Browsing by Subject "Packet networks"

Now showing 1 - 16 of 16

Open Access
AIMD-based online MPLS traffic engineering for TCP flows via distributed multi-path routing
(Springer, 2004) Alparslan O.; Akar, N.; Karasan, E.
With this paper, we propose a distributed online traffic engineering architecture for MPLS networks. In this architecture, a primary and secondary MPLS LSP are established from an ingress LSR to every other egress LSR. We propose to split the TCP traffic between the primary and secondary paths using a distributed mechanism based on ECN marking and AIMD-based rate control. Inspired by the random early detection mechanism for active queue management, we propose a random early reroute scheme to adaptively control the delay difference between the primary and secondary LSPS. Considering the adverse effect of packet reordering on TCP performance for packet-based load balancing schemes, we propose that the TCP splitting mechanism operates on a per-flow basis. Using flow-based models developed for Internet traffic and simulations, we show that flow-based distributed multi-path traffic engineering outperforms on a consistent basis the case of a single path in terms of per-flow goodputs. Due to the elimination of out-of-order packet arrivals, flow-based splitting also enhances TCP performance with respect to packet-based splitting especially for long TCP flows that are hit hard by packet reordering. We also compare and contrast two queuing architectures for differential treatment of data packets routed over primary and secondary LSPS in the MPLS data plane, namely first-in-first-out and strict priority queuing. We show through simulations that strict priority queuing is more effective and relatively more robust with respect to the changes in the traffic demand matrix than first-in-first-out queuing in the context of distributed multi-path routing.
Open Access
Available bit rate traffic engineering in MPLS networks with flow-based multipath routing
(Institute of Electronics Information and Communication Engineers, 2004) Akar, N.; Hökelek, İ.; Karasan, E.
In this paper, we propose a novel traffic engineering architecture for IP networks with MPLS backbones. In this architecture, two link-disjoint label switched paths, namely the primary and secondary paths, are established among every pair of IP routers located at the edges of an MPLS backbone network. As the main building block of this architecture, we propose that primary paths are given higher priority against the secondary paths in the MPLS data plane to cope with the so-called knock-on effect. Inspired by the ABR flow control mechanism in ATM networks, we propose to split traffic between a source-destination pair between the primary and secondary paths using explicit rate feedback from the network. Taking into consideration the performance deteriorating impact of packet reordering in packet-based load balancing schemes, we propose a traffic splitting mechanism that operates on a per-flow basis (i.e., flow-based multipath routing). We show via an extensive simulation study that using flow-based multipath traffic engineering with explicit rate feedback not only provides consistently better throughput than that of a single path but is also void of out-of-order packet delivery.
Open Access
Bluetooth broadcasting performance: reliability and throughput
(Springer, Berlin, Heidelberg, 2006) Doğan, Kaan; Gürel, Güray; Kamçı, A. Kerim; Körpeoğlu, İbrahim
This paper studies the performance of Bluetooth broadcasting scheme. The transmission of a Bluetooth broadcast packet is repeated several times to increase the reliability of broadcast. We have analyzed the effects of baseband ACL packet type preference, on the broadcast performance in terms of reliability and effective throughput, over different channel characteristics (i.e. bit error rate). As the result of our analysis, we determined the optimal packet type and re-transmission count combinations that can provide the highest effective throughput values for various practical BER ranges. These results can be used at Bluetooth baseband layer to dynamically adapt to varying channel conditions and to achieve a good broadcast performance.
Open Access
Delay analysis of timer-based frame coalescing in energy efficient ethernet
(IEEE, 2013) Akar, N.
IEEE 802.3az, also known as Energy Efficient Ethernet (EEE), aims at reducing the energy consumption of an Ethernet link by placing it in sleep mode when the link is idle. Frame coalescing mechanism proposed for EEE is an effective means to increase the average idle time of the link, thus reducing the overhead stemming from sleep/wake transitions, but at the expense of increased frame delays. Therefore, it is imperative to quantify the energy-delay trade-off while employing frame coalescing. As opposed to existing delay models that focus only on the average delays, a simple but exact queuing model is introduced for timer-based frame coalescing to find the delay distribution when the frame arrival process is Poisson and frame lengths are generally distributed. An expression for average saving in power consumption is also provided.
Open Access
Detecting compromised routers via packet forwarding behavior
(2008) Mizrak, A.T.; Savage, S.; Marzullo, K.
While it is widely understood that criminal miscreants are subverting large numbers of Internet-connected computers (e.g., for bots, spyware, SPAM forwarding), it is less well appreciated that Internet routers are also being actively targeted and compromised. Indeed, due to its central role in end-to-end communication, a compromised router can be leveraged to empower a wide range of direct attacks including eavesdropping, man-in-the-middle subterfuge, and denial of service. In response, a range of specialized anomaly detection protocols has been proposed to detect misbehaving packet forwarding between routers. This article provides a general framework for understanding the design space of this work and reviews the capabilities of various detection protocols. © 2008 IEEE.
Open Access
Dimensioning shared-per-node recirculating fiber delay line buffers in an optical packet switch
(Elsevier, 2013) Akar, N.; Gunalay, Y.
Optical buffering based on fiber delay lines (FDLs) has been proposed as a means for contention resolution in an optical packet switch. In this article, we propose a queuing model for feedback-type shared-per-node recirculating FDL optical buffers in asynchronous optical switching nodes. In this model, optical packets are allowed to recirculate over FDLs as long as the total number of recirculations is less than a pre-determined limit to meet signal loss requirements. Markov Modulated Poisson Process (MMPP)-based overflow traffic models and fixed-point iterations are employed to provide an approximate analysis procedure to obtain blocking probabilities as a function of various buffer parameters in the system when the packet arrival process at the optical switch is Poisson. The proposed algorithm is numerically efficient and accurate especially in a certain regime identified with relatively long and variably-sized FDLs, making it possible to dimension optical buffers in next-generation optical packet switching systems.
Open Access
Dynamic capacity management for voice over packet networks
(2003-06-07) Akar, Nail; Şahin, Cem
In this paper, dynamic capacity management refers to the process of dynamically changing the capacity allocation (reservation) of a pseudo-wire established between two network end points. This process is based on certain criteria including instantaneous traffic load for the pseudo-wire, network utilization, time of day, or day of week. Frequent adjustment of the capacity yields a scalability issue in the form of a significant amount of message processing in the network elements involved in the capacity update process. On the other hand, if the capacity is adjusted once and for the worst possible traffic conditions, a significant amount of bandwidth may be wasted depending on the actual traffic load. There is then a need for dynamic capacity management that takes into account the tradeoff between scalability and bandwidth efficiency. This problem is motivated by voice over packet networks in which end-to-end reservation requests are initiated by PSTN voice calls and these reservations are aggregated into one signal reservation in the core packet network for scalability. In this paper, we introduce a Markov decision framework for an optimal reservation aggregation scheme for voice over packet networks. Moreover, for problems with large sizes, we provide a suboptimal scheme using reinforcement learning. We show a significant improvement in bandwidth efficiency in voice over packet networks using aggregate reservations. © 2003 IEEE.
Open Access
Effect of number of burst assemblers on TCP performance in optical burst switching networks
(IEEE, 2006-10) Gürel, Güray; Karasan, Ezhan
Burst assembly mechanism is one of the fundamental factors that determine the performance of an optical burst switching (OBS) network. In this paper, we investigate the influence of number of burstifiers on TCP performance for an OBS network. An ns2-based OBS network simulator is developed for simulating the optical network. The goodput of TCP flows between an ingress and an egress nodes traveling through an optical network is studied for different values of the number of assembly buffers per destination. First, the losses resulting from the congestion in the core OBS network are modeled using a burst independent Bernoulli loss model. Then, a background burst traffic is generated to create contention at a core node in order to realize a burst dependent loss model. Simulation results show that for an OBS network employing timer-based assembly algorithm, TCP goodput increases as the number of burst assemblers is increased for both types of loss models. The improvement from one burstifier to moderate number of burst assemblers is significant (15-50% depending on the burst loss probability, processing delay and the TCP version), but the goodput difference between moderate number of buffers andperflow aggregation is relatively small, implying that a cost-effective OBS edge switch implementation should use moderate number of assembly buffers per destination for enhanced TCP performance. © 2006 IEEE.
Open Access
Impact of scalability in video transmission in promotion-capable differentiated services networks
(IEEE, 2002-09) Gürses, E.; Akar, G. B.; Akar, Nail
Transmission of high quality video over the Internet faces many challenges including unpredictable packet loss characteristics of the current Internet and the heterogeneity of receivers in terms of their bandwidth and processing capabilities. To address these challanges, we propose an architecture in this paper that is based on the temporally scalable and error resilient video coding mode of the H.263+ codec. In this architecture, the video frames will be transported over a new generation IP network that supports differentiated services (Diffserv). We also propose a novel Two Rate Three Color Promotion-Capable Marker (trTCPCM) to be used at the edge of the diffserv network. Our simulation study demonstrates that an average of 30 dB can be achieved in case of highly congested links.
Open Access
Packet loss analysis of synchronous buffer-less optical switch with shared limited range wavelength converters
(IEEE, 2007) Raffaelli, C.; Savi, M.; Akar, Nail; Karasan, Ezhan
Application of synchronous optical switches in Optical Packet/Burst switched networks is considered. The shared per node architectural concept, where wavelength converters are shared among all input and output channels, is applied for contention resolution in the wavelength domain. A semi-analytical traffic model suitable to represent the different contributions to packet loss is proposed and validated. Full and limited range wavelength conversion capabilities are considered, and loss results obtained to support switch design. An approximated fully analytical approach for the limited range case is also described and comparison with simulation results is presented to assess the capability to capture the main aspects of packet loss behavior.
Open Access
Performance analysis of an optical packet switch employing full/limited range share per node wavelength conversion
(IEEE, 2007) Akar, Nail; Karasan, Ezhan; Muretto, G.; Raffaelli, C.
In this paper, we study an asynchronous optical packet switching node equipped with a number of limited range or full range wavelength converters shared per node. The packet traffic is realistically modeled by a superposition of a finite number of on-off sources as opposed to the traditional Poisson model which ignores the limited number of ports on a switch. We both study circular and non-circular limited range wavelength conversion schemes. In our simulations, we employ the far conversion policy where the optical packet is switched onto the farthest available wavelength in the tuning range, which is known to outperform the random conversion policy. We propose an approximate analytical method based on block tridiagonal Markov chains and fixed point iterations to solve for the blocking probabilities in share per node wavelength conversion systems. The method provides an accurate approximation for full range systems and acceptable results for limited range systems.
Open Access
A performance study of limited range partial wavelength conversion for asynchronous optical packet/burst switching
(IEEE, 2006) Doğan, Kaan; Akar, Nail
In this work, we study an asynchronous optical packet/burst switching node equipped with a number of limited range wavelength converters shared per output link. A wavelength conversion policy is one by which the outgoing wavelength for an optical packet is selected if its incoming wavelength is in use. Through simulations, we show that the so-called "far conversion" policy in which the optical packet is switched onto the farthest available wavelength in the tuning range, outperforms the other policies we studied. We point out the "clustering effect" in the use of wavelengths to explain this phenomenon.
Open Access
Throughput modeling of single hop CSMA networks with non-negligible propagation delay
(IEEE, 2013) Koseoglu, M.; Karasan, E.
We analyze the performance of the CSMA protocol under propagation delays that are comparable with packet transmission times. We propose a semi-Markov model for the 2-node CSMA channel. For the 2-node case, the capacity reduces to 40% of the zero-delay capacity when the one-way propagation delay is 10% of the packet transmission time. We then extend this model and obtain the optimum symmetric probing rate that achieves the maximum network throughput as a function of the average propagation delay, d, and the number of nodes sharing the channel, N. The proposed model predicts that the total capacity decreases with d-1 as N goes to infinity when all nodes probe the channel at the optimum rate. The optimum probing rate for each node decreases with 1/N and the total optimum probing rate decreases faster than d-1 as N goes to infinity. We investigate how the short-term unfairness problem in CSMA worsens as the propagation delay increases and propose a back-off mechanism to mitigate this issue. The theoretical results presented in this paper can be used as a benchmark for the performance improvements provided by algorithms that have already been developed.
Open Access
Uçtan uca modelleme ile kesintisiz stereo video iletimi
(IEEE, 2008-04) Tan, A. Serdar; Aksay, A; Akar, G. B.; Arıkan, Erdal
Bu çalışmamızda, hata koruma yöntemi olarak oransız kodları (Raptor Kodları) kullanan kesintisiz bir stereo video iletim sistemi önermekteyiz. İlk olarak video kodlayıcının hızbozulum (HB) eğrisini ve kanal koruma kodunun performansını analitik olarak modelledik. Daha sonra, paket kayıplarından kaynaklanan stereo videodaki kalite bozulumunu kestirdik. Son olarak, analitik modelleri ve kestirilmiş paket kayıp bozulumlarını kullanarak uçtan uca bozulum enküçültmesi uyguladık ve en iyi video kodlayıcı bit hızlarını ve eşit olmayan hata koruması (EOHK) oranlarını elde ettik. Benzetim sonuçlarında, önerilen sistemin getirdiği önemli kalite kazanımları açıkça gözlenmektedir.
Open Access
Uniform weighted round robin scheduling algorithms for input queued switches
(IEEE, 2001-06) Rai, Idris A.; Alanyalı, Murat
This paper concentrates on obtaining uniform weighted round robin schedules for input queued packet switches. The desired schedules are uniform in the sense that each connection is serviced at regularly spaced time slots, where the spacing is proportional to the inverse of the guaranteed data rate. Suitable applications include ATM networks as well as satellite switched TDMA systems that provide per packet delay guarantees. Three heuristic algorithms are proposed to obtain such schedules under the constraints imposed by the unit speedup of input queued switches. Numerical experiments indicate that the algorithms have remarkable performance in finding uniform schedules.
Open Access
Wireless ATM: limits, challenges, and proposals
(Institute of Electrical and Electronics Engineers, 1996) Ayanoglu, E.; Eng, K. Y.; Karol, M. J.
Recently, there has been an increased interest in the topic of "wireless ATM." The subject matter raises interest due to the potential combination of two of the hottest topics in communications of the mid-'90s, but at the same time raises a natural question as to its viability, and sometimes even its desirability. In this article the authors survey potential applications of wireless ATM and describe what is usually meant by wireless ATM, why it may make sense, and some of the proposals to build systems based on it. The emphasis in this article is on the physical layer, the data link layer, and the access layer. The authors also present general observations on each of these layers, and some research solutions to these problems. Mobility issues and interoperability with the existing networks are addressed. Finally, the authors list some of the proposals to build wireless ATM systems from the literature.