330 research outputs found
On QoS-assured degraded provisioning in service-differentiated multi-layer elastic optical networks
The emergence of new network applications is driving network operators to not
only fulfill dynamic bandwidth requirements, but offer various grades of
service. Degraded provisioning provides an effective solution to flexibly
allocate resources in various dimensions to reduce blocking for differentiated
demands when network congestion occurs. In this work, we investigate the novel
problem of online degraded provisioning in service-differentiated multi-layer
networks with optical elasticity. Quality of Service (QoS) is assured by
service-holding-time prolongation and immediate access as soon as the service
arrives without set-up delay. We decompose the problem into degraded routing
and degraded resource allocation stages, and design polynomial-time algorithms
with the enhanced multi-layer architecture to increase the network flexibility
in temporal and spectral dimensions. Illustrative results verify that we can
achieve significant reduction of network service failures, especially for
requests with higher priorities. The results also indicate that degradation in
optical layer can increase the network capacity, while the degradation in
electric layer provides flexible time-bandwidth exchange.Comment: accepted by IEEE GLOBECOM 201
Energy-efficient traffic engineering
The energy consumption in telecommunication networks is expected to grow considerably, especially in core networks. In this chapter, optimization of energy consumption is approached from two directions. In a first study, multilayer traffic engineering (MLTE) is used to assign energy-efficient paths and logical topology to IP traffic. The relation with traditional capacity optimization is explained, and the MLTE strategy is applied for daily traffic variations. A second study considers the core network below the IP layer, giving a detailed power consumption model. Optical bypass is evaluated as a technique to achieve considerable power savings over per-hop opticalelectronicoptical regeneration.
Document type: Part of book or chapter of boo
GreenTouch GreenMeter core network power consumption models and results
This paper summarizes the energy efficiency improvement obtained by implementing a number of techniques in the core network investigated by the GreenTouch consortium. These techniques include the use of improved components with lower power consumption, mixed line rates (MLR), energy efficient routing, sleep and physical topology optimization. We consider an example continental network topology, NSFNET, to evaluate the total power consumption of a 2010 network and a 2020 network. The 2020 network results are based on traffic projections, the reductions in the equipment power consumption expected by 2020 and a range of energy saving measures considered by GreenTouch as outlined above. The projections of the 2020 equipment power consumption are based on two scenarios: a business as usual (BAU) scenario and a Green Touch (GT) (i.e. BAU+GT) scenario. The results show that the 2020 BAU scenario improves the network energy efficiency by a factor of 4.8x compared to the 2010 network as a result of the reduction in the network equipment power consumption. Considering the 2020 BAU+GT network where the equipment power consumption is reduced by a factor of 27x compared to the 2010 network, and where sleep, MLR and network topology are jointly optimized, a total improvement in energy efficiency of 64x is obtained
Energy Efficient Network Function Virtualisation in 5G Networks
Once the dust settled around 4G, 5G mobile networks become the buzz word in the world of communication systems. The recent surge of bandwidth-greedy applications and the proliferation of smart phones and other wireless connected devices has led to an enormous increase in mobile traffic. Therefore, 5G networks have to deal with a huge number of connected devices of different types and applications, including devices running life-critical applications, and facilitate access to mobile resources easily. Therefore given the increase in traffic and number of connected devices, intelligent and energy efficient architectures are needed to adequately and sustainably meet these requirements. In this thesis network function virtualisation is investigated as a promising paradigm that can contribute to energy consumption reduction in 5G networks.
The work carried out in this thesis considers the energy efficiency mainly in terms of processing power consumption and network power consumption. Furthermore, it considers the energy consumption reduction that can be achieved by optimising the locations of virtual machines running the mobile 5G network functions. It also evaluates the consolidation and pooling of the mobile resources. A framework was introduced to virtualise the mobile core network functions and baseband processing functions. Mixed integer linear programming optimisation models and heuristics were developed minimise the total power consumption. The impact of virtualisation in the 5G front haul and back haul passive optical network was investigated by developing MILP models to optimise the location of virtual machines. A further consideration is caching the contents close to the user and its impact on the total power consumption. The impact of a number of factor on the power consumption were investigated such as the total number of active users, the backhaul to the fronthaul traffic ratio, reduction/expansion in the traffic due to baseband processing, and the communication between virtual machines. Finally, the integration of network function virtualisation and content caching were introduced and their impact on improving the energy efficiency was investigated
Energy Efficient Core Networks with Clouds
The popularity of cloud based applications stemming from the high volume of connected mobile devices has led to a huge increase in Internet traffic. In order to enable easy access to cloud applications, infrastructure providers have invested in geographically distributed databases and servers. However, intelligent and energy efficient high capacity transport networks with near ubiquitous connectivity are needed to adequately and sustainably serve these requirements. In this thesis, network virtualisation has been identified as a potential networking paradigm that can contribute to network agility and energy efficiency improvements in core networks with clouds.
The work first introduces a new virtual network embedding core network architecture with clouds and a compute and bandwidth resource provisioning mechanism aimed at reducing power consumption in core networks and data centres. Further, quality of service measures in compute and bandwidth resource provisioning such as delay and customer location have been investigated and their impact on energy efficiency established. Data centre location optimisation for energy efficiency in virtual network embedding infrastructure has been investigated by developing a MILP model that selects optimal data centre locations in the core network. The work also introduces an optical OFDM based physical layer in virtual network embedding to optimise power consumption and optical spectrum utilization. In addition, virtual network embedding schemes aimed at profit maximization for cloud infrastructure providers as well greenhouse gas emission reduction in cloud infrastructure networks have been investigated. GreenTouch, a consortium of industrial and academic experts on energy efficiency in ICTs, has adopted the work in this thesis as one of the measures of improving energy efficiency in core networks
Resilient network design: Challenges and future directions
This paper highlights the complexity and challenges of providing reliable services in the evolving communications infrastructure. The hurdles in providing end-to-end availability guarantees are discussed and research problems identified. Avenues for overcoming some of the challenges examined are presented. This includes the use of a highly available network spine embedded in a physical network together with efficient crosslayer mapping to offer survivability and differentiation of traffic into classes of resilience. © 2013 Springer Science+Business Media New York
Multi-layer traffic engineering in optical networks under physical layer impairments
Ankara : The Department of Electrical and Electronics Engineering and the Institute of Engineering and Sciences of Bilkent University, 2010.Thesis (Ph. D.) -- Bilkent University, 2010.Includes bibliographical references leaves 153-165.We study Traffic Engineering (TE) in Multiprotocol Label Switching
(MPLS)/Wavelength Division Multiplexing (WDM) networks and propose a
multi-layer TE method. MPLS provides powerful TE features for IP networks
and is widely deployed in backbone networks. WDM can increase the transmission
capacity of optical fibers to tremendous amounts, therefore it has been the
dominant multiplexing technology used in the optical layer.
The proposed multi-layer TE solution facilitates efficient use of network resources
where the TE mechanisms in the MPLS and WDM layers coordinate.
We consider a static WDM layer and available traffic expectation information.
The TE problem arising in the considered scenario is the Virtual Topology Design
(VTD) problem, which involves the decision of WDM lightpaths to be established,
calculation of MPLS Label Switched Paths (LSPs) on the resulting
virtual topology, and calculation of the routes and wavelengths in the physical
topology that correspond to the lightpaths in the virtual topology. We assume
a daily traffic pattern changing with the time of day and aim to design a static
virtual topology that satisfies as much of the offered traffic as possible, over the
whole day.
In our proposed solution, the multi-layer VTD problem is solved by decomposing
it into two sub-problems, each involving in a single layer. The decomposition
approach is used in the thesis due to the huge computational burden of the combined
solution for real-life networks. The sub-problem in the MPLS layer is the
design of the lightpath topology and calculation of the LSP routes on this virtual
topology. This problem is known to be NP-complete and finding its optimum
solution is possible only for small networks. We propose a Tabu Search based
heuristic method to solve two versions of this problem, resource oriented and
performance oriented. Integer Linear Programming (ILP) relaxations are also
developed for obtaining upper and lower bounds. We show that the gap between
the produced solutions and the lower and upper bounds are around 10% and 7%
for the resource and performance oriented problems, respectively.
Since the actual traffic can show deviations from the expected values, we also
developed an MPLS layer online TE method to compensate the instantaneous
fluctuations of the traffic flows. In the proposed method, the LSPs are rerouted
dynamically using a specially designed cost function. Our numerical studies show
that using the designed cost function results in much lower blockings than using
commonly used Widest Shortest Path First and Available Shortest Path First
approaches in the literature.
The corresponding sub-problem of the multi-layer VTD problem in the WDM
layer is the Static Lightpath Establishment (SLE) problem. Along with the
capacity and wavelength continuity constraints, we also consider the Bit Error
Rate (BER) constraints due to physical layer impairments such as attenuation,
polarization mode dispersion and switch crosstalk. This problem is NP-complete
even without the BER constraints. We propose a heuristic solution method and
develop an exact ILP formulation to evaluate the performance of the proposed method for small problem sizes. Our proposed method produces solutions close
to the optimum solutions for the cases in which the ILP formulation could be
solved to optimality.
Then, these solution methods for the single layer sub-problems are combined
in a multi-layer TE scheme to solve the VTD problem in both layers jointly.
The proposed TE scheme considers the physical layer limitations and optical
impairments. This TE scheme can be applied by keeping each layer’s information
hidden from the other layer, but our simulations show that it can produce more
effective and efficient solutions when the physical layer topology information
is shared with the MPLS layer. We also investigate the effect of non-uniform
optical components in terms of impairment characteristics. The numerical results
show that more traffic can be routed when all the components in the network
have moderate impairment characteristics, compared to the case in which some
components have better and some have worse impairment characteristics.Şengezer, NamıkPh.D
- …