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The Internet Engineering Task Force (IETF) is currently working on the development of Differentiated Services (DiffServ). DiffServ seems to be a promising technology for next-generation IP networks supporting Quality-of-Services (QoS). Emerging applications such as IP telephony and time-critical business applications can benefit significantly from the DiffServ approach since the current Internet often can not provide the required QoS. This paper describes an implementation of Differentiated Services for Linux routers and end systems. The implementation is based on the Linux traffic control package and is, therefore, very flexible. It can be used in different network environments as first-hop, boundary or interior router for Differentiated Services. In addition to the implementation architecture, the paper describes performance results demonstrating the usefulness of the DiffServ concept in general and the implementation in particular.
WiFi-based Long Distance (WiLD) networks have emerged as a promising alternative approach for Internet in rural areas. However, the MAC layer, which is based on the IEEE802.11 standard, comprises contiguous stations in a cell and is spatially restricted to a few hundred meters at most. In this work, we summarize efforts by different researchers to use IEEE802.11 over long-distances. In addition, we introduce WiLDToken, our solution to optimizing the throughput and fairness and reducing the delay on WiLD links. Compared to previous alternative MAC layers protocols for WiLD, our focus is on optimizing a single link in a multi-radio multi-channel mesh. We implement our protocol in the ns-3 network simulator and show thatWiLDToken is superior to an adapted version of the Distributed Coordination Function (DCF) for different link distances. We find that the throughput on a single link is close to the physical data-rate without a major decrease over longer distances.
An Empirical Evaluation of the Received Signal Strength Indicator for fixed outdoor 802.11 links
(2015)
For the evaluation of the received signal strength indication (RSSI) a different methodology compared to previous publications is introduced in this paper by exploiting a spectral scan feature of recent Qualcomm Atheros WiFi NICs. This method is compared to driver reports and to an industrial grade spectrum analyzer. During the conducted outdoor experiments a decreased scattering of the RSSI compared to previous publications is observed. By applying well-known mathematical tests for normality it is possible to show that the RSSI does not follow a normal distribution in a line-of-sight outdoor environment. The evaluated spectral scan features offers additional possibilities to develop interference classifiers which is an important step for frequency allocation in long-distance 802.11 networks.
More and more devices will be connected to the internet [3]. Many devicesare part of the so-called Internet of Things (IoT) which contains many low-powerdevices often powered by a battery. These devices mainly communicate with the manufacturers back-end and deliver personal data and secrets like passwords.
ATM virtual studio services
(1996)
The term "virtual studio" refers to real-time 3D graphics systems used to render a virtual set in sync with live camera motion. As the camera pans and zooms, the virtual set is redrawn from the correct perspective. Using blue room techniques, actors in front of the real camera are then “placed in” the virtual set. Current virtual studio systems are centralized – the blue room, cameras, renderers etc. are located at a single site. However distributed configurations offer significant economies such as the sharing of expensive rendering equipment among many sites. This paper describes early expe- riences of the DVP1 project in the realization of a distributed virtual studio. In particular we de- scribe the first video production using a distributed virtual studio over ATM and make observations concerning network QOS requirements.
This work describes extensions to the well-known Distributed Coordination Function (DCF) model to account for IEEE802.11n point-to-point links. The developed extensions cover adaptions to the throughput and delay estimation for this type of link as well peculiarities of hardware and implementations within the Linux Kernel. Instead of using simulations, the approach was extensively verified on real-world deployments at various link distances. Additionally, trials were conducted to optimize the CWmin values and the number of retries to maximize throughput and minimize delay. The results of this work can be used to estimate the properties of long-distance 802.11 links beforehand, allowing the network to be planned more accurately.
With the rapid advances in multimedia content delivery technologies, there is an increasing challenge for efficient Quality of Service (QoS) based multicast transport in mobile Internet environment. This paper discusses architectural approach for provision of multicast services in heterogeneous mobile IPv6 environment using context transfer. Following issues of QoS based mobile multicast transport are addressed: - Application of context transfer between access routers for seamless handover of active multicast services; - Adaptation of multicast group management and routing designed for wired IPv6 infrastructures to heterogeneous mobile environment; - Candidate access router discovery and context aware user interfaces for optimised handover; - Reliable mobile multicast for content delivery supported by context transfer at access routers; - Distributed QoS management of multicast services in heterogeneous mobile environment. The work is part of the mobile architecture developed in the EU IST project DAIDALOS.
WiFi-based Long Distance (WiLD) networks have emerged as a promising alternative technology approach for providing Internet in rural areas. An important factor in network planning of these wireless networks is estimating the path loss. In this work, we present various propagation models we found suitable for point-to-point (P2P) operation in the WiFi frequency bands. We conducted outdoor experiments with commercial offthe- shelf (COTS) hardware in our testbed made of 7 different long-distance links ranging from 450 m to 10.3 km and a mobile measurement station. We found that for short links with omni-directional antennas ground-reflection is a measurable phenomenon. For longer links, we show that either FSPL or the Longley-Rice model provides accurate results for certain links. We conclude that a good site survey is needed to exclude influences not included in the propagation models.
SDN and WMN evolved to be sophisticated technologies used in a variety of applications. However, a combined approach called wmSDN has not been widely addressed in the research community. Our idea in this field consists of WiFi-based point-to-point links managed by the OpenFlow protocol. We investigate two different issues regarding this idea. First, which WiFi operational mode is suitable in an OpenFlow managed broadcast domain? Second, does the performance decrease compared with other routing or switching principles? Therefore, we set up a real-world testbed and a suitable simulation environment. Unlike previous work, we show that it is possible to use WiFi links without conducting MAC address rewriting at each hop by utilizing the 4-address-mode.