Performance analysis of general backoff protocols

In this paper, we analyze backoff protocols, such as the one used in Ethernet. We examine a general backoff function (GBF) rather than just the binary exponential backoff (BEB) used by Ethernet. Under some mild assumptions we find stability and optimality conditions for a wide class of backoff protocols with GBF. In particular, it is proved that the maximal throughput rate over the class of backoff protocols is a fixed function of the number of stations (N) and the optimal average service time is about Ne for large N. The reasons of the instability of the BEB protocol (for a big enough input rate) are explained. Additionally, the paper introduces novel procedure for analyzing bounded backoff protocols, which is useful for creating new protocols or improving existing, as no protocol can use unbounded counters

Performance analysis of general backoff protocols

In this paper, we analyze backoff protocols, such as the one used in Ethernet. We examine a general backoff function(GBF) rather than just the binary exponential backoff (BEB) used by Ethernet. Under some mild assumptions we find stability and optimality conditions for a wide class of backoff protocols with GBF. In particular, it is proved that the maximal throughput rate over the class of backoff protocols is a fixed function of the number of stations (N) and the optimal average service time is about Ne for large N. The reasons of the instability of the BEB protocol (for a big enough input rate) are explained. Additionally, the paper introduces novel procedure for analyzing bounded backoff protocols, which is useful for creating new protocols or improving existing, as no protocol can use unbounded counters

How Penalty Leads to Improvement: a Measurement Study of Wireless Backoff

Despite much theoretical work, different modifications of backoff protocols in 802.11 networkslack empirical evidence demonstrating their real-life performance. To fill the gap we have set out to experiment with performance of exponential backoff by varying its backoff factor. Despite the satisfactory results for throughput, we have witnessed poor fairness manifesting in severe capture effect. The design of standard backoff protocol allows already successful nodes to remain successful, giving little chance to those nodes that failed to capture the channel in the beginning. With this at hand, we ask a conceptual question: Can one improve the performance of wireless backoff by introducing a mechanism of self-penalty, when overly successful nodes are penalized with big contention windows? Our real-life measurements using commodity hardware demonstrate that in many settings such mechanism not only allows to achieve better throughput, but also assures nearly perfect fairness. We further corroborate these results with simulations and an analytical model. Finally, we present a backoff factor selection protocol which can beimplemented in access points to enable deployment of the penalty backoff protocol to consumer devices.Non Peer reviewe

06441 Abstracts Collection -- Naming and Addressing for Next Generation Internetworks

From 29.10.06 to 01.11.06, the Dagstuhl Seminar 06441``Naming and Addressing for Next-Generation Internetworks\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

Secure lightweight protocols for medical device monitoring

In the present days, the health care costs are sky-rocketing and most developed nations, including EU and US, are struggling to keep the costs under control. One of the areas is related to monitoring and control of medical appliances embedded to human bodies, such as insulin pumps as heart pacers. Fortunately, recent technology advances make it possible to monitor the medical appliances remotely, greatly decreasing the need for personal doctor visits. Naturally, remote wireless monitoring of such crucial appliances poses several formidable technological challenges including security of data communication, device authentication, attack resistance, and seamless connectivity. A remote monitoring protocol must be executed in a resource-constrained environment with energy efficiency. The recently proposed Diet Exchange for Host Identity Protocol (HIP) could solve most of security issues of remote appliance monitoring. However, it has to be developed to run in an embedded device environment; its security properties must be triple-checked against the stringent requirements; potential privacy issues must be addressed; protocol messages and cryptographic mechanisms must be adopted to wireless sensor standards. Although bearing high risks of provable security and patient faith, remote monitoring of health appliances could create breakthroughs in healthcare cost reduction and bring great benefits of individuals and the society