Marinos Charalambides

Management and orchestration challenges in network functions virtualization

NFV continues to draw immense attention from researchers in both industry and academia. By decoupling NFs from the physical equipment on which they run, NFV promises to reduce CAPEX and OPEX, make networks more scalable and flexible, and lead to increased service agility. However, despite the unprecedented interest it has gained, there are still obstacles that must be overcome before NFV can advance to reality in industrial deployments, let alone delivering on the anticipated gains. While doing so, important challenges associated with network and function MANO need to be addressed. In this article, we introduce NFV and give an overview of the MANO framework that has been proposed by ETSI. We then present representative projects and vendor products that focus on MANO, and discuss their features and relationship with the framework. Finally, we identify open MANO challenges as well as opportunities for future research.

Policy conflict analysis for quality of service management

Policy-based management provides the ability to (re-) configure differentiated services networks so that desired quality of service (QoS) goals are achieved. Relevant configuration involves implementing network provisioning decisions, performing admission control, and adapting bandwidth allocation dynamically according to emerging traffic demands. A policy-based approach facilitates flexibility and adaptability in that the policies can be changed without changing the implementation. However, as with any other complex system, conflicts and inconsistencies may arise in the policy specification. In this work, we concentrate on the policy conflicts that may occur for static resource management aspects of QoS provisioning, known as network dimensioning. The paper shows how conflict detection can be achieved using event calculus in conjunction with abductive reasoning techniques to detect the existence of potential conflicts in partial specification and generate explanations for the conditions under which the conflicts arise. We finally present some conflict detection examples from our initial implementation of a policy conflict analysis tool. Although we focus on network dimensioning, many of the types of conflicts we illustrate could arise in other applications.

Dynamic Policy Analysis and Conflict Resolution for DiffServ Quality of Service Management

Policy-based dynamic resource management may involve interaction between independent decision-making components which can lead to conflicts. For example, conflicts can occur between the policies for allocating resources and those setting quotas for users or classes of service. These policy conflicts cannot be detected by static analysis of the policies at specification-time as the conflicts arise from the current state of the resources within the system and so can only be detected at run-time. In this paper we use policies related to quality of service (QoS) provisioning for configuring differentiated services (DiffServ) networks to illustrate techniques for the dynamic detection and resolution of conflicts. Configuration includes implementing network provisioning decisions, performing admission control, and adapting bandwidth allocation dynamically according to emerging traffic demands. We identify possible conflicts between policies that manage the allocation of resources, and we also investigate conflicts that may arise between these policies and higher-level directives refined at the dynamic resource management level, acting as constraints. The paper shows how event calculus can be used to detect conflicts, focusing on the ones that emerge at run-time, and provides an approach for specifying policies to automate conflict resolution. The latter is demonstrated through our initial implementation of a dynamic conflict analysis tool

Adaptive Resource Management and Control in Software Defined Networks

The heterogeneous nature of the applications, technologies and equipment that todays networks have to support has made the management of such infrastructures a complex task. The Software-Defined Networking (SDN) paradigm has emerged as a promising solution to reduce this complexity through the creation of a unified control plane independent of specific vendor equipment. However, designing a SDN-based solution for network resource management raises several challenges as it should exhibit flexibility, scalability and adaptability. In this paper, we present a new SDN-based management and control framework for fixed backbone networks, which provides support for both static and dynamic resource management applications. The framework consists of three layers which interact with each other through a set of interfaces. We develop a placement algorithm to determine the allocation of managers and controllers in the proposed distributed management and control layer. We then show how this layer can satisfy the requirements of two specific applications for adaptive load-balancing and energy management purposes.

Using linear temporal model checking for goal-oriented policy refinement frameworks

Policy refinement is meant to derive lower-level policies from higher-level ones so that these more specific policies are better suited for use in different execution environments. Although it has been recognized as crucial, it has received relatively little attention. We present a policy refinement framework grounded in goal-elaboration methodologies and reactive systems analysis. Through linear-time model checking, we obtain system trace executions aimed at fulfilling lower-level goals refined with the KAOS goal-elaboration method. From system executions, we abstract managed entities, conditions and actions to encode the refined policies. We present our framework and provide a refinement scenario applied to the DiffServ QoS management domain.

Policy refinement for DiffServ quality of service management

Policy-based management provides the ability to dynamically re-configure DiffServ networks such that desired quality of service (QoS) goals are achieved. This includes network provisioning decisions, performing admission control, and adapting bandwidth allocation dynamically. QoS management aims to satisfy the service level agreements (SLAs) contracted by the provider and therefore QoS policies are derived from SLA specifications and the providers business goals. This policy refinement is usually performed manually with no means of verifying that the policies written are supported by the network devices and actually achieve the desired QoS goals. Tool support is lacking and policy refinement has rarely been addressed in the literature. This paper extends our previous approach to policy refinement and shows how to apply it to the domain of DiffServ QoS management. We make use of goal elaboration and abductive reasoning to derive strategies that achieves a given high-level goal. By combining these strategies with events and constraints, we show how policies can be refined, and what tool support can be provided for the refinement process using examples from the QoS management domain. However, the approach presented here can be used in other application domains such as storage area networks or security management.

Policy conflict analysis for diffserv quality of service management

Policy-based management provides the ability to (re-)configure differentiated services networks so that desired Quality of Service (QoS) goals are achieved. This requires implementing network provisioning decisions, performing admission control, and adapting bandwidth allocation to emerging traffic demands. A policy-based approach facilitates flexibility and adaptability as policies can be dynamically changed without modifying the underlying implementation. However, inconsistencies may arise in the policy specification. In this paper we provide a comprehensive set of QoS policies for managing Differentiated Services (DiffServ) networks, and classify the possible conflicts that can arise between them. We demonstrate the use of Event Calculus and formal reasoning for the analysis of both static and dynamic conflicts in a semi-automated fashion. In addition, we present a conflict analysis tool that provides network administrators with a user-friendly environment for determining and resolving potential inconsistencies. The tool has been extensively tested with large numbers of policies over a range of conflict types.

A Functional Solution for Goal-Ooriented Policy Refinement

Policy refinement is a key but still unsolved area of policy based management. Goal oriented requirements engineering methodologies have been suggested as a prominent alternative to address policy refinement. Practical approaches that capture the administrative requirements and enable systematic policy refinement are still missing although such integrated solutions are rather convenient to make policy-based management systems really useful. In this paper we present a functional solution for goal oriented policy refinement grounded in linear temporal logic and reactive systems analysis techniques. We describe the technical foundations and demonstrate how these were used to develop an integrated solution for policy refinement, focusing on the details of the implemented prototype. Our policy analysis techniques that enable systematic policy refinement are demonstrated through a scenario applied to the domain of QoS management for differentiated services (DiffServ) networks

A methodological approach toward the refinement problem in policy-based management systems

Policy refinement is meant to derive low-level enforceable policies from high-level guidelines. Although recent advances have been made to solve this open problem, the holistic implications confronting systematic policy refinement have not been explicitly addressed. This article presents a methodological approach towards the policy refinement problem. We provide a generic procedure to define policy hierarchies, which is essential to achieving systematic policy refinement. We also provide the considerations while defining high-level guidelines, and describe a policy refinement framework that formalizes the requirements to refine high-level guidelines into executable policies. We demonstrate the feasibility of our approach with a scenario applied to the quality of service (QoS) management domain

More control over network resources: An ISP caching perspective

Management operations performed by Content Delivery Network (CDN) providers consist mainly in controlling the placement of contents at different storage locations and deciding where to serve client requests from. Configuration decisions are usually taken by using only limited information about the carrier networks, and this can adversely affect network usage. In this work we propose an approach by which ISPs can have more control over their resources. This involves the deployment of caching points within their network, which can allow them to implement their own content placement strategies. The work presented in this paper investigates lightweight strategies that can be used by the ISPs to manage the placement of contents in the various network caching locations according to user demand characteristics. The proposed strategies differ in terms of the volume and nature of the information required to determine the new caching configurations. We evaluate the performance of the proposed strategies, in terms of network resource utilization, based on a wide range of user demand profiles and we compare the obtained performance according to metrics we define to characterize the demand. The results demonstrate that the proposed metrics can provide useful indications regarding the performance one strategy can achieve over another and, as such, can be used by the ISP to improve the utilization of network resources.