total number of retransmission timeout episodes. Each episode can consist of multiple timeouts.

SynRetrans

The total number of retransmitted synchronize control flags (SYNs).

SndLimTransRwin

The number of transitions into the "Receiver Limited" state from either the "Congestion Limited" or "Sender Limited" states.

SndLimTimeRwin

The cumulative time, in milliseconds, spent in the "Receiver Limited" state where TCP transmission stops because the sender has filled the announced receiver window.

SndLimBytesRwin

The total number of bytes sent in the "Receiver Limited" state.

SndLimTransCwnd

The number of transitions into the "Congestion Limited" state from either the "Receiver Limited" or "Sender Limited" states.

SndLimTimeCwnd

The cumulative time, in milliseconds, spent in the "Congestion Limited" state. When there is a retransmission timeout, it is counted in this member and not the cumulative time for some other state.

SndLimBytesCwnd

The total number of bytes sent in the "Congestion Limited" state.

SndLimTransSnd

The number of transitions into the "Sender Limited" state from either the "Receiver Limited" or "Congestion Limited" states.

SndLimTimeSnd

The cumulative time, in milliseconds, spent in the "Sender Limited" state.

SndLimBytesSnd

The total number of bytes sent in the "Sender Limited" state.

Remarks

To get an instance of this structure, call the WSAIoctl or LPWSPIoctl function with the SIO_TCP_INFO control code. Specify 1 for the lpvInBuffer field to retrieve the v1 version of this structure.

Requirements

Requirement Value
Minimum supported client Windows 10 Build 20348
Minimum supported server Windows 10 Build 20348
Header mstcpip.h

See also

SIO_TCP_INFO

TCPSTATE