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The Distributed Coordination Function (DCF) aims at fair and efficient medium access in IEEE 802.11. In face of its success, it is remarkable that there is little consensus on the actual degree of fairness achieved, particularly bearing its impact on quality of service in mind. In this paper we provide an accurate model for the fairness of the DCF. Given M greedy stations we assume fairness if a tagged station contributes a share of 1/M to the overall number of packets transmitted. We derive the probability distribution of fairness deviations and support our analytical results by an extensive set of measurements. We find a closed-form expression for the improvement of long-term over short-term fairness. Regarding the random countdown values we quantify the significance of their distribution whereas we discover that fairness is largely insensitive to the distribution parameters. Based on our findings we view the DCF as emulating an ideal fair queuing system to quantify the deviations from a fair rate allocation. We deduce a stochastic service curve model for the DCF to predict packet delays in IEEE 802.11. We show how a station can estimate its fair bandwidth share from passive measurements of its traffic arrivals and departures.

In conventional large-scale networks, creation and management of network services are costly and complex tasks that often consume a lot of resources, including time and manpower. Network softwarization and network function virtualization have been introduced to tackle these problems. They replace the hardware-based network service components and network control mechanisms with software components running on general-purpose hardware, aiming at decreasing costs and complexity of implementing new services, maintaining the implemented services, and managing available resources in service provisioning platforms and underlying infrastructures. To experience the full potential of these approaches, innovative development support tools and service provisioning environments are needed. To answer these needs, we introduce the SONATA architecture, a service programming, orchestration, and management framework. We present a development toolchain for virtualized network services, fully integrated with a service platform and orchestration system. We motivate the modular and flexible architecture of our system and discuss its main components and features, such as function-and service-specific managers that allow fine-grained service management, slicing support to facilitate multi-tenancy, recursiveness for improved scalability, and full-featured DevOps support.

The Service Programming and Orchestration for Virtualised Software Networks (SONATA) project targets both the flexible programmability of software networks and the optimisation of their deployments by means of integrating Development and Operations in order to accelerate industry adoption of software networks and reduce time-to-market for networked services. SONATA supports network function chaining and orchestration, making service platforms modular and easier to customise to the needs of different service providers, and introduces a specialised Development and Operations model for supporting developers.

Abstract. In this paper we present results from an extensive measurement study of wireless bandwidth estimation in IEEE 802.11 WLANs using the distributed coordination function. We show that a number of known iterative probing methods, which are based on the assumption of first-come first-serve scheduling, can be expected to report the fair bandwidth share of a new flow rather than the available bandwidth. Our measurement results confirm this view and we conclude that under the current probe gap and probe rate models the fair share can only be loosely related to the available bandwidth. Like a few other studies we report that packet sizes have a tremendous impact on bandwidth estimates. Unlike these studies we can, however, show that minor modifications to known methods for wired networks, such as Pathload, can solve previously indicated limitations of these methods in wireless networks.

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In this paper we present results from an extensive measurement study of various hardware and (virtualized) software routers using several queueing strategies, i.e. First-Come-First-Served and Fair Queueing. In addition to well-known metrics such as packet forwarding performance, per packet processing time, and jitter, we apply network calculus models for performance analysis. This includes the Guaranteed Rate model for Integrated Services as well as the Packet Scale Rate Guarantee model for Differentiated Services. Using a measurement approach that provides a means to estimate rate and error term of a real node, we propose an interpretation of router performance based on these parameters taking packet queueing and scheduling into account. Such estimated parameters should be used to make the analysis of real networks more accurate. We underpin the applicability of this approach by comparing analytical results of concatenated routers to real world measurements.

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