TCP_ESTATS_SND_CONG_ROS_v0 structure (tcpestats.h)

The TCP_ESTATS_SND_CONG_ROS_v0 structure contains read-only static information for extended TCP statistics on the maximum congestion window for a TCP connection.


typedef struct _TCP_ESTATS_SND_CONG_ROS_v0 {
  ULONG LimCwnd;



The maximum size, in bytes, of the congestion window that may be used.


The TCP_ESTATS_SND_CONG_ROS_v0 structure is used as part of the TCP extended statistics feature available on Windows Vista and later.

The TCP_ESTATS_SND_CONG_ROS_v0 is defined as version 0 of the structure for read-only dynamic information on basic sender congestion data for a TCP connection. This information is available after the connection has been established.

The TCP_ESTATS_SND_CONG_ROS_v0 structure is retrieved by calls to the GetPerTcp6ConnectionEStats or GetPerTcpConnectionEStats functions when TcpConnectionEstatsSndCong 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 on TCP Congestion Control. For more information, see

The members of this structure are defined in the IETF RFC on the TCP Extended Statistics MIB. For more information, see

The following is the mapping of the members in the TCP_ESTATS_SND_CONG_ROS_v0 structure to the entries defined in RFC 4898 for extended TCP statistics:

Term Description
LimCwnd tcpEStatsTuneLimCwnd


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

See also