Tcp window size windows xp

How is this possible? To have a 64K receive window, doesn't it need a 64K buffer? Are there two different buffers? So I believe data is read from the transport layer into the afd. That is unclear to me. Are you setting the window size yourself? Make sure you do that before connect 2 or accept 2. But again windows might be special in this regard, check the msdn. How are we doing? Please help us improve Stack Overflow.

Take our short survey. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Windows XP Ask Question. With a maximum window size of 65, bytes, this sampling rate was sufficient. Using window scaling, and a maximum window size of 1 Gigabyte, this RTT sampling rate isn't sufficient. Using this data, the RTT can be accurately calculated with large window sizes.

RTT is used to calculate retransmission intervals. Accurate RTT and retransmission time-outs are needed for optimum throughput. Either side can then use the TCP option during the session. The timestamp option field can be viewed in a Network Monitor trace by expanding the TCP options field, as shown below:. The TCP sequence number field is limited to 32 bits, which limits the number of sequence numbers available.

With high capacity networks and a large data transfer, it's possible to wrap sequence numbers before a packet traverses the network. If sending data on a one Giga-byte per second Gbps network, the sequence numbers could wrap in as little as 34 seconds. If a packet is delayed, a different packet could potentially exist with the same sequence number. To avoid confusion of duplicate sequence numbers, the TCP timestamp is used as an extension to the sequence number.

Packets have current and progressing time stamps. An old packet has an older time stamp and is discarded. Before SACK, a receiver could only acknowledge the latest sequence number of a contiguous data stream that had been received, or the "left edge" of the receive window. With SACK enabled, the receiver continues to use the ACK number to acknowledge the left edge of the receive window, but it can also acknowledge other blocks of received data individually.

The data blocks are identified using the sequence number at the start and at the end of that block of data. It's also known as the left and right edge of the block of data.

Length is the length in bytes of this TCP option. With SACK enabled default , a packet or series of packets can be dropped. The receiver informs the sender which data has been received, and where there may be "holes" in the data. The sender can then selectively retransmit the missing data without a retransmission of blocks of data that have already been received successfully.

The SackOpts value in the following registry key can be edited to control the use of selective acknowledgments:. The valid binary value is 0 or 1, the default value is 1.

The following Network Monitor trace illustrates a host acknowledging all data up to sequence number , plus the data from sequence number The missing data is from to As a review of normal retransmission behavior, TCP starts a retransmission timer when each outbound segment is handed down to the Internet Protocol IP.

If no acknowledgment has been received for the data in a given segment before the timer expires, then the segment is retransmitted. The timer for a given segment is doubled after each retransmission of that segment. Using this algorithm, TCP tunes itself to the normal delay of a connection.

TCP retransmits data before the retransmission timer expires under some circumstances. The most common cause is a feature known as fast retransmit. When a receiver that supports fast retransmit receives data with a sequence number beyond the current expected one, some data was likely dropped.

To help inform the sender of this event, the receiver immediately sends an ACK, with the ACK number set to the sequence number that it was expecting. It is the product of the available bandwidth and the latency, or RTT. The TCP Window is a buffer that determines how much data can be transferred before the server waits for acknowledgement.

It is in essence bound by the BDP. If the BDP or RWIN is lower than the product of the latency and available bandwidth, we can't fill the line since the client can't send acknowledgements back fast enough. You can choose a number of hosts, a number of pings per host, and ICMP packet size.

After clicking start, the tool will consecutively ping all hosts, then provide maximum and average latency measurements in milliseconds, as well as packet loss indication if present. In order to do that, we recommend using a larger number of hosts than the default 5, and a larger packet size since larger packets tend to have a bit higher latency.

This section of the Optimizer has been improved to include an actual Registry Editor. It is a direct interface to the Windows Registry, and only intended for advanced use! Please only use it carefully, and at your own risk. The File Pull-down menu contains a number of options for backing up, as well as exporting and importing all the related TCP Optimizer settings.

The Preferences menu , pictured on the right has two sections. It affects all the "Optimal settings" recommendations of the program, so if you're not sure what it does, leave it at the default ms. Basically, the larger this number, the larger RWIN values the program is going to recommend under "Optimal settings" for the same connection speed, and vice versa.

The second section in the Preferences menu, "Latency tab: hosts to ping" contains a list of URLs, used in the Latency section of the program for measuring current RTT round trip time, delay, ping, latency to multiple hosts.

The Help Menu of The Optimizer simply contains a link to this documentation, as well as the Software License Agreement, and some general information about the program. Username: Password: forgot password? All rights reserved. Broadband Forums General Discussions. Telefonica Incompetence, Xenophobia or Fraud? Wireless Networks and WEP. Tiny Software Personal Firewall v1.

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Menus 9. Using the program If you do not feel like reading the entire documentation below, or you simply need the tweaks NOW, without spending time in learning the meaning of all those settings, you can use the Optimizer by following these short instructions: - Choose your maximum Connection Speed from the slider bar the maximum available bandwidth, in kilobits per second - Choose your Network Interface, or check to Modify All Network Adapters - Pick " Optimal settings " from the radio-buttons near the bottom of the program - Click on the " Apply changes " button and reboot The Optimizer can do all the rest for you including a backup of the current registry settings, so you can revert the changes if you wish.

This setting should be tried first. It is not very aggressive, but it takes precedence over regular traffic and asks for low delay. For ToS, you get immediate precedence, low delay. For DiffServ, you get AF22 - class 2 traffic, medium drop probability.

This is a moderately aggressive precedence setting. For ToS, you get flash override precedence, high throughput. For DiffServ, you get AF41 - class 4 traffic, low drop probability. For ToS, you get critical precedence, low delay, high throughput.

The tables below explain the ToS and DiffServ values in more detail so you can choose your own numbers ToS Field in Detail: bit 0 1 2 3 4 5 6 7 Precedence 0 - routine 1 - priority 2 - immediate 3 - flash 4 - flash override 5 - critical 6 - Internetwork Control 7 - Network Control.

Throughput 0 - normal 1 - high. Reliability 0 - normal 1 - high. CU Currently unused, best kept at 00 for backward compatibility with ToS.