Simulation and analysis of adaptive routing and flow control in wide area communication networks

This thesis presents the development of new simulation and analytic models for the performance analysis of wide area communication networks. The models are used to analyse adaptive routing and flow control in fully connected circuit switched and sparsely connected packet switched networks. In particular the performance of routing algorithms derived from the L(_R-I) linear learning automata model are assessed for both types of network. A novel architecture using the INMOS Transputer is constructed for simulation of both circuit and packet switched networks in a loosely coupled multi- microprocessor environment. The network topology is mapped onto an identically configured array of processing centres to overcome the processing bottleneck of conventional Von Neumann architecture machines. Previous analytic work in circuit switched work is extended to include both asymmetrical networks and adaptive routing policies. In the analysis of packet switched networks analytic models of adaptive routing and flow control are integrated to produce a powerful, integrated environment for performance analysis The work concludes that routing algorithms based on linear learning automata have significant potential in both fully connected circuit switched networks and sparsely connected packet switched networks

Adaptive map configuration and dynamic routing to optimize the performance of a satellite communication network

Availability of alternate routes are shown to enhance the performance of non-hierarchical circuit switched networks at moderate load conditions on which the networks typically operate. But alternate routes introduce instability at heavy and overloaded conditions and at these load conditions the network performance is found to deteriorate. To alleviate this problem, one of the control mechanism used is to reserve a fraction of the capacity of each link for direct routed calls. In this work, the feasibility of changing the facilities of a satellite network is taken advantage in optimizing the performance of such a network. A mesh connected, circuit switched satellite communication network is optimized by reconfiguring the network with proper allocation of link capacities and placing an optimal reservation scheme. The network load is measured and the network is continually adapted by reconfiguring the map to suit the current traffic conditions. The routing is performed dynamically. The results from the simulation study shows this method of traffic management performs better than the pure dynamic routing with fixed configuration

Optimal admission policies for small star networks

In this thesis admission stationary policies for small Symmetric Star telecommunication networks in which there are two types of calls requesting access are considered. Arrivals form independent Poisson streams on each route. We consider the routing to be fixed. The holding times of the calls are exponentially distributed periods of time. Rewards are earned for carrying calls and future returns are discounted at a fixed rate. The operation of the network is viewed as a Markov Decision Process and we solve the optimality equation for this network model numerically for a range of small examples by using the policy improvement algorithm of Dynamic Programming. The optimal policies we study involve acceptance or rejection of traffic requests in order to maximise the Total Expected Discounted Reward. Our Star networks are in some respect the simplest networks more complex than single links in isolation but even so only very small examples can be treated numerically. From those examples we find evidence that suggests that despite their complexity, optimal policies have some interesting properties. Admission Price policies are also investigated in this thesis. These policies are not optimal but they are believed to be asymptotically optimal for large networks. In this thesis we investigate if such policies are any good for small networks; we suggest that they are. A reduced state-space model is also considered in which a call on a 2-link route, once accepted, is split into two independent calls on the links involved. This greatly reduces the size of the state-space. We present properties of the optimal policies and the Admission Price policies and conclude that they are very good for the examples considered. Finally we look at Asymmetric Star networks with different number of circuits per link and different exponential holding times. Properties of the optimal policies as well as Admission Price policies are investigated for such networks

Asymptotic Analysis of a Loss Model with Trunk Reservation I: Trunks Reserved for Fast Traffic

We consider a model for a single link in a circuit-switched network. The link has C circuits, and the input consists of offered calls of two types, that we call primary and secondary traffic. Of the C links, R are reserved for primary traffic. We assume that both traffic types arrive as Poisson arrival streams. Assuming that C is large and R=O(1), the arrival rate of primary traffic is O(C), while that of secondary traffic is smaller, of the order O(C). The holding times of the primary calls are assumed to be exponentially distributed with unit mean. Those of the secondary calls are exponentially distributed with a large mean, that is, O(C). Thus, the primary calls have fast arrivals and fast service, compared to the secondary calls. The loads for both traffic types are comparable (O(C)), and we assume that the system is “critically loaded”; that is, the system's capacity is approximately equal to the total load. We analyze asymptotically the steady state probability that n1 (resp., n2) circuits are occupied by primary (resp., secondary) calls. In particular, we obtain two-term asymptotic approximations to the blocking probabilities for both traffic types

Dynamic bandwidth allocation in multi-class IP networks using utility functions.

PhDAbstact not availableFujitsu Telecommunications Europe Lt

Samoorganiziranje u autonomnoj arhitekturi za pružanje diferenciranih usluga primjenom algoritma za balansiranje prometa

This paper is about the role of a heuristic algorithm for load balancing that can be incorporated in Multi-Protocol Label Switching/ Differentiated Services (MPLS/DS) networks based on self-management principles for automated traffic configuration. Delivery of Quality of Services (QoS) differentiation according to specific service level agreements, Service Level Agreement (SLA), has to be in relation to resource management and bandwidth allocation, to ensure better end-to-end QoS provisioning and to avoid traffic congestion. To ensure simultaneous traffic flows with different priorities we need some load-balancing procedure. It could start much earlier than usual, possibly during SLA negotiation. If SLA creation is supported by load control mechanism it can ensure better performances of the network in the moment of service invocation. LSP (Label Switching Path) creation could be influenced by former contracted SLAs and such approach could be more effective than pure routing technique based on the shortest path algorithm (LSP creation in the moment of service invocation). So we propose application of heuristic algorithm tested on numerical examples with maximum M routers on the path and with differentiation of N service classes. Further, we introduced some capacity state restrictions in the process of network optimization, considering different algorithm options. We compared their performances, especially the algorithm complexity that is very important for efficient load control in huge networks.Članak opisuje ulogu heurističkog algoritma za balansiranje opterećenja i dimenzioniranje prometa u MPLS/DiffServ mreži na načelu samoorganizacije i automatske konfiguracije. Ostvarenje QoS usluga mora biti u skladu s postojećim ugovorom za kvalitetu usluge (SLA), sklopljenim između korisnika i operatera, ali tako da se omogući upravljanje resursima mreže izbjegavajući moguća zagušenja. Da bi osigurali simultane prometne tokove uz razlikovanje kvalitativne razine, nužno je osigurati balansiranje prometa. Takvo balansiranje mreže može započeti i znatno ranije, moguće već u trenutku pregovaranja pri sklapanju SLA. Ako je ono podržano kontrolom mogućeg zagušenja mogu se značajno poboljšati QoS jamstva i uravnoteženost mreže. Kreiranje LSP puta s obzirom na prijašnje ugovoren (rezerviran) promet bilo bi bolje od samog usmjeravanja na načelu najkraćeg puta (usmjeravanje u trenutku pokretanja usluge). Za tu je namjenu u radu predložena primjena heurističkog algoritma testiranog na mnogim numeričkim primjerima s maksimalno M usmjerivača na putu s kraja-na kraj domene i s maksimalno tri vrste (N=3) različitih kvalitativnih razina (klase prometa). Razmatrana su daljnja poboljšanja algoritma u ograničavanju stanja kapacitivnih točaka u postupku mrežne optimizacije, tj. testirane su i uspoređene razne opcije algoritma. Neke od njih pokazuju značajno smanjenje složenosti uz zadovoljavajuću kvalitetu ostvarenih rezultata, što je važno za kontrolu opterećenja u velikim mrežama

An Efficient Algorithm for Congestion Control in Highly Loaded DiffServ/MPLS Networks

Optimal QoS path provisioning of coexisted and aggregated traffic in networks is still demanding problem. All traffic flows in a domain are distributed among LSPs (Label Switching Path) related to N service classes, but the congestion problem of concurrent flows can appear. As we know the IGP (Interior Getaway Protocol) uses simple on-line routing algorithms (e.g. OSPFS, IS-IS) based on shortest path methodology. In QoS end-to-end provisioning where some links may be reserved for certain traffic classes (for particular set of users) it becomes insufficient technique. On other hand, constraint-based explicit routing (CR) based on IGP metric ensures traffic engineering (TE) capabilities. But in overloaded and poorly connected MPLS/DiffServ networks the CR becomes insufficient technique. As we need firm correlation with bandwidth management and traffic engineering (TE) the initial (pro-active) routing can be pre-computed in the context of all priority traffic flows (former contracted SLAs) traversing the network simultaneously. It mean that LSP can be pre-computed much earlier, possibly during SLA (Service Level Agreement) negotiation process. In the paper a new load simulation technique for load balancing control purpose is proposed. The algorithm proposed in the paper may find a longer but lightly loaded path, better than the heavily loaded shortest path. It could be a very good solution for congestion avoidance and for better load-balancing purpose where links are running close to capacity. Also, such technique could be useful in inter-domain end-to-end provisioning, where bandwidth reservation has to be negotiated with neighbor ASes (Autonomous System). To be acceptable for real applications such complicated routing algorithm can be significantly improved. Algorithm was tested on the network of M core routers on the path (between edge routers) and results are given for N=3 service classes. Further improvements through heuristic approach are made and results are discussed

Robust admission control for streaming and elastic services in cellular networks

Abstract-The specific features of cellular networks and especially terminal mobility make the session admission control (SAC) in such networks more complex. This paper studies the robustness of the Virtual Partitioning (VP) admission policy in connection with multiservice cellular networks and considering streaming and elastic traffic in scenarios that must support high overloads. The VP policy is compared with the Multiple Fractional Guard Channel (MFGC) policy. The main contributions of the paper are the study of a new design method, the integration of streaming and elastic traffic, the study of the sensitivity to the channel holding time distribution and the use of absorbing Markov processes to calculate the probability that a handover occurs

Dynamic routing in circuit-switched non-hierarchical networks

This thesis studies dynamic routing in circuit-switched non-hierarchical networks based on learning automata algorithms. The application of a mathematical model for a linear reward penalty algorithm is explained. Theoretical results for this scheme verified by simulations shows the accuracy of the model. Using simulation and analysis, learning automata algorithms are compared to several other strategies on different networks. The implemented test networks may be classified into two groups. The first group are designed for fixed routing and in such networks fixed routing performs better than any dynamic routing scheme. It will be shown that dynamic routing strategies perform as well as fixed routing when trunk reservation is employed. The second group of networks are designed for dynamic routing and trunk reservation deteriorates the performance. Comparison of different routing algorithms on small networks designed to force dynamic routing demonstrates the superiority of automata under both normal and failure conditions. The thesis also considers the instability problem in non-hierarchical circuit-switched networks when dynamic routing is implemented. It is shown that trunk reservation prevents instability and increases the carried load at overloads. Finally a set of experiments are performed on large networks with realistic capacity and traffic matrices. Simulation and analytic results show that dynamic routing outperforms fixed routing and trunk reservation deteriorates the performance at low values of overload. At high overloads, optimization of trunk reservation is necessary for this class of networks. Comparison results show the improved performance with automata schemes under both normal and abnormal traffic conditions. The thesis concludes with a discussion of proposed further work including expected developments in Integrated Service Digital Networks