This article provides an overview of commonly used terminology related to quality of service assurance in IP networks. Several approaches to QoS definition, including those of IETF, ITU, and ETSI, are presented and compared. Terms associated with QoS like class of service, grade of service, service level agreement, as well as service level specification (SLS), traffic conditioning agreement (TCA), and traffic conditioning specification (TCS) are discussed. Terminology used in two QoS architectures, IntServ and DiffServ, is also introduced.

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.

This article introduces the concept, implementation and evaluation of Dynamic Traffic Management (DTM). This management mechanism minimizes traffic transfer costs on inter-domain links. It works for volume and 95th percentile tariffs. DTM reacts dynamically to traffic changes on inter-domain links shifting some part of traffic (manageable traffic) from one link to another. The management mechanism works in a distributed way. It requires cooperation between operators, namely Internet Service Providers (ISPs), receiving and generating traffic. Communication between ISPs is realized by SDN controllers (interdomain SDN). DTM has been applied to inter-cloud communication for Data Centers (DCs) located in different ISP domains. Moreover, it is cloud-agnostic, i.e., DTM does not engage Cloud Service Providers (CSPs) into management procedures. Evaluation performed in the testbed shows that DTM is capable of decreasing ISP costs of transit traffic up to 29%.

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 Internet's 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.