Solange Rito Lima

Admission Control in Multiservice IP Networks: Architectural Issues and Trends

The trend toward the integration of current and emerging applications and services in the Internet has launched new challenges regarding service deployment and management. Within service management, admission control has been recognized as a convenient mechanism to keep services under controlled load and ensure the required QoS levels, bringing consistency to the services offered. In this context, this article discusses the role of AC in multiservice IP networks, and surveys current and representative AC approaches. We address and compare the architectural principles of these AC approaches and their main features, virtues, and limitations that have an impact on the quality control of network services. We identify important design aspects that contribute to the successful deployment of flexible and scalable AC solutions in multiservice networks

Distributed Admission Control for QoS and SLS Management

This article proposes a distributed admission control (AC) model based on on-line monitoring to manage the quality of Internet services and Service Level Specifications (SLSs) in class-based networks. The AC strategy covers intra- and interdomain operation, without adding significant complexity to the network control plane and involving only edge nodes. While ingress nodes perform implicit or explicit AC resorting to service-oriented rules for SLS and QoS parameters control, egress nodes collect service metrics providing them as inputs for AC. The end-to-end operation is viewed as a cumulative and repetitive process of AC and available service computation. We discuss crucial key points of the model implementation and evaluate its two main components: the monitoring process and the AC criteria. The results show that, using proper AC rules and safety margins, service commitments can be efficiently satisfied, and the simplicity and flexibility of the model can be explored to manage successfully QoS requirements of multiple Internet services.

Self-adaptive distributed management of QoS and SLSs in multiservice networks

Distributed service-oriented traffic control mechanisms, operating with minimum impact on network performance, assume a crucial role as regards controlling services quality and network resources transparent and efficiently. In this way, we describe and specify a lightweight distributed admission control (AC) model which provides an uniform solution for managing QoS and SLSs in multiclass and multidomain environments. Taking advantage of the consensual need of on-line service monitoring and traffic control at the network edges, AC decisions are driven by feedback from systematic edge-to-edge measurements of relevant QoS parameters for each service type and SLS utilization. This allows self-adaptive service and resource management, while abstracting from network core complexity and heterogeneity. In this paper, introducing an expressive notation, we specify the high-level entities for multiservice provisioning in a domain and formalize service-dependent AC equations to assure both intra and interdomain model operation. A proof-of-concept of the AC criteria effectiveness in satisfying each service class commitments while achieving high network utilization is provided through simulation.

A distributed admission control model for CoS networks using QoS and SLS monitoring

Achieving an admission control strategy for CoS networks covering both intra-domain and end-to-end operation is still an open issue. This paper discusses how AC can be carried out without adding significant complexity to the network control plane and proposes a distributed service-oriented AC model for these networks. The model only involves the network edge nodes leaving the network core unchanged. Ingress nodes perform implicit or explicit service-dependent AC based on both QoS and SLSs utilization metrics, obtained through edge-to-edge online monitoring performed at egress nodes. From an end-to-end perspective, the flow request is used both for AC and available service computation. Relevant aspects of the model interrelated areas and implementation key points are also discussed.

An ontology for managing network services quality

The evolution of IP networks to a service-oriented paradigm poses new challenges to service providers regarding the management and auditing of network services. The upward trend in ubiquity, heterogeneity and virtualization of network services and resources demands for a formal and systematic approach to network management tasks. In this context, the semantic characterization and modeling of services provided to users is a key component to sustain autonomic service management, service negotiation and configuration. The semantic and formal description of services and resources is also relevant to assist paradigms such as cloud computing, where a large diversity of resources have to be described and managed in a highly dynamic way. This paper defines an ontology for multiservice IP networks targeting multiple service management goals, namely: (i) to foster client and service provider interoperability; (ii) to manage network service contracts, promoting the dynamic negotiation between parties; (iii) to access and query SLA/SLSs data on a individual or aggregated basis to assist service provisioning in the network; and (iv) to sustain service monitoring and auditing. A ServiceModel API is provided to take full advantage of the proposed semantic model, allowing Service Management Platforms to access the ontological contents. This ontological development takes advantage of SWRL to discover new knowledge, enriching the possibilities of systems described using this support.

A multiadaptive sampling technique for cost-effective network measurements

The deployment of efficient measurement solutions to assist network management tasks without interfering with normal network operation assumes a prominent role in todays high-speed networks attending to the huge amounts of traffic involved. From a myriad of proposals for traffic measurement, sampling techniques are particularly relevant contributing effectively for this purpose as only a subset of the overall traffic volume is handled for processing, preserving ideally the correct estimation of network statistical behavior.In this context, this paper proposes MuST - a multiadaptive sampling technique based on linear prediction, aiming at reducing significantly the measurement overhead and still assuring that traffic samples reflect the statistical characteristics of the global network traffic under analysis. Conversely to current sampling techniques, MuST is a multi and self-adaptive technique as both the sample size and interval between samples are self-adjustable parameters according to the ongoing network activity and the accuracy of prediction achieved.The tests carried out demonstrate that the proposed sampling technique is able to achieve accurate network estimations with reduced overhead, using throughput as reference parameter. The evaluation results, obtained resorting to real traffic traces representing wired and wireless aggregated traffic scenarios and actual network services, prove that the simplicity, flexibility and self-adaptability of the proposed technique can be successfully explored to improve network measurements efficiency over distinct traffic conditions. For optimization purposes, this paper also includes a study of the impact of varying the order of prediction, i.e., of considering different degrees of past memory in the self-adaptive estimation mechanism. The significance of the obtained results is demonstrated through statistical benchmarking.

XML service level specification and validation

This paper addresses the problem of formalizing service level specifications (SLSs) as a first step to simplify and automate the configuration and management of multiservice IP networks. A formal representation of SLSs will allow their automatic validation and processing, fostering the dynamic negotiation of SLSs and the interoperability among service management entities. In this way, taking advantage of XML extensibility and portability, a Schema is presented describing XML SLSs sections and their contents. In addition, an XML validator tool was built to check if SLSs are correctly specified. An XML SLS for an IP telephony service is used to exemplify this proposal expressiveness.

Measuring QoS in class-based IP networks using multipurpose colored probing patterns

Multiclass IP networks open new dimensions and challenges on active monitoring as efficient strategies of in-band probing are required to sense each class performance without causing noticeable side-effects on real traffic. In our study, we provide new insights on how to perform efficiently active monitoring in these networks, suggesting the use of light and multipurpose probing streams able to capture simultaneously the behavior of multiple QoS metrics of each class. Considering one-way-delay, jitter and loss metrics, we explore different spatial-temporal characteristics of probing, focusing on finding patterns adjusted to each class measurement requirements. We demonstrate that commonly used probing streams fail to capture these metrics simultaneously and we propose novel colored probing patterns able to increase multipurpose active monitoring efficiency. As test environment, we consider a diffserv domain where admission control resorts to feedback from edge-to-edge active monitoring to dynamically control hard real-time, soft real-time and elastic traffic classes. Comparing graphically and statistically the probing and passive measurement outcome of each class, the obtained results show that despite being difficult to match the scale and shape of multiple metrics, a single and properly colored probing stream can capture close and simultaneously the behavior of one-way-delay, jitter and loss, for low in-band probing rates.

A distributed admission control model for class-based networks using edge-to-edge QoS and SLS monitoring

The advent of class-based networks has brought new needs for network traffic control in order to assure a certain QoS level. Despite the existing proposals, achieving a generic admission control (AC) strategy for traffic entering these networks is still an open issue. This paper provides new insights on how AC shall be accomplished proposing an encompassing AC model for multi-service class-based networks, which covers both intra-domain and end-to-end operation, without requiring changes in the network core and complex AC signaling. For each service type, AC is distributed and based on both on-line edge-to-edge monitoring of relevant QoS parameters and SLSs utilization. Service monitoring, performed at egress nodes, provides adequate metrics to ingress nodes which take implicit or explicit AC decisions based on service-de pendent criteria. Although being oriented to flow AC. the model can easily be applied to SLS AC. SLS auditing and SLS traffic conditioning are tasks also covered.

Enhancing QoS metrics estimation in multiclass networks

This paper discusses the problematic of QoS monitoring, suggesting the use of on-line multipurpose active monitoring in multiclass networks as a powerful tool to efficiently assist and enhance the control of multiple service levels. To improve the simultaneous estimation of one-way QoS metrics, we propose a flexible probing source able to adjust probing patterns to the measurement requirements of each service class, exploring pattern coloring to better sense packet loss. The proof-of-concept provided shows that the proposed solution improves the estimation accuracy of multiple QoS metrics significantly, with a reduced probing overhead.