Admela Jukan

Architectural Requirements for Cloud Computing Systems: An Enterprise Cloud Approach

Cloud Computing is a model of service delivery and access where dynamically scalable and virtualized resources are provided as a service over the Internet. This model creates a new horizon of opportunity for enterprises. It introduces new operating and business models that allow customers to pay for the resources they effectively use, instead of making heavy upfront investments. The biggest challenge in Cloud Computing is the lack of a de facto standard or single architectural method, which can meet the requirements of an enterprise cloud approach. In this paper, we explore the architectural features of Cloud Computing and classify them according to the requirements of end-users, enterprises that use the cloud as a platform, and cloud providers themselves. We show that several architectural features will play a major role in the adoption of the Cloud Computing paradigm as a mainstream commodity in the enterprise world. This paper also provides key guidelines to software architects and Cloud Computing application developers for creating future architectures.

The Evolution of Cellular Backhaul Technologies: Current Issues and Future Trends

The rapid increase of the number of mobile subscribers as well as the deployment of 3G technologies are putting strain on mobile backhaul operational expenditures (OPEX) which amount to 20-40% of total mobile operators OPEX due to their reliance on T1/E1 copper lines. For these reasons, the current backhaul systems, a term commonly used to describe connectivity between base stations and radio controllers, are increasingly integrating more cost-effective, packet switched technologies, especially Ethernet/Internet technologies. In addition, Wi-Fi and WiMAX are emerging as promising backhaul solutions and initial findings have demonstrated their feasibility. However, the notion of network migration unavoidably raises new technical challenges relevant to aspects of TDM and packet network timing synchronization, QoS, and packet efficiency. This survey aims to provide a comprehensive study of state-of-the-art circuit switched and emerging packet switched backhaul technologies based on research articles and standard documents. For packet switched backhaul, we focus on the practically important Pseudowire approaches which are used to transport TDM services over packet switched networks. We also discuss the features and research findings on the use of Wi-Fi and WiMAX technologies which illustrate their potential for rapid and cost-efficient backhaul deployment. Finally, we highlight some open issues relevant to timing synchronization in wireless mesh backhaul and femtocells deployments, which offer a rich ground for further research.

Path selection methods with multiple constraints in service-guaranteed WDM networks

We propose a new approach to constraint-based path selection for dynamic routing and wavelength allocation in optical networks based on WDM. Our approach considers service-specific path quality attributes, such as physical layer impairments, reliability, policy, and traffic conditions, and uses a flooding-based transfer of path information messages from source to destination to find multiple feasible paths. It is fully decentralized, as it uses local network state information. To better understand how multiple constraints impact the efficiency of wavelength routing, and consequently provision the service guarantees, we specifically focus on electronic regenerators that, while being widely considered as the basic building blocks for optical switching nodes, are likely to impose conflicting constraints on routing. For example, electronic regenerators extend the optical reach and could perform wavelength shifting, but also induce impairments, such as delays and operational costs. The question for constraint-based routing is how to account for these conflicting effects. To validate the network modeling, a wide range of networking scenarios are simulated, such as ring, mesh and interconnections of all-optical networks with electronic gateways. For all these scenarios, our approach is shown to efficiently accommodate multiple, conflicting routing metrics related to different services and network architectures.

A survey of inter-domain peering and provisioning solutions for the next generation optical networks

The emergence of carrier grade transport technologies has led to a paradigm shift in inter-domain routing which became an important feature of the transport layer based on optical transmission and switching. While the new technologies have capabilities to provide end-to-end guaranteed quality of service (QoS), the lack of inter-operability between different technologies, administrative areas and control planes makes interdomain peering and provisioning below the conventional Internet Protocol (IP) layer a challenge. In this survey, we analyze various multi-domain routing models for emerging Layer 2 and WDM switched networks which have been proposed till date, and based on that survey, we highlight some open issues and future challenges pertaining to scalability, reliability, multi-domain QoS, control plane interworking and dynamic peering.

Service-specific resource allocation in WDM networks with quality constraints

The need to establish wavelength-routed connections in a service-differentiated fashion is becoming increasingly important due to a variety of candidate client networks (e.g., IP, SDH, ATM) and the requirements for QoS-delivery within transport layers. The multiservice operation changes the way we deal with wavelength-routed paths, as they are now being characterized by manifold properties, such as transmission quality, restoration, network management, and policies. We propose a generic approach to service-differentiated connection accommodation in wavelength-routed networks where, for the network state representation, the supplementary network graphs are defined and referred to as service-specific wavelength-resource graphs. These graphs are used for the appropriate allocation of wavelengths on concatenated physical resources building a wavelength route, along which the necessary transmission quality is achieved and the required management and surveillance functions are provided. By considering twofold wavelength routing metrics, i.e., QoS metrics (service requirements) and resource metrics (quality constraints), these graphs can yield the solution to the QoS-routing problem, i.e., the provision of service-specific guarantees under quality constraints-a feature that is still missing from the existing architectures. The numerical analysis of dynamically reconfigurable multiservice WDM networks is presented for regular network operation as well as for optical network service restoration.

Extending end-to-end optical service provisioning and restoration in carrier networks: opportunities, issues, and challenges

In this article, we address the opportunities, issues and challenges associated with end-to-end optical service provisioning and restoration in carrier networks. A number of scenarios are analyzed from a practical perspective, considering important aspects relevant to the management and control planes. Along the lines of three basic dimensions, to which we refer as locality, granularity, and ownership, we discuss the complexity associated with provisioning and restoring end-to-end optical services in regional (local scale) and national (global scale) networking scenarios. We identify a number of challenges in integrating a unified control plane solution and vendor-specific management and control planes with legacy carrier management systems.

A Cross-Layer Analysis of Session Setup Delay in IP Multimedia Subsystem (IMS) With EV-DO Wireless Transmission

This paper analyzes the session setup delay in the IP multimedia subsystem (IMS) with the CDMA2000 evolution data only rev. A (EV-DO rev. A) standard for wireless transmission. Session setup delay is particularly critical for interactive multimedia applications, such as gaming, push-to-X and voice over IP (VoIP), as it directly translates in user perception of service quality. Keeping signaling delay low, however, is a challenge in IMS due to the text-based nature of the session initiation protocol (SIP) for signaling, and, more significantly, due to the lossy and capacity constrained wireless links. To address this challenge, we analyze the session setup delay end-to-end, by taking into account key system properties across all layers, ranging from radio links to IMS signaling architecture. We present a model for cross-layer performance analysis and simulation, which includes the statistical properties of the EV-DO (rev. A) wireless channel, and also takes into consideration the properties of transport protocols (TCP, UDP) and SIP signaling (message size and compression). By means of analysis and simulations, we study the setup delay performance of a generic, multi-operator IMS communication scenario between two mobile users. We describe how session setup delay can be estimated and reduced in realistic IMS settings and we propose architecture alternatives to the basic IMS scenario. The results derived from this study show that the proposed methods can incrementally lead to a lower setup delay and less sensitivity to the radio transmission quality and frame error rate compared to the base IMS scenario

Divide and conquer: Partitioning OSPF networks with SDN

Software Defined Networking (SDN) is an emerging network control paradigm focused on logical centralization and programmability. At the same time, distributed routing protocols, most notably OSPF and IS-IS, are still prevalent in IP networks, as they provide shortest path routing, fast topological convergence after network failures, and, perhaps most importantly, the confidence based on decades of reliable operation. Therefore, a hybrid SDN/OSPF operation remains a desirable proposition. In this paper, we propose a new method of hybrid SDN/OSPF operation. Our method is different from other hybrid approaches, as it uses SDN nodes to partition an OSPF domain into sub-domains thereby achieving the traffic engineering capabilities comparable to full SDN operation. We place SDN-enabled routers as subdomain border nodes, while the operation of the OSPF protocol continues unaffected. In this way, the SDN controller can tune routing protocol updates for traffic engineering purposes before they are flooded into sub-domains. While local routing inside sub-domains remains stable at all times, inter-sub-domain routes can be optimized by determining the routes in each traversed sub-domain. As the majority of traffic in non-trivial topologies has to traverse multiple subdomains, our simulation results confirm that a few SDN nodes allow traffic engineering up to a degree that renders full SDN deployment unnecessary.

Constraint-based path selection methods for on-demand provisioning in WDM networks

We propose a framework for decentralized path selection and on-demand wavelength channel provisioning in WDM networks with routing constraints. Within this framework, the path information of choice, such as transmission quality, reliability, policy and traffic conditions, is updated following a connection request, based on a local, autonomous and service-differentiated characterization of optical network elements. It is this local and autonomous network state information that makes our approach particularly suitable for distributed implementation, and applicable to optical network architectures and control protocols that support service level guarantees. To illustrate this, we study mesh networks consisting of transparent, short-reach networking segments interconnected by long-reach WDM links with electronically regenerative gateways, where different link types show different SNR degradation, reliability and delay. On the example of electronically regenerative gateways, we address a new class of constraint-based path selection problems, where a certain a type of network element can at the same time deteriorate and improve network performance; e.g. electronic regenerators improve optical path quality and can adapt to wavelengths, but induce delays or operational costs. The performance study has shown the capability of our methods to accommodate arbitrary number and type of optical path properties, related to different network architectures and services.

A Survey on Internet Multipath Routing and Provisioning

Utilizing the dormant path diversity through multipath routing in the Internet to reach end users-thereby fulfilling their QoS requirements-is rather logical. While offering better resource utilization, better reliability, and often even much better quality of experience (QoE), multipath routing and provisioning was shown to help network and data center operators achieve traffic engineering in the form of load balancing. In this survey, we first highlight the benefits and basic Internet multipath routing components. We take a top-down approach and review various multipath protocols, from application to link and physical layers, operating at different parts of the Internet. We also describe the mathematical foundations of the multipath operation, as well as highlight the issues and challenges pertaining to reliable data delivery, buffering, and security in deploying multipath provisioning in the Internet. We compare the benefits and drawbacks of these protocols operating at different Internet layers and discuss open issues and challenges.