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  • 1. Abrahamsson, H
    et al.
    Hagsand, Olof
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Marsh, Ian
    TCP over high speed variable capacity links: A simulation study for bandwidth allocation2002Conference paper (Refereed)
    Abstract [en]

     New optical network technologies provide opportunities for fast, controllable bandwidth management. These technologies can now explicitly provide resources to data paths, creating demand driven bandwidth reservation across networks where an applications bandwidth needs can be meet almost exactly. Dynamic synchronous Transfer Mode (DTM) is a gigabit network technology that provides channels with dynamically adjustable capacity. TCP is a reliable end-to-end transport protocol that adapts its rate to the available capacity. Both TCP and the DTM bandwidth can react to changes in the network load, creating a complex system with inter-dependent feedback mechanisms. The contribution of this work is an assessment of a bandwidth allocation scheme for TCP flows on variable capacity technologies. We have created a simulation environment using ns-2 and our results indicate that the allocation of bandwidth maximises TCP throughput for most flows, thus saving valuable capacity when compared to a scheme such as link over-provisioning. We highlight one situation where the allocation scheme might have some deficiencies against the static reservation of resources, and describe its causes. This type of situation warrants further investigation to understand how the algorithm can be modified to achieve performance similar to that of the fixed bandwidth case.

  • 2. Biyani, Pravesh
    et al.
    Hagsand, Olof
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Karlsson, Gunnar
    Marsh, Ian
    Mas, Ignacio
    Early Estimation of Voice over IPQuality2003Conference paper (Refereed)
    Abstract [en]

    Users of Voice over IP (VoIP) applications are sensitive to the quality of an ongoing call. We hypothesize that the quality of a VoIP session can be estimated from the first few seconds of the session and this can be generalized to other VoIP calls. Our approach is an in-band probing mechanism and does not require any external monitoring schemes or network support. We show by post processing VoIP data from globally distributed sites that it is possible to determine the quality after an initial number of seconds. One application is admission control, where it would be possible to reject poor quality calls before they are fully established.

  • 3.
    Carlzon, Malin
    et al.
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis and Computer Science, NADA.
    Hagsand, Olof
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis and Computer Science, NADA.
    Widell, Fredrik
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis and Computer Science, NADA.
    Danielsson, Björn
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis and Computer Science, NADA.
    Blocking web contents using BGP: measurements and observations2006Report (Other academic)
  • 4.
    Carlzon, Malin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hagsand, Olof
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Widell, Fredrik
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Danielsson, Björn
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Blocking web-pages using BGP - measurements and observations2005In: 3rd Swedish National Computer Networking Workshop, SNCNW 2005, Halmstad, Sweden, 2005Conference paper (Refereed)
  • 5.
    Fu, Jing
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hagsand, Olof
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A Programming Model for a Forwarding Element2004In: 2nd Swedish National Computer Networking Workshop, SNCNW 2004, Karlstad, Sweden, 2004, p. 59-65Conference paper (Refereed)
    Abstract [en]

    The architectural complexity and diversity of current

    network devices make them complex to manage and

    difficult to program. In this work, we specify a

    programming model for network devices that function as

    forwarding elements. We first identify the key packet

    processing functions and analyze current network

    devices. Next, we derive a model that consists of

    processing blocks

    to represent simple packet processing

    functions running on a forwarding element. We further

    use a

    processing block topology

    to represent how the

    individual packet processing functions are interconnected

    on the datapath. We also demonstrate how to program a

    forwarding element and show an example IPv4

    forwarding service implementation. Finally, we evaluate

    programmability and the performance of the FE model.

  • 6.
    Fu, Jing
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Hagsand, Olof
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis and Computer Science, NADA.
    Designing and Evaluating Network Processor Applications2005In: IEEE Workshop on High Performance Switching and Routing: Hong Kong, PEOPLES R CHINA, MAY 12-14, 2005, 2005, p. 142-146Conference paper (Refereed)
    Abstract [en]

    Network processors try to achieve the performance of traditional ASICs while providing programmability of general-purpose processors. In short, a network processor provides a programming interface for implementing packet forwarding services. It is therefore important to study how efficient different designs are, as well as investigate how difficult they are to program. In this paper, a network processor model is introduced which is used as a basis for a simulation tool. By sending packets into the simulator, throughput, latency, and utilization can be measured. An IPv4 forwarding application is evaluated using two different processing element topologies: a pipelined and a pooled. In addition, the performance impact of using multiple threads inside a single processing element is evaluated. The results show that the use of parallelism is crucial to achieve high performance, but that both the pipelined topology and pooled topology achieve comparable performance.

  • 7.
    Fu, Jing
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Hagsand, Olof
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    An analysis of Queueing Behavior in Network Processor Systems2006In: 4th Swedish National Computer Networking Workshop, SNCNW 2006, Luleå, Sweden, 2006Conference paper (Refereed)
  • 8.
    Fu, Jing
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Hagsand, Olof
    KTH, School of Computer Science and Communication (CSC).
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Improving and Analyzing LC-Trie Performance for IP-Address Lookup2007In: Journal of Networks, ISSN 1796-2056, E-ISSN 1796-2056, Vol. 2, no 3, p. 18-27Article in journal (Refereed)
    Abstract [en]

    IP-address lookup is a key processing function of Internet routers. The lookupis challenging because it needs to perform a longest prefix match. In this paper, wepresent our modifications to an efficient lookup algorithm, the LC-trie, based ona technique called prefix transformation. Thereafter, the LC-trie’s performance isanalyzed for both the original and our modified algorithm using real and syntheticallygenerated traces. The performance study includes trie search depth, prefixvector access behavior, cache behavior and packet lookup time. The study is basedboth on experiments and a model for packet lookup time. The results show thatthe modified algorithm requires only 30% of the lookup time of the original algorithm.In particular, the modified algorithm is capable of performing 60 millionpacket lookups per second on a Pentium 4, 2.8 GHz, computer for a real traffictrace. Further, the results show that the performance is about five times better onthe real trace compared to a synthetically generated network trace. This illustratesthat the choice of traces may have a large influence on the results when evaluatinglookup algorithms.

  • 9.
    Fu, Jing
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Hagsand, Olof
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Performance Evaluation and Cache Behavior of LC-Trie for IP-Address Lookup2006In: Proc. of IEEE 2006 Workshop on High Performance Switching and Routing (HPSR 2006), IEEE , 2006, p. 29-35Conference paper (Refereed)
    Abstract [en]

    Many IP-address lookup software algorithms use a trie-like data structure to perform longest prefix match. LC-trie is an efficient algorithm that uses level compression and path compression on tries. By using realistic and synthetically generated traces, we study the performance of the LC-trie algorithm. Our study includes trie search depth, prefix vector access behavior, cache behavior, and packet lookup service time. The results show that for a realistic traffic trace, the LC-trie algorithm is capable of performing 20 million packet lookups per second on a Pentium 4, 2.8 GHz computer, which corresponds to a 40 Gb/s link for average sized packets. Further, the results show that LC-trie performs up to five times better on the realistic trace compared to a synthetically generated network trace. This illustrates that the choice of traces may have a large influence on the results when evaluating lookup algorithms.

  • 10.
    Fu, Jing
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Hagsand, Olof
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis and Computer Science, NADA.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Networks.
    Queueing Behavior and Packet Delays in Network Processor Systems2007In: 15th IEEE International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems: Bogazici Univ, Dept Comp Engn, Istanbul, TURKEY, OCT 24-26, 2007 / [ed] Caglayan M. U.; Field AJ; Gelenbe E., 2007, p. 217-224Conference paper (Refereed)
    Abstract [en]

    Network processor systems provide the performance of ASICs combined withthe programmability of general-purpose processors. One of the main challengesin designing these systems is the memory subsystem used when forwarding andqueueing packets. In this work, we study the queueing behavior and packet delaysin a network processor system which works as a router. We introduce a systemmodel and a simulation tool based on the model. Using the simulation tool, bothbest-effort and diffserv IPv4 forwarding were modeled and tested using real-worldand synthetically generated packet traces. The results on queueing behavior havebeen used to dimension various queues, and can be used as guidelines for designingmemory subsystems and queueing disciplines. In particular, a system withsmall queue sizes has been proposed. The results on packet delays also show thatour diffserv setup provides good service differentiation for best-effort and prioritypackets. Finally, the study reveals that the choice of traces has a large impact onthe results when evaluating router and switch architectures.

  • 11. Hagsand, Olof
    et al.
    Hanson, Kjell
    Marsh, Ian
    Measuring Internet telephony quality: Where are we today?1999In: Conference Record / IEEE Global Telecommunications Conference: GLOBECOM'99; Rio de Janeiro, Braz; 5 December 1999 through 9 December 1999, Rio de Janeiro, Braz, 1999, Vol. 3, no Piscataway, NJ, United States, p. 1838-1842Conference paper (Refereed)
    Abstract [en]

    Users of Internet telephony applications demand good quality audio playback. This quality is largely dependent on the instantaneous network conditions. In this paper we describe a scheme for measuring network connections as well as a motivation for including a new metric when assessing quality. The tests included a wide range of geographically distributed sites and our results can give useful feedback to users, operators and developers of Voice over IP applications. The results indicate that Internet telephony is feasible on todays Internet but we should envisage some problems if the Internet continues to grow at the rate so far.

  • 12.
    Hagsand, Olof
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hidell, Markus
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Sjödin, Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Design and implementation of a distributed router2005In: 2005 IEEE International Symposium on Signal Processing and Information Technology (ISSPIT), Vols 1 and 2, 2005, p. 227-232Conference paper (Refereed)
    Abstract [en]

    The requirements on 1P routers are increasing for every new generation of designs. The driving forces are growing traffic volumes and demands for new services. We argue that a decentralized modular system design would improve the scalability. flexibility, and reliability of future routers. We have designed and implemented such a distributed router. based on physical separation between different junctional modules for control and forwarding plane operations. This paper presents the design and implementation, focusing on the internal communication protocols and implementation aspects of the control plane.

  • 13.
    Hagsand, Olof
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Marsh, Ian
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hanson, K
    Sicsophone: A low-delay Internet telephony tool2003In: PROCEEDINGS OF THE 29TH EUROMICRO CONFERENCE - NEW WAVES IN SYSTEM ARCHITECTURE, 2003, p. 189-195Conference paper (Refereed)
    Abstract [en]

    The end to end delay is a critical factor in the perceived quality of service for Voice over IP applications. Sicsophone is a complete VoIP system that couples the low level features of audio hardware with a standard jitter buffer playout algorithm. Using, the sound card directly eliminates intermediate buffering as well as providing fine control over timers needed by a soft real-time application such as VoIP A statistical based approach for inserting packets into audio buffers is used in conjunction with a scheme for inhibiting unnecessary fluctuations in the system. We also present mouth-to-ear delay measurements for selected VoIP applications and show that several hundreds of milliseconds can be saved by using the techniques described in this paper A prototype for both UNIX and Windows platforms has been implemented, demonstrating that our system adapts to network: conditions whilst maintaining low delays.

  • 14.
    Hagsand, Olof
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Más, Ignacio
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Marsh, Ian
    Swedish Institute of Computer Science.
    Karlsson, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Self-Admission Control for IP Telephony using Early Quality Estimation2004In: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, Vol. 3042, p. 381-391Article in journal (Refereed)
    Abstract [en]

    If quality of service could be provided at the transport or the application layer, then it might be deployed simply by software upgrades, instead of requiring a complete upgrade of the network infrastructure. In this paper, we propose a self-admission control scheme that does not require any network support or external monitoring schemes. We apply the admission control scheme to IP telephony as it is an important application benefiting from admission control. We predict the quality of the call by observing the packet loss over a short initial period using an in-band probing mechanism. The quality prediction is then used by the application to continue or to abort the call. Using over 9500 global IP telephony measurements, we show that it is possible to accurately predict the quality of a call. Early rejection of sessions has the advantage of saving valuable network resources plus not disturbing the on-going calls.

  • 15.
    Hagsand, Olof
    et al.
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Olsson, Robert
    Uppsala Univ, Uppsala, Sweden.
    Control and forwarding plane separation on an open­source router2011Conference paper (Refereed)
    Abstract [en]

    In previous work[1-3] it has been shown how open-source routers on new PC hardware allows for forwarding speeds of 10Gb/s and above. In this work we extend the applicability of the results by showing how the new 10Gb/s interface classification techniques can be used to separate packet forwarding from control plane operation.It is important to isolate the control-plane from forwarding load, since it makes routing protocol and management operation independent of forwarding load. It also increases the resilience against denial-ofservice attacks. In addition, it relates to the forwarding and control element separation proposed by the IETF ForCES work[4], where we use one CPU core as control element and the remaining cores as forwarding elements.

    Many new interface cards have chipsets with advanced classification capabilities motivated by advances in virtualization and multicore architectures. We have chosen to study the Intel 82599 10Gb/s controller[5] and the Linux ixgbe driver. The 82599 has several mechanisms to control packet classification, including Receiver Side Scaling (RSS)[6], Flow director, and N-tuple filters. Other interface cards on the market use generic TCAMs providing similar functionality.

    The approach we used was to implicitly configure the Flow director by outgoing control traffic, so that return flows aimed at the control plane were identified and could be directed to a designed control processor. Flows not destined to the control processor were load balanced among the remaining cores using RSS. We found this to be a simple and straight-forward approach, and we present results that verifies this method. However, we have seen some cases in overload scenarios where packet drops are made in hardware before classification which need to be further analyzed.During the project we also explored some of the hardware capabilites new buses (PCIe gen2). We discovered with optimal setting that we could transmit (DMA) 92 Gb/s using 1500 byte packet

  • 16.
    Hagsand, Olof
    et al.
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Olsson, Robert
    Uppsala Univ, Uppsala, Sweden.
    Gördén, Bengt
    KTH, School of Computer Science and Communication (CSC).
    Open source routing at 10Gb/s2009In: Swedish National Computer Networking Workshop, SNCNW 2009, Uppsala, Sweden, 2009Conference paper (Refereed)
    Abstract [en]

    We present throughput measurements using the Bifrost Linux open source router on selected PC hardware. The hardware consists of eight CPU cores, NUMA architecture, double PCIe buses and Intel and SUN 10Gb/s interface cards. These cards are equipped with hardware classifiers that dispatch packets to multiple DMA queues which enables parallel processing of packet forwarding and load-balancing between the multiple CPUs.

    In our experiments, we send a multiflow, simplex packet stream through an open-source router. We measure the throughput and vary packet size, active CPUs, and router configuration. In the experiments, we use an IP flow and packet-length distribution that we claim is realistic for many network scenarios. Using these realistic traffic streams, we show how speeds close to10Gb/s is achievable for normal Internet traffic.

    In particular, we show how the use of multiple CPUs increases the throughput up to a breakpoint which in our setting is at four CPUs. Further, we show that adding filters and full BGP tables have minor effects in the performance.

    With these results, we claim that open source routers using new PC architectures are a viable option for use in 10Gb/s networks for many network scenarios.

  • 17.
    Hagsand, Olof
    et al.
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Olsson, Robert
    Uppsala Univ, Uppsala, Sweden.
    Gördén, Bengt
    KTH, School of Computer Science and Communication (CSC).
    Towards 10Gb/s open-source routing2008Conference paper (Refereed)
  • 18.
    Hagsand, Olof
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Olsson, Robert
    Uppsala University.
    Låås, Jens
    Uppsala University.
    Gördén, Bengt
    KTH, School of Computer Science and Communication (CSC).
    Measurement of IP forwarding performance on complex computer architectures2011In: Swedish National Computer Networking Workshop, SNCNW 2011, 2011Conference paper (Refereed)
    Abstract [en]

    Open-source routers on new PC hardware allows for forwarding speeds of 10Gb/s and above. We present detailed performance measurements using Linux on two complex PC hardware platforms. Both platforms use PCIe gen2, dual I/O bridges and have support for non-uniform memory access (NUMA). The AMD platform uses four processors equipped with eight cores and four nodes of local memory. The Intel platform has two quad-core CPUs each with local memory.

    Packets being forwarded through a PC-based router can be separated into three steps: receive-dma, lookup, and transmitdma. Each step was studied individually. In particular, we studied how varying the CPU core and memory node effects the forwarding speeds.

    Our results show a large performance dependency of selecting CPU cores and memory nodes. In particular, DMA works best with memory nodes closest to the I/O bridge where the interface card is connected. Correspondingly, CPU access is most efficient on local memory. Consequently, choosing CPU core and memory nodes badly leads to a significant performance decrease.

  • 19.
    Hidell, Markus
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hagsand, Olof
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Sjödin, Peter
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Distributed Control for Decentralized Modular Routers2004In: 2nd Swedish National Computer Networking Workshop, SNCNW 2004, Karlstad, Sweden, 2004, p. 9-13Conference paper (Refereed)
    Abstract [en]

    The requirements on IP routers continue to increase, both from the control plane and the forwarding plane perspectives. To improve scalability, flexibility, and availability we investigate new ways to build future routers. This paper presents a system model of a decentralized and modular router architecture. Design alternatives and implementation aspects are discussed, and a system implementation is presented.

  • 20.
    Hidell, Markus
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Sjödin, Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hagsand, Olof
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Control and forwarding plane interaction in distributed routers2005In: NETWORKING 2005: NETWORKING TECHNOLOGIES, SERVICES, AND PROTOCOLS; PERFORMANCE OF COMPUTER AND COMMUNICATION NETWORKS; MOBILE AND WIRELESS COMMUNICATIONS SYSTEMS / [ed] Boutaba, R; Almeroth, K; Puigjaner, R; Shen, S; Black, JP, 2005, Vol. 3462, p. 1339-1342Conference paper (Refereed)
    Abstract [en]

    The requirements on IP routers continue to increase, both from the control plane and the forwarding plane perspectives. To improve scalability, flexibility, and availability new ways to build future routers need to be investigated. This paper suggests a decentralized, modular system design for routers, based on control elements for functionalities like routing, and forwarding elements for packet processing. Further, we present measurements on the distribution of large routing tables in an experimental platform consisting of one control element and up to 16 forwarding elements.

  • 21.
    Hidell, Markus
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Sjödin, Peter
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Hagsand, Olof
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    NACK-Oriented Reliable Multicast for Routing Table Distribution in Decentralized Routers2005In: 3rd Swedish National Computer Networking Workshop, SNCNW 2005, Halmstad, Sweden, 2005Conference paper (Refereed)
    Abstract [en]

    The requirements on IP routers are increasing for every new generation of designs. The driving forces behind this development are growing traffic volumes and demands for new services. We believe that a modular decentralized router design is well-suited to meet future requirements. However, a distributed design may, compared to a centralized system, introduce an additional cost for internal communication between the elements. In this paper we evaluate different transaction mechanisms for the internal communication. We study the suitability of reliable multicast for the internal distribution of large amounts of routing information. In particular, we evaluate NORM (NACK-Oriented Reliable Multicast) as a candidate protocol for our purposes.

  • 22.
    Hidell, Markus
    et al.
    KTH, School of Electrical Engineering (EES).
    Sjödin, Peter
    KTH, School of Electrical Engineering (EES).
    Hagsand, Olof
    KTH.
    Reliable multicast for control in distributed routers2005In: 2005 Workshop on High Performance Switching and Routing, NEW YORK: IEEE , 2005, p. 133-137Conference paper (Refereed)
    Abstract [en]

    Growing traffic volumes and demands for new services rapidly increase the requirements imposed on network systems, such as IP routers. We argue that a decentralized modular system design would improve the scalability, flexibility, and reliability of future routers. We have designed an implemented such a distributed router, based on physical separation between control and forwarding elements. One challenge with the design concerns the internal communication between the elements constituting the router. This paper presents performance measurements of different internal transaction mechanisms between the control and forwarding planes. In particular, an existing protocol for reliable multicast has been integrated and evaluated in our experimental prototype. The prototype consists of one control element and up to 16 forwarding elements, interconnected by an internal control network based on Ethernet switches.

  • 23.
    Marsh, Ian
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hagsand, Olof
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Dimensioning Links for IP Telephony2001In: In Proceedings of the 2nd IP-Telephony Workshop, pages 14-24, New York, USA, April 2001., 2001, p. 14-24Conference paper (Refereed)
    Abstract [en]

    Packet loss is an important parameter for dimensioning networklinks or traffic classes carrying IP telephony traffic. We present amodel based on the Markov modulated Poisson process (MMPP) whichcalculates packet loss probabilities for a set of superpositioned voice inputsources and link properties. We do not introduce another new model tothe community, rather try and verify one of the existing models via extensivesimulation and a real world implementation. A plethora of excellentresearch on queuing theory is still in the domain of ATM researchers,hence we attempt to highlight their validity to the IP (Telephony) community.Packet level simulations show reasonable correspondence with the predictionsof the model. Our main contribution is the verification of theMMPP model with measurements in a laboratory environment. The lossrates predicted by the model are in general close to the measured lossrates and the loss rates obtained by simulation. The general conclusionis that the MMPP-based model is a tool well suited for dimensioninglinks carrying packetised voice in a system with limited buffer space.

  • 24.
    Morandi, Olivier
    et al.
    Politecnico di Torino, Italy.
    Risso, Fulvio
    Politecnico di Torino, Italy.
    Rolando, Pierluigi
    Politecnico di Torino, Italy.
    Hagsand, Olof
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Ekdahl, Peter
    Mapping Packet Processing Applications on a Systolic  Array Network Processor2008In: 2008 IEEE Workshop on High  Performance Switching and Routing (HPSR), Shanghai, China, IEEE , 2008, p. 30-37Conference paper (Refereed)
    Abstract [en]

    Systolic array network processors represent an effective alternative to ASICs for the design of multi-gigabit packet switching and forwarding devices because of their flexibility, high aggregate throughput and deterministic worst-case performances. However such advantages come at the expense of some limitations, given both by the specific characteristics of the pipelined architecture and by the lack of support for portable high-level languages in the software development tools, forcing software engineers to deal with low level aspects of the underlying hardware platform. In this paper we present a set of techniques that have been implemented in the Network Virtual Machine (NetVM) compiler infrastructure for mapping general layer 2-3 packet processing applications on the Xelerated X11 systolic-array network processor. In particular we demonstrate that our compiler is able to effectively exploit the available hardware resources and to generate code that is comparable to hand-written one, hence ensuring excellent throughput performances.

  • 25.
    Sjödin, Peter
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hidell, Markus
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hagsand, Olof
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Router architectures2004Conference paper (Refereed)
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