Modern connected devices are equipped with the ability to connect to the Internet using a variety of different wireless network technologies. Current network management solutions fail to provide a fine-grained, coordinated, and transparent answer to this heterogeneity, while the lower layers of the OSI stack simply ignore it by providing full separation of layers. To address this, we propose the ORCHESTRA framework to manage the different devices in heterogeneous wireless networks and introduce capabilities such as packet-level dynamic and intelligent handovers (both inter-and intra-technology), load balancing, replication, and scheduling. The framework is the first of its kind in providing a fine-grained packet-level control across different technologies by introducing a fully transparent virtual MAC layer and an SDN-like controller with global intelligence. Furthermore, we present a novel optimization problem formulation that can be solved to optimally configure the network. We provide a thorough evaluation through simulations and a prototype implementation. We show that our framework enables, in a real-life setting, transparent and real-time inter-technology handovers and that coordinated load balancing can double the network-wide throughput across different scenarios.
Abstract-Local area networks (LANs) are employed by a plethora of heterogeneous consumer devices, equipped with the ability to connect to the Internet using a variety of different wireless network technologies. Existing solutions and the lower layers of the OSI stack are unfit to cope with this heterogeneity. For instance, dynamical inter-technology switching is user-of application-based. We propose the ORCHESTRA framework to manage the different devices in heterogeneous wireless local area networks (WLANs) and introduce capabilities such as packetlevel dynamic and intelligent handovers (both inter-and intratechnology), load balancing, replication, and scheduling. The framework consists of a controller that is capable of communicating with both existing Software-Defined Networking (SDN) and Network Function Virtualization (NFV) controllers and with devices containing a newly introduced virtual Medium Access Control (MAC) layer. We show that the virtual MAC enables transparent and real-time inter-technology handovers and that our solution scales up to two thousands of clients.
Today's and tomorrow's networks are becoming increasingly complex and heterogeneous with a large diversity of devices and technologies. To meet growing demand, and support client mobility there is need for intelligent mechanisms like multi-technology load balancing and handovers. Current solutions, like Multipath Transmission Control Protocol (MPTCP), fail to provide a fine-grained, coordinated, and transparent answer to this heterogeneity, while the lower layers of the Open Systems Interconnection stack simply ignore it by providing full separation of layers. Therefore, we introduce ORCHESTRA, a data link layer framework for the management of multi-technology networks and devices, enabling packet-level dynamic handovers, load balancing, and duplication across network technologies. The framework is the first of its kind in providing fine-grained packet-level control across different technologies in a network-wide manner. Moreover, it works on top of existing standards without the need for hardware changes. This is achieved through a fully transparent virtual Medium Access Control layer and a Software-Defined Networking controller with global intelligence. The framework is implemented in a prototype running on off-the-shelf hardware and we demonstrate its features across different IEEE 802.11 technologies and 4G (Long Term Evolution). We demon-
Prostacyclin(PGI2)synthase is inactivated by lipidhydroperoxides and it has been suggested that this occurs in atheromatous plaques (S.Moncada & J.R.Vane, New Engl. J.Med.,300,ll42,1979). Glutathione peroxidase is a selenium(Se) containing enzyme which converts hydroperoxides to less toxic alcohols. Therefore, we investigated whether Se deficiency reduced the biosynthesis of PGI2. Rats were fed a diet with a reduced Se content(25 ppb) or a standard diet (l42 ppb Se). After 7months 4 rats from each group were killed. Urinary Se-excretion and Se content of the liver were significantly (P<0.05, Student-t test) reduced. Aorta's were removed and rings (about 2 mg) were stirred in l ml Krebs'solution. After 5 and 15 min, the release of endogenous PGI2 into the medium was assessed by its anti-aggregating capacity in rabbit platelet rich plasma and after 16 min the 6-oxo-PGF1α content of the medium was measured with RIA. Se deficient aorta’s released less PGI2 like activity (at 5 min, 46 % reduction, P<0.05; at 15 min, 25 % reduction) and less 6-oxo- PGFia (43% reduction, P<0.05). Similar experiments were performed with rings that were exhausted by 6 h preincubation in 100ml 50 mMTris, pH 7.5 in the absence of glucose. This procedure reduced the endogenous PGI2 release in control aortic rings with respectively 81 %(bioassay) or 89 % (RIA of 6-oxo-PGF]a). In Se deficient, exhausted rings the endogenous biosynthesis of PGI2 was strongly impaired as indicated by bioassay and measurements of 6-oxo- PGF1α (82 % reduction, P<0.05). Cyclo-oxygenase and PGI2# synthase activities were measured by incubation of 20 mg aorta with respectively 10/ug l-14C-arachidonic acid or 10μg l4C-PGH2. After 20 min the reactions were stopped and ihe products formed were extracted, radiochromatographed and quantified by liquid scintillation counting. In Se deficient aortas, cyclo oxygenase activity was not affected whereas PGl2-synthase activity showed 37 % reduction (P<0.05).These results support the hypothesis that a low peroxide tone is a prerequisite for an optimum biosynthesis of PGI2.
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