TCP_ESTATS_SEND_BUFF_ROD_v0 structure (tcpestats.h)

The TCP_ESTATS_SEND_BUFF_ROD_v0 structure contains read-only dynamic information for extended TCP statistics on output queuing for a TCP connection.

Syntax

typedef struct _TCP_ESTATS_SEND_BUFF_ROD_v0 {
  SIZE_T CurRetxQueue;
  SIZE_T MaxRetxQueue;
  SIZE_T CurAppWQueue;
  SIZE_T MaxAppWQueue;
} TCP_ESTATS_SEND_BUFF_ROD_v0, *PTCP_ESTATS_SEND_BUFF_ROD_v0;

Members

CurRetxQueue

Type: SIZE_T

The current number of bytes of data occupying the retransmit queue.

MaxRetxQueue

Type: SIZE_T

The maximum number of bytes of data occupying the retransmit queue.

CurAppWQueue

Type: SIZE_T

The current number of bytes of application data buffered by TCP, pending the first transmission (to the left of SND.NXT or SndMax).

This data will generally be transmitted (and SND.NXT advanced to the left) as soon as there is an available congestion window or receiver window. This is the amount of data readily available for transmission, without scheduling the application. TCP performance may suffer if there is insufficient queued write data.

MaxAppWQueue

Type: SIZE_T

The maximum number of bytes of application data buffered by TCP, pending the first transmission.

This is the maximum value of the CurAppWQueue member. The MaxAppWQueue and CurAppWQueue members can be used to determine if insufficient queued data is steady state (suggesting insufficient queue space) or transient (suggesting insufficient application performance or excessive CPU load or scheduler latency).

Remarks

The TCP_ESTATS_SEND_BUFF_ROD_v0 structure is used as part of the TCP extended statistics feature available on Windows Vista and later.

The TCP_ESTATS_SEND_BUFF_ROD_v0 is defined as version 0 of the structure for read-only dynamic information for extended TCP statistics on output queuing for a TCP connection. This information is available after the connection has been established.

The TCP_ESTATS_SEND_BUFF_ROD_v0 structure is retrieved by calls to the GetPerTcp6ConnectionEStats or GetPerTcpConnectionEStats functions when TcpConnectionEstatsSendBuff is passed in the EstatsType parameter. Extended TCP statistics need to be enabled to retrieve this structure.

The members of this structure are defined in the IETF RFC on the TCP Extended Statistics MIB. For more information, see http://www.ietf.org/rfc/rfc4898.txt.

The following is the mapping of the members in the TCP_ESTATS_SEND_BUFF_ROD_v0 structure to the entries defined in RFC 4898 for extended TCP statistics:

Requirements

See also

GetPerTcp6ConnectionEStats

GetPerTcpConnectionEStats

TCP_ESTATS_TYPE