Piotr Cholda

QoX: What is it really?

The article puts in order notions related to Quality of Service that are found in documents on service requirements. Apart from presenting a detailed description of QoS itself, it overviews classes of service (CoS) proposed by main standardization bodies and maps them across various transmission technologies. Standards and concepts related to less commonly used, though not less important, terms such as Grade of Service (GoS), Quality of Resilience (QoR), and Quality of Experience (QoE) are also discussed. While provisioning of QoS, CoS, GoS, and QoR is related to various aspects of networking and network performance, QoE describes resulting service features as perceived by the customer. Relations between those intrinsic network features and resulting human-experienced quality are discussed. The above set of QoX terms (where X stands for Service, Experience, etc.) is sufficient to describe and distinguish all aspects of service provisioning.

Recovery and Its Quality in Multilayer Networks

The paper presents a tutorial on multilayer recovery methods. Emphasis is laid not on their procedural operation, but rather on their quality assessment and differentiation based on reliability parameters (e.g., availability, recovery time) and other relevant features (e.g., affected traffic, state overhead). A brief outline of terminology related to multilayer networks is given. Then, an overview of recovery methods is presented, with focus on multilayer recovery. Next, quality features enabling assessment of multilayer recovery are given along with general approaches to service differentiation based on resilience.

Quality of resilience as a network reliability characterization tool

With the increased role of resilience in modern networks, the existing quality of service is required to be expanded with service availability and maintainability. Recently, studies have shown the strong limitation of the common availability metrics for measuring the users quality of experience. In this article a joint specification of QoS definitions with a sophisticated service resilience characterization is proposed, and a concept called quality of resilience is defined. In this unified performance metric, the frequency and length of service interruption are evaluated. It can be used as a tool for characterization of network reliability, as well as comparison and selection of recovery methods. Additionally, by including it in service level agreements, new and more complex requirements of commercial applications can be guaranteed.

Interaction patterns between P2P content distribution systems and ISPs

Peer-to-peer (P2P) content distribution systems are a major source of traffic in the Internet, but the application layer protocols they use are mostly unaware of the underlying network in accordance with the layered structure of the Internets protocol stack. Nevertheless, the need for improved network efficiency and the business interests of Internet service providers (ISPs) are both strong drivers toward a cross-layer approach in peer-to-peer protocol design, calling for P2P systems that would in some way interact with the ISPs. Recent research shows that the interaction, which can rely on information provided by both parties, can be mutually beneficial. In this article we first give an overview of the kinds of information that could potentially be exchanged between the P2P systems and the ISPs, and discuss their usefulness and the ease of obtaining and exchanging them. We also present a classification of the possible approaches for interaction based on the level of involvement of the ISPs and the P2P systems, and we discuss the potential strengths and the weaknesses of these approaches.

Reliability assessment of optical p-cycles

Two recovery techniques suited for the next generation Internet are studied: traditional protection rings (BLSRs) and a novel, preconfigured protection cycles (p-cycles) technique. Theoretical formulas describing the reliability function as well as mean time to failure are derived. On the basis of our analysis, we show that p-cycles should not be used in wide-area networks since their reliability performance is outside the desired bounds.

Reliability assessment of p-cycles

In the paper, theoretical formulas describing the reliability function as well as the mean time to failure for static p-cycles are derived. The practical conclusions concerning the design of p-cycles are drawn: p-cycles do not always have good properties from the reliability viewpoint; if an operator decides to use them, it has to ensure that the trade-off between sharing of resources and the availability is reasonable. An appropriate function on which such a choice can be based is introduced.

Joint Quantification of Resilience and Quality of Service

A new concept Quality of Resilience (QoR) presented in this paper is based on the distinction in the reliability-related Quality of Service (QoS) parameters of the short-term quality factors and the long-term quality factors. The former parameters are called availability parameters and the latter are called QoR parameters. In one hand by dividing the service duration time into intervals, the service is considered available during a time interval, if the Service Level Agreement (SLA) between the user and the network operator is satisfied. In the other hand the long-term characteristics of the service are derived from the service downtime distribution. With the downtime histograms the asymptotic characteristics of the service can be represented both at the transport and service layers. Since the resilience mechanism implemented into the network match the transport layer downtime histograms, this new characterization of the QoS helps to measure the impacts of a given recovery scheme on the next generation services.

Continuity-based resilient communication

The paper advocates that in some communication service providing settings, it is more appropriate to focus on the continuity of a connection as the prime reliability attribute for defining requirements and establishing Service Level Agreements, rather than the traditionally used availability. The justification for this approach and types of services where continuity is relevant are given. For illustration, a transport network with an optical control plane for a utility grid along with some theoretical background is studied.

Reliability, survivability, and quality of large scale telecommunications systems [Book Review]

Intermediate System to Intermediate System (IS-IS) is a powerful and flexible routing protocol often considered now as a prospective one for moderate and large IP networks. I S I S Deployment in IP Networks provides a comprehensive set of concepts related to the design and operation of this modern protocol in the 1P environment. Written with an overall intention to demystify the protocol for the networking engineers, the book begins with an introductory historical perspective to allow a reader to understand the very specific features of the protocol, and its foundations and terminology. The book is organized in six chapters. As already stated, Chapter 1 provides IS-IS fundamentals. Chapter 2 focuses on esscntials of IS-IS operation. Chapter 3 deals with dividing the routing domain. Chapter 4 is devoted to deployment considerations. Traffic engineering issues are subject of Chapter 5 , and Chapter 6 reports on numerous IS-IS enhancements that have recently been added or are being considered for inclusion in the protocol. The introductory chapters present essential mechanisms, including neighbor discovery, neighbor adjacency maintenance, and flooding, and delve into the operation of the protocol on point-topoint links and broadcast networks. Advanced topics that follow in subsequent chapters include domain partitioning, deployment considerations, and a case study. Next, intenvorking with multiprotocol label switching (MPLS), including general tunneling issues, setup of virtual private networks, and constrained SPF techniques aimed to help to engineer traffic flows are discussed. IS-IS enhancements are covered in detail in a separate chapter. Among the few things that could enrich.the’book would be always welcome case study sections on approaching and resolving problems related to managing IS-IS networks, as well as information on intenvorking with other legacy routing protocols. Nevertheless, the book is a valuable source of information, able to give a comprehensive understanding of the protocol. I t can satisfy a range of users,!ncluding routing beginners and experienced networking engineers. A demanding reader may benefit from sections on intenvorking of IS-IS with MPLS and protocol enhancements where new features such as IP over redundant packet rings, nonstop forwarding, fast rerouting, multitopology routing, and incremental SPF are iutroduccd. Review questions augment individual chapters and make the hook a good choice for both personal use and in courses on the topic.

Risk-Aware Design and Management of Resilient Networks

A current view on the design of networks resilient to non-malicious failures supported by risk engineering is presented in this keynote. The aspect of risk response is emphasized.