Browsing by Subject "TCP/IP"

Now showing 1 - 5 of 5

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.
Restricted
Bilkent Üniversitesi Kütüphanesi kurumsal haberleşme ağı "Intranet"
(Bilkent University Library, 2018-05-10) Korkmaz, Taner
İntranet, kütüphanemizde çalışanlar arası iletişimi sağlamak ve bilgi paylaşmak amacıyla geliştirilmiş özel bir iş ağıdır (network). Esas olarak, İntranet kütüphanemizin kendi özel Web sitesidir; İnternet ile aynı network protokollerini ve aynı altyapıyı kullanır. TCP/IP (Transmission Control Protocol/Internet Protocol – Gönderim Kontrol İletişim Kuralı/İnternet İletişim Kuralı) tabanlıdır ve yetkisiz kullanıcılardan bir firewall (güvenlik duvarı) ile korunur. Bu güvenlik tedbiri sayesinde çift yönde iletişim trafiği kontrol edilir ve iç ağın korunması sağlanır. Kütüphane İntranet, çalışanlar arası var olan iletişimi geliştirir ve ortak bir depolama alanı sağlar. Ayrıca çalışanların kütüphane verilerine, sistem bilgilerine ve e-postalarına kolaylıkla erişimlerini sağlar. İntranet, İnternet üzerinden kolaylıkla erişilebilir olduklarından kütüphane çalışanları, bir tarayıcı (browser) ile herhangi bir yerden Bilkent Üniversitesi VPN kullanarak İntranete ulaşabilirler. Web ofis kullanmak, kütüphane çalışanlarının bilinen tarayıcı özelliklerini kullanarak iş bilgilerini düzenlemelerini ya da doküman ve takvimleri paylaşmalarını sağlar.
Open Access
Comparison of PI controllers designed for the delay model of TCP/AQM networks
(Elsevier, 2013) Ünal H. U.; Melchor-Aguilar, D.; Üstebay, D.; Niculescu, S. -I.; Özbay, Hitay
One of the major problems of communication networks is congestion. In order to address this problem in TCP/IP networks, Active Queue Management (AQM) scheme is recommended. AQM aims to minimize the congestion by regulating the average queue size at the routers. To improve upon AQM, recently, several feedback control approaches were proposed. Among these approaches, PI controllers are gaining attention because of their simplicity and ease of implementation. In this paper, by utilizing the fluid-flow model of TCP networks, we study the PI controllers designed for TCP/AQM. We compare these controllers by first analyzing their robustness and fragility. Then, we implement these controllers in ns-2 platform and conduct simulation experiments to compare their performances in terms of queue length. Taken together, our results provide a guideline for choosing a PI controller for AQM given specific performance requirements.
Open Access
nOBS: an ns2 based simulation tool for performance Evaluation of TCP Traffic in OBS networks
(Springer-Verlag France, 2007) Gurel, G.; Alparslan, O.; Karasan, E.
Performance evaluation of TCP traffic in OBS networks has been under intensive study, since TCP constitutes the majority of Internet traffic. As a reliable and publicly available simulator, ns2 has been widely used for studying TCP/IP networks; however ns2 lacks many of the components for simulating optical burst switching networks. In this paper, an ns2 based OBS simulation tool (nOBS), which is built for studying burst assembly, scheduling and contention resolution algorithms in OBS networks is presented. The node and link objects in OBS are extended in nOBS for developing optical nodes and optical links. The ingress, core and egress node functionalities are combined into a common optical node architecture, which comprises agents responsible for burstification, routing and scheduling. The effects of burstification parameters, e.g., burstification timeout, burst size and number of burstification buffers per egress node, on TCP performance are investigated using nOBS for different TCP versions and different network topologies.
Open Access
A simulation study on congestion control for the ATM ABR service
(1997) Ülkü, Sezer
In this thesis, we have performed a simulation study on congestion control for the asynchronous transfer mode (ATM) available bit rate (ABR) service. Even though ABR is primarily intended for applications that can not describe their characteristics appropriately, it can be used by a wider range of applications since it provides some minimal guarantees for bandwidth. For the simulations, the ABR mechanisms specified in The ATM Forum Specification, Version 4.0 have been implemented to a great extent. Relative marking, enhanced proportional rate control (EPRCA) and efficient rate allocation algorithms (ERAA) have been realized, and their performances at ATM, TCP and application layers have been examined based on robustness, efficiency, fairness, buffer requirements and response time. The beat-down problem and large buffer requirements for the relative marking scheme have been illustrated. EPRCA was shown to be sensitive to parameters and result in oscillations in allowed cell rate. Finally, ERAA was shown to work efficiently with small buffers.