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TCP-FIT is a novel congestion control algorithm targeting both emerging wireless networks such as LTE, WiMax, WiFi and HSPA and high speed long delay (large BDP) networks.

The Internet is built on TCP, however, to date TCP congestion control has been implemented in inefficient ways. Standard congestion control algorithms such as TCP-Reno and TCP-NewReno, achieved great success for several decades but are found to perform poorly over wireless and/or high Bandwidth Delay Product (BDP) links. To improve TCP performance over wireless and high BDP networks, many TCP variants have been proposed, including TCP Westwood, TCP Veno for wireless applications and Compound TCP, TCP CUBIC for high BDP networks. Although these algorithms have achieved success in their respective target applications, designing a TCP congestion control algorithm that perform gracefully in both wireless and high BDP networks is still a great challenge. On the other hand however, with the deployment of wireless networks, such as LTE, WiMAX, as well as high bandwidth, real time applications such as multimedia over TCP/HTTP, it is required for the TCP congestion algorithm to handle both wireless connections with random radio related losses as well as congestion-introduced issues typical for wired high BDP networks.

In this TCP-FIT study, we first consider wireless and large BDP as the same challenge to overcome, and propose a novel congestion avoidance algorithm which can perform excellently over both wireless and large BDP links while maintaining good fairness with the standard TCP Reno algorithm. TCP-FIT, the underlying algorithm is applicable to many network topographies and characteristics without modifications to other layers (e.g. the application layer) of the end-to-end system need to be made. The algorithm utilizes both the packet loss rate and the queuing delay as estimated by the sender for the adjustment of the congestion window size. It leverages ideas in network optimization algorithms above and beyond TCP congestion control while mitigating the complexity, latency and other drawbacks of these techniques and maintaining TCP protocol compliance. As a result, network bandwidth can be more utilized, while at the same time, the queuing delay is kept at an acceptable level, so that the session remains fair.

We are launching a startup company, TCP Engines, to pursue real-world applications of TCP-FIT. The business name of TCP-FIT based network acceleration sulution is TCP-MAX 

Inventors: Jingyuan Wang (, Jiangtao Wen (, Jun Zhang, Erica Han (


Samsung licenses TCP-FIT for cloud, data center and mobile handset applications

April 29, 2014 -- Samsung, the world leader mobile technology, licensed TCP Engines' solutions, which enable Samsung handsets and other devices to transfer photos, videos, documents, and presentations with greater speed than any other in the market. Originally developed at Tsinghua University's Future Internet Technology (FIT) Lab, the TCP-FIT algorithms and software form the foundation of TCP Engines' solutions.

TCP-FIT brings Ustream increased video quality and reduced buffering

May 13, 2014 -- Ustream announced a partnership with TCP Engines, the leading supplier of TCP optimization solutions, as we are now taking advantage of the company's TCP-MAX solution for streaming optimization. The Ustream Cloud Platform is built on a proprietary technology stack: Ustream Content Delivery Network (UCDN), Ustream Media Server (UMS) and Ustream TCP Congestion Control Algorithm (UTCP). TCP Engines is at the core of the TCP Congestion Control Algorithm (TCP-FIT algorithm). TCP Engines congestion control solutions effectively unclog networks and find more bits to deliver to consumers, increasing the video quality and experience for consumers.

DATATECH GLOBAL increases video quality using TCP-FIT for streaming optimization

May 28, 2014 -- DATATECH GLOBAL, a leader in video-on-demand, licensed TCP Engines' TCP-MAX solutions (a business name of TCP-FIT) to increase the throughput and quality of DataTech Global's video streaming service, creating higher customer retention, conversion and revenues for DataTech Global and their affiliates.  TCP Engines bandwidth optimization and network acceleration solutions deliver more bits, increasing the video quality and experience for consumers, and creating higher retention and revenue for partners.

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Jingyuan Wang, Jiangtao Wen, Jun Zhang and Yuxing Han, "TCP-FIT - an improved TCP congestion control algorithm and its performance", Proc. 2011 IEEE Infocom, Shanghai, October, 2011. (PDF)

Jingyuan Wang, Jiangtao Wen, Jun Zhang, Yuxing Han, "A demonstration of a new TCP congestion control algorithm over LTE and other challenging networks," MobiCom 2010 Demo, Sept. Chicago, IL. (PDF)

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Jingyuan Wang; Jiangtao Wen; Yuxing Han. TCP congestion control for heterogeneous networks. Appl. No.: 13/085,516. Patent No.: US 8,547,839 B2. Date of Patent: Oct. 1, 2013 (PDF)

Jingyuan Wang; Jiangtao Wen; Yuxing Han. TCP congestion control for heterogeneous networks. Appl. No.: 14/021,218.  Pub. No.: US 2013/0343187 A1. Pub. Date: Dec. 26,2013 (PDF)

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Case Studies


For over 70 years, Samsung has been dedicated to making a better world through diverse businesses that today span advanced technology, semiconductors, skyscraper and plant construction, petrochemicals, fashion, medicine, finance, hotels, and more. Our flagship company, Samsung Electronics, leads the global market in high-tech electronics manufacturing and digital media. Through innovative, reliable products and services; talented people; a responsible approach to business and global citizenship; and collaboration with our partners and customers, Samsung is taking the world in imaginative new directions. (Case study PDF)

China Mobile

China Mobile Limited (the "Company", and together with its subsidiaries, the "Group") was incorporated in Hong Kong on 3 September 1997. The Company was listed on the New York Stock Exchange ("NYSE") and The Stock Exchange of Hong Kong Limited ("HKEx" or the "Stock Exchange") on 22 October 1997 and 23 October 1997, respectively. The Company was admitted as a constituent stock of the Hang Seng Index in Hong Kong on 27 January 1998.  (Case study PDF)


Renren Inc. operates a leading real-name social networking internet platform in China. Renren, which means 'Everyone' in Chinese, enables users to connect and communicate with each other, share information, create user generated content, play online games, watch videos and enjoy a wide range of other features and services. We believe real name relationships create a stronger and more enduring social graph that is essential in the mobile internet world and difficult to replicate. As of June 30, 2013, our social network had approximately 194 million activated users with over 75% of user time accessing our services through mobile. (Case study PDF)


Drenalina Srl is a provider of high availability Linux cloud hosting services, TCP acceleration, HTTP acceleration (both via server tuning and geographically redundant content delivery networks). Their service includes: 1) Email services: high availability mail server, CalDAV (calendar) server, CardDAV (addressbook) server, mailwashing / proxying services for Microsoft Exchange servers (frontend MX + antispam filter + POP3) . 2) Newsletter sending: proprietary Saas tool (MoxieMail) for campaign management + reporting. (Case study PDF)

Ustream is the leading video technology platform for live business communications, powered by the company's Ustream Cloud Platform. The company was founded in 2007 with a vision to bring live online broadcasting technology mainstream; Ustream was originally created to connect military service members to family and friends across the world. Since then, the company has established itself as a socially fueled video platform for broadcasters of any size to easily reach an infinite audience and share experiences in real-time. Their mission is to empower anyone around the world to reach new audiences through the power of live experiences. (Case study PDF)

Data Center

An infrastructure based solutions provider who designs and deploys Scalable Cloud and Data Center offerings for their clients. Provides the ability to utilize dedicated, scalable and dynamic computing resources without having to purchase, configure, maintain, and manage the underlying network application. (Case study PDF)


One of the world's largest, best performing, and most highly available content delivery networks which has powerful software to optimize content for the best viewing experience on any device and hundreds of CDN and software experts with decades of experience. (Case study PDF)


A handset manufacturer which built its reputation as the behind-the-scenes designer and manufacturer of many of the most popular OEM-branded mobile devices on the market. (Case study PDF)

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Video Demo

A demo comparison between TCP-FITand existing TCP algorithms over a wireless network is shown in the following video. In this demo, two servers are located in San Diego, California at the same location, with identical hardware and software setup. One is utilizing TCP-FIT, while the other is using standard TCP algorithm. This video is recorded at a Starbucks in Beijing with HTTP streaming from both servers. Significant advantage of TCP-FIT algorithm can be seen in the demo.

Significant advantage of TCP-FIT algorithm can be seen starting 30 seconds.

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Lab of Multimedia and Networking
Institute of HCI and Media Integration
Department of Computer Science and Technology
Tsinghua University


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Address: Room 1-512, FIT Building , Tsinghua University, Beijing 100084, China