Browsing by Subject "Packet switching"

Now showing 1 - 10 of 10

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 threshold-based assembly algorithms for optical burst switching networks subject to burst rate constraints
(Springer, 2010-04-17) Toksöz, M. A.; Akar, N.
Control plane load stems from burst control packets which need to be transmitted end-to-end over the control channel and furtherprocessed at core nodes of an optical burst switching (OBS) network for reserving resources in advance for an upcoming burst. Burst assembly algorithms are generally designed without taking into consideration the control plane load they lead to. In this study, we propose traffic-adaptive burst assembly algorithms that attempt to minimize the average burst assembly delay subject to burst rate constraints and hence limit the control plane load. The algorithms we propose are simple to implement and we show using synthetic and real traffic traces that they perform substantially better than the usual timer-based schemes.
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
Markov modulated periodic arrival process offered to an ATM multiplexer
(IEEE, 1993-11-12) Akar, Nail; Arıkan, Erdal
When a superposition of on/off sources is offered to a deterministic server, a particular queueing system arises whose analysis has a significant role in ATM based networks. Periodic cell generation during active times is a major feature of these sources. In this paper a new analytical method is provided to solve for this queueing system via an approximation to the transient behavior of the nD/D/1 queue. The solution to the queue length distribution is given in terms of a solution to a linear differential equation with variable coefficients. The technique proposed here has close similarities with the fluid flow approximations and is amenable to extension for more complicated queueing systems with such correlated arrival processes. A numerical example for a packetized voice multiplexer is finally given to demonstrate our results.
Open Access
Markov modulated periodic arrival process offered to an ATM multiplexer
(Elsevier BV * North-Holland, 1995-04) Akar, N.; Arıkan, E.
When a superposition of on/off sources is offered to a deterministic server, we are faced with a particular queueing system, the analysis of which has a significant role in ATM networks. Periodic cell generation during active times is a major feature of these sources. We provide an analytical approach to solve for this queueing system via an approximation to the transient behavior of the nD/D/1 queue. The solution to the queue length distribution is given in terms of a solution to a linear differential equation with variable coefficients. The technique proposed here has close similarities with the fluid flow approximation and is amenable to extension for more complicated queueing systems with such correlated arrival processes. A numerical example for a packetized voice multiplexer is finally given to demonstrate our results.
Open Access
On the design of AQM supporting TCP flows using robust control theory
(IEEE, 2003) Quet, P. F.; Özbay, Hitay
Recently it has been shown that the AQM (Active Queue Management) schemes implemented in the routers of communication networks supporting TCP (Transmission Control Protocol) flows can be modeled as a feedback control system. Based on a delay differential equations model of TCP's congestion-avoidance mode different control schemes have been proposed. Here a robust controller is designed based on the known techniques for ℋ ∞ control of systems with time delays.
Open Access
Optical core networks research in the e-Photon-ONe+ project
(2009) Callegati F.; Cugini F.; Ghobril P.; Gunreben, S.; López V.; Martini, B.; Pavón-Mariño P.; Perényi, M.; Sengezer, N.; Staessens, D.; Szigeti J.; Tornatore, M.
This paper reports a summary of the joint research activities on Optical Core Networks within the e-Photon-ONe+ project. It provides a reasonable overview of the topics considered of interest by the European research community and supports the idea of building joint research activities that can leverage on the expertise of different research groups. © 2009 IEEE.
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 simulation study of forward error correction for lost packet recovery in B-ISDN/ATM
(IEEE, 1993-05) Oğuz, Nihat Cem; Ayanoğlu, E.
We present the results of a simulation study for a virtual circuit connection over an ATM network where forward error correction is performed at both the ATM cell level and the packet data unit (PDU) level. A main conclusion of this study is that at low loads ATM cells from the same source dominate in the switch buffers, while at high loads there is a mixing of ATM cells from different sources. For the latter case. ATM cell level coding performs better, while for the former, PDU level coding performs better. The combination of the two techniques has the best overall performance.
Open Access
A simulation study of two-level forward error correction for lost packet recovery in B-ISDN/ATM
(IEEE, 1993) Oğuz, Nihat Cem; Ayanoğlu, E.
The major source of errors in B-ISDN/ATM systems is expected to be buffer overflow during congested conditions, resulting in lost packets. A single lost or errored ATM cell will cause retransmission of the entire packet data unit (PDU) that it belongs to. The performance of the end-to-end system can be made much less sensitive to cell loss by means of forward error correction. In this paper, we present the results of a simulation study for an ATM network where forward error correction is performed at both the cell level and the PDU level. The results indicate that (i) cell losses are highly correlated in time, and analytical models ignoring this fact will not yield accurate results, (ii) the correlation of cell losses is similar to burst errors in digital communication, and similar code interleaving techniques should be used, (iii) coding cells and PDUs separately provides this interleaving effect, and this joint code outperforms coding only at the cell level or only at the PDU level in almost all cases simulated.