For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base: How to back up and restore the registry in Windows. The TCP receive window size is the amount of receive data in bytes that can be buffered during a connection.
The sending host can send only that amount of data before it must wait for an acknowledgment and window update from the receiving host. Instead of using a hard-coded default receive window size, TCP adjusts to even increments of the maximum segment size MSS. The MSS is negotiated during connection setup. Adjusting the receive window to even increments of the MSS increases the percentage of full-sized TCP segments used during bulk data transmissions. For Ethernet connections, the window size will normally be set to 17, bytes 16K rounded up to twelve byte segments.
These two options increase the TCP header size to more than 20 bytes, which results in less room for data. In previous versions of Windows NT, the window size for an Ethernet connection was 8, bytes, or six byte segments. To set the receive window size to a specific value, add the TcpWindowSize value to the registry subkey specific to your version of Windows. To do so, follow these steps:.
This value isn't present by default. When you add the TcpWindowSize value, it overrides the default window size algorithm discussed above. TcpWindowSize can also be added to the Parameters key to set the window size globally for all interfaces. Previously, TCP options were used primarily for negotiating maximum segment sizes. Kind: 3 Length: 3 Option: Window Scale Option Description: Identifies the scaling factor to be used when using window sizes larger than 64k. For more efficient use of high-bandwidth networks, a larger TCP window size may be used.
The TCP window size field controls the flow of data and is limited to 2 bytes, or a window size of 65, bytes. Since the size field can't be expanded, a scaling factor is used. TCP window scale is an option used to increase the maximum window size from 65, bytes to 1 Gigabyte. The window scale option is used only during the TCP three-way handshake. The window scale value represents the number of bits to left-shift the bit window size field.
The window scale value can be set from 0 no shift to If the window size is 65, bytes with a window scale factor of 3. The window size used in the actual three-way handshake isn't the window size that's scaled, per RFC section 2. It means that the first data packet sent after the three-way handshake is the actual window size.
If there's a scaling factor, the initial window size of 65, bytes is always used. The window size is then multiplied by the scaling factor identified in the three-way handshake. The table below represents the scaling factor boundaries for various window sizes. If the window size in the registry is entered as M in decimal, the scaling factor during the three-way handshake is A scaling factor of 12 only allows a window size up to ,, bytes M. The initial window size in this example would be calculated as follows: 65, bytes with a window scale factor of Expert Info will show " tcp window specified by the receiver is now completely full ".
One is simply that "the buffer on the data receiving side overflows, tells the sender to stop sending data ZeroWindow , when the buffer is created it tells its capacity Window Update and before the client side handles it The sending side sends it to the limit of buffer capacity. In other words, it is the case that the processing capacity of the data receiving side is very slow compared to the network speed. The other is the possibility that the client intentionally created such a condition for bandwidth control.
The IPv4 workaround simply requires further hardening against the use of Source Routing, which is disallowed in Windows default state. Note: IPv4 Source Routing requests and IPv6 fragments can be blocked on an edge device, such as a load balancer or a firewall. This option can be used to mitigate systems with high-risk exposure and then allow the systems to be patched following their standard cadence.
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