8584874
Throughput Optimization and Fair Bandwidth Allocation in Multi-Hop Wireless LANs
There is an inherent well-known conflict between fairness and throughput that arises in many networking scenarios. A number of researchers have studied this problem in the context of (single-hop) wireless local area networks (WLANs), where clients directly exchange traffic with access points (APs). More recently, researchers have proposed multi-hop extensions to WLANs where client traffic is forwarded via a series of client-client links. In this paper, we show that the objective of improving throughput without sacrificing fairness can be much better met in multi-hop WLANs. We decouple this objective into two separate but related problems. First, we need an algorithm to organize clients into a multi-hop structure such that fair bandwidth allocation within this structure leads to improved throughput. Second, we need algorithms for performing fair bandwidth allocation within the determined multi-hop structure. In this paper, we first design optimal fair bandwidth allocation algorithms for both max-min throughput fairness and max-min time fairness in multi-hop WLANs. Subsequently, we design an efficient algorithm to find desirable multi-hop structures. With slight modifications, our results in this paper can be generalized to other multi-hop wireless networks as well. Our proposed solutions seamlessly integrate with legacy devices and hence are incrementally deployable. Simulation results demonstrate that our solutions can effectively improve throughput (by up to 114% or more) as well as network coverage while preserving fairness.
7316736
Efficient probabilistic packet marking
Probabilistic packet marking is a general technique which routers can use to reveal internal network information to end-hosts. Such information is probabilistically set by the routers in headers of regular IP packets on their way to destinations. A number of potential applications have been identified, such as IP traceback, congestion control, robust routing algorithms, dynamic network reconfiguration, and locating Internet bottlenecks, etc. In this paper, we define EPPM, an efficient general probabilistic packet marking scheme with a wide range of potential applications, of which locating Internet bottlenecks and IP traceback are investigated as two representative examples to demonstrate its effectiveness. Our proposed scheme imposes only a single-bit overhead in the IP packet headers. More importantly, it significantly reduces the number of IP packets required to convey the relevant information when compared to the prior best known scheme (almost by two orders of magnitude)
14357613
Construction of an efficient overlay multicast infrastructure for real-time applications
This paper presents an overlay architecture where service providers deploy a set of service nodes (called MSNs) in the network to efficiently implement media-streaming applications. These MSNs are organized into an overlay and act as application-layer multicast forwarding entities for a set of clients. We present a decentralized scheme that organizes the MSNs into an appropriate overlay structure that is particularly beneficial for real-time applications. We formulate our optimization criterion as a "degree-constrained minimum average-latency problem" which is known to be NP-hard. A key feature of this formulation is that it gives a dynamic priority to different MSNs based on the size of its service set. Our proposed approach iteratively modifies the overlay tree using localized transformations to adapt with changing distribution of MSNs, clients, as well as network conditions. We show that a centralized greedy approach to this problem does not perform quite as well, while our distributed iterative scheme efficiently converges to near-optimal solutions.
14498501
A clustering scheme for hierarchical control in multi-hop wireless networks
In this paper we present a clustering scheme to create a hierarchical control structure for multi-hop wireless networks. A cluster is defined as a subset of vertices, whose induced graph is connected. In addition, a cluster is required to obey certain constraints that are useful for management and scalability of the hierarchy. All these constraints cannot be met simultaneously for general graphs, but we show how such a clustering can be obtained for wireless network topologies. Finally, we present an efficient distributed implementation of our clustering algorithm for a set of wireless nodes to create the set of desired clusters.
3056111
An Analysis of Wireless Network Coding for Unicast Sessions: The Case for Coding-Aware Routing
A recent approach, COPE, for improving the throughput of unicast traffic in wireless multi-hop networks exploits the broadcast nature of the wireless medium through opportunistic network coding. In this paper, we analyze throughput improvements obtained by COPE-type network coding in wireless networks from a theoretical perspective. We make two key contributions. First, we obtain a theoretical formulation for computing the throughput of network coding on any wireless network topology and any pattern of concurrent unicast traffic sessions. Second, we advocate that routing be made aware of network coding opportunities rather than, as in COPE, being oblivious to it. More importantly, our work studies the tradeoff between routing flows "close to each other" for utilizing coding opportunities and "away from each other" for avoiding wireless interference. Our theoretical formulation provides a method for computing source-destination routes and utilizing the best coding opportunities from available ones so as to maximize the throughput. We handle scheduling of broadcast transmissions subject to wireless transmit/receive diversity and link interference in our optimization framework. Using our formulations, we compare the performance of traditional unicast routing and network coding with coding-oblivious and coding-aware routing on a variety of mesh network topologies, including some derived from contemporary mesh network testbeds. Our evaluations show that a route selection strategy that is aware of network coding opportunities leads to higher end-to-end throughput when compared to coding-oblivious routing strategies.
15760
Energy-Efficient Reliable Paths for On-Demand Routing Protocols
We define techniques to compute energy-efficient reliable paths within the framework of on-demand routing protocols. The choice of energy-efficient reliable paths depend on link error rates on different wireless links, which in turn depend on channel noise. We show how our scheme accounts for such channel characteristics in computing such paths. Additionally, we perform a detailed study of the AODV protocol and our energy-efficient variants, under various noise and node mobility conditions. Our results show that our proposed variants of on-demand routing protocols can achieve orders of magnitude improvement in energy-efficiency of reliable data paths.
20080343
A survey of adaptive bandwidth control algorithms
In packet-switched network traffic management and control, efficiently allocating bandwidth to provide quantitative packet-level QoS to aggregate traffic has been difficult due to unpredictable, unknown statistical characteristics of the aggregate traffic. With inaccurate traffic information, using static bandwidth allocation results in the network being underutilized, or the QoS requirement not being satisfied. An alternative is to use adaptive bandwidth control (ABC), whereby the allocated bandwidth is regularly adjusted over the packet-level time scale to attain a given QoS requirement. This paper provides a literature review of ABC algorithms that guarantee aggregate traffic packet-level QoS metrics, such as the average queue length, packet loss, and packet delay. We describe different ABC algorithms, identify their advantages and shortcomings, and provide some comparative performance evaluation results. Open issues in ABC for future research directions are also discussed.
15267355
A-DRAFT: an adaptive QoS mechanism to support absolute and relative throughput in 802.11 wireless LANs
Several distributed QoS mechanisms have been proposed to augment the existing distributed coordination function of the IEEE 802.11 MAC protocol to provide QoS support for QoS-sensitive applications. These mechanisms use well-known QoS enabling techniques such as priority assignment and fair scheduling within existing 802.11 MAC parameters. Although these mechanisms provide differentiated throughput for different classes of traffic, they cannot provide both relative and absolute throughput support simultaneously.In this paper, we propose a new mechanism called A-DRAFT that supports both absolute and relative throughput in an adaptive and a fully distributed manner. This paper describes an adaptive mechanism that supports absolute throughput as long as the total demand from this class is below the effective channel capacity. The proposed mechanism also provides relative or fair throughput support with low variation and a high degree of fairness even in a saturated network with a large number of MSs. We make use of deficit round robin scheduling with different levels of quantum rate to provide fairness, and different weights to provide absolute and relative throughput. We evaluate the performance of the proposed mechanism via mathematical analysis and confirm this analysis with simulations.
206575726
Regular multihop logical topologies for lightwave networks
Several government- and industry-funded prototyping and development activities in WDM optical networks are being conducted at various R&D centers. Optical networks can be deployed on top of an existing physical fiber plant that can provide a transparent all-optical signal path to its upper layer, thereby providing broadband services. For instance, an all-optical layer between the physical and ATM layers in a B-ISDN network will significantly improve both efficiency and flexibility for the provision of broadband services. One attractive feature of optical networks is the ease of its logical reconfigurability, i.e., any desired logical network topology can be embedded on top of any given physical fiber plant, subject to the limitations on the number of available wavelengths and transceivers. The logical topologies can be broadly classified into two categories: arbitrary and regular. Nodal connectivity patterns in regular topologies are very systematic and well defined, which simplifies routing and management operations. However, it is difficult to add an arbitrary number of nodes to a regular topology and still maintain its well-defined structure. Over the past few years, several regular logical topologies have been proposed for optical networks. In this article we provide brief descriptions of these regular logical network topologies and a comparative study of their various performance metrics, e.g., average hop distance (viz. network utilization), routing, fault tolerance, and scalability.
16981937
Network traffic characterization of distributed database applications
The authors' efforts in characterizing the traffic of distributed database systems are described. This is an important class of applications considering that database or transaction processing systems form the core of several key commercial applications. Specific traffic source models for this application class have not been developed which is imperative for their successful deployment in emerging networks. The main contribution of the paper is to present the relationship between a distributed database application scenario and the corresponding network traffic characteristics, thus providing guidelines to these applications to compute their traffic descriptors accurately.
13128696
Media-friendliness of a slowly-responsive congestion control protocol
Streaming media transfers over the Internet are expected to behave in a TCP-friendly manner while reacting slower to congestion than TCP. For this purpose, a number of slowly-responsive congestion control protocols have been developed. In this paper, we present our study on the media-friendliness of TFRC, one of the recently developed slowly-responsive congestion control mechanisms. With both simulation and Internet experiments, we show that TFRC is not necessarily smooth enough to be "media-friendly". We also discuss our approach to improve a congestion control mechanism's media-friendliness.