| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- Carlsson, Patrik
(författare)
-
Multi-Timescale Modelling of Ethernet Traffic
- 2003
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)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 thesis we describe an Ethernet traffic model. The model aims at matching multiple moments of the bit rate at several timescales. To match the model parameters to measured traffic, four methods have been developed and tested on real traffic traces. Once a model has been created, it can be used directly in a fluid flow performance analysis. 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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Multifractal Products of Stochastic Processes : Fluid Flow Analysis
- 2000
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Konferensbidrag (refereegranskat)abstract
- The consideration of multifractal properties in network traffic has become a well-known issue in network performance evaluation. We analyze the performance of a fluid flow buffer fed by multifractal traffic described by Norros, Mannersalo and Riedi [1]. We describe specific steps in fluid flow analysis, both for finite and infnite buffer sizes, and point out how toovercome numerical problems. We discuss performance results in form of waiting time quantiles and loss probabilities, which help to estimate whether a trffic concentrator constitutes a bottleneck or not.
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| 6. |
- 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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| 7. |
- Carlsson, Patrik, et al.
(författare)
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On an Implementation of a Distributed Passive Measurement Infrastructure
- 2003
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Having access to relevant, up-to-date measurement data is a key issue for network analysis in order to allow for efficient Internet performance monitoring and management. New applications keep appearing; user and protocol behavior keep evolving; traffic mixes and characteristics are continuously changing, which implies that some year old traffic traces may not reflect reality any more. In order to give a holistic view of what is going on in the network, passive measurements have to be carried out at different places simultaneously. Other challenges relate to the simultaneous use of one specific measurement point at a certain location for different measurement processes, and to continuously ongoing measurements needed for capturing long-term traffic behaviors. On this background, this paper proposes a passive measurement infrastructure for a campus backbone, consisting of distributed coordinated measurement points, collected in measurement areas, measurement administration and data management. … The framework is generic with regards to the capturing equipment, ranging from simple PCAP based devices to high-end DAG cards, and dedicated ASICs, in order to promote a large deployment of measurement points. This structure allows for an efficient use of passive monitoring equipment in order to supply researchers and network managers with up-to-date and relevant data.
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| 8. |
- Constantinescu, Doru, et al.
(författare)
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Measurement of One-Way Internet Packet Delay
- 2004
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Konferensbidrag (refereegranskat)abstract
- The paper reports on a dedicated measurement system for delay measurements in IP routers, which follows specifications of the IETF RFC 2679. The system uses both passive and active measurements. Dedicated application-layer software is used to generate traffic. Pareto traffic models are used to generate self-similar traffic in the link. Both packet inter-arrival times and packet sizes are matching real traffic models. A passive measurement system is used for data collection that is based on using several so-called Measurement Points, each of them equipped with DAG monitoring cards. Hashing is used for the identification and matching of packets. The combination of passive measurements and active probing, together with using the DAG monitoring system, gives us an unique possibility to perform precise traffic measurements as well as the flexibility needed to compensate for the lack of analytic solutions.
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| 9. |
- Constantinescu, Doru, et al.
(författare)
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One-Way Transit Time Measurements
- 2004
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Rapport (refereegranskat)abstract
- This report is a contribution towards a better understanding of traffic measurements associated with e2e delays occurring in best-effort networks. We describe problems and solutions associated with OWTT delay measurements, and give examples of such measurements. A dedicated measurement system is reported for delay measurements in IP routers, which follows specifications of the IETF RFC 2679. The system uses both passive measurements and active probing. Dedicated application-layer software is used to generate traffic. Pareto traffic models are used to generate self-similar traffic in the link. Both packet inter-arrival times and packet sizes are matching real traffic models. A passive measurement system is used for data collection that is based on using several so-called Measurement Points, each of them equipped with DAG monitoring cards. Hashing is used for the identification and matching of packets. The combination of passive and active measurements, together with using the DAG monitoring system, gives us an unique possibility to perform precise traffic measurements as well as the flexibility needed to compensate for the lack of analytic solutions. The real value of our study lies in the hop-by-hop instrumentation of the devices involved in the transfer of IP packets. The mixture of passive and active traffic measurements used, allows us to study changes in traffic patterns relative to specific reference points and to observe different contributing factors to the observed changes. This approach offers us the choice of better understanding diverse components that may impact on the performance of packet delay as well as to to measure queueing delays in operational routers.
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| 10. |
- 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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