The intent of this report is to expose the audience to the contemporary organization of the Internet and to highlight the challenges it has to deal with in the future as well as the current efforts being made to overcome such threats. This report aims to build a frame of reference for how the Internet is currently structured and how the different layers interact together to make it possible for the Internet to exist as we know it. Additionally, the report explores the challenges the current Internet architecture design is facing, the reasons why these challenges are arising, and the multiple efforts taking place to keep the Internet working. In order to reach these objectives I visited multiple sites of organizations whose only reason for existence is to support the Internet and keep it functioning. The approach used to write this report was to research the topic by accessing multiple technical papers extracted from the IEEE database and network conferences reviews and to analyze and expose their findings. This report utilizes this vii information to elaborate on how network engineers are handling the challenges of keeping the Internet functional while supporting dynamic requirements. This report exposes the challenges the Internet is facing with scalability, the existence of debugging tools, security, mobility, reliability, and quality of service. It is explained in brief how each of these challenges are affecting the Internet and the strategies in place to vanquish them. The final objectives are to inform the reader of how the Internet is working with a set of ever changing and growing requirements, give an overview of the multiple institutions dedicated to reinforcing the Internet and provide a list of current challenges and the actions being taken to overcome them. / text

Η μερική αντικατάσταση των παραδοσιακών ενσύρματων επικοινωνιών από ασύρματες οδήγησε στην ανάγκη για κατάλληλη σχεδίαση των ασύρματων δικτύων, ώστε να υποστηρίζουν τα απαιτούμενα επίπεδα ποιότητας. Η προσφερόμενη ποιότητα περιορίζεται σίγουρα από φυσικά εμπόδια όπως τα όρια που έθεσε ο Shannon, αλλά και από την περιορισμένη γνώση μας στην εκπομπή και διάδοση κυμάτων. Η διαρκής βελτίωση της ικανότητας των ασύρματων δικτύων να προσφέρουν υψηλής ποιότητας υπηρεσίες είναι όμως γεγονός και οφείλεται σε δύο βασικούς ερευνητικούς άξονες, αυτόν που εφευρίσκει νέες μεθόδους επικοινωνίας (διαμόρφωση, κωδικοποίηση, πολυπλεξία, κεραίες κ.α.) και αυτόν που προσπαθεί να βελτιώσει τη διαχείριση των ήδη υπαρχόντων πόρων. Η παρούσα διατριβή προσφέρει επιστημονικές ιδέες και μοντέλα, που έχουν σαν σκοπό την καλύτερη διαχείριση των πόρων. Τα παραδοσιακά αλλά και τα μοντέρνα δίκτυα κινητής τηλεφωνίας έχουν κατακλύσει την αγορά. Η λειτουργία τους όμως, παραμένει να κινείται στα πλαίσια συμβιβασμών, προσφέροντας χαμηλή ποιότητα υπηρεσίας. Η είσοδος των ασύρματων δικτύων υπολογιστών στην αγορά, ως ανταγωνιστές παροχής κλασικών υπηρεσιών (υπηρεσία φωνής και υπηρεσία δεδομένων), δίνει μια ώθηση αναπροσαρμογής των στόχων των δικτύων κινητής τηλεφωνίας. Οι προτεινόμενοι αλγόριθμοι διαχείρισης των δικτύων αυτών προσφέρουν καλύτερη ποιότητα υπηρεσιών με αλλαγή μεμονωμένων μόνο τμημάτων του δικτύου, χωρίς την ασύμφορη ολική επανασχεδίασή του. Αποτελούν δηλαδή πρακτικές λύσεις για την αποδοτικότερη λειτουργία των ήδη εγκατεστημένων δικτύων. Από την άλλη πλευρά, η ανερχόμενη τεχνολογία των ασύρματων δικτύων υπολογιστών βρίσκεται περισσότερο σε ανταγωνισμό με τα κλασικά ενσύρματα δίκτυα υπολογιστών. Το πλεονέκτημα της ελεύθερης κίνησης μετατρέπεται σε δυσβάσταχτο περιορισμό όταν η σύγκριση ποιότητας των δύο δικτύων είναι αναπόφευκτη. Για το λόγο αυτό, υπάρχει η μεγάλη ανάγκη τα ασύρματα δίκτυα να γίνουν ανταγωνιστικά των ενσύρματων και κυρίως να παρέχουν ποιότητα ικανού επιπέδου, ώστε οι διάφορες υπηρεσίες να μπορούν να λειτουργήσουν ανεπηρέαστες από την χρήση του ασύρματου καναλιού. Οι προτεινόμενοι αλγόριθμοι σε αυτόν τον τομέα αποσκοπούν στην βελτίωση της λειτουργίας των ασύρματων δικτύων με τελικό σκοπό την εξασφάλιση επιπέδων ποιότητας. Για την μελέτη των ασύρματων δικτύων κινητής τηλεφωνίας και υπολογιστών και την εξαγωγή συμπερασμάτων απαιτούνται αναλυτικές μέθοδοι περιγραφής και εξομοιώσεις των δικτύων αυτών ώστε να γίνουν και οι κατάλληλες συγκρίσεις της προσφερόμενης ποιότητας. Ο τομέας αυτός της επιστήμης είναι διαρκώς ενεργός καθώς νέες τεχνικές και αναλύσεις προτείνονται συνεχώς. Με στόχο την ανάλυση και την εξομοίωση των προηγούμενα αναφερθέντων αλγορίθμων αναπτύχθηκε ένας αριθμός τεχνικών, που αποτελούν αναπόσπαστο τμήμα της διατριβής αυτής. Στα πλαίσια της διατριβής αυτής και συγκεκριμένα στο τμήμα μελέτης της επίδοσης των δικτύων, προτείνεται η μετατροπή μη γραμμικών αλυσίδων Markov σε γραμμικές, για χρήση σε προβλήματα κίνησης ταυτόχρονων πολλαπλών υπηρεσιών. Η προτεινόμενη μεθοδολογία οδηγεί σε ταχύτατο υπολογισμό της αλυσίδας με τη χρήση μιας προσέγγισης. Παράλληλα, αναλύεται ο χρόνος διαμονής και ο εναπομένων χρόνος διαμονής σε μια κυψέλη. Η ανάλυση γίνεται εκ του μηδενός και με χρήση βασικών στοχαστικών μοντέλων, ενώ το αποτέλεσμα καταλήγει σε κατανομή gamma, κάτι που είχε ήδη παρατηρηθεί από πειράματα στην βιβλιογραφία. Στη συνέχεια κατασκευάζεται ένα ντετερμινιστικό μοντέλο εξομοίωσης που μπορεί να εφαρμοστεί εύκολα μέσω ενός χάρτη σε κάθε πόλη με ορθογώνια δόμηση. Στο τμήμα των δικτύων κινητής τηλεφωνίας προτείνεται ένας αλγόριθμος διαχείρισης και αποδοχής κλήσεων που προκαλεί μεταπομπές συστήματος (system initiated handover). Η χρήση των μεταπομπών αυτών επιφέρει μεταβλητή χωρητικότητα (soft capacity) σε μια ομάδα κυψελών με αποτέλεσμα την αποδοτικότερη διαχείριση πόρων σε περιπτώσεις άνισης κατανομής κίνησης. Ένας άλλος αλγόριθμος προτείνεται για διαρκή διαπραγμάτευση (real-time negotiation) ποιότητας μεταξύ του δικτύου και του χρήστη με αποτέλεσμα την καλύτερη οργάνωση και διαχείριση των πόρων. Αποδεικνύονται η δυνατότητα χρήσης του αλγορίθμου σε πραγματικό χρόνο και τα οφέλη που αποκομίζονται από αυτήν. Στο τμήμα ασύρματων δικτύων υπολογιστών προτείνεται ένα νέο πρωτόκολλο πρόσβασης μέσου, για χρήση στα ασύρματα τοπικά δίκτυα. Το πρωτόκολλο αυτό είναι πλήρως κατανεμημένο (μπορεί να χρησιμοποιηθεί και σε αυτοοργανονούμενα δίκτυα - ad hoc), ενώ προσφέρει τη δυνατότητα παροχής διαφορετικών επιπέδων ποιότητας, από άριστη ποιότητα για κλήσεις πραγματικού χρόνου μέχρι ποιότητα καλύτερης δυνατής προσπάθειας (best effort). Επίσης προτείνονται αλγόριθμοι βελτίωσης των ασύρματων δικτύων αισθητήρων. Αναλύεται συγκεκριμένα ο αυτόματος εντοπισμός κόμβων με χρήση τριγωνισμού και μεταβλητής ισχύος σημάτων-φάρων και η εξοικονόμηση ενέργειας με χρήση συστημάτων πολλαπλών κεραιών (MIMO). / The trend of replacing the traditional wired communications with their wireless counterparts led to the need for better design and organization of wireless networks so as to provide the necessary Quality of Service (QoS) levels. The offered QoS is bounded by Shannon’s limit and from the limitation of human knowledge on the wireless channel matters. However, the constant improvement of network performance is a fact based on two parallel scientific axes, the one that provides new communication techniques (modulation, coding, multiple access, antennas, etc) and the one that handles the already invented methods in an optimized manner. This thesis offers new scientific ideas and models for better resource management of wireless networks. Traditional and modern mobile telephone networks have occupied the market. Nevertheless, their functionality is still based on compromising of offered quality with the needs of a two-way voice application. Wireless computer networks appear in the market as contenders of voice service, acting like a threat to telephone networks. The proposed models for the mobile telephone networks provide solutions for improving overall QoS by altering only minor parts of these already-installed networks. On the other hand, the advancement of the wireless technology gives rise to visions of the so called Broadband Wireless Access. Computer Networks are expected to offer global roaming and provide traditional services over the IP protocol. In this context, QoS is necessary for guaranteeing service levels of quality. The proposed models in this part are focused in offering acceptable quality levels over the wireless channel for these services. The performance analysis of wireless networks requires the use of analytical approaches and simulation of these networks in order to assess the final offered quality. This section of science is constantly developing since new methods and techniques are applied to different parts of research. Through the procedure of analyzing the wireless networks in this thesis, a number of new techniques have been invented which constitute an important part of it. In terms of network traffic description, a new transformation of nonlinear markov chain to linear is proposed. By means of this transformation, the calculation of unbalanced nonuniform traffic can be accelerated. In the section of performance analysis, the sojourn time and the remaining sojourn time are analytically calculated. These cell parameters are found to follow a gamma distribution, a result that is backed from simulations in bibliography. Moreover, a deterministic simulation model is derived to enable easy calculation of these parameters from a map. As regards the mobile telephone networks, a new call admission control scheme is proposed in order to simulate soft capacity functionality in 2G networks. This feature, organizes better the resources in a cluster in cases of inhomogeneous network traffic. Moreover, a QoS negotiation algorithm is proposed for use in 3G networks (e.g. UMTS). Real-time negotiation is proposed for better resource organization and management. The gain from these schemes is calculated and presented. A new Medium Access Control (MAC) protocol is proposed for use in 802.11 Wireless Local Area Networks. This protocol is backward compatible with the protocol 802.11e and offers better quality infrastructure for VoIP services. The proposed protocol is analyzed and simulated and the results are compared to the previously used protocols to showcase the improvements. A new analytical approach with better accuracy is proposed for this reason. Finally, two techniques are proposed for improving the quality of wireless sensor networks. Firstly, a technique for low cost real-time localization with a small number of GPS or other beacons is proposed and tested. Secondly, a means of energy conservatiοn by use of Multiple Input Multiple Output (MIMO) systems is proposed, and then the gain from a QoS scheme is derived.

Στόχος της εργασίας είναι να εμβαθύνει πάνω στο σημαντικό θέμα της ποιότητας υπηρεσίας, εξειδικεύοντας το θέμα για τα ATM switches. Μελετά τους αλγορίθμους που εφαρμόζονται ή λειτουργούν σε θεωρητικό επίπεδο για τα ATM switches και τον τρόπο που επηρεάζουν τις διάφορες παραμέτρους του QoS. Για το λόγο αυτό ορισμένοι αλγόριθμοι εφαρμόζονται σε εξομοιωτή δικτύων και με βάση τη συμπεριφορά τους εκτιμάται η επίδραση των διαφόρων αλγορίθμων στην απόδοση και τη συμπεριφορά των δικτύων. / This research examines closely the important issue of quality of service, specializing the issue on ATM switches. It examines the algorithms that are applied or used on theoretical level on ATM switches and the way they affect the QoS parameters. For this reason some algorithms are applied on a network simulator and according the network’s behavior we estimate the effect of different algorithms on networks’ performance and behavior.

The rapid growth in client application demands, in terms of bandwidth and (QoS), has motivated the deployment of the optical technology at Metro Access and Metro Core Networks. More diverse and more intelligent optic devices are required for efficiently management of huge capacity in the network. The explosion in demand for network bandwidth is mainly due to the growth in data traffic whose nature is also becoming more and more complex. In general, most of service-based traffics are transported in networks which are now being dominated by the optical switching technology. Nevertheless, such technology has some drawbacks such as inflexible and non-scalable properties. (OPS), which offers significant benefits in terms of both network efficiency and control scalability, may overcome these limitations. This has motivated the orientation from optical circuit switching to optical packet switching in the future network infrastructure. In reality, optical packet switching ring (OPSR) networks, which combine the packet switching technology with the well-known advantages of ring topology such as fast service restoration in cases of failure and high gain of statistical traffic multiplexing over the ring, appear to be the technology of choice for the next generation of Metro Area Networks. A new OPSR architecture which is based on the all-optical infrastructure that offers intelligent features with lower cost while maximizing processing time and is now considering being replaced existing opto-electronic architectures such as Resilient Packet Ring, have been presented in the scope of the dissertation. The key element of such network is Packet Optical Add/Drop Multiplexer (POADM) which is implemented inside a ring node, allowing the node to exploit the optical transparency. This dissertation hence focuses on the performance evaluation of the new generation of OPSR network. In this dissertation, we have investigated the performance analysis (in terms of packet delay and queue-length distribution of access nodes) of an optical synchronous bus-based metropolitan network supporting fixed-size packets. We have modeled each access node by an embedded discrete time Markov chain (EDTMC). The solution of the EDTMC allows us to compute the approximate probability that access nodes on the bus "see" free slots in the transit line. Using a recursive analysis technique, we approximately outline the mean waiting time of client packets coming from the upper layer as well as an approximate queue-length distribution of local buffers at access nodes in two cases: with and without QoS guarantees. To characterize the performance of an asynchronous OPSR network, we have evaluated the impact of Optical fixed-Size Packet Creation on the network performance without and with different quality of services (QoS) requirements. Performance analysis of such systems has allowed us to identify a reasonable combination of some parameters (timeslot duration, timer expiration values, profile of client traffic and network load) which may be able to improve the bandwidth utilization of the network for a given traffic matrix. The most important point that we have mentioned in the dissertation is the comparison of two architectural approaches: Variable Length - Optical Packet Format (VL-OPF) model supporting empty packets versus Fixed Length - Optical Packet Format (FL-OPF) model. In addition to CoS-Upgrade Mechanism (CUM) which is proposed to improve the filling ratio of the optical container, we have proposed a novel mechanism named Dynamic CoS-Upgrade Mechanism (DCUM) where timers are dynamically changed according to the state of the local buffer of network nodes and the traffic circulating in the network, in order to create containers with a high filling ratio while limiting the time needed for their creation.

Problema: Kiekvienas klientas nori gauti kokybiškas ir nepriekaištingas paslaugas, svarbu klientui kaip yra pateikiama paslauga, ir ar ji atitinka jų lūkesčius. Norint patenkinti klientų lūkesčius, visų pirma, svarbu juos tinkamai aptarnauti, išsiaiškinti jų poreikius. Tačiau ne visada klientas lieka patenkintas suteiktu aptarnavimu. Kokios yra klientų aptarnavimo kokybės tobulinimo galimybės, kad atitiktų klientų lūkesčius? Darbo tikslas – nustatyti klientų aptarnavimo kokybės tobulinimo galimybes Kauno miesto kelionių agentūrose. Darbo objektas – klientų aptarnavimo kokybės tobulinimo galimybės Kauno miesto kelionių agentūrose. Darbo uždaviniai: 1. Pateikti kokybės sampratos esmę; 2. Išskirti paslaugų kokybės vertinimo parametrus bei metodus ir įvertinti jų privalumus bei trūkumus; 3. Nustatyti klientų pagrindines aptarnavimo klaidas bei jų tobulinimo galimybes turizmo srityje; 4. Sukurti klientų aptarnavimo kokybės tobulinimo galimybių vertinimo modelį; 5. Pagal sukurtą modelį įvertinti klientų aptarnavimo kokybę Kauno miesto kelionių agentūrose bei jų tobulinimo galimybes. Magistro darbe siekiama apibendrinti klientų aptarnavimo kokybę bei jos tobulinimo galimybes Kauno miesto kelionių agentūrose. Išanalizavus kliento aptarnavimo kokybės įvertinimo metodikos mokslinius sprendimus, atliktas klientų aptarnavimo kokybės tobulinimo galimybių tyrimas Kauno miesto kelionių agentūrose. Remiantis įvairių užsienio autorių išanalizuota literatūra galima daryti išvadą, kad... [toliau žr. visą tekstą] / The problem: Every client wants to get high quality and impeccable service, it is important to the customer as the service is provided, and whether it meets their expectations. To meet customers' expectations, in particular, it is important to properly handle them, ascertain their needs. However, it is not always the customer remains satisfied with obtaining a service. So the need to seek answers to the question: what is the customer service quality improvement opportunities? Research aim - to improve the quality of customer service capabilities in Kaunas travel agencies. Research object - customer service quality improvement opportunities in Kaunas travel agencies. Research tasks: 1. The quality of the concept of the essence; 2. To distinguish the quality of service parameters and the assessment methods and assess their strengths and weaknesses; 3. Identify the key customer service mistakes and improvement opportunities in the tourism field; 4. Create customer service quality improvement opportunities for the assessment model; 5. In the developed model to assess the quality of customer service in Kaunas travel agencies and their development potential. Master's work aims to summarize the theory of customer service quality and its development opportunities in Kaunas travel agencies. The analysis of the customer service quality evaluation methodology of scientific decisions, made in customer service quality improvement opportunities for study in Kaunas travel agencies... [to full text]

The multitude of services delivered over the Internet would have been difficult to fathom 40 years ago when much of the initial design was being undertaken. As a consequence, the resulting architecture did not make provisions for differentiating between, and managing the potentially conflicting requirements of different types of services such as real-time voice communication and peer-to-peer file sharing. This shortcoming has resulted in a situation whereby services with conflicting requirements often interfere with each other and ultimately decrease the effectiveness of the Internet as an enabler of new and transformative services. The ability to passively identify different types of Internet traffic then would address this shortcoming and enable effective management of conflicting types of services, in addition to facilitating a better understanding of how the Internet is used in general. Recent attempts at developing such techniques have shown promising results in simulation environments but perform considerably worse when deployed into real-world scenarios. One possible reason for this descrepancy can be attributed to the implicit assumption shared by recent approaches regarding the degree of similarity between the many networks which comprise the Internet. This thesis quantifies the degradation in performance which can be expected when such an assumption is violated as well as demonstrating alternative classification techniques which are less sensitive to such violations.

In this thesis we propose a cloud Input Shaper and Dynamic Resource Controller to provide application-level quality of service guarantees in cloud computing environments. The Input Shaper splits the cloud into two areas: one for shaped traffic that achieves quality of service targets, and one for overflow traffic that may not achieve the targets. The Dynamic Resource Controller profiles customers’ applications, then calculates and allocates the resources required by the applications to achieve given quality of service targets. The Input Shaper then shapes the rate of incoming requests to ensure that the applications achieve their quality of service targets based on the amount of allocated resources. To evaluate our system we create a new benchmark application that is suitable for use in cloud computing environments. It is designed to reflect the current design of cloud based applications and can dynamically scale each application tier to handle large and varying workload levels. In addition, the client emulator that drives the benchmark also mimics realistic user behaviors such as browsing from multiple tabs, using JavaScript, and has variable thinking and typing speeds. We show that a cloud management system evaluated using previous benchmarks could violate its estimated quality of service achievement rate by over 20%. The Input Shaper and Dynamic Resource Controller system consist of an application performance modeler, a resource allocator, decision engine, and an Apache HTTP server module to reshape the rate of incoming web requests. By dynamically allocating resources to applications, we show that their response times can be improved by as much as 30%. Also, the amount of resources required to host applications can be decreased by 20% while achieving quality of service objectives. The Input Shaper can reduce VMs’ resource utilization variances by 88%, and reduce the number of servers by 45%.

With the growth of wireless networks and the increase in personal internet use for a wide diversity of applications, the importance of the quality of service (QoS) delivered to clients has become of great importance. In order to evaluate QoS, this study explores the application of the linear response surface analysis (LRSA) technique as an evaluation tool for QoS factors such as Throughput and Delay. An 802.11n prototype wireless network is constructed in order to capture QoS data that is then used to construct LRSA models in order to evaluate the QoS factors. The LRSA models are maximised and minimised while constraining specific measured QoS factors and the subsequent results are analysed. Based on this analysis, recommendations for the improvement of wireless networks are made as well as the use of the LRSA technique to evaluate QoS within a wireless network. / Thesis (MSc (Computer Science))--North-West University, Potchefstroom Campus, 2013

With the growth of wireless networks and the increase in personal internet use for a wide diversity of applications, the importance of the quality of service (QoS) delivered to clients has become of great importance. In order to evaluate QoS, this study explores the application of the linear response surface analysis (LRSA) technique as an evaluation tool for QoS factors such as Throughput and Delay. An 802.11n prototype wireless network is constructed in order to capture QoS data that is then used to construct LRSA models in order to evaluate the QoS factors. The LRSA models are maximised and minimised while constraining specific measured QoS factors and the subsequent results are analysed. Based on this analysis, recommendations for the improvement of wireless networks are made as well as the use of the LRSA technique to evaluate QoS within a wireless network. / Thesis (MSc (Computer Science))--North-West University, Potchefstroom Campus, 2013

Consider the concept of the Utility Model [5]: the optimal allocation of resources of a server or network while meeting the absolute Quality of Service (QoS) requirements of users' multimedia sessions. Past algorithms and heuristics to solve the Utility Model mapped the problem onto a variant of the Combinatorial Knapsack Problem, with server utility (e.g. revenue) as the quantity to be optimized and with user QoS requirements expressed as constraints on the resource allocation. Both optimal (algorithmic) and fast but sub-optimal (heuristic) methods were derived to solve the resulting Multidimensional Multiconstraint Knapsack Problem (MMKP) and hence to perform admission control of proposed user sessions However, previous algorithms and heuristics were restricted to solving the Utility Model on an enterprise network (a network of less than 30 nodes), owing to the need in admission control to solve the problem in real time, typically a few seconds or less. The methods used for the path finding and admission processes had unfavorable computational complexities. As a result, only small (i.e. enterprise) networks could be treated in real time. Also, considerable time was wasted on frequently unnecessary traversals during upgrading. In this thesis we attempt to solve and implement the Utility Model using a modified version of a Multicommodity Flow algorithm, which has better computational complexity than Knapsack Algorithms or many heuristics and hence is capable of finding paths relatively quickly for larger networks. What's more, the Multicommodity flow algorithm used keeps essential information about the current networks and user sessions, thus further reducing the overall admission time.