Efficient frontier formulation for additive and restrictive metrics in hierarchical routing

Dynamic transition matrix generation for topology aggregation

Analysis of adaptive cost functions for dynamic update policies for QoS routing in hierarchical networks

Rapid development of optical communication techniques has made possible large scale wavelength routing optical networks. Nowadays, these networks are deployed worldwide. Large scale networks have natural hierarchies due to either geographical reasons or administrative consideration and are therefore managed in a hierarchical way correspondingly. That is, networks are composed of several subnetworks, which are themselves composed of other even smaller subnetworks. Erlang fixed point approximation (reduced load approximation) has been extensively used in performance evaluation of end to end call blocking probability in traditional circuit switching networks, which are also called loss networks. This method has also been extended for hierarchical loss networks. However, performance evaluation of call blocking probability in hierarchical wavelength routing optical networks has not yet been presented. In this paper, a kind of approximation method is developed for analyzing end to end call blocking probability in hierarchical wavelength routing optical networks. By iteratively running processes combining a top-down load distribution and a bottom-up calculation of node-pair blocking in the network hierarchy, a steady state will be reached and approximate end to end call blocking probability in hierarchical wavelength routing optical network is obtained. Both the link independent model and the link correlation model are used in our analysis. By comparing theoretical results derived from our approximation method and results obtained from discrete event simulation, we illustrate that our method gives reasonable estimate of end to end call blocking probability in hierarchical wavelength routing optical networks, with the correlation model giving much more accurate estimate than the independent model.

This paper describes the path selection function in Networking BroadBand Services (NBBS), which is IBM's architecture for high-speed, multimedia networks. The distinguishing feature of a multimedia network is its ability to integrate different applications with different traffic characteristics and service requirements in the network, such as voice, video, and data. In order to meet their service requirements, it is necessary for the network to provide unique quality-of-service (QOS) guarantees to each application. QOS guarantees, specified as multiple end-to-end performance objectives, translate into path and link constraints in the shortest path routing problem. For a general cost function, shortest path routing subject to path constraints is known to be a nonpolynomial- (NP-) complete problem. The NBBS path selection algorithm, a heuristic solution based on the Bellman-Ford algorithm, has a polynomial order of complexity. The algorithm finds a minimum hop path satisfying an end-to-end delay (or delay variation) constraint, that in most cases also optimizes a load balancing function. To reduce the number of path constraints, other QOS requirements such as packet loss ratio are implemented as a link constraint. The notion of primary and secondary links is used to minimize the long-term overall call blocking probability by dynamically limiting the hop count of a given path. The path selection algorithm developed for point-to-point connections is described first, followed by its extension to the case of point-to-multipoint connections.

In the future automated battle field communications will be supported in part by a hierarchical wireless network that includes: ad hoc ground radio subnets; point to point wireless long haul backbone, and; unmanned aerial vehicles (UAVs). In such a hierarchical network, nodes are generally partitioned into groups. Each group has one or more backbone nodes that provide access points to the backbone network and to UAVs. Communications between groups can thus utilize links at higher level. A critical protocol in the operation of such a large mobile network is routing. Previous research of UAV based systems has generally assumed the use of a hierarchical routing scheme, for example, extended hierarchical state routing (EHSR). However, a hierarchical scheme like EHSR has some limitations. In this paper, we extend landmark ad hoc routing (LANMAR) to a hierarchical structure with backbone nodes, high quality backbone links and UAVs. We show that the basic LANMAR scheme can be extended to incorporate backbone and UAV links. We will also show how backbone links and UAV links are automatically discovered by the LANMAR routing algorithm and are used effectively to reach remote destinations (thus reducing the hop distance). In other words, our scheme will combine the benefits of flat LANMAR routing and physical network hierarchy, without suffering of the intrinsic EHSR limitations.

Modeling and analyzing the performance of adaptive hierarchical networks

In this paper, we propose a scalable Label Switched Path (LSP) management architecture for Multiprotocol Label Switching (MPLS) traffic engineering using a hierarchical network model. MPLS introduces the concept of a label hierarchy to support scalability by lessening the complexity of transit routers for the computation of complete routing tables. However, this hierarchical network model creates a critical disadvantage in providing a globally-optimal route because of topology abstraction or aggregation. This paper proposes a hierarchical routing scheme that can provide a globally-optimal route in hierarchical MPLS networks using propagation from the Condensed Subordinate Route Information (CSRI). CSRI is summarized route information among border nodes in the lower layer network and is reflected in the process of the LSP path computation in the higher layer network. We also propose the algorithms for generation of CSRI, for reflection CSRI to higher layer network topology, and for computation of an optimal LSP in a higher layer.

An efficient routing algorithm called hierarchical routing is presented in this paper. The algorithm assumes that the network is divided into logical clusters. In each cluster a so-called central controller stores the routing information and exchanges it with its neighboring central controllers. Each routing entry contains a time index which is used to react to dynamic topology changes and to minimize the amount of exchanged routing information. The presented algorithm is best suited for mobile ad hoc networks. The algorithm has been especially designed for a centralized ad hoc network HEE based on the HIPERLAN/2 standard standardized by ETSI but may be used in any ad hoc network configuration. The performance of the algorithm is analytically compared to the performance of the dynamic source routing algorithm.

For reducing routing information to achieve scalability in large ATM networks, ATM private network-to-network interface (PNNI) adopts hierarchical routing. In order to provide efficient routing, a large ATM network is decomposed into subnetworks, called peer groups (PG), and peer groups will advertise aggregated routing information only. Because the aggregated information is not very precise, a call set up message may be rejected on a chosen route. When an ATM node discovers a call set up message cannot proceed due to insufficient resource, it initiates a back-tracking procedure called against call blocking. Although crankback reduces blocking probability, it also causes additional overhead, such as longer setup delay. Therefore, in this paper, we propose two approaches to reduce crankback overhead, The first approach adds additional information into the set up message, referred to as CIS (crankback information stack), to reduce crankback overhead. The other approach, referred to as CT (cost threshold), uses aggregated path cost and the cost information of a previously rejected call set up message to determine whether call setup on the next alternate path should be tried. Our simulation results show that both of the proposed approaches reduce crankback overhead significantly. Especially, the combination of CIS and CT approach achieves further improvement.

In industrial monitoring and control applications, a server often has to send a command to a node or group of nodes in wireless sensor networks. Flooding achieves high reliability of message delivery by allowing nodes to take the redundancy of receiving the identical message multiple times. However, nodes consume much energy due to this redundancy and the long duty cycle. A reliable slotted broadcast protocol (RSBP) tackles this problem by allocating a distinct broadcast slot (BS) to every node using a tree topology. Not only does it remove collision, but it also minimizes energy consumption such that every node remains active only during its parent’s broadcast slot and its own broadcast slot to receive and rebroadcast a message, respectively. However, it suffers from low reliability in harsh environments due to the compete removal of redundancy and low responsiveness to the changes in network topology due to the global scheduling of slots. Our approach allocates one distinct broadcast sharable slot (BSS) to each tree level, thus making a BSS schedule topology-independent. Then, nodes at the same level compete to rebroadcast a message to nodes at one level higher within the BSS, thus allowing the redundancy. In addition, it uses a slot-scheduled transmission within BSS that can further improve reliability by reducing message collisions and also enables the precise management of energy. According to simulations and experiments, the proposed approach can achieve high reliability comparable to flooding and low-energy consumption comparable to RSBP.

Mobile ad hoc network (MANET) is a group of mobile nodes that communicates with each other without any supporting infrastructure. These networks have some unique features such as dynamic mobility, open nature, lack of infrastructure, limited physical security and they are vulnerable to several security threats. Malicious node can drop all or partial received packets instead of forwarding them to the next hop through the path. In order to find the malicious nodes, an initial transmission is made between the source and destination nodes. Using fuzzy rules, the trust value of each node is computed and it varies from 0 to 1. A common threshold value is set for each node and by using this threshold value, every node in the network can be identified as either a malicious node or a regular node. After identifying the malicious nodes, these nodes are eliminated by muting the power to off state. As the malicious nodes are eliminated between source and destination nodes, source node can select another trusted path to its destination
 node. For security and authentication of routing information, hybrid cryptography is employed, using advanced encryption standard (AES) and elliptic curve cryptography (ECC) algorithms. AES algorithm is used as symmetric algorithm to encrypt the routing information and ECC algorithm is used as asymmetric algorithm to encrypt the public key. During encryption, the original plain text is converted into cipher text with encrypted public key and similarly during decryption cipher text is converted into original plain text with decrypted private keys. So the proposed method involves both AES and ECC algorithms which provides security mechanism as efficient and sufficient one. The experimental simulations are carried for the proposed model using network simulator 2 (NS-2) for Throughput, Delay, Packet delivery ratio, Packet overhead and Packet drop.

ABSTRACTWe propose two methods for aggregation of peer group topology in hierarchical ATM networks. Both proposed aggregation methods transform a given peer group into a star graph representation. Our first approach optimally preserves, in a least square sense, the original costs of routing through the peer group. Our second approach assigns a weighted vector to the nucleus of the Logical Group Node, which quantifies the error in the compact representation. The two schemes are dual, in the sense that the first is best suited for peergroups where traffic patterns are unpredictable, and the second is suited for peergroups where traffic patterns can be characterized. Both the proposed schemes are practical: For peer groups with nodes V, links E, and n border nodes B ⊂ V, the approaches run in O(n|V|log|V| + n|E|+ poly(n)) time. The size of the final representation is small (linear in the number of border nodes) and can be computed efficiently. The scalability of the proposed algorithms makes them well-suited...

Mobile Ad hoc Networks (MANET) comprises of self-organizing autonomous mobile nodes. MANETs are open and decentralized. Therefore they are vulnerable to malicious entities. MANETs are multi-hop wireless network where all nodes supportively maintain network connectivity without a centralized infrastructure. Since MANETs are infrastructure less and independent, the secure communication is the main issue. Therefore they are vulnerable to malicious entities. Here the location identity and traffic can be traced out by an outside observer. Anonymity means secure communications by hiding node identities and preventing traffic analysis attacks by outside observers. This paper proposes Position based Anonymous Routing Scheme in MANETs (PARS).Here the routing is based on Greedy Perimeter Stateless Routing Protocol. The objective is an anonymous routing protocol for the network. The proposed one is a zone based anonymous GPSR based protocol that can provide source, destination and route anonymity. Performance of the proposed system is compared with that of GPSR and AODV using Network Simulator. Index Terms: Anonymous routing, position-based routing, random forwarder, zone partition. I. Introduction Mobile Ad hoc Networks are collection of independent mobile nodes that can communicate by radio waves. It is an infrastructure less self-organizing network. The nodes that are in radio range can communicate by single hop or by multi hop with the help of intermediate nodes. The network is open and decentralized and fully distributed. So they are perfect choice for communication and information sharing. MANETs are susceptible to malicious entities that aim to alter and analyzed the traffic analysis by communication eaves dropping or attacking routing protocols. MANETs are characterized by their distributed operation, multi hop routing, dynamic topology and shared physical medium. Nodes in a MANET are independently free to move in any direction. Due to the lack of a centralized coordinator security is the major concern here. Wireless communication can endure interferences or malicious interceptions; whereas multi-hop communication assumes that each node will perform properly its functions to support network services. Further, self-organization increases the complexity of security management operations as access control, node authentication, secure routing and cryptographic key distribution. There is no fixed infrastructure and the topology is frequently changing due to node mobility or environmental changes. Therefore, it is very hard to maintain a stable and efficient end-to-end route in an ad-hoc network. Each node in MANET is energy constrained. There is verylimited physical security in MANET. The type of attacks can be Active attacks or Passive attacks. The common security issues are Passive attacks which include eaves dropping and information disclosure. Active attacks include Do Sand Data modification. There are other more specific problems with mobile ad hoc network such as vulnerability of channels and nodes, Byzantine black hole and Byzantine wormhole attack. The security issue also includes attacks that may inject erroneous routing information and diverting network traffic thus making routing inefficient. There are many methods to reduce the impact of these attacks, which include a secure routing using public and private key s to get a certification authority and use of digital signatures and prior it rust relationships. Routing is the process of communication from one node to the other host in a network. Routing is the process off or warding packet towards its destination using most efficient path. Routing efficiency is measured in terms of Number of hops, traffic, security, etc. Routing protocols in MANETs are divided as reactive proactive and hybrid. Reactive Protocol maintains the routes in on demand manner. In route discovery phase it floods the route request (RREQ) packets throughout the network. Dynamic source Routing (DSR), ad hoc on- demand distance vector routing (AODV) are some of the examples of reactive protocols. In proactive approach every node in the MANET continuously maintains the complete routing information of the entire network. This is accomplished by flooding network periodically with network status information. Global State Routing (GSR), Hierarchical State Routing (HSR) and Destination Sequenced Distance Vector Routing (DSDV) are some of the examples of proactive

A near-optimal multicast scheme for mobile ad hoc networks using a hybrid genetic algorithm

Hierarchical spanning tree network design with Nash genetic algorithm