Showing papers on "Overlay network published in 1995"

Enhancement of network operation and performance

Abstract: A set of logical networks is established on top of a physical network. Next, a predefined objective function, closely related to the operation and performance of the physical network, which physical network is viewed as the set of logical networks, is optimized with respect to at least one set of decision variables. Finally, the decision variables in accordance with the optimization are used to control the operation of the overall network system. Each set of decision variables relates to a separate aspect of the invention. A method and device for partitioning physical transmission resources among logical networks is provided. There is also provided a method and device for distributing offered traffic load among routes interconnecting the nodes of node pairs. Furthermore, a combination of the sets of decision variables relates to yet another aspect of the invention. Accordingly, a method and device for partitioning physical transmission resources among logical networks and distributing offered traffic load among routes interconnecting the nodes of node pairs is disclosed.

Routing in data communications network

Abstract: The invention provides data communication systems and methods in which information for routing of messages between nodes of a commnunications network is provided by a directory service (300 such as DCE directory service), accessible from all network nodes. The provision of such information by the directory service removes the requirement for routing tables to be set up and maintained at each of the network nodes, which maintenance can involve considerable network traffic in dynamically changing networks or problems of inconsistent data being held at different nodes. The invention also identifies what minimum network configuration information must be held in a directory service for use in message-route determination, providing systems for and methods of route determination which use a directory service storing lists of each node's nearest neighbour nodes only.

Communication system providing mobility management internetworking between a C-interface radio system and an overlay mobile radio network

Abstract: A communication system providing mobility management interworking between a C-interface radio system and an overlay mobile radio network. In the first embodiment the radio system uses NCAS signalling and communicates with the SCP using the MMAP protocol. The SCP then makes the conversion to traditional MAP protocol when necessary to communicate with other network entities. The SCP takes care of the interworking between these transactions. In the second embodiment the SCP only relays the MAP operations embedded into TCAP messages transparently between the radio system RS and the overlay network element when the communication takes place between the RS and the overlay network. Thus the transaction is between the RS and the overlay network element. A Relay Protocol is needed between the RS and the SCP to carry the appropriate address information and to discriminate between the transparent MAP operations and non-transparent MMAP operations.

Algorithms for network reliability and connection availability analysis

Abstract: Communications networks used for transmitting and receiving voice or digital data involve copper wire, fiber optics, radio, satellite, and microwave links. In general, these networks are large, diffuse, and complex. Even using modern high-speed computers, exact computations of the network reliability for use as a figure of merit in an interactive network design procedure can take an inordinate amount of time. This paper discusses various exact techniques whose complexity results in run-times short enough for practical network design. We model the network by an undirected probabilistic graph whose vertices represent the nodes and whose edges represent the links. A special feature of our model is that it allows nodes to be imperfect and associates a reliability measure with each node, assumed to succeed or fail independently. Therefore, the network reliability measure is based upon the reliability measures of the individual links and nodes. >

Method for adaptive routing in a communication network

Abstract: The communication network has a plurality of mutually connected network nodes (NR1,...,NK5), in which in each case network data relating to the network topology of the entire communication network are maintained and, depending on said network data, routing tables for connection paths to all remaining network nodes are created. If an event that influences the network topology of the communication network occurs, on the one hand the network data maintained therein are updated by the network node detecting said event. On the other hand a broadcast message corresponding to the event is transmitted to the other network nodes, following the reception of which the respective network nodes update the network data maintained therein. It is provided here that, for the transmission of the broadcast message within the communication network, a connection path network is defined from the plurality of possible connection paths between the individual network nodes, via which network the broadcast message reaches the respective network node via only a defined number of independent connection paths.

Dynamic network evolution, with examples from AT&T's evolving dynamic network

Abstract: Dynamic network evolution achieves network performance improvement and cost reduction by taking advantage of new advanced technologies being introduced into the network to achieve greater network flexibility and efficiency. The author describes the evolution of dynamic networks, with examples drawn from the AT&T DNHR network deployed in the '80s and RTNR network deployed in the '90s. Dynamic traffic routing implements an integrated class-of-service routing feature for extending dynamic routing to emerging services, and provides a self-healing network capability to ensure a network-wide path selection and immediate adaptation to failure. Dynamic traffic routing brings benefits to customers in terms of new service flexibility and improved service quality and reliability, at reduced cost. >

Resource separation in a call and connection separated network

Abstract: In a call and connection separated network a method of providing distribution of resources of a physical network (1-11) among different logical networks (LN1-LN3) which are using the physical network for establishing connections. All of the physical resources of the physical network are mapped network onto a single logical network description that will comprise nodes (F1-F3), trunk groups (17-20) interconnecting the nodes, and resource pools. The different logical networks are created by routing tables (24, 27) located at each of the nodes. The routing tables are provided with a fixed maximum percentage figure (MAX SEIZURE) relating to the maximum amount by which an individual logical network is allowed to use a common resource thus distributing said resources between the different logical networks. By assigning an individual maximum percentage figure to each of the logical networks and in so doing observing the sum of the maximum percentages for all logical networks it is possible to create complete resource separation of the resource or competition for the resource among the logical networks.

Improved survivability with multi-layer dynamic routing

Abstract: The article deals with the integrated design and analysis of a telecommunications network to achieve specified levels of survivability under various failure modes and conditions. The main goal of the article is: given a criterion for network survivability, develop a unified theory for network planning at different "layers" of the network, and for coordinated restoration methods after a failure. While most of the discussion relates to modern circuit-switching architectures, for completeness, asynchronous transfer mode technology is also considered. >

Dynamic VP rearrangement in an ATM network

Abstract: In this paper, we introduce a VP rearrangement scheme to realize the dynamic control of ATM network. We demonstrate its effectiveness for the transport of B-ISDN traffic which is both fluctuating and hard to predict. First, we present a strategy for the ATM network provisioning, used to manage both the logical VP network and the underlying physical transport network. We then propose a VP rearrangement scheme and discuss its performance. Lastly, we analyze the proposed scheme by simulations, and confirm that its performance, in comparison to the conventional, dynamic VP bandwidth control scheme, is superior.

Connectionless communications using the Asynchronous Transfer Mode

Abstract: For a large number of applications, there is a strong need for the provision of a connectionless service by the B-ISDN. However, the cell-based ATM, which is used for switching and multiplexing in this public telecommunication network, is a connection-oriented technique. The B-ISDN should therefore be extended with functionality to allow for connectionless communications. This dissertation addresses the design and analysis of such an extension. An architectural framework is presented, which places the protocols to be used in perspective. Two possible network architectures result from the functional decomposition of the connectionless service into cooperating protocol entities and the underlying ATM service. In the first one, end-systems of the B-ISDN are interconnected by means of end-to-end ATM connections. In the second one, endsystems are connected to special entities in the B-ISDN, called Connectionless Servers (CLSs). The CLSs are interconnected by ATM connections, thus constituting a connectionless overlay network on top of ATM. A number of different implementation architectures for a CLS are proposed, and analysed with respect to effectiveness, availability, scalability, and in particular, performance. The major distinction between these implementation architectures is the distribution of functionality over modules. Furthermore, two different modes of operation are identified for a CLS. In the message mode of operation, a packet is reassembled from the incoming cells before it is processed and forwarded. In streaming mode of operation, the first cell of a packet is immediately processed and forwarded upon arrival, while state information is maintained for the processing and forwarding of subsequent cells of the packet. A number of performance models are developed in this dissertation. An approximate model of a CLS is analysed to allow for comparison of the delay which is experienced by cells for different implementation architectures and modes of operation. If the bandwidth assigned to ATM connections between CLSs is relatively high, message mode of operation yields the lowest delay, otherwise streaming mode performs best. In order to support the dimensioning of a reassembly buffer in a CLS operating in message mode, another, more detailed model is developed and analysed. It allows the computation of the packet loss probability of a buffer, as a function of its size. An essential function for the provision of a connectionless service using ATM is connection management. This function instructs the signalling system of the B-ISDN to establish and release ATM connections as needed for the transfer of packets. A new mechanism is proposed that exploits the expected correlation between subsequent packet arrivals to reduce the average bandwidth that needs to be reserved by the ATM network. A performance model is developed and analysed to determine the optimal control parameters of the new mechanism, and to evaluate its behaviour. It is shown that bandwidth reductions of up to 95% can be obtained, compared to conventional mechanisms, without affecting the average delay experienced by packets.

On multicasting in a communication network

Abstract: An important problem in communication networks is to be able to efficiently multicast information to a group of network sites. Multicasting reduces the transmission overhead of the network and the time it takes for all the nodes in the subset to receive the information. Recent advances in network speed, switching technology, and the asynchronous transfer mode (ATM) networks have introduced new applications and provided new services which were not feasible before. Today's network applications such as multimedia, video, audio, resource discovery, teleconferencing, distributed/replicated database management can benefit immensely from efficient multicasting techniques. We discuss methods of establishing efficient multicasting in a communication network. We discuss an efficient implementation of a widely used multicasting method that produces a solution no greater than twice that of an optimal solution. We also present two efficient multicast tree constructions for a general version of the multicasting problem in which a network consists of different classes of nodes.

Description of all-optical network test bed and applications

Abstract: We describe an all-optical network testbed deployed in the Boston metropolitan area, and some of the experimental applications running over the network. The network was developed by a consortium of AT&T Bell Laboratories, Digital Equipment Corporation, and Massachusetts Institute of Technology under a grant from ARPA. The network is an optical WDM system organized as a hierarchy consisting of local, metropolitan, and wide area nodes that support optical broadcast and routing modes. Frequencies are shared and reused to enhance network scalability. Electronic access is provided through optical terminals that support multiple services having data rates between 10 Mbps/user and 10 Gbps/user. Novel components used to implement the network include fast-tuning 1.5 micrometers distributed Bragg reflector lasers, passive wavelength routers, and broadband optical frequency converters. An overlay control network implemented at 1.3 micrometers allows reliable out-of-band control and standardized network management of all network nodes. We have created interfaces between the AON and commercially available electronic circuit-switched and packet-switched networks. We will report on network applications that can dynamically allocate optical bandwidth between electronic packet-switches based on the offered load presented by users, without requiring interfaces between users and the AON control system. We will also describe video and telemedicine applications running over the network. We have demonstrated an audio/video codec that is directly interfaced to the optical network, and is capable of transmitting high-rate digitized video signals for broadcast or videoconferencing applications. We have also demonstrated a state-of-the-art radiological workstation that uses the AON to transport 2000 X 2000 X 16 bit images from a remote image server.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Network management for all-optical networks

Abstract: We have developed a network-management subsystem for a wavelength-division-multiplexed all-optical network (AON) test bed being developed by AT&T Bell Laboratory, Digital Equipment Corporation, and the Massachusetts Institute of Technology under a grant from ARPA. Network management is required in national- or global-scale networks, where the number of network entities combines with geographic and administrative considerations to increase the difficulty of performing functions such as network configuration, initialization, resource scheduling, fault detection, and performance estimation.

B-CDMA overlay forward link and reverse link capacity based on random traffic and a new CDMA call blocking model

Abstract: This paper addresses the capacity of the B-CDMA macrocellular overlay system. The B-CDMA overlay method enables cellular systems to provide wireless high speed communications. The novelty in this paper is the introduction of a new CDMA blocking model to calculate the capacity of the B-CDMA overlay system under various AMPS and B-CDMA traffic intensities. Forward and reverse link capacities are both calculated. We show that a B-CDMA overlay can accommodate 10-22 times more users than the existing FDMA system. These results are obtained by incorporating the effects of implementation loss, APC inaccuracy due to multipath fading and spillover. Simulation results are included.

Modelling and evaluating network formation functions in self-organising radio networks

Abstract: In self-organising radio networks, capable of supporting terminal mobility and distributed operations, the time required to form and reconfigure the network is an important design issue. In this paper we explain the design policies applicable to the network formation process, and propose measures which can be used for its evaluation. In a dynamic environment, we can monitor the stability of network connectivity information, and use the results to trigger various network control procedures. We present and compare results of simulations involving multi-hop radio networks with large numbers of nodes (up to 169) and varying nodal degrees (up to 20), for fixed and adaptive transmission policies. We show that the use of adaptive control policies greatly improves the performance of self-organisation, when no knowledge about the distribution of network nodes can be assumed at the start-up time.

Reconfigurable segmentation and subnetworking for all-optical transmission using an optical cross-connect

Abstract: In many networks a nodes throughput or deliverable data rate does not match the nodes network access rate. This is particularly true in fiber-optic LANs where many users must share a single communications channel and a nodes network throughput is a fraction of the rate at which its transmitter may access the fiber. Even in broadband networks which offer transport rates in excess of the access rate, the throughput still may be network topology limited by congestion, queuing and other transport delays. This paper will demonstrate how an optical cross-connect can be used in the LAN environment to segment a network into new and separate broadcast domains, which improve the overall network capacity. It also demonstrates how an optical cross-connect can be used to groom traffic in a multihop network to better utilize the network's existing bandwidth capacity.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The role of human operators in configuring, managing, and troubleshooting interconnected computer networks

Abstract: The number of interconnected computer networks that form the Internet has been growing at an exponential rate. Components of the networks tend to be highly heterogeneous in both hardware and software. The Internet is managed via a number of standard protocols and interfaces that provide the constraints and guidelines for interconnection and operation. While these protocols offer some help, there is still a lack of formal methods to manage the networks due to the rapid rate of evolution that characterizes these networks. A related problem is the ability to view the network at different levels of detail. We have been investigating the tasks and functions of operators and studying traffic patterns on networks with the goal of developing comprehensive tools to assist operators in performing a wide range of tasks. In this paper, we describe the role of the humans and an outline of our research aimed at assisting the operators at various levels.

Network management and system-level diagnosis

Abstract: Fault management, which consists of fault detection, diagnosis, and recovery is one of the key goals of network management. We consider an application of system-level diagnosis concepts to the problem of fault diagnosis in networks. Since the primary function of the nodes in a communication network is to route messages, the diagnosis is done with respect to the ability of the nodes to accomplish routing correctly. We propose a basic test model in which a node is tested with the help of two other nodes (a tester and a helper node) that check the ability of the tested node to correctly route the messages between the tester and the helper nodes. Necessary conditions are derived for a network to be t-diagnosable under this model. The proposed model does not require tests with perfect coverage.

Virtual channel and path allocation in ATM networks

Abstract: An asynchronous transfer mode (ATM) network provides a connection-oriented service by establishing a virtual channel (VC) between a source and destination node. Virtual paths (VPs) facilitate virtual channel allocation by partitioning network resources along pre-calculated routes. This paper proposes a framework for the allocation of VCs and VPs in an ATM network. Our approach is based on approximating the required resources of calls and then formulating a multirate loss network model for an ATM network. We propose a decentralized algorithm for adaptively adjusting offered loads to network routes and VP bandwidth assignments.

Heterogeneous broadband network

Abstract: Although the vision for the future Integrated Broadband Communication Network (IBCN) is an all optical network, it is certain that for a long period to come, the network will remain very heterogeneous, with a mixture of different physical media (fiber, coax and twisted pair), transmission systems (PDH, SDH, ADSL) and transport protocols (TCP/IP, AAL/ATM, frame relay). In the current work towards the IBCN, the ATM concept is considered the generic network protocol for both public and private network, with the ability to use different underlying transmission protocols and, through adaptation protocols, provide the appropriate services (old as well as new) to the customer. One of the major difficulties of heterogeneous network is the restriction that is usually given by the lowest common denominator, e.g. in terms of single channel capacity. A possible way to overcome these limitations is by extending the ATM concept with a multilink capability, that allows us to use separate resources as one common. The improved flexibility obtained by this protocol extension further allows a real time optimization of network and call configuration, without any impact on the quality of service seen from the user. This paper describes an example of an ATM based multilink protocol that has been experimentally implemented within the RACE project 'STRATOSPHERIC'. The paper outlines the complexity of introducing an extra network functionality compared with the added value, such as an improved ability to recover an error due to a malfunctioning network component.

Phasing ATM technology into an IP environment

Abstract: We examine two key aspects of the ATM deployment in the TCP/IP environment-logical IP sub-networks (LISs) and address mapping servers, with a specific emphasis on how different alternatives for LISs and address mapping servers enable efficient exploration of all the capabilities that ATM promises to deliver. We propose an approach for ATM deployment in the TCP/IP environment that leverages the existing technologies (e.g. DNS, routing protocols), minimizes new development, imposes no new requirements on ATM, allows for small, incremental changes with immediate payoffs, while at the same time retains backward compatibility with the existing schemes, such as LAN Emulation and "classical" IP over ATM. The proposed approach combines a switch-based infrastructure with router-based overlay and uses each for that which it is best suited: switch-based infrastructure for applications that can justify an SVC establishment; router-based overlay for all other applications.