Showing papers presented at "International Conference on Computer Communications and Networks in 2003"

Mitigating the exposed node problem in IEEE 802.11 ad hoc networks

Abstract: The enhancements to the IEEE 802.11 DCF MAC protocol which enable nodes to identify themselves as exposed nodes and to opportunistically schedule concurrent transmissions whenever possible, thereby improving utilization and mitigating the exposed node problem are described. The algorithm makes minimal changes to the IEEE 802.11 MAC protocol. It does not require the introduction of new frame types or changes to existing frame formats. We show, using simulations in GloMoSim, that it provides significant improvement in throughput.

PINCO: a pipelined in-network compression scheme for data collection in wireless sensor networks

Abstract: In this paper, we present PINCO, an in-network compression scheme for energy constrained, distributed, wireless sensor networks. PINCO reduces redundancy in the data collected from sensors, thereby decreasing the wireless communication among the sensor nodes and saving energy. Sensor data is buffered in the network and combined through a pipelined compression scheme into groups of data, while satisfying a user-specified end-to-end latency bound. We introduce a PINCO scheme for single-valued sensor readings. In this scheme, each group of data is a highly flexible structure so that compressed data can be recompressed without decompressing, in order to reduce newly available redundancy at a different stage of the network. We discuss how PINCO parameters affect its performance, and how to tweak them for different performance requirements. We also include a performance study demonstrating the advantages of our approach over other data collection schemes based on simulation and prototype deployment results.

DDoS attack detection and wavelets

Abstract: This paper presents a systematic method for DDoS attack detection. DDoS attack can be considered system anomaly or misuse from which abnormal behavior is imposed on network traffic. Attack detection can be performed via abnormal behavior identification. Network traffic characterization with behavior modeling could be a good guidance of attack detection. Aggregated traffic has been found to be strong bursty across a wide range of time scales. Wavelet analysis is able to capture complex temporal correlation across multiple time scales with very low computational complexity. We utilize energy distribution based on wavelet analysis to detect DDoS attack traffic. Energy distribution over time would have limited variation if the traffic keeps its behavior over time (i.e. attack-free situation); while an introduction of attack traffic in the network would elicit significant energy distribution deviation in short time period. Our experimental results with typical Internet traffic trace show that energy distribution variance changes markedly causing a "spike" when traffic behaviors affected by DDoS attack In contrast, normal traffic exhibits a remarkably stationary energy distribution. In addition, this spike in energy distribution variance can be captured in early stage of attack, for ahead of congestion build-up, making it an effective attack detection.

Protocol for peer-to-peer networking in mobile environments

Abstract: Peer-to-Peer (P2P) as well as mobile ad hoc networks (MANETs) follow the same idea of creating a network without the help of central entities. However P2P and MANETs operate on different network layers. A combination of both, creates new services and possibilities, but also faces several problems. Introducing P2P computing in ad-hoc networks without considering the particular requirements of ad hoc networks has a poor performance. This paper addresses these problems and introduces the mobile peer-to-peer protocol (MPP) suite as novel approach. It spans from the network layer to the application layer, and tries to reuse existing protocols as far as possible. MPP allows a realistic operation of Peer-to-Peer services over ad hoc networks. The Peer-to-Peer layer must be well aware about the wireless network to minimize the traffic and to cope with frequent route breaks. Additionally the network layer needs knowledge about the Peer-to-Peer application, in order to establish routes only to appropriate communication partners. MPP thus forms the necessary framework to allow the creation of a vast variety of different services over ad hoc networks.

Cellular SCTP: a transport-layer approach to Internet mobility

Abstract: In this paper, we describe a transport layer mobility scheme termed Cellular SCTP, or cSCTP for short, based on the stream control transmission protocol (SCTP), for seamless soft handoff. We compare mobile IPv6 and two of its variants (mobile IPv6 with fast-handover and hierarchical mobile IPv6) with cSCTP on various aspects (especially the handoff process of micro-mobility). We also analyze the mobile IPv6 handover mechanism in detail to reveal the operations that constitutes extra delays or packet losses caused by handoffs. Furthermore, we describe the interworking of cSCTP with SIP for mobility management.

Mesh implementation of light-trails: a solution to IP centric communication

Abstract: Light-trails communication (Chlamtac and Gumaste, 2003) proposes a solution for implementing a conceptual framework for IP centric communication in the optical domain which is a combination of node architecture and protocol for realizing efficient optical communications from IP bursts to dynamic lightpaths. In this paper we introduce a Light-trails solution that is applicable to mesh networks. Contrary to existing proposals for IP type communication in the optical domain light-trail node architecture also presents the first practically implementable solution to enable optical transport with mature technology, nonstringent optical switching requirements, and potentially presents a cost effective alternative to electronics in supporting IP networks.

A novel caching scheme for Internet based mobile ad hoc networks

Abstract: Internet based mobile ad hoc network (IMANET) is an emerging technique that combines a wired network (e.g. Internet) and a mobile ad hoc network (manet) for developing a ubiquitous communication infrastructure. However, imanet has several limitations to fulfill users' demands to access various kinds of information such as limited accessibility to the wired Internet, insufficient wireless bandwidth, and longer message latency. In this paper, we address the issues involved in information search and access in IMANET. A broadcast based simple search (SS) algorithm and an aggregate caching mechanism are proposed for improving the information accessibility and reducing average communication latency in imanet. As part of the aggregate cache, a cache admission control policy and a cache replacement policy, called time and distance sensitive (TDS) replacement, are developed to reduce the cache miss ratio and improve the information accessibility. We evaluate the impact of caching, cache management, and access points, which are connected to the Internet, through extensive simulation. The simulation results indicate that the proposed aggregate cache can significantly improve an imanet performance in terms of throughput and average number of hops to access data. In particular, with aggregate caching, more than 200% improvement in throughput is achieved compared to the imanet with no cache case, when the access pattern follows a Zipf distribution.

An analytical model for IEEE 802.11e EDCF differential services

Abstract: Having been originally developed as an extension of the wired LANs, IEEE 802.11 lacks support for QoS and differential services. Since its introduction various extensions and modifications have been studied to address this current need and the IEEE 802.11 Task Group E is responsible for developing a QoS-aware MAC protocol that considers several service differentiation mechanisms. In this paper, we first consider the enhanced DCF access method of IEEE 802.11e. We then introduce an analytical model, which can be used to calculate the traffic priority and throughput corresponding to the configuration of multiple DCF contention parameters under saturation condition. A detailed simulation is provided to validate the proposed model.

Routing anomaly detection in mobile ad hoc networks

Abstract: Intrusion detection systems (IDSs) for mobile ad hoc networks (MANETs) are necessary when we deploy MANETs in reality. In this paper, focusing on the protection of MANET routing protocols, we present a new intrusion detection agent model and utilize a Markov chain based anomaly detection algorithm to construct the local detection engine. The details of feature selection, data collection, data preprocess, Markov chain construction, classifier construction and parameter tuning are provided. Based on the routing disruption attack aimed at the dynamic source routing protocol (DSR), we study the performance of the algorithm at different mobility levels. Simulation results show that our algorithm can achieve low false positive ratio, high detection ratio, and small MTFA (mean time to the first alarm), especially when the mobility is low. Detailed analysis of simulation results is also presented.

Robust sensor localization algorithm in wireless ad-hoc sensor networks

Abstract: Wireless ad-hoc sensor networks are being developed to collect data across the area of deployment. To stamp the collected data and facilitate communication protocols, it is necessary to identify the location of each sensor. Most existing localization algorithms make use of trilateration or multilateration based on range measurements obtained from RSSI, TOA, TDOA and AoA. In the paper, we first study some situations that most existing sensor localization methods fail to perform well. An example of such situations is when the topology of a sensor network is anisotropic. We propose a distributed sensor localization method with estimation-comparison-correction paradigm to address these conditions. In detail, multidimensional scaling (MDS) technique is applied to recover a series of local maps for adjacent sensors in two (or three) dimensional space. The maps along the route from an anchor to another anchor are stitched together to estimate the sensors' physical locations. Then, the estimated anchor locations are compared with the anchors' physical locations for correction, and estimated sensor locations are corrected at the same time to approximate their physical locations. By iterative estimation, comparison, and correction, the method reduces sensor localization errors caused by anisotropic network topology and complex terrain, which were seldom addressed in previous research.

Topology design for free space optical networks

Abstract: In this paper, we consider the problem of designing a topology for deploying a free space optical (FSO) link based network. The problem is to create a topology with strong connectivity and short diameter with uniform degree bounds on each node. Two centralized approaches are presented. The first approach constructs a backbone network by Delaunay triangulation. The basic structure is then refined to meet the design objectives. The second approach called the closest neighbor (CN) algorithm constructs a degree constrained minimum weight spanning tree. The tree is developed into a network with good connectivity and small diameter by forming edges with the closest neighbors. We prove that the CN algorithm forms a connected network. Through simulation and analysis we also show that this approach results in high reliability and small diameter.

Mandatory human participation: a new authentication scheme for building secure systems

Abstract: Mandatory human participation (MHP) is a novel authentication scheme that asks the question "are you human?" (Instead of "who are you?"), and upon the correct answer to this question, can prove a principal to be a human being instead of a computer program. MHP helps solve old and new problems in computer security that existing security measures cannot address properly, including password (or PIN number) guessing attacks and application-level denial of service. A key component of this "are you human?" authentication process is a character morphing algorithm that transforms a character string into its graphical form in such a way that a human being won't have any problem recognizing the original string, while a computer program (e.g., an optical character recognition program), will not be able to decipher it or make a correct guess with nonnegligible probability. The basic idea of the MHP scheme is to ask an agent to recognize the string before its login attempts or transaction requests can be honored. Here a protocol is needed to send a puzzle to an agent, check if the answer supplied by the agent is correct, and most importantly make sure that the agent cannot cheat in the process. A number of system and security issues that relate to the protocol need to be addressed for the protocol to be secure, efficient, robust, and user-friendly. The MHP scheme contributes to the foundation of the computer security by faithfully implementing novel security semantics, "human," which existing cryptographic measures cannot express accurately. As many real-world security applications involve the interaction between a human and a computer, which naturally contains "human" as a part of its protocol semantics, we believe that the MHP scheme will find many new applications in the future.

Effect of TCP on self-similarity of network traffic

Abstract: It is now well known that Internet traffic exhibits self-similarity, which cannot be described by traditional Markovian models such as the Poisson process. In this work, we simulate a simple network with a full implementation of TCP-Reno. We also assume Poisson arrivals at the application layer specifically to determine whether TCP can cause self-similarity even when input traffic does not exhibit long-range dependence. Our study shows that, at some loads TCP can induce the appearance of self-similarity. In particular, when load is low and loss is rare, traffic looks Poisson. When load is high and the network is overloaded, TCP congestion control can smooth out the burstiness of the aggregate stream so that traffic at the bottleneck tends to Poisson. However, when load is intermediate and the network is prone to occasional bouts of congestion, as is typical of many networks, traffic can become self-similar. Moreover, factors such as round trip time and number of streams passing through the bottleneck can cause the network to become congested at different loads, and consequently affect the range of load over which self-similarity can be observed. The impact of one self-similar TCP stream has also been observed. In particular, our study show that if one or more streams passing through the bottleneck is self-similar and the aggregate flow does not exceed the capacity, traffic observed at the bottleneck will also be self-similar.

ATM dynamic bandwidth allocation using F-ARIMA prediction model

Abstract: Measurements of high-speed network traffic have shown that traffic data exhibits a high degree of self-similarity. Traditional traffic models such as AR and ARMA are not able to capture this long-range-dependence making them ineffective for the traffic prediction task. In this paper, we apply the fractional ARIMA (F-ARIMA) model to predict one-step-ahead traffic value at different timescales. F-ARIMA has the ability to capture both the short- and long-range dependent characteristics of the underlying data. We present a simplified adaptive prediction scheme to reduce the F-ARIMA computational complexity. The performance of the proposed F-ARIMA prediction model is tested on four different types of traffic data: MPEG and JPEG video, Ethernet and Internet. We also apply the F-ARIMA prediction model to a dynamic bandwidth allocation scheme. The results show that the performance of F-ARIMA outperforms the AR model. They also show that the prediction performance depends on the traffic nature and the timescale.

The mote connectivity protocol

Abstract: An attractive architecture for sensor networks is to have the sensing devices mounted on small computers, called motes. Motes are battery-powered, and can communicate in a wireless fashion by broadcasting messages over radio frequency. In mote networks, the connectivity of a mote u can be defined by those motes that can receive messages from u with high probability and those motes from which u can receive messages with high probability. In this paper, we describe a protocol that can be triggered by any mote in a mote network in order that each mote in the network computes its connectivity. The protocol is simple and has several energy saving features. We implemented this protocol over TinyOS and discuss the results of some execution runs of this implementation.

A fast ternary CAM design for IP networking applications

Abstract: In this paper we describe a VLSI implementation and complete circuit design of a fast ternary CAM (TCAM). TCAMs are commonly used to perform routing lookups in the backbone of IP networks and small gateways. Our TCAM is designed to have a greater capacity and speed than any commercial offering at this time. In contrast with existing TCAM approaches, our TCAM allows complete flexibility in the location where any new entry is inserted. This is achieved by a novel longest prefix match (LPM) determination circuit, whose delay increases logarithmically with the number of bits to be looked up. We have implemented our TCAM with 512 bits of prefix entry with 512 bits of destination information, allowing it to implement large address lookups as well as quality of service mechanisms. This would make our TCAM design particularly suitable for IPv6 routing lookup applications. The speed improvement of our TCAM over currently available TCAMs results from various carefully selected VLSI architectural and implementation choices. The TCAM size is 21 Mb and is broken up into a regular grid of 13x13 smaller TCAM blocks for improved speed characteristics. Routing lookup operations use a heavily pipelined approach for maximum throughput, while ensuring a lookup latency of 3 clock cycles. Individual match lines in these blocks are split into 4 sections to reduce RC delay in the lookup process. Our LPM determination circuit is implemented using an efficient wired-NOR circuit for further reduced delay. Sense amplifiers are utilized in the LPM and SRAM sections of the TCAM and are located in the center of each TCAM subblock in order to improve lookup speed. We have implemented and validated our design using state-of-the-art circuit analysis and design tools. We have also generated mask layouts of the entire TCAM design using current layout tools. The complete TCAM circuit design is approximately 18mm on a side, with a total capacity of 21Mb. Our TCAM has an ability to perform routing lookups at a line rate of 76.8Gb/s which is twice as fast as the fastest commercially available TCAM today.

Enhanced dominant pruning applied to the route discovery process of on-demand routing protocols

Abstract: Dominant pruning (DP) is a distributed connected dominating-set algorithm that can be used for reducing the impact of flooding in wireless ad hoc networks. We propose an enhanced dominant pruning (EDP) approach to be used in the route discovery process of on-demand routing protocols. To show the benefits of EDP, we integrate EDP into the ad-hoc on-demand distance vector (AODV) protocol. We present detailed simulation results showing that our approach improves standard AODV in most aspects, and that it is simple and easy to implement. Our approach is compared against AODV and OLSR, as good representatives of on-demand and proactive routing for ad-hoc wireless networks.

Evaluation of SCTP multistreaming over wireless/satellite links

Abstract: In this paper, we study the impact of multistreaming on the performance of SCTP over satellite networks. We first show that multistreaming results in higher goodput than single streams when the receiver buffer is constrained as in the case of wireless handheld devices. We then demonstrate that the multistreaming feature of SCTP results in reduced buffer requirements at the receiver in the presence of losses in the satellite network. The above advantages makes SCTP an attractive transport protocol for wireless handheld devices.

A cooperative nearest neighbours topology control algorithm for wireless ad hoc networks

Abstract: In this paper, we introduce a simple distributed algorithm that assigns appropriate individual transmission powers to devices in a wireless ad hoc network. In contrast to many other proposed algorithms, it does not depend on special hardware. It requires only local neighbourhood information and therefore avoids flooding information throughout the network. Finally, the cooperative nature of the algorithm avoids that devices cause excessive interference by using unnecessarily high transmission powers. We show by means of simulation that the topologies created by this algorithm without any global knowledge are as effective as topologies resulting from a good choice of a common transmission power (which would require global knowledge) in terms of the achievable throughput.

An architecture for flexible service discovery in OCTOPUS

Abstract: Service discovery has been drawing much attention from researchers and practitioners. The existing service discovery systems, like SLP, Jini, UPnP and Salutation, provide basic infrastructures where services can announce their presence and users can locate these services across the network. However there are several key issues which are partially solved or have not been well addressed - such as scalability, availability, dynamics and support for multiple matching mechanisms. In this paper, we propose a design for a service locating manager (SLM) system which addresses some of these issues. The SLM system adopts a dynamic hierarchical tree structure and service aggregation for scalability, availability and dynamics, and introduces multiple matching mechanisms which contain an attribute-based and a semantic matching engine. It provides a scalable, distributed, dynamic and robust solution to establish a flexible service discovery architecture. We describe our concepts, architecture and implementation, and present a performance study for our prototype.

A hybrid optical network architecture consisting of optical cross connects and optical burst switches

Abstract: Optical burst switches (OBSes) have been proposed to improve the utilization of a network of optical cross connect (OXCs). Current studies on OBS assume a network consisting of OBSes alone. While this is a reasonable assumption for evaluating a new technology, the question of how a network of OXCs can be evolved to a network of OBSes has not been studied. In this paper, we propose a hybrid architecture consisting of OBSes at the network edge and OXCs in the network core. This architecture allows carriers to gradually migrate from an OXC-based network to an OBS-based network with an improved network utilization. In addition, we use queueing analysis to study the performance of this new architecture.

Performance analysis of multihop traffic grooming in mesh WDM optical networks

Abstract: With the "bandwidth-on-demand" as a promising service provisioning model for next-generation IP over WDM optical networks, online traffic grooming emerges as a fundamental issue. This paper studies the performance analysis of the multihop online traffic grooming algorithm in mesh WDM optical networks, and develops a theoretical performance analysis model.

VirtualLength: a new packet scheduling algorithm for proportional delay differentiation

Abstract: One of the important issues in building differentiated services is how to support relative differentiated queueing delay services for packets from different classes. This paper presents a new packet scheduling algorithm, called virtual-length, to address this issue. It provides effective control over the relative average queueing delay ratio between two classes of traffic by monitoring their average arrival rates and cumulative queue lengths. The packets of different classes are forwarded according to their weighted queue lengths with respect to predefined proportional delay parameters. The simulation results show that virtualLength is capable of providing controllable and predictable services for classes with different load distributions under various load conditions. In particular, it can provide more accurate control over classes of traffic in short timescales than other packet scheduling algorithms, and comparable service in long timescales. The results also show that the performance of virtualLength is independent of the distributions of packet arrivals and sizes.

Analysis and improvement on IPSec anti-replay window protocol

Abstract: The anti-replay sliding window is used in IPSec to resist the replay attack. However, when experiencing the severe packet reordering, IPSec anti-replay sliding window can potentially drop a lot of good but late packets, thus the end-to-end performance is dramatically degraded. In this paper, we rigorously analyze the performance of IPSec anti-replay sliding window under the different reordering models and then come up with a set of robust anti-replay window protocols. The performance and efficiency of each protocol are compared through the simulation. Also we argue that by deploying our new proposal, it is possible to dramatically reduce the overhead of IPSec and save a lot of bandwidth.

An efficient scheduling discipline for packet switching networks using earliest deadline first round robin

Abstract: In this paper we propose a frame-oriented scheduling discipline, EDF-RR (earliest-deadline-first round-robin), for OQ (output-queued) switch architecture and data traffic consisting of fixed-length cells. Bandwidth reservation for an active session is performed by holding a number of cell slots for the session in frames. Each cell that is going to be transferred in a frame is assigned a virtual release time and a virtual deadline according to the bandwidth reservation scheme. The transmitting order of the cells in frames is thus determined by nonpreemptive nonidling EDF algorithm so that cells of a backlogged session in frames are distributed as uniformly as possible. Through the analysis applying real-time scheduling theory and network calculus as well as network simulation, EDF-RR takes the advantage of low computational complexity, and possesses tight delay bounds and lenient buffer requirements. The proposed scheduling discipline is appropriate for distributed real-time systems as we show that sessions can be configured based on message traffic models and deadline requirements. Also, a modified version of EDF-RR, called EDF-DRR, can be applied as traffic regulator when jitter requirements exist among active sessions.

Link layer support for streaming MPEG video over wireless links

Abstract: Streaming video as a form of media is becoming increasingly popular on the Internet. Real-time media such as video requires delay constraints from the network to ensure good quality at the receiver. While watching a video stream on his portable device connected to the Internet through the last-hop wireless link, the mobile user of tomorrow will expect a good experience. But, the time-varying nature of the wireless link can cause video frames to be dropped/delayed, affecting the quality of video at the receiver. In this paper, we propose a link layer approach to improve the quality of MPEG video streaming over a wireless link. We use Bluetooth as the wireless technology on which to test our scheme. Our results show that the quality of streaming video can be substantially improved with our scheme, particularly in bad channel conditions.

Long-range oversea wireless network using 2.4 GHz wireless LAN installation and performance

Abstract: High-quality 2.4 GHz wireless LAN over long-range oversea paths was installed using a space diversity technique. The installed network consists of five wireless links, including a long-range 11.3 km link. To lower the adverse affect of fluctuation in the tidal level, two wireless LAN devices with different antenna heights were installed at one side of the longest link. The antenna heights were suitably determined on the basis of link profile and gained data at the deployment of the equipment. The measured performance indicates that the link with space diversity achieves 100% operating rate in a measured period of time, while the link without space diversity achieves an approximately 90% operating rate in the same time. This method effectively improves the quality of conventional wireless LAN systems.

Modelling TCP Reno with spurious timeouts in wireless mobile environments

Abstract: TCP has been found to perform poorly in the presence of spurious timeouts (ST) caused by delay spikes which are especially more frequent in today's wireless mobile networks than in traditional wired network. Because STs are generally considered to represent a transient state in wired networks, previous research did not consider the effects of ST on the steady state performance of TCP. In this paper, we propose an analytical model for the sending rate and throughput of TCP Reno as a function of packet error rate and characteristics of spurious timeouts. The proposed model has been validated against simulation results and has been found to be more accurate than previous models in the presence of spurious timeouts.

A pay word-based micropayment protocol supporting multiple payments

Abstract: In this paper, we propose an efficient micropayment protocol by improving PayWord, which is one of the representative micropayment protocols. In the original PayWord system, it was designed for a customer who generates paywords by performing hash chain operation for payments to an only designated vendor. In other words, the customer has to create new paywords in order to establish commercial transactions with different vendors on the Internet. To supplement this drawback, our proposed scheme provides a useful method to do business with multiple vendors for a customer with only one hash chain operation. In our proposed protocol, a broker creates a new series of hash chain values along with a certificate for the certificate request of a customer. This certificate is signed by the broker to give authority enabling the customer to make paywords. Our proposed scheme provides an efficient means for the customer to do business with multiple vendors.

VoIP network failure detection and user notification

Abstract: The impact of network failures can be minimized if users are promptly notified by appropriately designed applications. Specifically, for voice-over-IP (VoIP) networks, an RTP/RTCP-based detection method can be used to rapidly distinguish between network congestion and network failures. Users and network managers can exploit this information in various ways, such as rapid network recovery or seeking alternatives at the application layer. In this paper, we present the main ideas behind these proposals, some analytical/simulation results, insights from a Linux-based implementation and experimental results.