Department of Computer Science & Technology

Joined Department: 2001

Email:zhaoyoujian@tsinghua.edu.cn

Phone:+86-10-62603055

Fax:+86-10-62603064

Bachelor of Computer Science & Technology, Tsinghua University, Beijing China, 1991;

Master of Computer Architecture, China Academy of Sciences, Computing Institute of Shenyang, China, 1994;

Ph.D. in Computer Architecture, Northeastern University, Shenyang, China, 1999.

National Engineering Laboratory of Next-Generation Internet and Interconnecting Equipment: Deputy Director (2009-);

National Standardization Technical Committee: Member (2008-);

Teaching Laboratory, Department of Computer Science & Technology: Director (2006-).

High-Speed Internet Architecture

Switching and Routing, High-Speed Network Equipment

National Natural Science Foundation of China: Research on Scalable and Predictable Switching Structure based on Uniform Buffered Crossbar Switches (2008-2010);

National 863 High-Tech Program: Reconfigurable Routing and Switching Platform (2008-2010).

In recent years, I have mainly engaged in the research of computer network architecture and new generation Internet. I have published 41 papers, among which 3 papers are indexed by SCI and 28 indexed by EI. Five patents have been filed and authorized. My research areas and contributions include:

1. Realization of High-Performance IPv4/v6 Router Architecture

As a beginner in China of high-performance routers research, I have presided over many national programs relating to the research of high-performance IPv4/v6 routers. Our development of high-performance IPv6 routers began in 2000, and succeeded in 2004. In the R&D of routers, I was in charge of the design and development of hardware architecture and system, proposing a series of key technologies in router hardware including self-adaptive allocation method in large-scale dual-stack routing table, hardware redundancy method, high-speed switching technology, high-speed serial transmission technology, and hardware dual-stack wire-speed forwarding engine. They are capable of addressing the design and implementation of computing processing plane, network switching plane, high-speed serial backplane, 10G line cards, 2.5G line card, gigabit Ethernet line cards, system electromagnetic shielding, and ventilation of system routing.

Our IPv6 Core Router passed the Network Access Test organized by Ministry of Information Industry, becoming the first equipment passing this high-end network accessing test. It was also appraised by Ministry of Information Industry in May 2004, and the comments acquired regarding hardware design and implementation are as follows: "Key technologies such as routing table allocation method by dynamic self-adaptive dual-stack forwarding engines, and hardware redundancy method, realize major innovations. Among them, dual-stack mixed routing table technology has reached international leading level."

2. Scalable Switching Network and Reconfigurable Routers

I have engaged in the research of key technologies of scalable router architectures for a long time. My focus is hardware structure of scalable routers, which has issues including switching network structure of scalable routers, routing structure and strategies of scalable routers, and QoS issues of scalable routers.

1) Switching Network Architecture of Scalable Routers. At present, almost all core routers in the world adopt Cross Bar switching structure. Its hardware complexity is O(n2) and its scalability complexity is high. Therefore, switching networks of core routers all have this scalability issue. I proposed a switching network architecture namedH-Torus, which is applicable to scalable routers by combining and improving 3D-Torus and cellular structure. Its hardware complexity is reduced to O (n), which has good scalability and switching performance.

2) Routing Structure and Strategies of Scalable Routers. Due to the length difference of IPv6 and IPv4 addresses, the design and lookup method of dual-stack mixed routing table are design challenges of core routers and scalable routers. International companies such as Cisco and Juniper adopt independent IPv6/Ipv4 routing tables. I proposed a dynamic self-adaptive routing table allocation method for IPv6/v4 dual-stack forwarding engine. This method dynamically allocates the content of IPv6 and IPv4 routing table, solving the dual-stack mixed lookup issue. Besides, it supports dynamic allocation of IPv6/v4 routing table in the same physical system. Fast routing lookup can be achieved based on the flexible allocation of IPv6/IPv4 routing table numbers. This method improves the forwarding speed of routers, and has been successfully applied to core routers.

3) QoS Issue of Scalable Routers. QoS control/guarantee is end-to-end behavior. Being one of the key issues, network equipment supporting QoS control is the basis of the whole network QoS. I proposed a multi-constraint QoS routing structure and caching management mechanism. The mechanism solves the linear increase issue of QoS routing tables, and reduces both time and space complexity of routing lookup algorithm.

China Youth Science and Technology Award (2010);

Science and Technology Progress Award by China Communications Standards Association(CCSA), First Class-IPv6 Core Router (2004);

National Science and Technology Progress Award, Second Class-IPv6 Core Router (2005);

China Computer Federation: Wang Xuan Award, First Class-IPv6 Core Router (2006).

[1] Ruisheng Wang;Youjian Zhao; Hongtao Guan; Guanghui Yang. HOBRP: A hardware optimized packet scheduler that provides tunable end-to-end delay bound. 17th IEEE International Workshop on Quality of Service(IWQoS),July 13-15, 2009, Charleston, South Carolina, USA

[2] Youjian Zhao,Zuhui Yue, Jianping Wu, Research on Next-Generation Scalable Routers Implemented with H-Torus Topology, Journal of Computer Science and Technology. VOL 23, NO.4 July, 2008: 684-693. (EI: 20083411470354; SCI: 328PI)

[3] Si-Min He, Shu-Tao Sun, Hong-Tao Guan, Qiang Zheng, Youjian Zhao On Guaranteed Smooth Switching for Buffered Crossbar Switches,IEEE/ACM Transactions on Networking, vol. 16, no. 3, June 2008. 718-732. (EI: 20082711341658; SCI: 316RJ)

[4] Wang, Yi;He, SiMin;Zhao, Youjian;Zheng, Qiang;Gao, Wen Bandwidth regulation for rate-based switching IEEE Global Telecommunications Conference, GLOBECOM 2007 Proceedings, 2007, p 2483-2487. (EI: 20080811112715, ISTP: BHY77)

[5] Youjian Zhao, Zuhui Yue, Jianping Wu, Xiaoping Zhang. Topological Properties and Routing Algorithms in Cellular Router. International conference on Networking and Services (ICNS'06), 2006:101-110. (EI: 20082111262957)