Åke Arvidsson

Understanding the characteristics of cellular data traffic

Because of rapidly growing subscriber populations, advances in cellular communication technology, increasingly capable user terminals, and the expanding range of mobile applications, cellular networks have experienced a significant increase in data traffic, the dominant part of which is carried by the http protocol. Understanding the characteristics of this traffic is important for network design, traffic modeling, resource planning and network control. In this study we present a comprehensive characterization study of mobile http-based traffic using packet level traces collected in a large cellular network. We analyze the traffic using metrics at packet level, flow level and session level. For each metric, we conduct a comparison between traffic from different applications, as well as comparison to traffic in a wired network. Finally, we discuss the implications of our findings for better resource utilization in cellular infrastructures.

On the effects of caching in access aggregation networks

All forecasts of Internet traffic point at a substantial growth over the next few years. From a network operator perspective, efficient in-network caching of data is and will be a key component in trying to cope with and profit from this increasing demand. One problem, however, is to evaluate the performance of different caching policies as the number of available data items as well as the distribution networks grows very large. In this work, we develop an analytical model of an aggregation access network receiving a continuous flow of requests from external clients. We provide exact analytical solutions for cache hit rates, data availability and more. This enables us to provide guidelines and rules of thumb for operators and Information-Centric Network designers. Finally, we apply our analytical results to a real VoD trace from a network operator and show that substantial bandwidth savings can be expected when using in-network caching in a realistic setting.

Real time management of virtual paths

Proposes a simple and robust automatic strategy for managing SDH/SONET and/or ATM virtual paths in real time to handle slow traffic variations. It consists of on-line measurements of offered traffic followed by the design and possible implementation of a new virtual path network in a repeated cycle. Methods and parameters for traffic measurements and network updating are studied and optimised to achieve maximal traffic carrying capability at minimal cost. Applying the strategy to networks subject to partially unknown, variable traffic the author discovers a considerable adaptivity, large sayings in transmission capacity, and a performance far better than achieved by deterministic management.

Analysis of user demand patterns and locality for YouTube traffic

Video content, of which YouTube is a major part, constitutes a large share of residential Internet traffic. In this paper, we analyse the user demand patterns for YouTube in two metropolitan access networks with more than 1 million requests over three consecutive weeks in the first network and more than 600,000 requests over four consecutive weeks in the second network. In particular we examine the existence of “local interest communities”, i.e. the extent to which users living closer to each other tend to request the same content to a higher degree, and it is found that this applies to (i) the two networks themselves; (ii) regions within these networks (iii) households with regions and (iv) terminals within households. We also find that different types of access devices (PCs and handhelds) tend to form similar interest communities. It is also found that repeats are (i) “self-generating” in the sense that the more times a clip has been played, the higher the probability of playing it again, (ii) “long-lasting” in the sense that repeats can occur even after several days and (iii) “semiregular” in the sense that replays have a noticeable tendency to occur with relatively constant intervals. The implications of these findings are that the benefits from large groups of users in terms of caching gain may be exaggerated, since users are different depending on where they live and what equipment they use, and that high gains can be achieved in relatively small groups or even for individual users thanks to their relatively predictable behaviour.

A study of a distributed approach for VPC network management

By reserving transmission capacity on a series of links from one node to another, making a virtual path connection (VPC) between these nodes, several benefits are made. VPCs will enable segregation of traffic with different QoS, simplify routing at transit nodes, and simplify connection admission control. As telecommunications traffic experience variations in the number of calls per time unit, due to office hours, inaccurate forecasting, quick changes in traffic loads, and changes in the types of traffic (as in introduction of new services), there is a need to cope for this by adaptive capacity reallocation between different VPCs. The focus of this paper is to introduce a distributed approach for VPC management and compare it to a centralised one. Our results show that the distributed approach is an interesting alternative.

A Distributed Scheme for Value-Based Bandwidth Reconfiguration

This paper presents a scheme for reallocating bandwidth in path-oriented transport networks. At random time points, bandwidth is allocated to those paths that (possibly temporarily) value it most highly. The scheme acts according to local rules and without centralised control. The proposed scheme is thus distributed and scalable. Previous studies have shown that bandwidth reallocation, together with the provision of appropriate amounts of spare capacity on certain links, can be used to rapidly deploy and capacitate equivalent recovery routes in the event of network equipment failure. The purpose of this study is to determine if the same reallocation mechanism can also deal effectively with repeated, small scale random traffic fluctuations and with time varying traffics. We present a simulation model of a 30-node 46-link network which we use to evaluate the efficacy of the bandwidth reallocation scheme. The simulation study shows that bandwidth reconfiguration can substantially reduce the connection loss probabilities.

Co-operating Market/Ant Based Multi-agent Systems for Intelligent Network Load Control

Recent years have seen increases in the number, complexity and usage of telecommunications services, many of which are realised by systems based on the Intelligent Network (IN) architecture. As the volume of traffic carried by INs has increased there has been a realisation that flexible and efficient load control strategies are required to ensure that Quality-of-Service levels meet desired targets. In this paper we present an agent-based IN load control strategy, realised by two co-operating multi-agent systems making use of Market-based Control and Ant Colony Optimisation paradigms respectively.

Understanding HTTP flow rates in cellular networks

Data traffic in cellular networks increased tremendously over the past few years and this growth is predicted to continue over the next few years. Due to differences in access technology and user behavior, the characteristics of cellular traffic can differ from existing results for wireline traffic. In this study we focus on understanding the flow rates and on the relationship between the rates and other flow properties by analyzing packet level traces collected in a large cellular network. To understand the limiting factors of the flow rates, we further analyze the underlying causes behind the observed rates, e.g., network congestion, access link or end host configuration. Our study extends other related work by conducting the analysis from a unique dimension, the comparison with traffic in wired networks, to reveal the unique properties of cellular traffic. We find that they differ in variability and in the dominant rate limiting factors.

The design and management of ATM virtual path connection networks

Modern communication networks can cross connect traffic flows to form logical end-to-end connections between all origin-destination pairs and thus create fully meshed logical networks upon sparse physical networks. Such logical connections are known as virtual path connections (VPCs) and a logical network formed by VPCs is known as a VPC network (VPCN). We present an efficient algorithm called XFG to compute optimal configurations for VPCNs carrying multiservice traffic. We compare the features of the XFG algorithm and the characteristics of standard nonlinear programming solvers. We present a model where a sequence of busy period multiservice traffic is offered to a network. The XFG algorithm is used to compute an optimal VPCN design for each busy period. We compare the grade of service attained by VPCN redesign, dynamic alternative routing (DAR), and a combination of VPCN redesign, call queueing and DAR.

Performance analysis of local caching replacement policies for internet video streaming services

In this work, the performance of 5 representative caching replacement policies was investigated and compared for caching Internet video-on-demand (VoD) in local access networks. Two measured traces of end-user requests were used in the analyses for two typical VoD services: TV-on-demand and user generated content represented by YouTube. The studied policies range from simple least recently used (LRU) and least frequently used (LFU) algorithms to more advanced ones denoted as LFU-dynamic lifespan (LFU-DL), Adaptive replacement cache (ARC) and Greedy-dual size frequency (GDSF). Our results show that the ARC policy always outperforms the other policies due to its adaptive nature and its ability to track changes in the traffic patterns. On the other hand, the simple LRU policy can also achieve a caching performance which is comparable to that of the more advanced ARC policy especially for the TV-on-demand service when the potential caching gain is high. On the contrary, the simple LFU policy always shows the poorest performance. However, by applying a proper lifespan supplement under the LFU-DL policy, the caching performance can be effectively enhanced to the level achievable using ARC and LRU policies. Moreover, the GDSF policy does not outperform simple LRU or LFU-DL, especially for YouTube video clips when the potential caching gain is relatively low. The advantage of GDSF manifested in our analysis is, however, its outstanding cache space usage efficiency among the five studied caching algorithms.