Traffic measurement and analysis

Measurement and analysis of real traffic is important to gain knowledge about the characteristics of the traffic. Without measurement, it is impossible to build realistic traffic models. It is recent that data traffic was found to have self-similar properties. In this thesis work traffic captured on the network at SICS and on the Supernet, is shown to have this fractal-like behaviour. The traffic is also examined with respect to which protocols and packet sizes are present and in what proportions. In the SICS trace most packets are small, TCP is shown to be the predominant transport protocol and NNTP the most common application. In contrast to this, large UDP packets sent between not well-known ports dominates the Supernet traffic. Finally, characteristics of the client side of the WWW traffic are examined more closely. In order to extract useful information from the packet trace, web browsers use of TCP and HTTP is investigated including new features in HTTP/1.1 such as persistent connections and pipelining. Empirical probability distributions are derived describing session lengths, time between user clicks and the amount of data transferred due to a single user click. These probability distributions make up a simple model of WWW-sessions

DTMsim - DTM channel simulation in ns

Dynamic Transfer Mode (DTM) is a ring based MAN technology that provides a channel abstraction with a dynamically adjustable capacity. TCP is a reliable end to end transport protocol capable of adjusting its rate. The primary goal of this work is investigate the coupling of dynamically allocating bandwidth to TCP flows with the affect this has on the congestion control mechanism of TCP. In particular we wanted to find scenerios where this scheme does not work, where either all the link capacity is allocated to TCP or congestion collapse occurs and no capacity is allocated to TCP. We have created a simulation environment using ns-2 to investigate TCP over networks which have a variable capacity link. We begin with a single TCP Tahoe flow over a fixed bandwidth link and progressively add more complexity to understand the behaviour of dynamically adjusting link capacity to TCP and vice versa

Traffic engineering in ambient networks: challenges and approaches

The focus of this paper is on traffic engineering in ambient networks. We describe and categorize different alternatives for making the routing more adaptive to the current traffic situation and discuss the challenges that ambient networks pose on traffic engineering methods. One of the main objectives of traffic engineering is to avoid congestion by controlling and optimising the routing function, or in short, to put the traffic where the capacity is. The main challenge for traffic engineering in ambient networks is to cope with the dynamics of both topology and traffic demands. Mechanisms are needed that can handle traffic load dynamics in scenarios with sudden changes in traffic demand and dynamically distribute traffic to benefit from available resources. Trade-offs between optimality, stability and signaling overhead that are important for traffic engineering methods in the fixed Internet becomes even more critical in a dynamic ambient environment

Network overload avoidance by traffic engineering and content caching

The Internet traffic volume continues to grow at a great rate, now driven by video and TV distribution. For network operators it is important to avoid congestion in the network, and to meet service level agreements with their customers. This thesis presents work on two methods operators can use to reduce links loads in their networks: traffic engineering and content caching. This thesis studies access patterns for TV and video and the potential for caching. The investigation is done both using simulation and by analysis of logs from a large TV-on-Demand system over four months. The results show that there is a small set of programs that account for a large fraction of the requests and that a comparatively small local cache can be used to significantly reduce the peak link loads during prime time. The investigation also demonstrates how the popularity of programs changes over time and shows that the access pattern in a TV-on-Demand system very much depends on the content type. For traffic engineering the objective is to avoid congestion in the network and to make better use of available resources by adapting the routing to the current traffic situation. The main challenge for traffic engineering in IP networks is to cope with the dynamics of Internet traffic demands. This thesis proposes L-balanced routings that route the traffic on the shortest paths possible but make sure that no link is utilised to more than a given level L. L-balanced routing gives efficient routing of traffic and controlled spare capacity to handle unpredictable changes in traffic. We present an L-balanced routing algorithm and a heuristic search method for finding L-balanced weight settings for the legacy routing protocols OSPF and IS-IS. We show that the search and the resulting weight settings work well in real network scenarios

Design and implementation of the node identity internetworking architecture

The Internet Protocol (IP) has been proven very flexible, being able to accommodate all kinds of link technologies and supporting a broad range of applications. The basic principles of the original Internet architecture include end-to-end addressing, global routeability and a single namespace of IP addresses that unintentionally serves both as locators and host identifiers. The commercial success and widespread use of the Internet have lead to new requirements, which include internetworking over business boundaries, mobility and multi-homing in an untrusted environment. Our approach to satisfy these new requirements is to introduce a new internetworking layer, the node identity layer. Such a layer runs on top of the different versions of IP, but could also run directly on top of other kinds of network technologies, such as MPLS and 2G/3G PDP contexts. This approach enables connectivity across different communication technologies, supports mobility, multi-homing, and security from ground up. This paper describes the Node Identity Architecture in detail and discusses the experiences from implementing and running a prototype

Analys och värdering av räddningstjänstens operativa förmåga

Att analysera och värdera räddningstjänstens operativa förmåga är nödvändigt för att tydligt och transparent kunna dimensionera verksamheten. I den här rapporten presenterar vi ett förslag på hur sådana analyser och värderingar kan genomföras med fokus på skydd mot olyckor och kommunal räddningstjänst. Rapporten är framtagen på uppdrag av Malmö stad och Lunds kommun, vilket innebär att den data som används kommer från Räddningstjänsten Syd.Att ta fram en metod för värdering av operativ förmåga innebär att man måste göra avvägningar mellan viktiga aspekter. Som vägledning för att göra dessa avvägningar inledde vi arbetet med att fastställa följande kriterier för metoden: 1) Dimensionering av räddningstjänst ska ske med utgångspunkt i riskbild och gällande lagstiftning, 2) Metoden ska vara evidensbaserad, 3) Analyser som genomförs med metoden ska vara transparenta och spårbara, 4) Metoden ska täcka in alla möjliga händelser som räddningstjänsten kan tänkas hantera, 5) Metoden ska vara data-driven och 6) Systemet måste kunna hantera professionella bedömningar.Utifrån dessa kriterier utvecklades och motiverades ett förslag på hur räddningstjänstens operativa förmåga kan analyseras och värderas. Förslaget innehåller definitioner av nyckelbegrepp, och förslag på hur dessa begrepp praktiskt kan användas i analyserna. Det kan viktigaste begreppet är operativ förmåga. I detta sammanhang, då fokus är på räddningstjänst och olyckor, föreslår vi att operativ förmåga definieras som räddningstjänstens ”möjligheter att åstadkomma positiv effekt med avseende på det skyddsvärda, givet att en olycka har inträffat”.Med utgångspunkt i definitionen beskriver vi därefter hur man kan genomföra en analys som resulterar i en beskrivning av operativ förmåga. Denna beskrivning kan sedan presenteras som ett eller flera mått på operativ förmåga. Vi visar också hur sådana mått kan användas som underlag för att fatta beslut om räddningstjänstens operativa förmåga. Rapporten presenterar konkreta exempel på hur man skulle kunna analysera om skyddet som räddningstjänstens operativa förmåga upprätthåller är tillfredsställande och likvärdigt. Dessa exempel tar sin utgångspunkt i olyckstyperna brand i bostad och drunkning.I slutet av rapporten diskuterar vi hur metoden för analys och värdering av operativ förmåga skulle kunna implementeras i praktiken, samt hur utvecklingsarbetet skulle kunna fortsätta i framtiden