Yuu-Heng Cheng

IEEE 802.21: Media independent handover: Features, applicability, and realization

Providing users of multi-interface devices the ability to roam between different access networks is becoming a key requirement for service providers. The availability of multiple mobile broadband access technologies, together with the increasing use of real-time multimedia applications, is creating strong demand for handover solutions that can seamlessly and securely transition user sessions across different access technologies. A key challenge to meeting this growing demand is to ensure handover performance, measured in terms of latency and loss. In addition, handover solutions must allow service providers, application providers, and other entities to implement handover policies based on a variety of operational and business requirements. Therefore, standards are required that can facilitate seamless handover between such heterogeneous access networks and that can work with multiple mobility management mechanisms. The IEEE 802.21 standard addresses this problem space by providing a media-independent framework and associated services to enable seamless handover between heterogeneous access technologies. In this article, we discuss how the IEEE 802.21 standard framework and services are addressing the challenges of seamless mobility for multi-interface devices. In addition, we describe and discuss design considerations for a proof-of-concept IEEE 802.21 implementation and share practical insights into how this standard can optimize handover performance.

Policy-based mobile ad hoc network management

Ad hoc networking is the basis of the future military network-centric warfare architecture. Such networks are highly dynamic in nature, as mobile ad hoc networks are formed over wireless links that are susceptible to failure. Strict requirements on security and reliability combined with the dynamic nature of the network provide a strong motivation for self-forming, self-configuring, and self-healing capabilities in the network. This paper describes a policy-based mobile ad hoc network management system that addresses these needs. The system provides the capability to express networking requirements in the form of policies at a high level and have them automatically realized in the network by intelligent agents. Our system provides the following capabilities: flexible monitoring and reporting that enables collection of management information from network elements at configurable intervals; automated configuration and reconfiguration of network elements based on reported network status; user-definable aggregation and filtering of monitored management information at the source of the data so as to reduce management station processing and network transmission overhead.

Performance Analysis of Drama: A Distributed Policy-Based System for Manet Management

DRAMA is a distributed policy-based management system designed to manage mobile ad hoc networks (MANETs). Its design philosophy is to create intelligent, self-adaptive policy agents to manage dynamic networks without human intervention. Network management functions are performed in a distributed fashion by these policy agents, rather than being controlled by a centralized management station. Policies are used to control the frequency and content of network management messages exchanged among policy agents in a way that reduces bandwidth usage and increases the utility of management messages. This greatly enhances management efficiency and reduces the bandwidth overhead required for network management. As with any new technology, there is a question about the scalability of this approach. The purpose of the work described in this paper is to study whether the DRAMA policy-based network management system can scale to networks of 500+ nodes. The study uses a novel simulation-based approach to evaluate DRAMA performance when DRAMA is used to manage MANETs of up to 500 nodes. The results confirm that the DRAMA distributed policy-based management paradigm provides superior performance over a centralized management paradigm for MANETs

Policy-based mobile ad hoc network management for drama

Ad hoc networking is the basis of the future military network-centric warfare architecture. Such networks are highly dynamic in nature, as mobile ad hoc networks are formed over wireless links that are susceptible to failure. Strict requirements on security and reliability combined with the dynamic nature of the network provide a strong motivation for self-forming, self-configuring, and self-healing capabilities in the network. This paper describes a policy-based mobile ad hoc network management system that addresses these needs. The system provides the capability to express networking requirements in the form of policies at a high level and have them automatically realized in the network by intelligent agents. Our system provides the following capabilities: flexible monitoring and reporting that enables collection of management information from network elements at configurable intervals; automated configuration and re-configuration of network elements based on reported network status; user-definable aggregation and filtering of monitored management information at the source of the data so as to reduce management station processing and network transmission overhead.

PECAN: policy-enabled configuration across networks

The Internet is growing to the point of needing more serious, scalable management infrastructure. Telecommunications companies and Internet service providers alike face the pressures of upgrading and provisioning their networks while constraining their infrastructure costs to maintain profitability and to stay competitive in an industry that is financially stressed with tight profit margins. In order to be financially successful in this environment, service providers will have to support a variety of services and applications on a combined packet infrastructure, carrying increased varieties of traffic with different performance characteristics and predictable levels of managed quality of service (QoS). Multi-protocol label switching (MPLS) traffic engineering enables service providers to engineer their networks to provide such QoS; however, this task brings along with it a plethora of management challenges. We discuss these management challenges and our experience with the design and implementation of a policy-based management system, PECAN, for managing MPLS networks. PECAN provides the ability for a network operator to define high-level policies that control the operation of the management system. These high-level policies control admission of traffic into the network based on the QoS guarantees required; placement of traffic flows on MPLS traffic engineered paths; and the feedback loop between network fault/performance monitoring and reconfiguration of the network to alleviate the effects of any observed problems.

Scalable policy management for ad hoc networks

The characteristics of mobile ad hoc networks (commonly called MANETs) are sufficiently different from commercial wireline networks to have generated a great deal of work in alternate management paradigms. The task of managing MANETs involves frequent reconfiguration, due to node mobility and consequently dynamically changing network topology. Network nodes often have limited battery power and storage capacity, and wireless radio link capacity and quality varies dynamically based on environmental conditions (weather, terrain, foliage, etc.). These differences have resulted in a need for paradigms particularly suited for managing MANETs. In this paper, we describe a distributed, hierarchical management system that implements policy-based control of a MANET. Policies are used to enable flexible composition of diverse management actions based on network conditions and external events. A policy conflict detection mechanism based on event calculus is used to detect certain types of policy conflicts. The rapidly changing network topology and link characteristics typical of a MANET are managed by an adaptive, self-forming hierarchy of policy agents that implement the appropriate management actions based on their management role. The system described in this paper has been prototyped and demonstrated in a laboratory environment

Realization of IEEE 802.21 services and preauthentication framework

Providing users of multi-interface devices the ability to roam between different access networks is becoming a key requirement for service providers. The availability of multiple mobile broadband access technologies together with increasing use of real time multimedia applications is creating strong demand for handover solutions that can seamlessly and securely transfer user sessions across different access technologies. In this paper, we discuss how the IEEE 802.21 standard and its services address the challenges of seamless mobility for multi-interface devices. We focus on a proof-of-concept implementation that integrates IEEE 802.21 services and a pre-authentication framework, realizing different possible usage scenarios to optimize handover performance. We describe the implementation of two handover scenarios using the 802.21 Services: the first one is initiated by the mobile node and the second one is initiated by the operator network. We compare the two scenarios and discuss their respective benefits. Finally, we describe the implementation challenges and lessons learned through this exercise.

AMS: an adaptive middleware system for wireless ad hoc networks

The characteristics of ad hoc networks greatly increase the complexity of programming distributed applications with respect to both sending and receiving messages. This is because the network programming API based upon TCP and UDP was designed for the relatively stable, stationary Internet. The semantics of the API does not address the emerging issues from the dynamic mobile wireless ad hoc networks. One promising approach for alleviating this problem is to develop applications on top of a middleware system to shield applications from dealing with the dynamics of ad hoc networks. However, conventional middleware systems were not designed to cope with the frequently changing communications characteristics of military ad hoc networks. In order to address the above problem, we have designed and implemented a prototype of AMS , an Adaptive Middleware System with the following features. First, this middleware system is specifically designed to deal with dynamic and unreliable networks. Second, it shields communicating entities from coping with frequently changing networks via an API with semantics that provide a suitable abstraction of the underlying dynamic networks. Third, it allows individual applications to define their own communications requirements while the middleware system can set the lowest common requirements for all the communications per the military situations. Lastly, this middleware system has an interface that allows an external control system to adjust the values of its parameters to optimize the overall system performance.

Novel software agent framework with embedded policy control

In general, agent frameworks allow the functionality of their agents to be augmented with plug-ins, and agents in a multi-agent system collaborate with other agents to achieve their collective and/or individual goals. This model poses a few issues in terms of function coordination: (i) to allow the insertions of plug-ins on-the-fly, an agent framework needs to properly schedule the execution of plug-ins in a timely, coordinated fashion; (ii) plug-ins may conflict with each other in their behavior; and (in) agents may need to adapt their behavior based on their environments, in addition to coordinating their actions according to their objectives. Recent advances in policy-based management research suggest a promising direction to remedy the deficiency of existing software agent frameworks. We envision that the coordination between the plug-ins within an agent as well as the compliance of agents with environmental requirements can be achieved via policy control. With policy control, agents can adapt their behavior dynamically to meet the ever-changing environmental requirements such as those posed by military wireless ad hoc networks. In this paper, we present a novel software agent framework with seamlessly integrated policy control. We first describe the concept of policy control and how it is integrated into this framework. Next we explain the process of policy in action, discuss in detail the functions and benefits of policy control, and elaborate on the agent behavior adaptation that enables agents to achieve their goals while meeting dynamic environmental requirements.

Managing network security policies in tactical MANETs using DRAMA

Military networks are required to adapt their access control policies to the Information Operations Condition (INFOCON) levels to minimize the impact of potential malicious activities. Such adaptations must be automated to the extent possible, consistent with mission requirements, and applied network-wide. In this paper, we present a Policy-Based Network Security (PBNS) management approach for tactical MANETs. This approach leverages the DRAMA policy based network management system and the Smart Firewall system to meet the above requirement. It allows administrators to specify low-level network access control policies for each INFOCON level using high-level policies (adapted from the Smart Firewalls approach). The high-level policies are securely distributed to all the policy decision points in the network, which evaluate and enforce policies in a distributed manner. As a consequence of enforcing policies in response to INFOCON level changes, appropriate access control policies will be derived and applied to local firewall devices without human intervention. Thus, operator burden can be significantly reduced and inadvertent errors can be avoided.