370 research outputs found
Service Chain (SC) Mapping with Multiple SC Instances in a Wide Area Network
Network Function Virtualization (NFV) aims to simplify deployment of network
services by running Virtual Network Functions (VNFs) on commercial
off-the-shelf servers. Service deployment involves placement of VNFs and
in-sequence routing of traffic flows through VNFs comprising a Service Chain
(SC). The joint VNF placement and traffic routing is usually referred as SC
mapping. In a Wide Area Network (WAN), a situation may arise where several
traffic flows, generated by many distributed node pairs, require the same SC,
one single instance (or occurrence) of that SC might not be enough. SC mapping
with multiple SC instances for the same SC turns out to be a very complex
problem, since the sequential traversal of VNFs has to be maintained while
accounting for traffic flows in various directions. Our study is the first to
deal with SC mapping with multiple SC instances to minimize network resource
consumption. Exact mathematical modeling of this problem results in a quadratic
formulation. We propose a two-phase column-generation-based model and solution
in order to get results over large network topologies within reasonable
computational times. Using such an approach, we observe that an appropriate
choice of only a small set of SC instances can lead to solution very close to
the minimum bandwidth consumption
A Scalable Approach for Service Chain (SC) Mapping with Multiple SC Instances in a Wide-Area Network
Network Function Virtualization (NFV) aims to simplify deployment of network
services by running Virtual Network Functions (VNFs) on commercial
off-the-shelf servers. Service deployment involves placement of VNFs and
in-sequence routing of traffic flows through VNFs comprising a Service Chain
(SC). The joint VNF placement and traffic routing is called SC mapping. In a
Wide-Area Network (WAN), a situation may arise where several traffic flows,
generated by many distributed node pairs, require the same SC; then, a single
instance (or occurrence) of that SC might not be enough. SC mapping with
multiple SC instances for the same SC turns out to be a very complex problem,
since the sequential traversal of VNFs has to be maintained while accounting
for traffic flows in various directions. Our study is the first to deal with
the problem of SC mapping with multiple SC instances to minimize network
resource consumption. We first propose an Integer Linear Program (ILP) to solve
this problem. Since ILP does not scale to large networks, we develop a
column-generation-based ILP (CG-ILP) model. However, we find that exact
mathematical modeling of the problem results in quadratic constraints in our
CG-ILP. The quadratic constraints are made linear but even the scalability of
CG-ILP is limited. Hence, we also propose a two-phase column-generation-based
approach to get results over large network topologies within reasonable
computational times. Using such an approach, we observe that an appropriate
choice of only a small set of SC instances can lead to a solution very close to
the minimum bandwidth consumption. Further, this approach also helps us to
analyze the effects of number of VNF replicas and number of NFV nodes on
bandwidth consumption when deploying these minimum number of SC instances.Comment: arXiv admin note: substantial text overlap with arXiv:1704.0671
Virtual-Mobile-Core Placement for Metro Network
Traditional highly-centralized mobile core networks (e.g., Evolved Packet
Core (EPC)) need to be constantly upgraded both in their network functions and
backhaul links, to meet increasing traffic demands. Network Function
Virtualization (NFV) is being investigated as a potential cost-effective
solution for this upgrade. A virtual mobile core (here, virtual EPC, vEPC)
provides deployment flexibility and scalability while reducing costs,
network-resource consumption and application delay. Moreover, a distributed
deployment of vEPC is essential for emerging paradigms like Multi-Access Edge
Computing (MEC). In this work, we show that significant reduction in
networkresource consumption can be achieved as a result of optimal placement of
vEPC functions in metro area. Further, we show that not all vEPC functions need
to be distributed. In our study, for the first time, we account for vEPC
interactions in both data and control planes (Non-Access Stratum (NAS)
signaling procedure Service Chains (SCs) with application latency requirements)
using a detailed mathematical model
QUICK/SLOW BIPHASIC RELEASE OF A POORLY WATER SOLUBLE ANTIDIABETIC DRUG FROM BI-LAYER TABLETS
Objective: The objective of the present work is to develop a bi-layer tablet consisting of an Immediate Pulse Release [IPR] layer and a sustained release [SR] layer that can produce a distinct biphasic release having two different drug release rates. The IPR layer is intended to release a fraction of the dose rapidly at a faster rate and the SR layer is meant for slow release of the remaining dose at a slower rate for a desired period of time.Methods: The quantitative determination was carried out by UV spectrophotometer. Solid dispersion was prepared by melt method. IPR layer was prepared by direct compression method, SR layer was prepared by wet granulation method. In-vitro drug release study from tablets was carried out in USP II tablet dissolution rate test apparatus. FTIR, DSC, XRD studies were performed.Results: 89% of the incorporated drug was released within 30 min in acid solution of pH 1.2 from the IPR tablet prepared with the highest amount of gelucire due to solid state transformation of the drug. The SR layer (SR8) comprising of SAL, CG and CMC produced prolonged drug release (70% in 10 h). The optimized IPR3 layer and SR layers were compressed to form bi-layer tablets from which 23-37% drug was released immediately in 30 min, and the remaining drug was released slowly for 7 to 10 h depending upon the compositions of the tablets.Conclusion: This study revealed that bi-phasic release of GPZ consisting of an initial quick release and subsequent slow release could be achieved by formulating bi-layer tablets using the existing tablet technology, and such formulation may be able to control hyperglycaemia effectively for a longer period of timeÂ
Insights from Analysis of Video Streaming Data to Improve Resource Management
Today a large portion of Internet traffic is video. Over The Top (OTT)
service providers offer video streaming services by creating a large
distributed cloud network on top of a physical infrastructure owned by multiple
entities. Our study explores insights from video streaming activity by
analyzing data collected from Korea's largest OTT service provider. Our
analysis of nationwide data shows interesting characteristics of video
streaming such as correlation between user profile information (e.g., age, sex)
and viewing habits, viewing habits of users (when do the users watch? using
which devices?), viewing patterns (early leaving viewer vs. steady viewer),
etc. Video on Demand (VoD) streaming involves costly (and often limited)
compute, storage, and network resources. Findings from our study will be
beneficial for OTTs, Content Delivery Networks (CDNs), Internet Service
Providers (ISPs), and Carrier Network Operators, to improve their resource
allocation and management techniques.Comment: This is a preprint electronic version of the article accepted to IEEE
CloudNet 201
Disaster-Resilient Control Plane Design and Mapping in Software-Defined Networks
Communication networks, such as core optical networks, heavily depend on
their physical infrastructure, and hence they are vulnerable to man-made
disasters, such as Electromagnetic Pulse (EMP) or Weapons of Mass Destruction
(WMD) attacks, as well as to natural disasters. Large-scale disasters may cause
huge data loss and connectivity disruption in these networks. As our dependence
on network services increases, the need for novel survivability methods to
mitigate the effects of disasters on communication networks becomes a major
concern. Software-Defined Networking (SDN), by centralizing control logic and
separating it from physical equipment, facilitates network programmability and
opens up new ways to design disaster-resilient networks. On the other hand, to
fully exploit the potential of SDN, along with data-plane survivability, we
also need to design the control plane to be resilient enough to survive network
failures caused by disasters. Several distributed SDN controller architectures
have been proposed to mitigate the risks of overload and failure, but they are
optimized for limited faults without addressing the extent of large-scale
disaster failures. For disaster resiliency of the control plane, we propose to
design it as a virtual network, which can be solved using Virtual Network
Mapping techniques. We select appropriate mapping of the controllers over the
physical network such that the connectivity among the controllers
(controller-to-controller) and between the switches to the controllers
(switch-to-controllers) is not compromised by physical infrastructure failures
caused by disasters. We formally model this disaster-aware control-plane design
and mapping problem, and demonstrate a significant reduction in the disruption
of controller-to-controller and switch-to-controller communication channels
using our approach.Comment: 6 page
Priprava i in vitro karakterizacija alginatnih nanokapsula za polagano oslobađanje testosterona
Slow release testosterone-loaded nanocapsules in alginate, biodegradable hydropolymer, were prepared by in situ nanoemulsion-polymer crosslinking approach. Different formulations varying in the drug loading solvent phase were prepared. Four different drug-loading solvents were assayed and the food grade hexane provided nanocapsules testosterone load of 30%. Testosterone loading was confirmed by FT-IR, DSC and quantitated by HPLC. Prepared nanocapsules appeared spherical with a dense drug core in transmission electron microscopy studies. Hydrodynamic diameter of nanocapsules was 34.5 ± 1.7 nm, with a Gaussian distribution and the zeta potential –5.0 meV. Sustained diffusive drug release was observed in vitro, following zero order kinetics releasing the drug payload over a period of 48 hours. Embedding testosterone in alginate provided sustained release.
Different drug loading solvents have distinct influence on drug loading and nanocapsules size distribution. The nanocapsulation technique developed can be a good choice for the development of different sustained steroid hormonal drug carriers.U radu je opisana priprava nanokapsula za polagano oslobađanje testosterona. Nanokapsule su pripravljene iz biorazgradljivog hidrofilnog polimera alginata umrežavanjem in situ. Varirajući udio lijeka u tekućoj fazi pripravljeno je nekoliko različitih nanokapsula. Upotreba heksana kao otapala omogućila je visoki sadržaj testosterona u nanokapsulama (30%). Prisutnost testosterona potvrđena je pomoću FT-IR i DSC, a za kvantitativno određivanje upotrebljena je HPLC metoda. Pomoću transmisijskog elektronskog mikroskopa utvrđeno je da su pripravljene nanokapsule sferno simetrične i imaju gustu ovojnicu s ljekovitom supstancijom. Hidrodinamički promjer nanokapsula bio je 34,5 ± 1,7 nm (Gaussova raspodjela), a zeta potencijal –5,0 meV. Oslobađanje testosterona in vitro bilo je polagano tijekom 48 sati, a slijedilo je kinetiku nultog reda. Otapalo koje je upotrebljeno za punjenje nanokapsula ljekovitom tvari utječe na količinu ljekovite tvari i raspodjelu veličine nanokapsula. Opisana metoda nanokapsuliranja može se primijeniti i na druge steroidne hormone
A disaster-resilient multi-content optical datacenter network architecture
Cloud services based on datacenter networks are becoming very important. Optical networks are well suited to meet the demands set by the high volume of traffic between datacenters, given their high bandwidth and low-latency characteristics. In such networks, path protection against network failures is generally ensured by providing a backup path to the same destination, which is link-disjoint to the primary path. This protection fails to protect against disasters covering an area which disrupts both primary and backup resources. Also, content/service protection is a fundamental problem in datacenter networks, as the failure of a single datacenter should not cause the disappearance of a specific content/service from the network. Content placement, routing and protection of paths and content are closely related to one another, so the interaction among these should be studied together. In this work, we propose an integrated ILP formulation to design an optical datacenter network, which solves all the above-mentioned problems simultaneously. We show that our disaster protection scheme exploiting anycasting provides more protection, but uses less capacity, than dedicated single-link protection. We also show that a reasonable number of datacenters and selective content replicas with intelligent network design can provide survivability to disasters while supporting user demands
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