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Spam emails are flooding the Internet. Research to prevent spam is an ongoing concern. SMTP traffic was collected from different sources in real networks and analyzed to determine the difference regarding SMTP traffic characteristics of legitimate email clients, legitimate email servers and spam relays. It is found that SMTP traffic from legitimate sites and non-legitimate sites are different and could be distinguished from each other. Some methods, which are based on analyzing SMTP traffic characteristics, were purposed to identify spam relays in the network in this thesis. An autonomous combination system, in which machine learning technologies were employed, was developed to identify spam relays in this thesis. This system identifies spam relays in real time before spam emails get to an end user by using SMTP traffic characteristics never involving email real content. A series of tests were conducted to evaluate the performance of this system. And results show that the system can identify spam relays with a high spam relay detection rate and an acceptable ratio of false positive errors.

The 3G and 4G networks have drastically improved availability and quality in data transmission for bandwidth hungry services such as video streaming and location-based services. As 3G networks are very widely deployed, there exists increased capacity requirement and transport channel allocation to simultaneous users under a particular cell. Due to this reason, adequate resources are not available, which in turn degrades both service quality and user experienced quality. This research aims at understanding the characteristics of buffer filling during dedicated channel (DCH) transmission under fixed bit-rate assumptions on a per-user level taking different services into consideration. Furthermore, the resource utilisation in terms of empty buffer durations and user throughput achieved during dedicated channel transmission are also analysed for different data services existing in the mobile networks. The traces are collected from a real network and characteristics of the traffic are analysed prior to understanding its buffer filling in Radio Network Controller (RNC) during downlink data transmission. Furthermore, the buffer is modelled with some series of assumptions on channel bit-rates and simulations are performed taking single user scenario into consideration, for different services with the help of obtained traces as input to the buffer. This research is helpful in understanding the RNC buffer filling for different services, in turn yielding possible understanding on the existing transport channel switching scenario. With the help of analysing the buffer filling for different services and transport channel utilisation, we learn that most of the data services show low DCH utilisation of approximately around 20% and also found to have 80% of the total DCH session duration with empty buffer, causing sub-optimal radio resource utilization.

Machine-to-machine, machine-to-man, or man-to-machine (M2M) communications is expected to grow very rapidly over the next few years with an anticipated 50 billion devices being connected to broadband connections by 2020 [35]. To be able to plan and dimension for the expected (increase) in data traffic it is important to have a model for the traffic that will flow through the network. A concept often talked about in conjunction with M2M communications is the “Internet of things”, where billions of “smart” objects are connected to the Internet and can be easily shared and used or re-used by many applications. One sub-field of M2M communications is sensor/actuator networks that are installed in households, creating automated homes by enabling home appliances to talk to each other and to applications that can be running on hosts connected to the Internet. Such sensor/actuator networks extend the uses of home appliances into completely new and exciting applications, while also potentially making homes more energy efficient by smarter management and operation of these appliances. The thesis was proposed by and carried out at Ericsson in Kista, Sweden during the summer and fall of 2009. The academic advisor was G. Q. Maguire Jr. of the Royal Institute of Technology (KTH) and industrial advisor was Per Ljungberg at Ericsson. This thesis has an industrial focus, specifically to produce models and prototypes that benefit Ericsson as a company and the Ericsson Connected Home project. This thesis has evaluated the available standards and designed, buildt, and evaluated a prototype application for one of these standards to operate with this home gateway. Additionally, the thesis should also benefit the academic world by offering tractable models for M2M traffic that have a foundation in reality, rather than solutions in search of a problem. / Maskin-till-maskin, maskin-till-man, eller man-till-maskin (M2M) kommunikation förväntas växa mycket snabbt under de närmaste åren med förväntade 50 miljarder enheter anslutna till en bredbandsuppkoppling år 2020 [35]. För att kunna planera och dimensionera för den förväntade (ökningen) i datatrafik är det viktigt att ha en modell för den trafik som kommer att flöda genom nätverket. Ett begrepp det ofta talas om i samband med M2M-kommunikation är " Internet of things ", där miljarder "smarta" objekt är anslutna till Internet och enkelt kan delas och användas på nytt sätt och av många användare. En undergrupp inom M2M-kommunikation är sensor nätverk som installeras i hushåll, för att skapa automatiserade hem där hemelektroniken kan prata med andra apparater och program som körs på datorer anslutna till Internet. Sådana sensornätverk utvidgar användningen av hushållsapparater till helt nya och spännande applikationer, samtidigt som det potentiellt göra bostäder mer energisnåla genom smartare förvaltning och drift av dessa apparater. Detta examensarbete görs på uppdrag av Ericsson i Kista, Sverige under sommaren och hösten 2009. Akademisk rådgivare är GQ Maguire Jr från Kungliga Tekniska Högskolan (KTH) och industriell rådgivare är Per Ljungberg på Ericsson. Examensarbetet har som industriellt fokus att tillverka modeller och prototyper för att modellera trafiken i Ericssons nätverk. Examensarbetets akademiska värde är genom att erbjuda lättgörliga modeller för M2M trafik som har en grund i verkligheten, snarare än lösningar på jakt efter ett problem.