Yongguang Zhang
HRL Laboratories
Wednesday, August 18 at 2:00pm PDT
11th floor large CR

An Implementation and Experimental Study of the eXplicit Control Protocol (XCP)

The eXplicit Control Protocol (XCP) has been proposed as a multi-level network feedback mechanism for congestion control of Internet transport protocols. Theoretical and simulation results have suggested that the protocol is stable and efficient over high bandwidth-delay product paths, while being more scalable to deploy than mechanisms that do require per-flow state in routers. However, there is little operational experience with the approach. Since the deployment of XCP would require changes to both the end hosts and routers, it is important to study the implications of this new architecture before advocating such wide scale changes to internets. This paper presents the results of an experimental study of XCP. We first implemented XCP in the Linux kernel and solved various systems issues. After validating previously reported simulation results, we studied the sensitivity of XCP's performance to various environmental factors and identified two sources that can significantly reduce XCP's ability to control congestions and achieve fairness. Our contributions are two fold. First, through implementation we have revealed the challenges in platforms that lack large native data types or floating point arithmetic, and the need to keep fractions in XCP protocol header. Second, through experiments and analysis we have identified several possibilities that XCP can enter into incorrect feedback control loops and adversely affect the performance. These are deployment challenges intrinsic to XCP design. More research is needed before we can advocate a wide scale adoption.

Bio:
Yongguang Zhang is a Senior Research Scientist at HRL (a central research laboratory for Boeing, Raytheon, and GM). His main research interests include mobile wireless networks, wireless security, satellite networks, sensors and embedded systems, Internet and distributed systems, operating systems and platforms. He was co-PIs and has provided technical lead in several DARPA projects on wireless network research. He has published over 50 technical papers and one edited book, and was a guest editor in ACM MONET Journal. He has helped organize and has chaired/co-chaired several conferences/workshops and IETF working groups. He received his Ph.D. in computer science from Purdue University in 1994 and was an adjunct professor of computer science at the University of Texas at Austin from 2001 to 2003.