Raymond R.-F. Liao

The mobiware toolkit: programmable support for adaptive mobile networking

Existing mobile systems (e.g., mobile IP, mobile ATM, and third-generation cellular systems) lack the intrinsic architectural flexibility to deal with the complexity of supporting adaptive mobile applications in wireless and mobile environments. We believe that there is a need to develop alternative network architectures from the existing ones to deal with the tremendous demands placed on underlying mobile signaling, adaptation management, and wireless transport systems in support of new mobile services (e.g., interactive multimedia and Web access). We present the design, implementation, and evaluation of mobiware, a mobile middleware toolkit that enables adaptive mobile services to dynamically exploit the intrinsic scalable properties of mobile multimedia applications in response to time-varying mobile network conditions. The mobiware toolkit is software-intensive and is built on CORBA and Java distributed object technology. Based on an open programmable paradigm developed by the COMET Group, mobiware runs on mobile devices, wireless access points, and mobile-capable switch/routers providing a set of open programmable interfaces and algorithms for adaptive mobile networking.

A utility-based approach for quantitative adaptation in wireless packet networks

This paper assesses the state-of-the-art in Quality-of-Service (QoS) adaptive wireless networks and proposes new adaptation techniques that better suit application specific needs. The contribution of the paper is as follows: we propose an adaptive service comprising (i) bandwidth utility functions, which capture the adaptive nature of mobile applications in terms of the range of bandwidth over which they prefer to operate; and (ii) adaptation scripts, which enable adaptive mobile applications to program the per-flow adaptation time scale and bandwidth granularity realizing application-specific adaptive services. To maintain adaptive services in wireless packet access networks, we propose a split level adaptation control framework that operates at the network and application levels. Network level control employs a periodic probing mechanism between mobile devices and network gateways in support of utility based max–min fair resource allocation. Application level control is managed by a set of distributed adaptation handlers that operate at mobile devices realizing application-specific adaptation strategies.

On utility-fair adaptive services in wireless networks

Adaptive quality-of-service (QoS) techniques can effectively respond to time-varying channel conditions found in wireless networks. In this paper, we assess the state-of-the-art in QoS adaptive wireless systems and argue for new adaptation techniques that are better suited to respond to application-specific adaptation needs. A QoS adaptive data link control model is presented that accounts for application-specific adaptation dynamics that include adaptation time scales and adaptation policies. A centralized adaptation controller employs a novel utility-fair bandwidth allocation scheme that supports the dynamic bandwidth needs of adaptive flows over a range of operating conditions. Three wireless service classes play an integral role in accommodating a wide variety of adaptation strategies. In this paper, we discuss the design of the utility-fair allocation scheme and the interaction between the centralized adaptation controller and a set of distributed adaptation handlers, which play a key role in intelligently responding to the time-varying channel capacity experienced over the air-interface.

Dynamic core provisioning for quantitative differentiated services

Efficient network provisioning mechanisms that support service differentiation are essential to the realization of the Differentiated Services (DiffServ) Internet. Building on our prior work on edge provisioning, we propose a set of efficient dynamic node and core provisioning algorithms for interior nodes and core networks, respectively. The node provisioning algorithm prevents transient violations of service level agreements (SLA) by predicting the onset of service level violations based on a multiclass virtual queue measurement technique, and by automatically adjusting the service weights of weighted fair queueing schedulers at core routers. Persistent service level violations are reported to the core provisioning algorithm, which dimensions traffic aggregates at the network ingress edge. The core provisioning algorithm is designed to address the difficult problem of provisioning DiffServ traffic aggregates (i.e., rate-control can only be exerted at the root of any traffic distribution tree) by taking into account fairness issues not only across different traffic aggregates but also within the same aggregate whose packets take different routes through a core IP network. We demonstrate through analysis and simulation that the proposed dynamic provisioning model is superior to static provisioning for DiffServ in providing quantitative delay bounds with differentiated loss across per-aggregate service classes under persistent congestion and device failure conditions when observed in core networks.

Peering and provisioning of differentiated Internet services

A key consideration in building differentiated network services is the feasibility of maintaining stable and consistent service level agreements across multiple networks where allocations are made only on the edges. To investigate this, we consider a game theoretic model of capacity provisioning in a differentiated services Internet. The players are one raw-capacity seller per network, one broker per service per network, and users, to play the roles of wholesellers, retailers and end users respectively in a two-tier wholeseller/retailer market. Based on this model, we are able to construct an explicit necessary and sufficient condition for the stability of the game, which determines the sustainability of a given set of SLA configurations among peering ISP. The analytical results are validated with simulations of user and broker dynamics, using distributed progressive second price auctions as the spot market mechanism in a scenario with three interconnected networks, and two services.

Market pricing of differentiated Internet services

This paper presents a decentralized auction-based approach to pricing of edge-allocated bandwidth in a differentiated services model for the Internet. The players in this architecture are users, one raw-capacity seller per network and one broker per service per network. With the progressive second price auction mechanism as the basic building block, we conduct a game theoretic analysis, deriving optimal strategies for buyers and brokers, and show the existence of network-wide equilibria. We investigate the system dynamics by simulating a scenario with three interconnected networks, and two types of services built on the proposed standard expedited forwarding (EF) and assured forwarding (AF) per-hop-behaviors.

Incentive engineering in wireless LAN based access networks

Traffic regulation in public and private wireless LANs face a number of significant challenges, particularly in commercial networks where there is a need for efficient regulation of bursty transactional applications, support for bandwidth reservation services while inhibiting bandwidth hogging by mobile devices, and providing incentives for user cooperation. We take a new approach to solving these problems by applying incentive engineering techniques to wireless access networks. We design two incentive-based allocation service classes: an instantaneous allocation (IA) class, which provides better throughput, and a stable allocation (SA) class, which provides better allocation stability. Our approach possesses a number of beneficial properties including minimizing the algorithmic and protocol overhead on mobile devices, Nash bargaining fairness for the IA service, and incentive compatibility for mobile users promoting the truthful selection of service class and bandwidth declaration. We use analysis, simulation and experimental results from a wireless testbed to demonstrate the effectiveness of wireless incentive engineering.

Dynamic Core Provisioning for Quantitative Differentiated Service

Efficient network provisioning mechanisms supporting service differentiation and automatic capacity dimensioning are important for the realization of a differentiated service Internet. In this paper, we extend our prior work on edge provisioning [7] to interior nodes and core networks including algorithms for: (i) dynamic node provisioning and (ii) dynamic core provisioning. The dynamic node provisioning algorithm prevents transient violations of service level agreements by self-adjusting per-scheduler service weights and packet dropping thresholds at core routers, reporting persistent service level violations to the core provisioning algorithm. The dynamic core provisioning algorithm dimensions traffic aggregates at the network ingress taking into account fairness issues not only across different traffic aggregates, but also within the same aggregate whose packets take different routes in a core IP network. We demonstrate through analysis and simulation that our model is capable of delivering capacity provisioning in an efficient manner providing quantitative delay-bounds withdifferen tiated loss across per-aggregate service classes.

Programmable mobile networks

Existing mobile systems (e.g., mobile IP, mobile ATM and third generation cellular systems) lack the intrinsic architectural flexibility to deal with the complexity of supporting adaptive mobile applications in wireless and mobile environments. We believe that there is a need to develop alternative network architectures from the existing ones to deal with the demands placed on underlying mobile signalling, adaptation management and wireless transport systems in support of new mobile services, e.g. interactive multimedia and web access. In this paper we present the design, implementation and evaluation of mobiware, a middleware technology that enables the introduction of new services in mobile networks. Mobiware provides a toolkit that service providers can utilize to build services that can dynamically exploit the intrinsic scalable properties of mobile multimedia applications in response to time-varying mobile network conditions. Based on an open programmable networking paradigm, mobiware runs on mobile devices, wireless access points and mobile-capable switch/routers providing a set of open programmable interfaces and distributed objects for adaptive mobile networking. Mobiware is software-intensive and is built on CORBA and Java distributed object technologies. The source code for mobiware v1.0 is freely available (comet.columbia.edu/mobiware) for experimentation.

Dynamic edge provisioning for core IP networks

Effective edge capacity provisioning is an important architectural component of the emerging differentiated service Internet. We propose a set of dynamic provisioning algorithms, which are operational at the edge routers of a differentiated services core network. These edge mechanisms include: (i) ingress dynamic link sharing, which augments class based queueing techniques with bandwidth utility functions so that dynamic link sharing can be used to distribute bandwidth among traffic conditioners located at edge routers; and (ii) egress dynamic capacity dimensioning, which formulates bandwidth dimensioning at egress links to peering/transit networks taking into account measured core network traffic conditions. We demonstrate through analysis and simulation that the proposed edge provisioning architecture is efficient and effective at supporting user link sharing policies while taking into account the dynamics of traffic load measured in the core network.