Haci Ali Mantar

A scalable model for interbandwidth broker resource reservation and provisioning

As the Internet evolves into global communication and commercial infrastructure, the need for quality-of-services (QoSs) in the Internet becomes more and more important. With a bandwidth broker (BB) support in each administrative domain, differentiated services (Diffserv) is seen as a key technology for achieving QoS guarantees in a scalable, efficient, and deployable manner in the Internet. In this paper, we present a scalable model for inter-BB resource reservation and provisioning. Our BB uses centralized network state maintenance and pipe-based intradomain resource management schemes that significantly reduce admission control time and minimize scalability problems present in prior research. For inter-BB communication, we design and implement a BB resource reservation and provisioning protocol (BBRP). BBRP performs destination-based aggregated resource reservation based on bilateral service level agreements (SLAs) between peer-BBs. BBRP significantly reduces the BB and border routers state scalability problem by maintaining reservation state based only on destination region. It minimizes inter-BB signaling scalability by using aggregated type resource reservation and provisioning. Both analytical and experimental results verify the BBRP achievements.

Inter-domain LSP setup using bandwidth management points

Bandwidth management points (BMP) are a necessity to manage the intra and inter-domain resources in the Internet. We propose a way to setup inter-domain label switched path (LSP) with the help of a BMP in a multiprotocol label switching (MPLS) over the Diffserv network. We use extended simple inter-domain bandwidth broker signalling protocol (SIBBS) to distribute the labels inter-domain. We also use a BMP to interact with the MPLS to setup the intra-domain LSP and to provision the intra-domain traffic. With the help of a BMP, we show how end-to-end quality of service (QoS) can be achieved.

Inter-domain QoS routing on Diffserv networks: a region-based approach

Quality of Service (QoS) routing is inherently a difficult problem. Inter-domain QoS routing is even harder, because it involves entities residing in distinct administrative domains. There are two problems that need to be solved in inter-domain QoS routing: topology distribution in a scalable fashion and finding paths that satisfy QoS constraints and provide connectivity. In this paper we present region-based, link-state, source-specified, inter-domain QoS routing architecture that addresses these questions. Our architecture is scalable and does not suffer from the problems caused by hierarchical routing. Analysis results show that the average region size and the average shortest path length (SPL) are inversely proportional and scalability of the approach increases as the region size decreases. Gain from the scalability is far more than the loss from the average SPL, especially with larger topologies.

An implementation study of a dynamic inter-domain bandwidth management platform in DiffServ networks

In this paper, we assess the scalability and efficiency of a scalable bandwidth management point (BMP) for guaranteed quality-of-service in DiffServ networks. Our BMP uses centralized network state maintenance and pipe-based intra-domain resource management schemes that significantly reduce the admission control time and minimize the scalability problems present in prior research. We have designed, developed and implemented an enhanced Simple Inter-Domain Bandwidth Broker Signaling (SIBBS) protocol for inter-domain communication. The BMP uses dynamic inter-domain pipes to handle inter-domain provisioning and dynamic provisioning schemes to increase signaling scalability. To assess our BMP implementation in terms of signaling scalability and effective resource utilization, we conducted experiments on a test-bed demonstrating how a BMP substantially increases resource utilization and scalability while requiring minimum changes in the underlying infrastructure.

A cross layer QoS algorithm to improve wireless link throughput and voice quality over multi-rate WLANs

Voice over IP (VoIP) applications over wireless local area networks (WLANs) has become increasingly popular in recent years. VoIP is sensitive to delay and variations in packet inter-arrival times and require a steady and a dependable stream of packets to provide reasonable voice quality. Therefore, it is important to analyze the performance of the IEEE 802.11 protocol accurately by considering the effects of channel conditions, frame size, number of nodes and collision probability. In this paper, we present an analysis of link layer behavior for ideal and error prone channels by classifying the packet loss caused either by congestion or wireless medium errors and propose an efficient, adaptive, codec and frame size modification algorithm for the optimization of maximum throughput and voice quality on multirate WLANs.

A Beacon-Based Collision-Free Channel Access Scheme for IEEE 802.11 WLANs

In IEEE 802.11 based WLAN standard, distributed coordination function is the fundamental medium access control (MAC) technique. It employs a CSMA/CA with random binary exponential backoff algorithm and provides contention-based distributed channel access for stations to share the wireless medium. However, performance of this mechanism drops dramatically due to random structure of the backoff process, high collision probability and frame errors. That is why development of an efficient MAC protocol, providing both high throughput for data traffic and quality of service (QoS) support for real-time applications, has become a major focus in WLAN research. In this paper, we propose an adaptive beacon-based collision-free MAC adaptation. The proposed scheme makes use of beacon frames sent periodically by access point, lets stations enter the collision-free state and reduces the number of idle slots regardless of the number of stations and their traffic load (saturated or unsaturated) on the medium. Simulation results indicate that the proposed scheme dramatically enhances the overall throughput and supports QoS by reducing the delay, delay variation and dropping probability of frames.

A novel energy-efficient QoS-aware handover scheme over IEEE 802.11 WLANs

Energy efficiency in wireless networks is one of the major issues for mobile devices since they rely on their batteries. In this context, the wireless network interface card (WNIC) has to be taken into account carefully as it consumes a significant portion of the overall system energy. In this paper, we aim to reduce the energy consumption of mobile devices in wireless networks by performing specific solutions, such as reducing the overhead of the periodic background channel scanning, keeping mobile stations in the doze state as much as possible, proposing a smart selective channel scanning during the handover preparation phase and associating with an access point (AP) that is expected to consume the least energy among all APs. Stations performing the proposed scheme can fairly coexist with the other stations in the network. In the proposed scheme, each station makes use of its local information and the information provided by the IEEE 802.21 information server (IS). The proposed scheme can be easily implemented without any changes on the current IEEE 802.11 standard. Performance of the proposed scheme was investigated by numerical analyses and extensive simulations. The results illustrate that the proposed scheme is very efficient and reduces the energy consumptions of mobile stations under a wide range of contention and signal strength levels.

A scalable QoS routing model for diffserv over MPLS networks

Abstract In this paper, we present a new Quality of Service (QoS) routing model for Differentiated Services (Diffserv) over Multiprotocol Label Switching (MPLS) networks. We use a pre-established multi-path model in which several MPLS label switching paths (LSPs) are established between each ingress-egress router pair in advance. Ingress routers perform per-request admission control and bulk-type resource reservation based on the resource availability on the associated LSPs. We use a utilization-based dynamic load balancing scheme to increase resource utilization across LSPs. The proposed model increases signaling and state scalability in the network core. It also provides hard QoS guarantees and minimizes admission control time. The experimental results verify the achievements of our model under various network topologies and traffic conditions.

Exploiting the channel using uninterrupted collision-free MAC adaptation over IEEE 802.11 WLANs

IEEE 802.11 wireless local area networks WLANs have reached an important stage and become a common technology for wireless access due to its low cost, ease of deployment, and mobility support. In parallel with the extensive growth of WLANs, the development of an efficient medium access control protocol that provides both high throughput performance for data traffic and quality of service support for real-time applications has become a major focus in WLAN research. The IEEE 802.11 Distributed Coordination Functions DCF/EDCA provide contention-based distributed channel access mechanisms for stations to share the wireless medium. However, performance of these mechanisms may drop dramatically because of high collision probabilities as the number of active stations increases. In this paper, we propose an adaptive collision-free MAC adaptation. The proposed scheme prevents collisions and allows stations to enter the collision-free state regardless of the traffic load saturated or unsaturated and the number of stations on the medium. Simulation results show that the proposed scheme dramatically enhances the overall throughput and supports quality of service for real-time services over 802.11-based WLANs. Copyright

Minimizing Communication Interruptions Using Smart Proactive Channel Scanning Over IEEE 802.11 WLANs

Wireless connectivity is becoming pervasive in our lives as wireless networks and mobile devices have been undergoing a magnificent evolution. In this context, consumers demand to access to the wireless communication services anytime and anywhere with high performance. IEEE 802.11 wireless local area networks (WLANs) have a direct impact on this widespread use. Nevertheless, as any standard procedure, WLAN also has its own drawbacks. In IEEE 802.11 wireless networks, periodic channel scanning is an essential procedure to discover available access points in the vicinity and to achieve fast handover. However, this procedure leads to unnecessary overhead in wireless networks and also interrupts ongoing communications of stations. In this paper, we propose a smart proactive channel scanning scheme that allows stations to achieve fast handover with minimized communication interruptions. In the proposed scheme, periodic channel scanning is scheduled based on adaptive channel scanning intervals and activated after a frame transmission only if the mobile station is on move or the received signal strength indicator value drops below a pre-specified threshold. The proposed scheme is a client-side software solution that any station can benefit from, without changing the standard in any existing IEEE 802.11 environment. Analytical and simulation results show that the proposed channel scanning scheme reduces the channel scanning overhead dramatically, minimizes communication interruptions and improves the overall throughput of stations.