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University: Queen Mary, University of London
Professor: Dr Chris Philips
Department: Department of Electronic Engineering

The Department uses OPNET for postgraduate research and within its undergraduate teaching programme. This provides our students with an opportunity to develop valuable engineering skills in simulation and analysis and to gain proficiency in this leading toolset.

Research: Postgraduate Projects

OPNET Modeler is used by many of our Postgraduate research students for exploring novel networking concepts. Here are a number of ongoing and recently completed academic research projects built upon the OPNET toolset:

• Optical Burst Switching
• QoS Provisioning for Mobile Ad Hoc Networks
• CDMA Bus Lane for QoS Support in MANET
• Intelligent Resource Management for Next Generation Optical Networks
• Inter-provider Dynamic VPNs
• QoS based, IEEE 802.21 Compatible Vertical Handoff
• Intelligent Radio Access Network (RAN) Selection in Heterogeneous Wireless Networks Environment
• Secure Group Working
• Dynamic Tree Switching for IP Networks
• Simulation Acceleration for Packet Buffers with non FIFO Scheduler
  

More information regarding these topics is given below in the Research Projects section.

Teaching: Undergraduate Study

Undergraduates wishing to use the OPNET Modeler package should refer to the Network Modelling and Performance course (ELEM005). Additionally, OPNET has been successfully used for a number of years as a simulation platform for various BEng and MEng final year projects. For example, OPNET has been used to examine various enhancements to the Transmission Control Protocol (TCP), IP routing, QoS-aware mobile ad hoc networking, wavelength-constrained optical networks and new scheduling mechanisms.

Contacts

• Dr Chris Phillips (opnet for research)
• Dr John Schormans (opnet for teaching - ELEM005)

Research Projects

Intelligent Resource Management for Next Generation Optical Networks

All-optical D-WDM networking is a promising technology for next generation optical networks (NGON). One of the desirable features of NGON is fast and automatic service provisioning. Traditionally, global-optimum search schemes like integer linear programming (ILP) are used to find an optimal solution. However such schemes become unusable for connection provisioning in dynamic environment. To perform dynamic provisioning, different heuristic and stochastic techniques are used. Unlike global optimal search schemes, these dynamic provisioning schemes place connections over the network according to the information available at that moment. Constant dynamic provisioning can lead the network configuration away from optimal/near-optimal configuration.

An intelligent hybrid architecture has been proposed in this research for resource management using particle swarm optimization. The architecture employs pro-active resource management for subsequent connection requests using traffic prediction information so that minimal re-deployments of lightpaths are required to bring the network back to an optimal / near-optimal configuration. Currently, OPNET is being used to implement the PSO algorithm for dynamic routing and wavelength assignment in WDM (wavelength division multiplexed) networks, in order to investigate different network performance measures like connection set up time, blocking probability, effect of different algorithm parameters and so forth.

Papers published:

Hassan, A., Phillips, C., "Static Routing and Wavelength Assignment Inspired by Particle Swarm Optimization", Information and Communication Technologies: From Theory to Applications, 2008. ICTTA 2008. 3rd International Conference on, 7-11 April 2008 Page(s):1 - 6.

A. Hassan, C. Phillips, “Dynamic Routing and Wavelength Assignment using Hybrid Particle Swarm Optimization for WDM Networks”, EPSRC PGNet2007, June 2007.

Ali Hassan and Chris Phillips, “Particle Swarm Optimization Based DRWA for Wavelength Continuous WDM Optical Networks using a Novel Fitness Function", Springer, Artificial Intelligence Review, Special Issue on Artificial Intelligence & Pervasive Computing, accepted for publication 2009.

Optical Burst Switching

Optical Burst Switching (OBS) is one of the viable candidates for the next generation optical backbone, providing a buffer-less transportation medium. The main feature of OBS is the separated transmission of the burst data and the corresponding control information (called Burst Head Packet (BHP)). Each burst is preceded by its own BHP, which travels slightly ahead, configuring the switches and reserving a wavelength path for the upcoming burst. When the BHP is processed, it undergoes optical-electro-optical (OEO) conversion at each hop, whilst the data burst is transparently switched in all-optical manner. There is still scope for further exploration in the OBS realm, mainly in delay reduction, burst loss reduction, and QoS provisioning. This research proposes a novel resource reservation mechanism that can operate with existing Optical Burst Switching (OBS) architectures, providing an efficient infrastructure for multi-service “bandwidth on demand” transport.

Papers published:

Huifang Kong and Chris Phillips, “Improved Dynamic Lightpath Provisioning for Large Wavelength-Division Multiplexed Backbones", IEEE Journal of Lightwave Technology, Vol 25 No 7, July 2007, Page(s):1693 – 1701.

Huifang Kong and Chris Phillips, “Pre-booking for Reduced Reservation Overhead in Long Haul Wavelength-Division Multiplexed (WDM) Networks”, IEE Proc. Communications Vol. 153, No. 5, October 2006, pp. 779-786.

Huifang Kong, “Pro-active Reservation Mechanisms for Next Generation Optical Networks”, PhD thesis, University of London, UK 2006.

Huifang Kong and Chris Phillips, “Pre-booking Reservation Mechanism for Next Generation Optical Networks”, IEEE Journal of Selected Topics in Quantum Electronics, Vol. 12 No. 4, July/August 2006.

Huifang Kong and Chris Phillips, “Prediction and Pre-booking for Guaranteed Service Provisioning in Future Wavelength-Division Multiplexing (WDM) Networks”, 19th Internet Teletraffic Congress (ITC19), China, 2005.

Huifang Kong and Chris Phillips, “A Fast Two-Stage Routing and Wavelength Assignment (RWA) Mechanism for Optimal Max-RWA Problem in Wavelength Constrained WDM Networks”, Proceedings of 10th European Conference on Networks & Optical Communications (NOC 2005), University College London (UCL), London, UK, July, 2005.

Huifang Kong and Chris Phillips, “Pre-booking for Latency-Sensitive Service Provisioning in Future Long Haul Wavelength-Division Multiplexing (WDM) Networks with Dynamic Lightpath”, Proceedings of 10th European Conference on Networks & Optical Communications (NOC 2005), University College London (UCL), London, UK, July, 2005.

Huifang Kong and Chris Phillips, “A Two-Stage Routing and Wavelength Assignment Mechanism for Paths Calculations in Lambda Switched GMPLS Networks”, Proceeding of IV Workshop in MPLS/GMPLS networks, Girona, Spain, April 2005.

Huifang Kong and Chris Phillips, “Hybrid Resource Reservation Mechanism for Optical Burst Switched Networks”, Proceeding of SECOND INTERNATIONAL WORKING CONFERENCE, HET-NETs ’04, Ilkley, West Yorkshire, U.K, July 2004.

Huifang Kong and Chris Phillips, “Intelligent Pre-Booking for Optical Burst Switching”, Proceeding of the International Network Optimization Conference – INOC '2003, Paris (Evry), France, October 2003.

Huifang Kong and Chris Phillips, “Pre-booking for Optical Burst Switching”, Proceedings of the London Communications Symposium 2003 (LCS), London, UK, September 2003.

Resilient Overlay for Inter-AS Communication

This research is developing a Resilient Overlay for Mission Critical Applications (ROMCA); a novel operator-independent overlay architecture that provides a resilient and reliable service across wide-area networks. One feature of ROMCA is that its overlay topology can be altered according to the underlying network conditions. Moreover, resilience is achieved by combining centralized topology construction control and distributed dynamic mapping of paths onto the overlay topology according to network conditions. ROMCA can mitigate the shortcomings of the Internet network infrastructure and provide low recovery times in the event of network failure(s). ROMCA consists of an Overlay Directory Service (ODS) and Overlay Gateways (OG) chosen from different ASes. The ODS is a centralized component with the responsibility for service access and managing the overlay topology, including not only the acceptance and removal of overlay nodes, but also selection of the OG adjacencies. Overlay Gateways (OGs) maintain a series of point-to-point “links” between adjacent OGs that are monitored to determine their availability and other performance metrics. These nodes are in turn arranged into an inter- Autonomous System (AS) meshed network.

Work is currently underway to model this architecture within Opnet, capitalising on it's support for BGP.

Papers published:

Xian Zhang and Chris Phillips, “Network Operator Independent Resilient Overlay for Mission Critical Applications (ROMCA) ", 4th International Conference on Communications and Networking in China, to be published in August 2009.

QoS Provisioning for Mobile Ad Hoc Networks

Future mobile Ad hoc networks (MANETs) are expected to be based on all-IP architecture and be capable of carrying multitude real-time multimedia applications such as voice, video and data. It is very necessary for MANETs to have an efficient routing and quality of service (QoS) mechanism to support diverse applications. Providing multipath routing is beneficial to avoid traffic congestion and frequent breaks in communication due to mobility in MANETs. Differentiated Services (DiffServ), which have simple, efficient and scalable characteristics, can be used to classify network traffic into different priority levels and apply priority scheduling and queuing management mechanisms to obtain QoS guarantees. We propose a novel node-disjoint Multipath QoS Routing protocol for DiffServ (MQRD). It makes DiffServ readily over a node-disjoint multipath routing protocol. OPNET Modeler is used to develop and simulate Node-Disjoint Multipath Routing Protocol (NDMR) and MQRD. Simulation results show that MQRD achieves better performance in terms of packet delivery ratio and average delay.

Papers published:

L. Liu and L. Cuthbert, “QoS in Node-disjoint Routing for Ad Hoc networks”, in proceedings of Wireless Communications, Networking and Mobile Computing (WiCom 2007), Shanghai, China, September, 2007.

L. Liu and L. Cuthbert, “QoS in Node-disjoint Routing for Ad Hoc networks”, in proceedings of 4th ACM International Workshop on Performance Evaluation of Wireless Ad Hoc, Sensor, and Ubiquitous Networks (4th ACM PE-WASUN 2007), Chania, Crete Island, Greece. October, 2007.

L. Liu and L. Cuthbert, “QoS in Node-disjoint Routing for Ad Hoc networks”, International Journal of Communications, Network and System Sciences, Vol.1, No.1, February, 2008.

L. Liu and L. Cuthbert, “A novel QoS in Node-disjoint Routing for Ad Hoc networks”, in proceedings of 13th ICC IEEE International Workshop on Computer-Aided Modeling, Analysis and Design of Communication Links and Networks (13th ICC CAMAD 2008), Beijing, China, May, 2008.

Xuefei Li and Laurie Cuthbert, "Distributed Cross-Layer QoS Provisioning in Mobile Ad Hoc Networks", ITS Telecommunications Proceedings, 2006 6th International Conference on, June 2006 Page(s):706 - 709.

Xuefei Li and Laurie Cuthbert, "Node-Disjoint Multipath Routing and Distributed Cross-Layer QoS Guarantees in Mobile Ad hoc Networks", Software Engineering, Artificial Intelligence, Networking, and Parallel/Distributed Computing, 2006. SNPD 2006. Seventh ACIS International Conference on, 19-20 June 2006 Page(s):243 - 248.

Xuefei Li and Laurie Cuthbert, "Multipath QoS routing of supporting DiffServ in mobile ad hoc networks", Software Engineering, Artificial Intelligence, Networking and Parallel/Distributed Computing, 2005 and First ACIS International Workshop on Self-Assembling Wireless Networks. SNPD/SAWN 2005. Sixth International Conference on, 23-25 May 2005 Page(s):308 - 313.

Xuefei Li and Laurie Cuthbert, "DiffServ over Multipath Routing: QoS Provisioning for Mobile Ad hoc Networks", 19th Internet Teletraffic Congress (ITC19), China, 2005.

Xuefei Li and Laurie Cuthbert, "Stable node-disjoint multipath routing with low overhead in mobile ad hoc networks", Modeling, Analysis, and Simulation of Computer and Telecommunications Systems, 2004. (MASCOTS 2004). Proceedings. The IEEE Computer Society's 12th Annual International Symposium on, 4-8 Oct. 2004 Page(s):184 - 191.

CDMA Bus Lane for QoS Support in MANET

This project focuses on a mobile ad hoc environment. As part of this research, attention is being given to the enhancement of ad hoc protocols for the support of QoS. In the initial stages of this project an implementation of the ad hoc On-demand Distance Vector (AODV) routing protocol is being developed within OPNET. AODV has received the most attention of all the ad hoc routing protocols of late and its importance in this area has made it a prime candidate for enhancement. Following validation of the basic model a number of novel enhancements have been considered for QoS support. This work has led to the development of a novel protocol called “CDMA Bus Lane” to solve the QoS routing in ad hoc networks. The code allocation scheme has been simulated using OPNET to analyze the performance of this new protocol.

Papers published:

Lin Xiao and Eliane Bodanese, "QoS Routing for Real-time Applications in CDMA Based Ad Hoc Networks" Mobile Adhoc and Sensor Systems (MASS), 2006 IEEE International Conference on, Oct. 2006 Page(s):206 - 215.

Lin Xiao and Eliane Bodanese, "CDMA Bus Lane: Build Constant Routes for Real-time Traffic in Ad Hoc Networks", Communications, 2006. APCC '06. Asia-Pacific Conference on, Aug. 2006 Page(s):1 - 5.

Lin Xiao and Eliane Bodanese, "A Novel Bus Lane Scheme for QoS Routing in Mobile Ad Hoc Networks", International Workshop on Wireless Ad-hoc Networks (IWWAN2005), London UK, May 2005.

Lin Xiao and Eliane Bodanese, “CDMA Bus Lane: a novel QoS solution for real-time traffic in ad hoc networks”, 19th Internet Teletraffic Congress (ITC19), China, 2005.

Inter-provider Dynamic VPNs

This research proposes a scheme for inter-provider Virtual Private Networks (VPNs) employing Dynamic VPN Manager (DVM) entities. The proposed architecture is flexible and supports dynamic VPNs via on-demand VPN management and service resource allocation. The DVM is employed to interact with the MPLS connection management control plane and the Border Gateway Protocol (BGP) routing/reachability layer to build up and manage the dynamic MPLS/BGP VPN across Autonomous System (AS) domains. In the network, it is possible to provide QoS guarantee among ASs, due to negotiation among the DVMs, before the inter-AS routing decision is made. The route is built based on the result of the negotiation. At the same time the architecture is able to provide dynamic failure recovery both inside AS and inter-AS. In the latter case, the BGP edge routers can act as proxy ingress points to the adjacent domains and may have pre-established backup LSPs that are AS diverse. In the event of a failure, the egress BGP router can perform path switch-over, though this may isolate small clusters of the VPN community within the affected AS. Additionally, with the DVM concept, it is easy to select optimal route for multicast because DVMs can build multicast trees based on complete local network information, and limited inter-AS information piggybacked on BGP messages.

We believe that the proposed architecture is more flexible than current inter-AS VPN schemes in that it provides a suitable framework for automated VPN management, together with the ability for operators to integrate VPN management with value-added service resources such as processor “farms”, archival systems and so forth. This dynamic VPN architecture is being developed within OPNET using C++.

Papers published:

Gao, Yiran, Phillips, Chris, He, Liwen, "A GA Based Real-Time Resource Scheduling Algorithm", Information and Communication Technologies: From Theory to Applications, 2008. ICTTA 2008. 3rd International Conference on, 7-11 April 2008 Page(s):1 - 6.

Yiran Gao, Chris Phillips “Inter-Provider Dynamic VPNs”, WGN5: 5th Workshop in G/MPLS networks, Girona, Spain March 2006.

Yiran Gao, Chris Phillips “Inter-Provider Dynamic VPNs”, PGNeT 2005, Liverpool, June 2005

QoS based, IEEE 802.21 Compatible Vertical Handoff

This research aims to optimise the vertical handoff between WLAN (802.11e) and WiMAX (IEEE 802.16). The handoff initiation and decision making are based on QoS criteria. The nodes' model and signalling procedure are designed to be compatible with the IEEE 802.21 and provides Media Independent Handoff (MIH) services.

The intention of integrating WLAN and WiMAX is to utilise the strengths of both types of network whilst avoiding their individual shortcomings. WLAN has low deployment cost and provides a high data rate (more accurately, lower cost per bit of data). In contrast to this, it lacks support for mobility, especially high speed mobility due to its small coverage. Meanwhile, WiMAX achieves universal mobility support by IEEE 802.16e, although it has a higher deployment cost and can support only a limited number of users under a relatively large coverage area. Thus, an integrated system of WLAN and WiMAX provides flexibility for a mobile station to select suitable radio access network according to its condition. Vertical handoff (handoff between different types of networks) is required to support such an integrated system

QoS discrepancy is an important issue for vertical handoff between WLAN and WiMAX. IEEE 802.11 is originally designed for best effort data traffic and does not provide any QoS support. IEEE 802.11e is established to provide QoS differentiated service by introducing four access categories in its enhanced distributed coordinate function (EDCF). However, this does not guarantee QoS for the applications. Conversely, WiMAX provides a QoS mechanism supporting four traffic classes with QoS guarantee.

This research mainly focuses on exploiting these QoS discrepancies to optimise the handoff initiation and decision making, in order to provide the users better QoS support and maximize the system utilization while minimize the cost for users and network operators. A packet level simulation model is built using OPNET, which includes bespoke WLAN model, WiMAX model and WLAN-WiMAX dual-mode station model. The simulation results show that the network throughput has been improved by using QoS based VHO parameters while acceptable QoS of the applications are maintained.

Papers published:

Lina Men, Eliane L. Bodanese, "Investigating efficient triggers for vertical handoff", NAEC 2008, September, 2008 in Riva Del Garda , Italy.

Intelligent Radio Access Network (RAN) Selection in Heterogeneous Wireless Networks Environment

The heterogeneity characteristics of various wireless technologies means that it is necessary to develop some methods to evaluate the performance of different wireless networks. The evaluation methods are call level based and OPNET is used to perform packet level simulations for validation. In order to perform an intelligent RAN selection, a signalling framework has to be developed to integrate different wireless networks together. OPNET is used to construct this framework and maintain the connectivity between the core and different RANs. OPNET is also used to perform simulations for RAN selection decision-making. A variety of services are considered within the simulations and users start their services gradually.

Papers published:

Weizhi Luo and Eliane Bodanese, "Optimizing Access in an Integrated Wireless Network Environment", SPECTS 2008, Edinburgh, June 16-18, 2008.

Secure Group Working

This research examines enhancements to existing security solutions for distributed communication networks, by novel ways of combining several related features: secure communication, distributed firewalls, dynamic Closed User Groups (CUGs) and intelligence used within the system. A distributed firewall architecture is combined with a secure communication mechanism, where one or more administration facilities control many concurrent distributed firewall instantiations localized to individual host terminals, such as a personal computer or mobile communications device. Each host instantiation enables its client user(s) to be members of one or more CUGs for the purpose of business transactions. All hosts then become part of a large distributed firewall providing all the features offered by traditional firewall choke point with improved security and better scalability, and avoiding topological restrictions. To prevent the data being inadvertently passed to the wrong groups, either within or without an organisation, the distributed firewall is augmented by a mechanism of certification that governs the firewall behaviour.

A hybrid protocol combining aspects of hierarchical and peer-to-peer communication has been implemented, as well as Administrator and Client nodes. The protocol operates satisfactorily regarding creation and removal of CUGs and distribution of information related to the updates of the CUG status, and is enhanced with features such as ARQ and processing delay on the queues and network management mechanisms of all the nodes. Nodes representing legitimate and malicious users have been implemented, as well as mechanisms that trigger actions and reactions among them, all as an attempt to simulate security breaches and response actions.

OPNET has been used to construct and simulate the model. The most commonly used kernel packages that facilitated building of model, are (but not limited to): programming, packet, interrupt, ici. The OPNET’s ODB, as well as functionalities for collecting the statistics, such as analysis and probe models, running of batch of simulations, etc. are being thoroughly used.

Papers published:

Djordjevic I.: Architecture for Dynamic and Secure Group Working, PhD Thesis, University of London, London, UK, June 2004

Djordjevic, I.; Phillips, C.; Dimitrakos, T.; "An architecture for dynamic security perimeters of virtual collaborative networks", Network Operations and Management Symposium, 2004. NOMS 2004. IEEE/IFIP Volume 1, 23-23 April 2004 Page(s):249 - 262 Vol.

Djordjevic I., Phillips C.: Architecture for Secure Work of Dynamic Distributed Groups. Proc of 1st IEEE Consumer Communication and Networking Conference (CCNC'04), Las Vegas, Nevada, USA, January 2004.

Dimitrakos T., Djordjevic I., Milosevic Z., Jøsang A., Phillips C.: Contract Performance Assessment for Secure and Dynamic Virtual Collaborations. Proc of 7th IEEE International Enterprise Distributed Object Computing Conference (EDOC'03), Brisbane, Australia, September 2003.

Dynamic Tree Switching for IP Networks

The main objective of this research is to produce a novel data-link forwarding mechanism complementing existing routing protocols for use within an Autonomous System (AS). More precisely, using an appropriate signalling mechanism, the forwarding tables at all of the nodes within the AS will be configured such that there exists a single layer-2 forwarding path tree from all nodes to a given destination. The path to all destinations is thus realised as an overlay of these multi-point to point trees. In addition, separate trees may be provided for different service classes, exploiting appropriate scheduling, and potentially dissimilar pathways, based on service delay constraints. To date a new scheme and protocol called DAM (Dynamically Adaptive Multipoint to Point) has been designed to address these issues.

Papers published:

Constantinos Neophytou: Dynamic Tree Switching for MPLS Networks, PhD Thesis, University of London, London, UK, 2007

Constantinos Neophytou and Chris Phillips, “Self-Healing Multipoint-to-Point Label Switched Paths”, IEEE International Conference on Information & Communication Technologies: from Theory to Applications - ICTTA’06, Syria, 2006.

Constantinos Neophytou and Chris Phillips, “A Scheme for the Dynamic Formation of Robust Multipoint to Point LSPs” IEEE CCNC, Las Vegas, Nevada, January 2004

Constantinos Neophytou and Chris Phillips, “Dynamically Adaptive Mulitipoint to Point LSPs”, Proceedings of the London Communications Symposium, London, September 2003

Simulation Acceleration for Packet Buffers with non FIFO Scheduler

The research is about accelerating simulation time. The conventional method of simulating network, i.e. packet-by-packet, always consumes many hours and often days of ‘real’ time just to simulate a few hours of ‘simulation’ time. Faster analysis feedback for rare events probability (i.e. buffer overflows) is expected. The technique proposed in this research is called Enhanced Traffic Aggregation (E_TA) that has Power-law ON/OFF traffic to represent the self-similar and long-range dependence (LRD) characteristics of packet-switched network inputs i.e. internet, FTP, telnet and etc. The algorithms of Traffic Aggregation (TA) for Power law Traffic is used in E_TA. However the source structure of E_TA model does not generate packets but instead instantaneous batch of excess-rate packet (ER batch). A simulation event in E_TA is defined when there is a change from ON state to OFF and vice versa. Theoretically less simulation events mean less execution time. All simulations in this research which has been published in [1, 2] used OPNET 8.1. This acceleration simulation model allowed more than one priority level; high priority (i.e. VoIP) and low priority (i.e. ftp, emails). The high priority traffic is modelled using the simple-source process model where the mean packet size is fixed. The low priority traffic is modelled using a user defined Power law ON/OFF process model. A user-defined scheduler (modified from acp_FIFO queue) is used as the non FIFO scheduler. The distribution probability of the waiting time of the low priority is determined prior to the execution of simulation and stored in the PDF editor. The outcome of this distribution is used to calculate the new service time of each ER batch in the E_TA model as the accelerated simulation is executed.

Papers published:

Sharifah H.S. Ariffin, John A. Schormans, “Accelerated Simulation Method Involving Markovian And Self-Similar Traffic Sources With Non-FIFO Scheduler”, UKSIM04, St. Catherine’s College, Oxford, March 2004

Sharifah H.S. Ariffin, John A. Schormans, “Efficient Accelerated Simulation Technique for Packet Switched Networks: A Buffer with Two Priority Inputs”, IEEE International Conference on Communication, ICC04, Paris, June 2004

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