Probing Overhead Research Articles

Distributed Proportional Fair Scheduling for IEEE802.11 Wireless LANs

In the time varying wireless channel, opportunistic scheduling is one of the important techniques to achieving the rich diversities inherent in wireless communications. However, most existing scheduling schemes require centralized scheduling and little work has been done on developing distributed algorithms The proportional fair scheduling is one of the representative opportunistic scheduling for centralized networks. In this paper, we propose distributed proportional fair scheduling (DPFS) scheme for wireless LAN network. In the proposed DPFS scheme, each receiver estimates channel condition and calculates independently its own priority with probabilistic manner, which can reduce excessive probing overhead required to gather the channel conditions of all receivers. We evaluate the proposed DPFS using extensive simulation and simulation results show that DPFS obtains higher network throughput than conventional scheduling schemes while maintaining fairness among users.

Collision-aware design of rate adaptation for multi-rate 802.11 WLANs

One of the key challenges in designing a rate adaptation scheme for IEEE 802.11 wireless LANs (WLANs) is to differentiate bit errors from link-layer collisions. Many recent rate adaptation schemes adopt the RTS/CTS mechanism to prevent collision losses from triggering unnecessary rate decrease. However, the RTS/CTS handshake incurs significant overhead and is rarely activated in today's infrastructure WLANs. In this paper we propose a new rate adaptation scheme that mitigates the collision effect on the operation of rate adaptation. In contrast to previous approaches adopting fixed rate-increasing and decreasing thresholds, our scheme varies threshold values based on the measured network status. Using the "retry" information in 802.11 MAC headers as feedback, we enable the transmitter to gauge current network state. The proposed rate adaptation scheme does not require additional probing overhead incurred by RTS/CTS exchanges and can be easily deployed without changes in firmware. We demonstrate the effectiveness of our solution by comparing with existing approaches through extensive simulations.

Link stress reduction in topology-aware overlay path monitoring

Overlay networks often employ end-to-end probes to track network performance. These probes are routed through overlay paths, which usually overlap at the overlay level. In addition, two seemingly disjoint overlay paths may share many physical links at the IP level, causing high link stress. Several monitoring algorithms have been proposed to reduce the overall probing overhead. Surprisingly, they do not address the associated problem of high link stress. The high link stress presents an additional load on the network links, which could cause congestion, delay, and measurement conflict. In this paper, we aim at reducing the link stress associated with probing algorithms by introducing the concept of Internal Probing, where readily available IP-level topology information is used in conjunction with the overlay topology to reduce the link stress on highly shared path segments. Simulation results show that the proposed scheme can reduce the link stress by up to 30%.

Topology-aware overlay path probing

Path probing is essential to maintaining an efficient overlay network topology. However, the cost of a full-scale probing is as high as O( n 2), which is prohibitive in large-scale overlay networks. Several methods have been proposed to reduce probing overhead, although at a cost in terms of probing completeness. In this paper, an orthogonal solution is proposed that trades probing overhead for estimation accuracy in sparse networks such as the Internet. The proposed solution uses network-level path composition information (for example, as provided by a topology server) to infer path quality without full-scale probing. The inference metrics include latency, loss rate and available bandwidth. This approach is used to design several probing algorithms, which are evaluated through extensive simulation. The results show that the proposed method can reduce probing overhead significantly while providing bounded quality estimations for all of the n × ( n − 1) overlay paths. The solution is well suited to medium-scale overlay networks in the Internet. In other environments, it can be combined with extant probing algorithms to further improve performance.

Estimating network proximity and latency

Network proximity and latency estimation is an important component in discovering and locating services and applications. With the growing number of services and service providers in the large-scale Internet, accurately estimating network proximity/latency with minimal probing overhead becomes essential for scalable deployment. Although there exist a number of network distance estimation schemes, they either rely on extensive infrastructure support, require the IP address of the potential targets, falsely cluster distant nodes, or perform poorly with even few measurement errors. We propose Netvigator , a scalable network proximity and latency estimation tool that uses information obtained from probing a small number of landmark nodes and intermediate routers (termed milestones) that are discovered en route to the landmarks, to identify the closest nodes. With very little additional probing overhead, Netvigator uses distance information to the milestones to accurately locate the closest nodes. We developed a Netvigator prototype and report our performance evaluation on PlanetLab and in the intranet of a large enterprise. Netvigator is a running service on PlanetLab as a part of HP Labs' S 3 (Scalable Sensing Service).

Packet management techniques for measurement based end-to-end admission control in IP networks

End-to-end Measurement Based connection Admission Control (EMBAC) mechanisms have been proposed to support real-time flows quality of service requirements over a Differentiated Services Internet architecture. The EMBAC basic idea is to decentralize the admission control decision, by requiring each individual user to probe the network path during flow setup, and by basing the accept/reject decision on the probing traffic statistics measured at the destination. In conformance with the differentiated services framework, routers are oblivious to individual flows and only need to serve data packets with a higher priority than probing traffic. In this paper, we build upon the observation that some form of congestion control of the probing packets queue at each router is a key factor to provide performance effective EMBAC operation. The original contribution of the paper is twofold. First, we provide a thorough investigation, by means of both approximate analytical modeling and extensive simulation, of an EMBAC scheme (denoted in the following EMBAC-PD), in which probing queues congestion control is enforced by means of a probing packet expiration deadline at each router. Second, by means of extensive performance evaluation, we show that EMBAC-PD can provide strict QoS guarantees even in the presence of very light probing overhead (few probing packets per flow setup). Most interesting, EMBAC-PD does not necessarily require long probing phases to accurately estimate the network load subject to statistical fluctuations, but can provide effective operation even in the presence of extremely short probing phase duration (e.g., few hundreds of ms, acceptable for practical applications).