Browsing by Subject "Network protocols"

Now showing 1 - 20 of 31

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
Analysis of concurrency control protocols for real-time database systems
(Elsevier, 1998) Ulusoy, Özgür
This paper provides an approximate analytic solution method for evaluating the performance of concurrency control protocols developed for real-time database systems (RTDBSs). Transactions processed in a RTDBS are associated with timing constraints typically in the form of deadlines. The primary consideration in developing a RTDBS concurrency control protocol is the fact that satisfaction of the timing constraints of transactions is as important as maintaining the consistency of the underlying database. The proposed solution method provides the evaluation of the performance of concurrency control protocols in terms of the satisfaction rate of timing constraints. As a case study, a RTDBS concurrency control protocol, called High Priority, is analyzed using the proposed method. The accuracy of the performance results obtained is ascertained via simulation. The solution method is also used to investigate the real-time performance benefits of the High Priority over the ordinary Two-Phase Locking.
Open Access
Capture resilient ElGamal signature protocols
(Springer, 2006-11) Acan, Hüseyin; Kaya, Kamer; Selçuk, Ali Aydın
One of the fundamental problems of public key cryptography is protecting the private key. Private keys are too long to be remembered by the user, and storing them in the device which performs the private key operation is insecure as long as the device is subject to capture. In this paper, we propose server-assisted protocols for the ElGamal signature scheme which make the system capture resilient in the sense that the security of the system is not compromised even if the signature device is captured. The protocols also have a key disabling feature which allows a user to disable the device's private key in case both the device and the password of the user are compromised simultaneously. © Springer-Verlag Berlin Heidelberg 2006.
Open Access
Client-server synchronization and buffering for variable rate multimedia retrievals
(1996) Hui J.Y.; Karasan, E.; Li J.; Zhang, J.
We consider the use of large buffers and feedback as a mechanism to maintain loosely coupled synchronization between a multimedia server and a client. The multimedia stream is modeled as a fluid flow through rate controlled valves and buffers with multiple thresholds. These thresholds are used to control the rates upstream. The quality of service for the multimedia connection is characterized in terms of the jitter in the received media stream due to buffer underflow and overflow. This quality of service is used to exercise rate and admission control in the presence of congestion. The feedback mechanism is, implemented in GRAMS, an adaptive multimedia client-server system. Experimental statistics are gathered for the purpose of traffic engineering. We employ a fluid flow and first passage time analysis to understand the traffic process through the pipelines and the buffers and to estimate the amount of signaling required by the feedback mechanism.
Open Access
A connection management protocol for promoting cooperation in Peer-to-Peer networks
(Elsevier BV, 2008-02-05) Karakaya, M.; Körpeoǧlu, I.; Ulusoy, Özgür
The existence of a high degree of free riding in Peer-to-Peer (P2P) networks is an important threat that should be addressed while designing P2P protocols. In this paper we propose a connection-based solution that will help to reduce the free riding effects on a P2P network and discourage free riding. Our solution includes a novel P2P connection type and an adaptive connection management protocol that dynamically establishes and adapts a P2P network topology considering the contributions of peers. The aim of the protocol is to bring contributing peers closer to each other on the adapted topology and to push the free riders away from the contributors. In this way contribution is promoted and free riding is discouraged. Unlike some other proposals against free riding, our solution does not require any permanent identification of peers or a security infrastructure for maintaining a global reputation system. It is shown through simulation experiments that there is a significant improvement in performance for contributing peers in a network that applies our protocol. © 2007 Elsevier B.V. All rights reserved.
Open Access
Design of translucent optical networks: Partitioning and restoration
(Kluwer, 2004) Karasan, E.; Arisoylu, M.
We discuss the problem of designing translucent optical networks composed of restorable, transparent subnetworks interconnected via transponders. We develop an integer linear programming (ILP) formulation for partitioning an optical network topology into subnetworks, where the subnetworks are determined subject to the constraints that each subnetwork satisfies size limitations, and it is two-connected. A greedy heuristic partitioning algorithm is proposed for planar network topologies. We use section restoration for translucent networks where failed connections are rerouted within the subnetwork which contains the failed link. The network design problem of determining working and restoration capacities with section restoration is formulated as an ILP problem. Numerical results show that fiber costs with section restoration are close to those with path restoration for mesh topologies used in this study. It is also shown that the number of transponders with the translucent network architecture is substantially reduced compared to opaque networks.
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
Differentiated ABR: a new architecture for flow control and service differentiation in optical burst switched networks
(IEEE, 2005) Akar, Nail; Boyraz, Hakan
In this paper, we study a new control plane protocol, called Differentiated ABR (D-ABR), for flow control and service differentiation in optical burst switched networks. Using D-ABR, we show using simulations that the optical network can be designed to work at any desired burst blocking probability by the flow control service of the proposed architecture. This architecture requires certain modifications to the existing control plane mechanisms as well as incorporation of certain scheduling mechanisms at the ingress nodes; however we do not make any specific assumptions on the data plane for the optical core nodes. Moreover, with this protocol, it is possible to almost perfectly isolate high priority and low priority traffic throughout the optical network as in the strict priority-based service differentiation in electronically switched networks.
Open Access
A distributed and dynamic data gathering protocol for sensor networks
(IEEE, 2007-05) Tan, Hüseyin Özgür; Körpeoğlu, İbrahim; Stojmenović, I.
In this paper we propose a distributed, self organizing, robust and energy efficient data gathering algorithm for sensor networks operating in environments where all the sensor nodes are not in direct communication range of each other and data aggregation is used while routing. Proposed algorithm is based on local minimum spanning tree (LMST) structure, which nodes can construct from the position of their 1-hop neighbors. Reporting tree is constructed from the sink by allowing only edges of LMST to join the tree, plus possibly some direct links to the sink. Each node selects as parent the LMST neighbor so that the total energy cost of route to the sink is minimal. We also describe route maintenance protocols to respond to predicted sensor failures and addition of new sensors. Our simulation results show that our algorithm prolongs the network lifetime significantly compared to some alternative schemes. © 2007 IEEE.
Open Access
Distributed and location-based multicast routing algorithms for wireless sensor networks
(SpringerOpen, 2009-01) Korpeoglu, I.; Bagci, H.
Multicast routing protocols in wireless sensor networks are required for sending the same message to multiple different destinations. In this paper, we propose two different distributed algorithms for multicast routing in wireless sensor networks which make use of location information of sensor nodes. Our first algorithm groups the destination nodes according to their angular positions and forwards the multicast message toward each group in order to reduce the number of total branches in multicast tree which also reduces the number of messages transmitted. Our second algorithm calculates an Euclidean minimum spanning tree at the source node by using the positions of the destination nodes. The multicast message is forwarded to destination nodes according to the calculated MST. This helps in reducing the total energy consumed for delivering the message to all destinations by decreasing the number of total transmissions. Evaluation results show that the algorithms we propose are scalable and energy efficient, so they are good candidates to be used for multicasting in wireless sensor networks. Copyright © 2009 H. Bagci and I. Korpeoglu.
Open Access
A distributed and measurement-based framework against free riding in peer-to-peer networks
(IEEE, 2004) Karakaya, Murat; Korpeoglu, İbrahim; Ulusoy, Özgür
In this paper, we propose a distributed and measurement-based method to reduce the degree of free riding in P2P networks. We primarily focus on developing schemes to locate free riders and on determining policies that can be used to take actions against them. Our proposed schemes require each peer to monitor its neighboring peers, make decisions if they exhibit any kind of free riding, and take appropriate actions if required.
Open Access
Distributed interactive video system design and analysis
(Institute of Electrical and Electronics Engineers, 1997) Wu, Tsong-Ho; Korpeoglu, I.; Cheng, Bo-Chao
The interactive video (IV) market has been expected to capture a significant share of the huge potential revenues to be generated by the business and residential markets. The level of revenues generated depends on the completion rate of calls the service provider can support, no matter what the IV system or network condition. Thus, a cost-effective, scalable fault-tolerant IV system is needed to maximize the video call completion rate at an affordable cost. This article describes design methodologies for a scalable, fault-tolerant IV system and an IV system design and analysis research prototype called IVSDNA (IV System Designer and Analyzer). The IVSDNA prototype is designed to help network planners and engineers to evaluate quantitative trade-offs (in terms of network communications costs, video storage costs, and degree of system fault tolerance) between two major IV system architectures (centralized and distributed) with a variety of video distribution methods, replication strategies, and fault-tolerant access protocols.
Open Access
DSSP: A Dynamic Sleep Scheduling Protocol for prolonging the lifetime of wireless sensor networks
(IEEE, 2007-05) Bulut, Eyüphan; Körpeoğlu, İbrahim
This paper presents DSSP (Dynamic Sleep Scheduling Protocol), a centralized scheme for extending the lifetime of densely deployed wireless sensor networks by keeping only a necessary set of sensor nodes active. We present an algorithm for finding out which nodes should be put into sleep mode, and the algorithm preserves coverage and connectivity while trying to put as much nodes as possible into sleep mode. The algorithm is executed at the base station periodically. In this way, the network is reconfigured periodically, which also helps to a more even distribution of energy consumption load to sensor nodes. We evaluated our protocol via simulations and observed a significant increase in the lifetime, depending on the node density, while providing good coverage. © 2007 IEEE.
Open Access
An efficient virtual topology design and traffic engineering scheme for IP/WDM networks
(Springer, 2007) Şengezer, Namık; Karasan, Ezhan
We propose an online traffic engineering (TE) scheme for efficient routing of bandwidth guaranteed connections on a Multiprotocol label switching (MPLS)/wavelength division multiplexing (WDM) network with a traffic pattern varying with the time of day. We first consider the problem of designing the WDM virtual topology utilizing multi-hour statistical traffic pattern. After presenting an effective solution to this offline problem, we introduce a Dynamic tRaffic Engineering AlgorithM (DREAM) that makes use of the bandwidth update and rerouting of the label switched paths (LSPs). The performance of DREAM is compared with commonly used online TE schemes and it is shown to be superior in terms of blocked traffic ratio.
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
Mesh topology design in overlay virtual private networks
(IET, 2002) Karasan, E.; Ekin-Karasan, O.; Akar, N.; Pinar, M. C.
The mesh topology design problem in overlay virtual private networks is studied. Given a set of customer nodes and an associated traffic matrix, tunnels that connect node pairs through a service provider network are determined such that the total multi-hopped traffic is minimised. A tabu search based heuristic is proposed.
Open Access
On the design of AQM supporting TCP flows using robust control theory
(IEEE, 2004) Quet, P-F.; Özbay, Hitay
Recently it has been shown that the active queue management schemes implemented in the routers of communication networks supporting transmission control protocol (TCP) flows can be modeled as a feedback control system. Based on a delay differential equations model of TCPs 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
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
Rate-controlled optical burst switching for both congestion avoidance and service differentiation
(Elsevier, 2005) Boyraz, H.; Akar, N.
Optical Burst Switching (OBS) has recently been proposed as a candidate architecture for the next generation optical Internet. Several challenging issues remain to be solved to pave the way for the OBS vision. Contention arises in OBS networks when two or more bursts are destined for the same wavelength, and a wide variety of reactive contention resolution mechanisms have been proposed in the literature. One challenging issue in OBS is proactively controlling the traffic flowing through the OBS network so that the network does not stay in a persistent state of contention, which we call the congestion avoidance problem. Another challenging issue is the need for service differentiation, which is common today in electronically switched networks via the use of advanced buffer management and scheduling mechanisms. However, such mechanisms cannot be used in OBS networks due to the limited use, or total absence, of buffering. One of the popular existing approaches to service differentiation in OBS networks is the use of larger offset times for high-priority bursts which, however, increases the delays and may adversely affect application-level performance. In this paper, we propose a feedback-based rate control protocol for the control plane of the OBS network to both address the congestion avoidance and service differentiation issues. Using this protocol, the incoming traffic is dynamically shaped at the edge of the OBS network in order to avoid potential congestion in the burst-switched core. Moreover, the traffic shaping policies for the low and high priority traffic classes are different, and it is possible using the proposed protocol to isolate high-priority and low-priority traffic almost perfectly over time scales on the order of a few round-trip times. Simulation results are reported to validate the congestion avoidance and service differentiation capabilities of the proposed architecture. © 2006 Elsevier B.V. All rights reserved.
Open Access
Reducing Router-Crossings in a Mobile Intranet
(Springer, 1998) Korpeoglu, I.; Dube, R.; Tripathi, S. K.
Current general purpose mobility solutions like Mobile-IP involve multiple router-crossings even when the mobile host moves within an intranet from one subnet of a router to another. An environment consisting of a large number of mobile hosts would congest the router causing hosts to experience high latency and jitter. This paper presents a mechanism to eliminate multiple router-crossings in a mobile intranet by making the routers aware of mobility, which reduces the load on the routers and the hand-off and data latency at the mobile hosts.