Transport Control Protocol (TCP) over Optical Burst Switched Networks

Transport Control Protocol (TCP) is the dominant protocol in modern communication networks, in which the issues of reliability, flow, and congestion control must be handled efficiently. This thesis studies the impact of the next-generation bufferless optical burst-switched (OBS) networks on the performance of TCP congestion-control implementations (i.e., dropping-based, explicit-notification-based, and delay-based). The burst contention phenomenon caused by the buffer-less nature of OBS occurs randomly and has a negative impact on dropping-based TCP since it causes a false indication of network congestion that leads to improper reaction on a burst drop event. In this thesis we study the impact of these random burst losses on dropping-based TCP throughput. We introduce a novel congestion control scheme for TCP over OBS networks, called Statistical Additive Increase Multiplicative Decrease (SAIMD). SAIMD maintains and analyzes a number of previous round trip times (RTTs) at the TCP senders in order to identify the confidence with which a packet-loss event is due to network congestion. The confidence is derived by positioning short-term RTT in the spectrum of long-term historical RTTs. The derived confidence corresponding to the packet loss is then taken in to account by the policy developed for TCP congestion-window adjustment. For explicit-notification TCP, we propose a new TCP implementation over OBS networks, called TCP with Explicit Burst Loss Contention Notification (TCP-BCL). We examine the throughput performance of a number of representative TCP implementations over OBS networks, and analyze the TCP performance degradation due to the misinterpretation of timeout and packet-loss events. We also demonstrate that the proposed TCP-BCL scheme can counter the negative effect of OBS burst losses and is superior to conventional TCP architectures in OBS networks. For delay-based TCP, we observe that this type of TCP implementation cannot detect network congestion when deployed over typical OBS networks since RTT fluctuations are minor. Also, delay-based TCP can suffer from falsely detecting network congestion when the underlying OBS network provides burst retransmission and/or deflection. Due to the fact that burst retransmission and deflection schemes introduce additional delays for bursts that are retransmitted or deflected, TCP cannot determine whether this sudden delay is due to network congestion or simply to burst recovery at the OBS layer. In this thesis we study the behaviour of delay-based TCP Vegas over OBS networks, and propose a version of threshold-based TCP Vegas that is suitable for the characteristics of OBS networks. The threshold-based TCP Vegas is able to distinguish increases in packet delay due to network congestion from burst contention at low traffic loads. The evolution of OBS technology is highly coupled with its ability to support upper-layer applications. Without fully understanding the burst transmission behaviour and the associated impact on the TCP congestion-control mechanism, it will be difficult to exploit the advantages of OBS networks fully

Evaluation Study for Delay and Link Utilization with the New-Additive Increase Multiplicative Decrease Congestion Avoidance and Control Algorithm

As the Internet becomes increasingly heterogeneous, the issue of congestion avoidance and control becomes ever more important. And the queue length, end-to-end delays and link utilization is some of the important things in term of congestion avoidance and control mechanisms. In this work we continue to study the performances of the New-AIMD (Additive Increase Multiplicative Decrease) mechanism as one of the core protocols for TCP congestion avoidance and control algorithm, we want to evaluate the effect of using the AIMD algorithm after developing it to find a new approach, as we called it the New-AIMD algorithm to measure the Queue length, delay and bottleneck link utilization, and use the NCTUns simulator to get the results after make the modification for the mechanism. And we will use the Droptail mechanism as the active queue management mechanism (AQM) in the bottleneck router. After implementation of our new approach with different number of flows, we expect the delay will less when we measure the delay dependent on the throughput for all the system, and also we expect to get end-to-end delay less. And we will measure the second type of delay a (queuing delay), as we shown in the figure 1 bellow. Also we will measure the bottleneck link utilization, and we expect to get high utilization for bottleneck link with using this mechanism, and avoid the collisions in the link

Performance evaluation of TCP over software-defined optical burst-switched data centre network

In this paper, we consider the performance of TCP when used in data centre networks (DCNs) featuring optical burst switching (OBS) using two-way reservation. The two-way reservation is not suitable in wide-area OBS networks due to high bandwidth-delay product (BDP). The burst loss using traditional methods of one-way reservation can be mistakenly interpreted by the TCP layer as congestion instead of contention in OBS network, leading to serious degradation of the TCP performance. The reduced BDP in DCNs allows the use of two-way reservation that results in zero burst loss. The modelled architecture features fast optical switches in a single hop topology. We apply different workloads with various burst assembly parameters to evaluate the performance of TCP. Our results show significant improvement in TCP performance as compared to traditional methods of OBS as well as to a conventional electronic packet switching DCN

Study on the Performance of TCP over 10Gbps High Speed Networks

Internet traffic is expected to grow phenomenally over the next five to ten years. To cope with such large traffic volumes, high-speed networks are expected to scale to capacities of terabits-per-second and beyond. Increasing the role of optics for packet forwarding and transmission inside the high-speed networks seems to be the most promising way to accomplish this capacity scaling. Unfortunately, unlike electronic memory, it remains a formidable challenge to build even a few dozen packets of integrated all-optical buffers. On the other hand, many high-speed networks depend on the TCP/IP protocol for reliability which is typically implemented in software and is sensitive to buffer size. For example, TCP requires a buffer size of bandwidth delay product in switches/routers to maintain nearly 100\% link utilization. Otherwise, the performance will be much downgraded. But such large buffer will challenge hardware design and power consumption, and will generate queuing delay and jitter which again cause problems. Therefore, improve TCP performance over tiny buffered high-speed networks is a top priority. This dissertation studies the TCP performance in 10Gbps high-speed networks. First, a 10Gbps reconfigurable optical networking testbed is developed as a research environment. Second, a 10Gbps traffic sniffing tool is developed for measuring and analyzing TCP performance. New expressions for evaluating TCP loss synchronization are presented by carefully examining the congestion events of TCP. Based on observation, two basic reasons that cause performance problems are studied. We find that minimize TCP loss synchronization and reduce flow burstiness impact are critical keys to improve TCP performance in tiny buffered networks. Finally, we present a new TCP protocol called Multi-Channel TCP and a new congestion control algorithm called Desynchronized Multi-Channel TCP (DMCTCP). Our algorithm implementation takes advantage of a potential parallelism from the Multi-Path TCP in Linux. Over an emulated 10Gbps network ruled by routers with only a few dozen packets of buffers, our experimental results confirm that bottleneck link utilization can be much better improved by DMCTCP than by many other TCP variants. Our study is a new step towards the deployment of optical packet switching/routing networks

STCP: A New Transport Protocol for High-Speed Networks

Transmission Control Protocol (TCP) is the dominant transport protocol today and likely to be adopted in future high‐speed and optical networks. A number of literature works have been done to modify or tune the Additive Increase Multiplicative Decrease (AIMD) principle in TCP to enhance the network performance. In this work, to efficiently take advantage of the available high bandwidth from the high‐speed and optical infrastructures, we propose a Stratified TCP (STCP) employing parallel virtual transmission layers in high‐speed networks. In this technique, the AIMD principle of TCP is modified to make more aggressive and efficient probing of the available link bandwidth, which in turn increases the performance. Simulation results show that STCP offers a considerable improvement in performance when compared with other TCP variants such as the conventional TCP protocol and Layered TCP (LTCP)

On the use of balking for estimation of the blocking probability for OBS routers with FDL lines

Trabajo presentado en la International Conference on Information Networking (ICOIN) 2006, Sendai (Japón), 16-19 de enero de 2006This paper deals with estimation of blocking probabilities for OBS switches with Fiber Delay Lines (FDLs) and full wavelength conversion. An incoming burst that finds the wavelengths occupied is temporarily stored in a FDL. Hence, contention will be sorted out successfully if the residual life of the system is smaller than the maximum FDL delay. In order to derive the blocking probability, the most accurate methodology to date is the use of balking systems [1–4]. Even though the approach is accurate for very short lengths of the FDLs we identify the cases in which inaccuracy is detected. This happens precisely when the system works with low loss probabilities. Mainly for large number of wavelengths on the fibers and values of the FDL length at least in the vicinity of the burst service time.This work was funded by Spanish MEC (project CAPITAL subproject code: TEC2004-05622-C04-04 and project PINTA

Dimensionerings- en werkverdelingsalgoritmen voor lambda grids

Grids bestaan uit een verzameling reken- en opslagelementen die geografisch verspreid kunnen zijn, maar waarvan men de gezamenlijke capaciteit wenst te benutten. Daartoe dienen deze elementen verbonden te worden met een netwerk. Vermits veel wetenschappelijke applicaties gebruik maken van een Grid, en deze applicaties doorgaans grote hoeveelheden data verwerken, is het noodzakelijk om een netwerk te voorzien dat dergelijke grote datastromen op betrouwbare wijze kan transporteren. Optische transportnetwerken lenen zich hier uitstekend toe. Grids die gebruik maken van dergelijk netwerk noemt men lambda Grids. Deze thesis beschrijft een kader waarin het ontwerp en dimensionering van optische netwerken voor lambda Grids kunnen beschreven worden. Ook wordt besproken hoe werklast kan verdeeld worden op een Grid eens die gedimensioneerd is. Een groot deel van de resultaten werd bekomen door simulatie, waarbij gebruik gemaakt wordt van een eigen Grid simulatiepakket dat precies focust op netwerk- en Gridelementen. Het ontwerp van deze simulator, en de daarbijhorende implementatiekeuzes worden dan ook uitvoerig toegelicht in dit werk

Maximisation du débit TCP dans les réseaux OBS

Les réseaux optiques ont connu une émergence importante dans le domaine des télécommunications, et ceci grâce à leur bande passante offerte. Actuellement, la technique la plus prometteuse est la commutation optique de rafales (OBS). D'une part, OBS permet une meilIeure exploitation de la bande passante, tout en ayant un degré de complexité inférieur à OPS (Optical Packet Switching), d'autre part, OBS offre une gestion des ressources beaucoup plus efficace, comparée à OCS (Optical Circuit Switching). Plusieurs études ont démontré que le mécanisme « load-balancing » permet d'équilibrer le trafic à travers les différents noeuds, réduisant ainsi la probabilité de congestion dans les réseaux OBS. Cependant, l'utilisation du « load-balancing » a mis en évidence d'autres problèmes, particulièrement au niveau de la couche TCP (Transmission Control Protocol). De là, \ud « Source-ordering » a été proposé comme solution pour améliorer les performances de TCP, en effectuant l'ordonnancement des rafales au niveau des sources.\ud Dans ce travail, nous nous proposons d'étudier et d'approfondir le mécanisme du « load-balancing » afin de maximiser le débit TCP. Notre défi consiste a trouver un concept permettant d'éviter la réception en désordre des segments IP, au niveau de la couche TCP, et par conséquent à réduire le nombre de FTOs (False Time Out) et de FFRs (False Fast Retransmit). Nous avons implémenté une nouvelle technique basée sur le mécanisme de résolution de contention proactive « load-balancing » qu'on a appelée \ud « ordonnancement à la destination ». Les résultats obtenus montrent une amélioration importante du débit TCP lors de l'emploi du mécanisme d'ordonnancement à la destination. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Maximisation du débit TCP, OBS, TCP, Rafale, Résolution de contention, Mécanisme proactif, Chemins alternatifs, Equilibrage de charge