TCP_ESTATS_REC_ROD_v0 structure

The TCP_ESTATS_REC_ROD_v0 structure contains read-only dynamic information for extended TCP statistics on the local receiver for a TCP connection.

Syntax

typedef struct _TCP_ESTATS_REC_ROD_v0 {
  ULONG  CurRwinSent;
  ULONG  MaxRwinSent;
  ULONG  MinRwinSent;
  ULONG  LimRwin;
  ULONG  DupAckEpisodes;
  ULONG  DupAcksOut;
  ULONG  CeRcvd;
  ULONG  EcnSent;
  ULONG  EcnNoncesRcvd;
  ULONG  CurReasmQueue;
  ULONG  MaxReasmQueue;
  SIZE_T CurAppRQueue;
  SIZE_T MaxAppRQueue;
  UCHAR  WinScaleSent;
} TCP_ESTATS_REC_ROD_v0, *PTCP_ESTATS_REC_ROD_v0;

Members

CurRwinSent

Type: ULONG

The most recent window advertisement, in bytes, that has been sent.

MaxRwinSent

Type: ULONG

The maximum window advertisement, in bytes, that has been sent.

MinRwinSent

Type: ULONG

The minimum window advertisement, in bytes, that has been sent.

LimRwin

Type: ULONG

The maximum window advertisement, in bytes, that may be sent.

DupAckEpisodes

Type: ULONG

The number of Duplicate Acks Sent when prior Ack was not duplicate. This is the number of times that a contiguous series of duplicate acknowledgments have been sent.

This is an indication of the number of data segments lost or reordered on the path from the remote TCP endpoint to the near TCP endpoint.

DupAcksOut

Type: ULONG

The number of duplicate ACKs sent.

The ratio of the change in the DupAcksOut member to the change in the DupAckEpisodes member is an indication of reorder or recovery distance over some interval.

CeRcvd

Type: ULONG

The number of segments received with IP headers bearing Congestion Experienced (CE) markings.

EcnSent

Type: ULONG

Reserved for future use. This member is always set to zero.

EcnNoncesRcvd

Type: ULONG

Reserved for future use. This member is always set to zero.

CurReasmQueue

Type: ULONG

The current number of bytes of sequence space spanned by the reassembly queue.

This is generally the difference between rcv.nxt and the sequence number of the right most edge of the reassembly queue.

MaxReasmQueue

Type: ULONG

The maximum number of bytes of sequence space spanned by the reassembly queue.

This is the maximum value of the CurReasmQueue member.

CurAppRQueue

Type: SIZE_T

The current number of bytes of application data that has been acknowledged by TCP but not yet delivered to the application.

MaxAppRQueue

Type: SIZE_T

The maximum number of bytes of application data that has been acknowledged by TCP but not yet delivered to the application.

WinScaleSent

Type: UCHAR

The value of the transmitted window scale option if one was sent; otherwise, a value of -1.

Note that if both the WinScaleSent member and the WinScaleRcvd member of the TCP_ESTATS_OBS_REC_ROD_v0 structure are not -1, then Rcv.Wind.Scale will be the same as this value and used to scale receiver window announcements from the local host to the remote host.

Remarks

The TCP_ESTATS_REC_ROD_v0 structure is used as part of the TCP extended statistics feature available on Windows Vista and later.

The TCP_ESTATS_REC_ROD_v0 is defined as version 0 of the structure for read-only dynamic information for extended TCP statistics on the local receiver for a TCP connection. This information is available after the connection has been established.

The TCP_ESTATS_REC_ROD_v0 structure is retrieved by calls to the GetPerTcp6ConnectionEStats or GetPerTcpConnectionEStats functions when TcpConnectionEstatsRec is passed in the EstatsType parameter. Extended TCP statistics need to be enabled to retrieve this structure.

TCP congestion control and congestion control algorithms are discussed in detail in the IETF RFC 2581 on TCP Congestion Control. For more information, see http://www.ietf.org/rfc/rfc2581.txt.

Explicit Congestion Notification in IP is discussed in detail in the IETF RFC 2581 on The Addition of Explicit Congestion Notification (ECN) to IP. For more information, see http://www.ietf.org/rfc/rfc3168.txt.

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_REC_ROD_v0 structure to the entries defined in RFC 4898 for extended TCP statistics:

Term Description
CurRwinSent tcpEStatsPerfCurRwinSent
MaxRwinSent tcpEStatsPerfMaxRwinSent
MinRwinSent No mapping to this member.
LimRwin tcpEStatsTuneLimRwin
DupAckEpisodes tcpEStatsPathDupAckEpisodes
DupAcksOut tcpEStatsPathDupAcksOut
CeRcvd tcpEStatsPathCERcvd
EcnSent No mapping to this member.
EcnNoncesRcvd No mapping to this member.
CurReasmQueue tcpEStatsStackCurReasmQueue
MaxReasmQueue tcpEStatsStackMaxReasmQueue
CurAppRQueue tcpEStatsAppCurAppRQueue
MaxAppRQueue tcpEStatsAppMaxAppRQueue
WinScaleSent tcpEStatsStackWinScaleSent

Requirements

   
Minimum supported client Windows Vista [desktop apps only]
Minimum supported server Windows Server 2008 [desktop apps only]
Header tcpestats.h

See Also

GetPerTcp6ConnectionEStats

GetPerTcpConnectionEStats

TCP_ESTATS_TYPE