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Low Bandwith High Latency Flow Control Algorithm

IP.com Disclosure Number: IPCOM000028127D
Original Publication Date: 2004-Apr-27
Included in the Prior Art Database: 2004-Apr-27
Document File: 4 page(s) / 66K

Publishing Venue

IBM

Abstract

An algorithm for efficient transmission of data over low-bandwidth high latency connections over TCP/IP. It does not need any modification to the TCP/IP protocol, but works on top of TCP/IP. The algorithm is most advantageously used for terminal client like applications over e.g. cellphone connections.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 41% of the total text.

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Low Bandwith High Latency Flow Control Algorithm

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 .. IntroductionIntroduction We describe a method for increasing the performance of TCP /IP over low-bandwidth, high latency connections like eg. cellphone connections, especially for enabling efficient terminal client like access to applications on a server .

    TCP/IP was designed before the 1970s to function over long distances. TCP/IP´s flow control algorithm is perfectly suited to high bandwidth connections available in LAN environments and even works well for WAN connections . Even 40 years after TCP/IP's birth, low bandwidth is still an issue.

2. Problem Statement

    Known methods for increasing the performance over low bandwidth connections are typically data compression, TCP/IP header compression and reducing TCP/IP overhead by increased TCP window sizes.

    This all is not of much help when dealing with interactive applications over wireless, low bandwidth connections, since here an additional problem becomes visible: the high latency of these connections! Typically all wireless low bandwidth connections have a roundtrip times of at least 800ms.

    Another problem of state-of-the-art terminal client solutions is, that these applications do not really care about the limited bandwidth of a connection . After opening of a Web-Browser covering the whole screen these applications send all the update information over the low-bandwidth connection, even if the browser was closed just after being started. This leads to the overrun of the communication link and the unability to use the terminal client.

    To overcome all these problems for low bandwidth high latency connections a new technology called Corporate Wireless Connect (CWC) is used for the remote control of interactive applications. The server sends compressed screenshots to the client over a wireless low bandwidth connection, and the client displays the uncompressed screenshot. Mouse- and keyboard-events at the client are sent back to the server. For CWC it is necessary to see on the client, what is going on the server, as quickly as possible. Therefore it is of importance for low bandwidth connections to limit the data transmitted to the absolute necessarily .

3. Solution

    Think again of the opening of an application on the server covering the complete display. A screenshot takes the complete picture on the server, compresses it and transmits it to the client, in a sequence of small packets . If the user of the client during the incremental transfer of this picture just terminates the application by a click (resulting again in a huge amount of data to be sent from the server to the client), it might be better to ignore all the data not being sent and start a new transfer of a complete screenshot (full screen refresh) of the server after the application was closed. All pieces not being sent for the completion of the previous screenshot may now just be discarded and are not sent! Therefore the client is always quickly displaying the a...