Sharif Digital Repository

In recent years, the usage of Internet bandwidth has been increased by emerging applications such as Video on Demand (VoD).As the popularity of VoD increases among the Internet users, some new problems like bandwidth limitations and congestion embark. For solving mentioned problems, Content Delivery Networks (CDN) has been introduced. Using CDN approaches either in ISP or organization is also known as Telco CDN. Generally implementing CDN approaches to process all requests either in ISP or organization can cause bottleneck. On the other hand, Software Defined Networks (SDN) could bring us new tools and opportunities which enables us to implement novel methods to confront these problems.... 

consumption is an economical and environmental concern in nowadays world. Data centers (DC) are an important and energy power hunger part of modern life infrastructure. Many researches have shown that by considering special properties of DCs (e.g. redundancy) the energy consumption can be reduced. However new advances in hardware and software technologies have made DCs equipment more power proportional, i.e. they consume power proportional to their load. Unfortunately this new feature and many previous works do not have synergy. Also the performance of the DCs is so important that no DC owner is willing to trade it for lower power bills. Therefore algorithms that don’t consider the... 

IPTV is one of the developing technologies in recent years. This technology is used to broadcast TV programs over IP protocol stack. Video quality improvement is the most important advantage of this technology. Users can watch programs anytime they want in opposition to the traditional TV channels in which programs cast at certain times. One of the challenges in IPTV is high latency for channel switching. This latency is caused by different sources, including network delay. The delay between sending the channel switch request and receiving the first packet of the new channel is called network delay. In this thesis a new approach is proposed to decrease network delay. The proposed approach... 

Software-Defined Networking is a new approach in networking which provides a great opportunity to improve network management. Network policy decisions and reachability policies are one of the main concerns of the network administrators. These policies are traditionally configured in different network devices. The configurations are manually implemented using ACLs in routers, firewalls, VLANs, etc. Network engineers configure every single device on the network with its vendor-specific low level language. As a result, access control policies of the network lie in the configuration files of the network devices or even only in the minds of the network engineers. Moreover, access control policies... 

Wireless LANs are becoming widespread in enterprises due to extensive usage of mobile devices and appearance of bring-your-own-device policies. However, mechanisms common in home WLANs are not sufficient for managing lots of access point and clients in an enterprise WLAN and WLAN controllers which are used in enterprises nowadays are limited to a fixed set of commands operated from a CLI and the source code is not changeable. Also, their effectiveness can be harvested alongside access points from the same vendor. Thus, dynamic high level programming for whole network configuration is an absolute need in this changing business environment and Software-defined Networking (SDN) will empower us... 

Software defined networks are developed to provide programmability and a centralized view in networks by decoupling control plane from data plane. Software defined networks are now well received,and these networks are evolving every day. This is while more attention has been paid to widen the application of these networks and eliminating the shortcomings in their performance. On the other hand, in very large networks, the issue of efficiency and processing speed is of great importance. However, performance in these networks is not satisfactory, especially in single controller based SDN due to the complex processing of packets in a unique controller. Security needs are also of great... 

Network management includes a wide range of topics such as performance, security, monitoring, debugging and so on. The network monitoring plays a vital role and can cover a wide range of network management requirements. Monitoring is the only way to know the correct network performance in accordance with the network design. In order to understand what is happening on the network and how network performance over time, the network should have a reporting system. Today, the reporting is done using network monitoring tools. In traditional networks, network monitoring is done using additional hardware which imposes high costs, complexity and also additional traffic overheads to the network. But... 

In the recent years, cloud data center issues have been the center of attention. Also for them topologies with multi paths between end hosts are offered. For use of multi path traffic engineering is essential. Researches show congestion occurred in the cloud data center networks, because the mean of link utilization is down. This means, some of links are congested while there are some other with much available bandwidth. Currently, the most common method is Equal Cost Multipath (ECMP) algorithm for routing flows in the data center network. ECMP decides on routing without any attention to network congestion condition. There, may be two big flows placed in the one path and it causes creation... 

Widespread use of the interconnected devices has caused an increase in the number of online services and the Internet of Things applications. Some of the protocols used in networking equipment does not have the ability to manage the high volume of traffic, scalability and mobility. Existing networks with traditional protocols are rigid and the process of policy-making on network is slow. Manging the huge number of data flows is a complex and time-consuming task. To respond to such problems, in this study a Software defined architecture is proposed as an alternative to traditional network architecture. In this type of networks, administrators have overview on network controllers and network... 

5G networks are going to support a variety of vertical services, with a diverse set of key performance indicators (KPIs), by using enabling technologies such as software-defined networking and network function virtualization. It is the responsibility of the network operator to efficiently allocate the available resources to the service requests in such a way to honor KPI requirements, while accounting for the limited quantity of available resources and their cost. A critical challenge is that requests may be highly varying over time, requiring a solution that accounts for their dynamic generation and termination. With this motivation, we seek to make joint decisions for request admission,... 

Despite being widespread, traditional IP networks are complex and hard to manage.This complexity is due to tight coupling between network control and data planes. A Software-Defined Network is a network architecture in which data plane forwarding is managed by a decoupled control plane. In these networks, control logic is moved to a logically centralized external controller which builds a global network state view and uses it to allocate network resources and provide necessary abstraction to facilitate programming forwarding elements. Generally, traffic management refers to measurement and analysis of network traffic in order to improve network performance in traffic and resources levels... 

Controller placement affects all aspects of separating control plane from forwarding plane in SDN networks such as flow set up delay and reliability. Also it will limit Fault tolerance, and other performance evaluation measures such as propagation delay, accessibility and Convergence in WANs. These measures influence software designing with affecting controllers’ ability to respond to real-time events and push forwarding actions to forwarding elements. The placement problem consists of finding suitable places for controllers along with the number of them. Most of the works in this field try to decrease the delay between controllers to switches and between controllers themselves. Beside,... 

The significant increase in the penetration of mobile phones and the significant growth of traffic generated in these networks has posed many challenges in the field of cost management, and the expansion of the existing network for mobile operators and has encouraged operators to change the current network architecture. On the other hand, the standard of the next mobile communication, i.e. the fifth generation, has a completely different architecture from the current architecture. Many of the logical and physical entities of the current network have undergone fundamental changes in the new network, and at first glance it does not seem that there is a direct transition from the previous... 

"Programmable networks" are to facilitate and evolve the computer networks. Specifically, Network Defined Software (SDN) is an advanced and innovative solution in the new computer network in which the hardwares are completely independent of the control and decision regarding data transfer. Based on this logic, network management becomes much simpler and enables innovation and new solutions for different parts of the network. In SDN, the program or network intelligence is logically present in software-based controllers (on the control panel) and can be changed and programmed, and network devices are converted into network packet sending hardware (on the data page) through an interface, Such... 

In this dissertation a special category of RF filters known as multi-path filters are introduced, chracterized and implemented. The center frequency of the multi-path filters can be tuned by changing the frequency of the clocks applied to the filter, which makes them attractive for use in multi-standard receivers. In this thesis, different types of multi-path filters are studied and by proposing different circuits, their various applications are covered. First, the concept of multi-path filters and their chracteristics are studied. Then a novel technique to analyze these filters based on Fourier analysis is proposed and then, based on this analysis, a new circuit architecture with reduced... 

There is a plethora of research and implementations that intend to increase the performance and reduce implementation costs of network routers. In this work, we review previous designs and propose a new network router design that is based on software-defined networks. Our design separates the data plane and the control plane from each other and connects both parts by using OpenFlow protocol. The control plane consists of a general small computer that utilizes the Quagga software to enforce the routing protocols. The control plane translates routing decisions to OpenFlow instructions and sends them to the data plane. The data plane is based on a switch that supports the OpenFlow protocol... 

With a growing concern on the considerable energy consumed by data centers, research efforts are targeting toward green data centers with higher energy efficiency. Networks are essential to today’s highly instrumented and connected society. Currently responsible for a fraction of the energy the IT sector consumes, networks rely on equipments that often use a constant amount of power regardless of their utilization; a worsening scenario as traffic is expected to increase by a factor of three in the next few years. Datacenter networks, for instance, employ devices that consume several kilowatts of power even when idle. This work aims to improve the energy efficiency of datacenter networks by... 

Internet is the largest multi-purpose, self-reliant, complex and distributed computer network across the globe. The nodes of this network are placed in every place like homes, offices, military camps, schools and all other locations by utilizing many different communication protocols, media and capacities. Furthermore, by rapid technology development, there are many newly born applications utilizing internet in new ways such as Internet of Things systems. The explosive growth of technology causing accelerated addition of new nodes to the internet, and any new single node may have several new unpatched vulnerabilities. This is a serious issue for managing this vast chaotic configuration and... 

Software-defined networking (SDN) is a network management approach that allows centralized control of the network independently from network hardware. As a network management method, SDN provides many capabilities not traditionally found in existing hardware-based networks. However, one of the significant challenges of SDN is the placement of the controller within the network. In SDN, the central controller must be able to efficiently route all data flows separately to end devices. Therefore, the placement of the controller in the network is crucial. However, controller placement in the network poses a major challenge as it needs to be appropriately and optimally positioned to enhance... 

The widely used services such as search engines, websites and social networks are deployed on multiple servers for quick and reliable access. Therefore, there is need to load balancer for distributing requests. In traditional networks usually dedicated hardware load balancers are used, which are very expensive, inflexible, single point of failure and prone to congestion. To solve this problem, using software defined networks, a simple device which works based on OpenFlow protocol can turn into a powerful load balancer with installing the rules by the controller.In software defined networks, a controller is used for load balancing, which has two main problems. First, in case of a failure in...