Analysis of adaptive algorithms for an integrated communication network

Techniques were examined that trade communication bandwidth for decreased transmission delays. When the network is lightly used, these schemes attempt to use additional network resources to decrease communication delays. As the network utilization rises, the schemes degrade gracefully, still providing service but with minimal use of the network. Because the schemes use a combination of circuit and packet switching, they should respond to variations in the types and amounts of network traffic. Also, a combination of circuit and packet switching to support the widely varying traffic demands imposed on an integrated network was investigated. The packet switched component is best suited to bursty traffic where some delays in delivery are acceptable. The circuit switched component is reserved for traffic that must meet real time constraints. Selected packet routing algorithms that might be used in an integrated network were simulated. An integrated traffic places widely varying workload demands on a network. Adaptive algorithms were identified, ones that respond to both the transient and evolutionary changes that arise in integrated networks. A new algorithm was developed, hybrid weighted routing, that adapts to workload changes

Improved learning automata applied to routing in multi-service networks

Multi-service communications networks are generally designed, provisioned and configured, based on source-destination user demands expected to occur over a recurring time period. However due to network users' actions being non-deterministic, actual user demands will vary from those expected, potentially causing some network resources to be under- provisioned, with others possibly over-provisioned. As actual user demands vary over the recurring time period from those expected, so the status of the various shared network resources may also vary. This high degree of uncertainty necessitates using adaptive resource allocation mechanisms to share the finite network resources more efficiently so that more of actual user demands may be accommodated onto the network. The overhead for these adaptive resource allocation mechanisms must be low in order to scale for use in large networks carrying many source-destination user demands. This thesis examines the use of stochastic learning automata for the adaptive routing problem (these being adaptive, distributed and simple in implementation and operation) and seeks to improve their weakness of slow convergence whilst maintaining their strength of subsequent near optimal performance. Firstly, current reinforcement algorithms (the part causing the automaton to learn) are examined for applicability, and contrary to the literature the discretised schemes are found in general to be unsuitable. Two algorithms are chosen (one with fast convergence, the other with good subsequent performance) and are improved through automatically adapting the learning rates and automatically switching between the two algorithms. Both novel methods use local entropy of action probabilities for determining convergence state. However when the convergence speed and blocking probability is compared to a bandwidth-based dynamic link-state shortest-path algorithm, the latter is found to be superior. A novel re-application of learning automata to the routing problem is therefore proposed: using link utilisation levels instead of call acceptance or packet delay. Learning automata now return a lower blocking probability than the dynamic shortest-path based scheme under realistic loading levels, but still suffer from a significant number of convergence iterations. Therefore the final improvement is to combine both learning automata and shortest-path concepts to form a hybrid algorithm. The resulting blocking probability of this novel routing algorithm is superior to either algorithm, even when using trend user demands

TCP flow aware adaptive path switching in diffserv enabled MPLS networks

Cataloged from PDF version of article.We propose an adaptive flow-level multi-path routing-based traffic engineering solution for an IP backbone network carrying TCP/IP traffic. Incoming TCP flows are switched between two explicitly routed paths, namely the primary and secondary paths (PP and SP), for resilience and potential goodput improvement at the TCP layer. In the proposed architecture, PPs receive a preferential treatment over SPs using differentiated services mechanisms. The reason for this choice is not for service differentiation but for coping with the detrimental knock-on effect stemming from the use of longer SP that is well known for conventional network load balancing algorithms. Moreover, both paths are congestion-controlled using Explicit Congestion Notification marking at the core and Additive Increase Multiplicative Decrease rate adjustment at the ingress nodes. The delay difference between PP and SP is estimated using two per-egress rate-controlling buffers maintained at the ingress nodes for each path, and this delay difference is used to determine the path over which a new TCP flow will be routed. We perform extensive simulations using ns-2 in order to demonstrate the viability of the proposed distributed adaptive multi-path routing method in terms of per-flow TCP goodput. The proposed solution consistently outperforms the single-path routing policy and provides substantial per-flow goodput gains under poor PP conditions. Moreover, highest goodput improvements under the proposed scheme are achieved by flows that receive the lowest goodputs with single-path routing, while the performance of the flows with high goodputs with single-path routing does not deteriorate with the proposed path switching technique. Copyright # 2011 John Wiley & Sons, Ltd

Traffic Profiles and Performance Modelling of Heterogeneous Networks

This thesis considers the analysis and study of short and long-term traffic patterns of heterogeneous networks. A large number of traffic profiles from different locations and network environments have been determined. The result of the analysis of these patterns has led to a new parameter, namely the 'application signature'. It was found that these signatures manifest themselves in various granularities over time, and are usually unique to an application, permanent virtual circuit (PVC), user or service. The differentiation of the application signatures into different categories creates a foundation for short and long-term management of networks. The thesis therefore looks from the micro and macro perspective on traffic management, covering both aspects. The long-term traffic patterns have been used to develop a novel methodology for network planning and design. As the size and complexity of interconnected systems grow steadily, usually covering different time zones, geographical and political areas, a new methodology has been developed as part of this thesis. A part of the methodology is a new overbooking mechanism, which stands in contrast to existing overbooking methods created by companies like Bell Labs. The new overbooking provides companies with cheaper network design and higher average throughput. In addition, new requirements like risk factors have been incorporated into the methodology, which lay historically outside the design process. A large network service provider has implemented the overbooking mechanism into their network planning process, enabling practical evaluation. The other aspect of the thesis looks at short-term traffic patterns, to analyse how congestion can be controlled. Reoccurring short-term traffic patterns, the application signatures, have been used for this research to develop the "packet train model" further. Through this research a new congestion control mechanism was created to investigate how the application signatures and the "extended packet train model" could be used. To validate the results, a software simulation has been written that executes the proprietary congestion mechanism and the new mechanism for comparison. Application signatures for the TCP/IP protocols have been applied in the simulation and the results are displayed and discussed in the thesis. The findings show the effects that frame relay congestion control mechanisms have on TCP/IP, where the re-sending of segments, buffer allocation, delay and throughput are compared. The results prove that application signatures can be used effectively to enhance existing congestion control mechanisms.AT&T (UK) Ltd, Englan

Call admission and routing in telecommunication networks.

by Kit-man Chan.Thesis (M.Phil.)--Chinese University of Hong Kong, 1994.Includes bibliographical references (leaves 82-86).Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Overview of Integrated Service Digital Networks --- p.1Chapter 1.2 --- Multirate Loss Networks --- p.5Chapter 1.3 --- Previous Work --- p.7Chapter 1.4 --- Organization --- p.11Chapter 1.5 --- Publications --- p.12Chapter 2 --- Call Admission in Multirate Loss Networks --- p.13Chapter 2.1 --- Introduction --- p.13Chapter 2.2 --- Two Adaptive Routing Rules --- p.15Chapter 2.3 --- Call Admission Policies --- p.17Chapter 2.4 --- Analysis of Call Admission Policies --- p.25Chapter 2.4.1 --- "The CS, LO, GB and the EB Policies" --- p.25Chapter 2.4.2 --- The DP Policy --- p.29Chapter 2.5 --- Performance Comparisons --- p.32Chapter 2.6 --- Concluding Remarks --- p.35Chapter 3 --- Least Congestion Routing in Multirate Loss Networks --- p.41Chapter 3.1 --- Introduction --- p.41Chapter 3.2 --- The M2 and MTB Routings --- p.42Chapter 3.2.1 --- M2 Routing --- p.43Chapter 3.2.2 --- MTB Routing --- p.43Chapter 3.3 --- Bandwidth Sharing Policies and State Aggregation --- p.45Chapter 3.4 --- Analysis of M2 Routing --- p.47Chapter 3.5 --- Analysis of MTB Routing --- p.50Chapter 3.6 --- Numerical Results and Discussions --- p.53Chapter 3.7 --- Concluding Remarks --- p.56Chapter 4 --- The Least Congestion Routing in WDM Lightwave Networks --- p.60Chapter 4.1 --- Introduction --- p.60Chapter 4.2 --- Architecture and Some Design Issues --- p.62Chapter 4.3 --- The Routing Rule --- p.66Chapter 4.4 --- Analysis of the LC Routing Rule --- p.67Chapter 4.4.1 --- Fixed Point Model --- p.67Chapter 4.4.2 --- Without Direct-link Priority --- p.68Chapter 4.4.3 --- With Direct-link Priority --- p.72Chapter 4.5 --- Performance Comparisons --- p.73Chapter 4.6 --- Concluding Remarks --- p.75Chapter 5 --- Conclusions and Future Work --- p.79Chapter 5.1 --- Future Work --- p.8

Tunneling Horizontal IEC 61850 Traffic through Audio Video Bridging Streams for Flexible Microgrid Control and Protection

In this paper, it is argued that some low-level aspects of the usual IEC 61850 mapping to Ethernet are not well suited to microgrids due to their dynamic nature and geographical distribution as compared to substations. It is proposed that the integration of IEEE time-sensitive networking (TSN) concepts (which are currently implemented as audio video bridging (AVB) technologies) within an IEC 61850 / Manufacturing Message Specification framework provides a flexible and reconfigurable platform capable of overcoming such issues. A prototype test platform and bump-in-the-wire device for tunneling horizontal traffic through AVB are described. Experimental results are presented for sending IEC 61850 GOOSE (generic object oriented substation events) and SV (sampled values) messages through AVB tunnels. The obtained results verify that IEC 61850 event and sampled data may be reliably transported within the proposed framework with very low latency, even over a congested network. It is argued that since AVB streams can be flexibly configured from one or more central locations, and bandwidth reserved for their data ensuring predictability of delivery, this gives a solution which seems significantly more reliable than a pure MMS-based solution

Survivability and Traffic Grooming in WDM Optical Networks

The advent of fiber optic transmission systems and wavelength division multiplexing (WDM) have led to a dramatic increase in the usable bandwidth of single fiber systems. This book provides detailed coverage of survivability (dealing with the risk of losing large volumes of traffic data due to a failure of a node or a single fiber span) and traffic grooming (managing the increased complexity of smaller user requests over high capacity data pipes), both of which are key issues in modern optical networks. A framework is developed to deal with these problems in wide-area networks, where the topology used to service various high-bandwidth (but still small in relation to the capacity of the fiber) systems evolves toward making use of a general mesh. Effective solutions, exploiting complex optimization techniques, and heuristic methods are presented to keep network problems tractable. Newer networking technologies and efficient design methodologies are also described.https://lib.dr.iastate.edu/ece_books/1004/thumbnail.jp

Isochronets: a High-Speed Network Switching Architecture

Traditional switching techniques need hundred- or thousand-MIPS processing power within switches to support Gbit/s transmission rates available today. These techniques anchor their decision-making on control information within transmitted frames and thus must resolve routes at the speed in which frames are being pumped into switches. Isochronets can potentially switch at any transmission rate by making switching decisions independent of frame contents. Isochronets divide network bandwidth among routing trees, a technique called Route Division Multiple Access (RDMA). Frames access network resources through the appropriate routing tree to the destination. Frame structures are irrelevant for switching decisions. Consequently, Isochronets can support multiple framing protocols without adaptation layers and are strong candidates for all-optical implementations. All network-layer functions are reduced to an admission control mechanism designed to provide quality of service (QOS) guarantees for multiple classes of traffic. The main results of this work are: (1) A new network architecture suitable for high-speed transmissions; (2) An implementation of Isochronets using cheap off-theshelf components; (3) A comparison of RDMA with more traditional switching techniques, such as Packet Switching and Circuit Switching; (4) New protocols necessary for Isochronet operations; and (5) Use of Isochronet techniques at higher layers of the protocol stack (in particular, we show how Isochronet techniques may solve routing problems in ATM networks)

Learning algorithms for the control of routing in integrated service communication networks

There is a high degree of uncertainty regarding the nature of traffic on future integrated service networks. This uncertainty motivates the use of adaptive resource allocation policies that can take advantage of the statistical fluctuations in the traffic demands. The adaptive control mechanisms must be 'lightweight', in terms of their overheads, and scale to potentially large networks with many traffic flows. Adaptive routing is one form of adaptive resource allocation, and this thesis considers the application of Stochastic Learning Automata (SLA) for distributed, lightweight adaptive routing in future integrated service communication networks. The thesis begins with a broad critical review of the use of Artificial Intelligence (AI) techniques applied to the control of communication networks. Detailed simulation models of integrated service networks are then constructed, and learning automata based routing is compared with traditional techniques on large scale networks. Learning automata are examined for the 'Quality-of-Service' (QoS) routing problem in realistic network topologies, where flows may be routed in the network subject to multiple QoS metrics, such as bandwidth and delay. It is found that learning automata based routing gives considerable blocking probability improvements over shortest path routing, despite only using local connectivity information and a simple probabilistic updating strategy. Furthermore, automata are considered for routing in more complex environments spanning issues such as multi-rate traffic, trunk reservation, routing over multiple domains, routing in high bandwidth-delay product networks and the use of learning automata as a background learning process. Automata are also examined for routing of both 'real-time' and 'non-real-time' traffics in an integrated traffic environment, where the non-real-time traffic has access to the bandwidth 'left over' by the real-time traffic. It is found that adopting learning automata for the routing of the real-time traffic may improve the performance to both real and non-real-time traffics under certain conditions. In addition, it is found that one set of learning automata may route both traffic types satisfactorily. Automata are considered for the routing of multicast connections in receiver-oriented, dynamic environments, where receivers may join and leave the multicast sessions dynamically. Automata are shown to be able to minimise the average delay or the total cost of the resulting trees using the appropriate feedback from the environment. Automata provide a distributed solution to the dynamic multicast problem, requiring purely local connectivity information and a simple updating strategy. Finally, automata are considered for the routing of multicast connections that require QoS guarantees, again in receiver-oriented dynamic environments. It is found that the distributed application of learning automata leads to considerably lower blocking probabilities than a shortest path tree approach, due to a combination of load balancing and minimum cost behaviour