Dragos Ilie

A Survey of Reliable Multicast Communication

The paper reports on recent developments and challenges in reliable multicast communication, with special focus on reliable multicast communication at the application layer. The foundation of reliable multicast communication is given by several components, which are multicast communication, congestion control and error control. Our paper is providing a survey of these mechanisms in multicast environments.

BitTorrent Traffic Characteristics

This paper reports on a measurement and modeling study of session and message characteristics of BitTorrent traffic. BitTorrent is a peer-to-peer (P2P) replication and distribution system developed as an alternative to the classical client-server model to reduce the load on content servers and networks. Results are reported on measurement, modeling and analysis of application and link layer traces collected at the Blekinge Institute of Technology (BTH) and a local ISP in Sweden. Link layer traces and application logs were collected, modeled and analyzed using a dedicated measurement infrastructure developed at BTH to collect P2P traffic. New results are reported on important session and message characteristics of BitTorrent, i.e., session inter arrivals, sizes and durations, request rates and response times. Our results show that session interarrivals can be accurately modeled by a second-order hyper-exponential distribution while session durations and sizes can be reasonably well modeled by various mixtures of the log-normal and Weibull distributions. Response times have been observed to be modeled by a dual log-normal mixture, while request rates are modeled as dual Gaussian distributions

Statistical models for Gnutella signaling traffic

The paper is focused on signaling traffic between Gnutella peers that implement the latest Gnutella protocol specifications (v0.6). In particular, we provide analytically tractable statistical models at session level, message level and IP datagram level for traffic crossing a Gnutella ultrapeer at Blekinge Institute of Technology (BTH) in Karlskrona, Sweden. To the best of our knowledge this is the first work that provides Gnutella v0.6 statistical models at this level of detail. These models can be implemented straightforward in network simulators such as ns2 and OmNet++. The results show that incoming requests to open a session follow a Poisson distribution. Incoming Gnutella messages across all established sessions can be described by a compound Poisson distribution. Mixture distribution models for message transfer rates include a heavy-tailed component.

Unicast QoS routing in overlay networks

The goal of quality of service (QoS) routing in overlay networks is to address deficiencies in todays Internet Protocol (IP) routing. This is achieved by application-layer protocols executed on end-nodes, which search for alternate paths that can provide better QoS for the overlay hosts. In the first part of this paper we introduce fundamental concepts of QoS routing and the current state-of-the-art in overlay networks for QoS. In the remaining part of the paper we report performance results for the Overlay Routing Protocol (ORP) framework developed at Blekinge Institute of Technology (BTH) in Karlskrona, Sweden. The results show that QoS paths can be established and maintained as long as one is willing to accept a protocol overhead of maximum 1.5% of the network capacity.

Transfer Rate Models for Gnutella Signaling Traffic

This paper reports on transfer rate models for the Gnutella signaling protocol. New results on message-level and IP-level rates are presented. The models are based on traffic captured at the Blekinge Institute of Technology (BTH) campus in Sweden and offer several levels of granularity: message type, application layer and network layer. The aim is to obtain parsimonous models suitable for analysis and simulation of P2P workload.

A PMIPv6 approach to maintain network connectivity during VM live migration over the internet

We present a live migration solution based on Proxy Mobile IPv6 (PMIPv6), a light-weight mobility protocol standardized by IETF. PMIPv6 handles node mobility without requiring any support from the moving nodes. In addition, PMIPv6 works with IPv4, IPv6 and dual-stack nodes. Our results from a real testbed show that network connectivity is successfully maintained with little signaling overhead and with short virtual machine (VM) downtime. As far as we know, this is the first time PMIPv6 is used to enable live migration beyond the scope of a LAN.

An application layer architecture for seamless roaming

The paper advances a new architecture for seamless roaming, which is implemented at the application layer. This architecture is subject for the research projects PERIMETER and MOBICOME, recently granted by the EU STREP FP7 and EUREKA, respectively. The research challenges are on mobility management, security, QoE management, overlay routing, node positioning, mobility modeling and prediction, middleware and handover. The foundation of seamless handover is provided by several components, the most important ones being the handover, mobility management, connectivity management and Internet mobility. The paper provides an analysis of these components as well.

Measuring and modeling the BitTorrent content distribution system

The paper reports on a detailed study of the BitTorrent content distribution system. We first present a measurement infrastructure designed to allow detailed, message-level capture and analysis of P2P traffic. An associated modeling methodology is presented as well. These tools have been used to measure and model the BitTorrent protocol, which is observed to exhibit exponential characteristics of session interarrival times. We also observe that session durations and sizes are modeled with a log-normal distribution.

Cache Support in a High Performance Fault-Tolerant Distributed Storage System for Cloud and Big Data

Due to the trends towards Big Data and Cloud Computing, one would like to provide large storage systems that are accessible by many servers. A shared storage can, however, become a performance bottleneck and a single-point of failure. Distributed storage systems provide a shared storage to the outside world, but internally they consist of a network of servers and disks, thus avoiding the performance bottleneck and single-point of failure problems. We introduce a cache in a distributed storage system. The cache system must be fault tolerant so that no data is lost in case of a hardware failure. This requirement excludes the use of the common write-invalidate cache consistency protocols. The cache is implemented and evaluated in two steps. The first step focuses on design decisions that improve the performance when only one server uses the same file. In the second step we extend the cache with features that focus on the case when more than one server access the same file. The cache improves the throughput significantly compared to having no cache. The two-step evaluation approach makes it possible to quantify how different design decisions affect the performance of different use cases.

Seamless roaming: developments and challenges

The chapter reports on recent developments and challenges focused on seamless handover. These are subject for the research projects MOBICOME and PERIMETER, recently granted by the EU EUREKA and EU STREP FP7, respectively. The research projects are considering the recently advanced IP Multimedia Subsystem (IMS), which is a set of technology standards put forth by the Internet Engineering Task Force (IETF) and two Third Generation Partnership Project groups, namely 3GPP and 3GPP2. The foundation of seamless handover is provided by several components, the most important ones being the handover, mobility management, connectivity management and Internet mobility. The paper provides an intensive analysis of these components