Sharif Digital Repository

Up to now two kinds of hardware have been used in routers: ASIC processors or general purpose processors. These two solutions have their own flaws. ASIC hardwares are fast but they are not flexible for implementation or development of new applications. And general purpose processors are not fast enough for fast data rate of network. On the other hand, there is an ever increasing gap between the memory access speed and network data rate. At this time the main bottleneck in packet processing systems is memory. For solving this problem, two groups of solution have been introduced. The first group tries to reduce the demand for memory by using cache or longer system words. The second group uses... 

One way to control the type of data being transferred in the network is to check the header of the packet, but in networks that have high-speed data transmission or data can move through different routes, the probability of finding the first packet which contains the header reduces tremendously, and the usage of the methods mentioned below becomes clear. So even if the packet header isn’t received correctly, or the declarative features of these flows are changed, without having exact knowledge of the data transferred, you can use a limited number of packets to obtain information such as the type and protocol being used. This is possible with the help of statistical data analysis.Traffic... 

There is much interest in the theoretical study of the structure of hypercubes because their structure has played an important role in the development of parallel processing and is still quite popular and influential.This thesis will begin with an introduction to hypercubes and some of their problems. Then we study the following concepts: Arboricity (The minimum number of edge-disjoint forests into which a graph can be decomposed), Galactic number (similar to arboricity but such that each component of each forest is a star), Silver coloring (Given a set I of maximal independent vertices, a silver coloring with respect to I is such that every v 2 I sees every other colors in its closed... 

In this thesis we are going to study the effects of Non-Markovianity on the excitation energy transport(EET) and compare it with Markovian effects. We will see that the shape of a network affects its efficiency. The speed of EET in linear networks is slowed down as Non-Markovianity is increased and this in turn lowers the efficiency of linear networks in Non-Markovian regime. Finally, we compare the efficiency of different networks  

Software Defined Networking (SDN) provides a logically centralized view of the state of the network, and as a result opens up new ways to manage and monitor networks. In this dissertation a novel approach to network intrusion detection in SDNs is introduced that takes advantage of these attributes. This approach can detect compromised routers that produce faulty messages, copy or steal traffic or maliciously drop certain types of packets. To identify these attacks and the affected switches, we correlate the forwarding state of network---i.e. installed forwarding rules---with the forwarding status of packets---i.e. the actual route packets take in the network and detect anomaly in routes.... 

Since today graphs have many applications in different sciences including computer networks, in this thesis a number of graphs which have been widely used in computer networks, are studied.The graphs presented in this thesis are hypercubes, generalized hypercubes (Bhuyan and grawal, 1984), balanced hypercubes (Huang and Jie, 1992) and the star graphs (Sheldon and Akers, 1987), which are the generalization of the hypercubes and have similar properties.In general the graph which is considered for computer networks as an interconnection structure,should have small degrees of vertices, a small diameter, and a large number of paths between any two vertices. Thus in our studies these three... 

In many network which relationships between nodes are defined based on the similarity of attributes (Such as the World Wide Web and social networks), extracting information about networks object’s attributes may be difficult or even in many cases impossible.In these cases, predicting unknown attributes based on other objects attributes according to network structure can be extremely useful.Even more, finding a representative sample set of objects and trying to obtain their attributes in order to predict other object’s attributes with this obtained data can be an interesting problem. Finding such a set of objects with minimum size while giving maximizing accuracy in predicting other object’s... 

Network Motifs are subgraphs that appear more frequently in real networks than randomize networks. Frequent replication of a subgraph could imply evolution, network performance or some other particular reasons. From algorithmic perspective, network motif discovery in a graph is a difficult problem. Since, at least it includes the whole graph isomorphism. Hence, for solving this problem in practice, we need computable graphs. The existing algorithms so far, have high running times and memory usages. In this thesis, we present a new algorithm called CGQ. Within this algorithm, we use both QuateXelero and G-Trie algorithms which respectively have better performance in census of real networks... 

Networks and the epidemiology of directly transmitted infectious diseases are fun-damentally linked. The foundations of epidemiology and early epidemiological models were based on population wide random-mixing, but in practice each individual has a finite set of contacts to whom they can pass infection; the ensemble of all such contacts forms a network. Knowledge of the structure of the network allows models to compute the epidemic dynamics at the population scale from the individual-level behaviour of infections.Motivated by the analysis of social networks, we study a model of random net-works that has both a given degree distribution and a tunable clustering coefficient.We consider two...