| 1. |
- Arlos, Patrik, et al.
(författare)
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A Distributed Passive Measurement Infrastructure
- 2005
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Konferensbidrag (refereegranskat)abstract
- In this paper we describe a distributed passive measurement infrastructure. Its goals are to reduce the cost and configuration effort per measurement. The infrastructure is scalable with regards to link speeds and measurement locations. A prototype is currently deployed at our university and a demo is online at http://inga.its.bth.se/projects/dpmi. The infrastructure differentiates between measurements and the analysis of measurements, this way the actual measurement equipment can focus on the practical issues of packet measurements. By using a modular approach the infrastructure can handle many different capturing devices. The infrastructure can also deal with the security and privacy aspects that might arise during measurements.
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| 2. |
- Carlsson, Patrik, et al.
(författare)
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Delay Performance in IP Routers
- 2004
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Konferensbidrag (refereegranskat)abstract
- The main goals of the paper are towards an understanding of the delay process in best-effort Internet for both non-congested and congested networks. A dedicated measurement system is re-ported for delay measurements in IP routers, which follows specifications of the IETF RFC 2679. The system is using both passive measurements and active probing. Dedicated application-layer software is used to generate UDP traffic with TCP-like characteristics. Pareto traffic models are used to generate self-similar traffic in the link. The reported results are in the form of several impor-tant statistics regarding processing delay of a router, router delay for a single data flow, router delay for more data flows as well as end-to-end delay for a chain of routers. We confirm results reported earlier about the fact that the delay in IP routers is generally influenced by traffic characteristics, link conditions and, at some extent, details in hardware implementation and different IOS releases. The delay in IP routers usually shows heavy-tailed characteristics. It may also occasionally show extreme values, which are due to improper functioning of the routers.
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| 3. |
- Carlsson, Patrik, et al.
(författare)
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Matching Multi-Fractal Process Parameters Against Real Data Traffic
- 2002
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Konferensbidrag (refereegranskat)abstract
- Recent analyses of real data/internet traffic indicate that data traffic exhibits long-range dependence as well as self-similar or multi-fractal properties. By using mathematical models of Internet traffic that share these properties we can perform analytical studies of network traffic. This gives us an opportunity to analyse potential bottlenecks and estimate delays in the networks. Processes with multi-fractal properties can be modeled by multiplying the output of Markov Modulated Rate Processes (MMRP) [1] each defined by four parameters. The MMRP are easily used in stochastic fluid flow modeling. This model is also suited for analysis of other traffic types e.g. VoIP and thus, it allows for integration of different traffic types, i.e. time-sensitive voice traffic with best-effort data traffic. Using this model we can calculate performance parameters for each individual stream that enters the system/model. In this paper we show how to construct a multi-fractal process that is matched to measured data from MMRP sub processes.
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| 4. |
- Carlsson, Patrik, et al.
(författare)
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Modelling of Ethernet Traffic on Multiple Timescales
- 2004
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Konferensbidrag (refereegranskat)abstract
- Ethernet is one of the most common link layer technologies, used in local area networks, wireless networks and wide area networks. There is however a lack of traffic models for Ethernet that is usable in performance analysis. In this paper we use such a model. The model operates on matching multiple moments of the bit rate at several timescales. In order to match the model parameters to measured traffic, five methods have been developed. We use this to model three different links; the BCpOct89 Bellcore trace, an Internet access link and an ADSL link. Our results show that, as the number of sources present on an Ethernet link grows, the model becomes better and less complex.
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| 5. |
- Carlsson, Patrik, et al.
(författare)
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Obtaining Reliable Bit Rate Measurements in SNMP-Managed Networks
- 2002
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Konferensbidrag (refereegranskat)abstract
- The Simple Network Management Protocol, SNMP, is the most widespread standard for Internet management. As SNMP stacks are available on most equipment, this protocol has to be considered when it comes to performance management, traffic engineering and network control. However, especially when using the predominant version 1, SNMPv1, special care has to be taken to avoid erroneous results when calculating bit rates. In this work, we evalute six off-the-shelf network components. We demonstrate that bit rate measurements can be completely misleading if the sample intervals that are used are either too large or too small. We present solutions and work-arounds for these problems. The devices are evaluated with regards to their updating and response behavior.
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| 6. |
- Fiedler, Markus, et al.
(författare)
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Identification of performance degradation in IP networks using throughput statistics
- 2003
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Konferensbidrag (refereegranskat)abstract
- To be able to satisfy their users, interactive applications like video conferences require a certain Quality-of-Service from heterogeneous networks. This paper proposes the use of throughput histograms as Quality-of-Service indicator. These histograms are built from local, unsynchronized, passive measurements of packet streams from the viewpoint of an application. They can easily be exchanged between sender and receiver, and their comparison provides information about severity and type of a potential bottleneck. We demonstrate the usefulness of these indicators for evaluating the transport quality perceived by a video conferencing application and its users in the presence of a bottleneck.
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| 7. |
- Fiedler, Markus, et al.
(författare)
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Voice and Multi-fractal Data in the Internet
- 2001
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Konferensbidrag (refereegranskat)abstract
- In the Internet era there is a need to understand how traditional Public Switched Telephone Network (PSTN) services and the new Internet services can coexist. The best-effort based IP network will have to maintain the level of service that customers from the PSTN world expect. This study contributes to the traffic engineering of such a system by presenting an analytical model for integrating Voice over IP (VoIP) traffic with multi-fractal data traffic. This model is based on the stochastic fluid flow model. Effects on delay and loss performance of adding VoIP traffic to a data link as well as capacity requirements to maintain a certain quality of service are discussed
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| 8. |
- Isaksson, Lennart, et al.
(författare)
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Validation of Simulations of Bluetooth's Frequency Hopping Spread Spectrum Technique
- 2004
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Konferensbidrag (refereegranskat)abstract
- The need for performance studies avoiding expensive hardware installations and the lack of analytical models motivates the need of trustworthy simulation models for the cable-replacement technology Bluetooth. In this paper we show a detailed description of the Bluetooth technique and validation of different simulation models used today. To do this, a two-step approach for validation and credibility is necessary. First, a comprehensive empirical measurement was performed to establish a "status quo" of the behavior of today's Bluetooth technology. Second, a validation between empirical and simulation model is conducted to ensure the comparability. To accomplish these objectives we developed and validated a simulation model with frequency hopping algorithms and the whole state machine including collision detection. The results in form of histograms of different Bluetooth-specific durations indicate problems in case of already established simulation programs. So, finally, some changes and suggestions how to correct these defects are given.
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| 9. |
- Johnson, Henric, et al.
(författare)
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Analysis of IPSec Performance
- 2005
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Konferensbidrag (refereegranskat)abstract
- In this paper we present the results of an experimental analysis of IPSec performance. IPSec serves as a security service to protect a communication session over unreliable networks using several cryptographic functions. The different IPSec features used to obtain confidentiality, authentication, replay protection, and integrity introduce performance costs brought about by the increased processing overhead. The performance parameters of interest are delay and throughput. However, there is a tradeoff between performance and security. The results of the performance tests indicate the vulnerability of a Denial-of-Service attack against a gateway running IPSec due to resource exhaustion.
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| 10. |
- Johnson, Henric, et al.
(författare)
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Hierarchical Defense Structure for Mitigating DoS Attacks
- 2006
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Konferensbidrag (refereegranskat)abstract
- This paper provides the contribution of mitigating a Denial-of-Service (DoS) attack via a developed hierarchical defense structure with proactive functionality. An important aspect is the tradeoff between performance and security. This novel hierarchical architecture is presented with lightweight authentication protocols acting as a classifier to deny access to harmful traffic. An empirical test of the proposed structure has been performed and results are reported which display the capability of the structure to filter and separate the attack traffic before reaching the target of an IPSec gateway. Thus, the filtering of traffic is performed without being the target itself for new resource exhaustion attacks. The considered IPSec environment is based on IPSec gateways for the low-end market, i.e., for small businesses or private networks.
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