Showing papers on "Geographic routing published in 1996"

A survey of routing techniques for mobile communications networks

Abstract: Mobile wireless networks pose interesting challenges for routing system design. To produce feasible routes in a mobile wireless network, a routing system must be able to accommodate roving users, changing network topology, and fluctuat- ing link quality. We discuss the impact of node mobility and wireless communication on routing system design, and we survey the set of techniques employed in or proposed for routing in mobile wireless networks.

Internet long distance telephone service

Abstract: Long distance communications service between two communications systems is established by using a wide area packet switched network, for example the Internet, to transport signaling data and digitized communication traffic. Each communications system uses an interface server to encapsulate communication traffic and signaling data into data packets suitable for transport over the wide area packet switched network. The interface server accesses a routing and administration database to determine a destination address of a destination interface server based on the area code of the called number. Upon receiving the destination address and a prescribed bandwidth from the routing and administration database, the telephony server inserts the destination address to the data packets for a destination server for a second communications system. The packets are then output to the Internet, and subsequently routed to the destination server serving as an interface for the second communications system. Routing of packets is preferably performed using reserved virtual paths to guarantee quality of service.

Routing high-bandwidth traffic in max-min fair share networks

Abstract: We study how to improve the throughput of high-bandwidth traffic such as large file transfers in a network where resources are fairly shared among connections. While it is possible to devise priority or reservation-based schemes that give high-bandwidth traffic preferential treatment at the expense of other connections, we focus on the use of routing algorithms that improve resource allocation while maintaining max-min fair share semantics. In our approach, routing is closely coupled with congestion control in the sense that congestion information, such as the rates allocated to existing connections, is used by the routing algorithm. To reduce the amount of routing information that must be distributed, an abstraction of the congestion information is introduced. Using an extensive set of simulation, we identify a link-cost or cost metric for "shortest-path" routing that performs uniformly better than the minimal-hop routing and shortest-widest path routing algorithms. To further improve throughput without reducing the fair share of single-path connections, we propose a novel prioritized multi-path routing algorithm in which low priority paths share the bandwidth left unused by higher priority paths. This leads to a conservative extension of max-min fairness called prioritized multi-level max-min fairness. Simulation results confirm the advantages of our multi-path routing algorithm.

A necessary and sufficient condition for deadlock-free routing in cut-through and store-and-forward networks

Abstract: This paper develops the theoretical background for the design of deadlock-free adaptive routing algorithms for virtual cut-through and store-and-forward switching. This theory is valid for networks using either central buffers or edge buffers. Some basic definitions and three theorems are proposed, developing conditions to verify that an adaptive algorithm is deadlock-free, even when there are cyclic dependencies between routing resources. Moreover, we propose a necessary and sufficient condition for deadlock-free routing. Also, a design methodology is proposed. It supplies fully adaptive, minimal and non-minimal routing algorithms, guaranteeing that they are deadlock-free. The theory proposed in this paper extends the necessary and sufficient condition for wormhole switching previously proposed by us. The resulting routing algorithms are more flexible than the ones for wormhole switching. Also, the design methodology is much easier to apply because it automatically supplies deadlock-free routing algorithms.

Fault-tolerant routing in hypercube multicomputers using local safety information

Abstract: Previous methods of making wormhole-routed meshes fault tolerant have been based on adding virtual channels to the networks. This paper proposes an alternative method, one based on the turn model for designing wormhole routing algorithms. The turn model produces routing algorithms that are deadlock free, very adaptive, minimal or nonminimal, and livelock free for direct networks--whether or not they contain virtual channels. This paper illustrates how to modify the routing algorithms produced by the turn model to handle dynamic faults. This paper first describes how to modify the negative-first routing algorithm, which the turn model produces for n-dimensional meshes without virtual channels, to make it one-fault tolerant. Simulations of the one-fault-tolerant routing algorithm and other minimal and nonminimal routing algorithms in a two-dimensional mesh indicate that misrouting increases communication latencies significantly at high throughputs. The conclusion is that misrouting should be used only for increasing the degree of fault tolerance, never for just increasing adaptiveness. Finally , the paper describes how to modify the negative-first routing algorithm to make it (n - 1)-fault tolerant for n-dimensional meshes without virtual channels.

Method and apparatus for routing ATM cells in an ad-hoc ATM LAN

Abstract: In a system and method for routing ATM cells in a wireless ATM local area network (LAN) (60) that use portable base station (PBS) switching nodes (1 to 9), routing of cells to and from mobile users (x,y,z) within the network is accomplished utilizing a novel routing scheme which preserves cell sequence. Each user transmitting data to another user is asociated with a Source Home Station or node and each user receiving data is associated with a Destination Home Station or node. When a connection is established in the network between a first mobile user and a second mobile user, the ATM cells are routed along a fixed path from the first mobile user to the associated Source Home Station and along a fixed path between the Source Home Station to the Destination Home Station and then along a fixed path from the Destination Home Station to the second destination user. In this way cell sequence is maintained by utilizing the Source Home to Destination Home path. Mobile users within the network are also associated with a Local PBS which can be different from the Home Stations as the mobile moves around the network. The Local PBSs association with the mobile user are slowly updated to be the Home Stations to cure inefficient routing.

Method of automatic updating and use of routing information by programmable and manual routing information configuration based on least lost routing

Abstract: In an electronic messaging system which has multiple sites, and in which each site is defined by a unique address space and has connectivity to at least one other site, messages are sent by receiving at a first site message routing information from a second site. The message routing information defines routes from the second site to one or more of the plurality of sites. The received message routing information is assimilated into previously known routing information to generate an updated accumulation of routing information. The updated accumulation of routing information is used to route messages to one or more of the plurality of sites. The updated accumulation of routing information may be replicated to still other sites in the messaging system, which in turn assimilate the information into their respective collections of known routing information. This process of receiving, assimilating and replicating may be repeated until each of the sites has substantially the same updated accumulation of routing information.

High performance fault tolerant switching system for multimedia satellite and terrestrial communications networks

Abstract: A switch that has a plurality of inputs in which cells are received at these inputs. Each cell received at the inputs of the switch contain routing information. A routing means is employed to route the cells received at the inputs of the switch to outputs using routing information in which a number of the cells are misrouted by the routing means during the process of routing the cells to the outputs. Bus means is employed to route a cell to the destination in which the bus means is connected to the routing means. The bus means routes misrouted cells that are misrouted from the destination by some selected amount.

Adaptive routing in irregular networks using cut-through switches

Abstract: Many cut-through switches, which can greatly reduce network latency, are commercially available for the construction of high-speed local area networks. The interconnection of cut-through switches provides an excellent network platform for high-performance workstation clusters. A novel deadlock-free adaptive routing algorithm is proposed to allow irregular interconnection of cut-through switches. The adaptive routing algorithm is based on two unidirectional adaptive trails constructed from two opposite unidirectional Eulerian trails. Some heuristics are suggested in terms of the selection of Eulerian trails, the avoidance of long routing paths, and the degree of adaptivity. Extensive simulation experiments based on a more realistic finite input source model are conducted to evaluate the network performance under different network parameters and traffic conditions. Both bimodal and bursty messages are considered. Such switch-based irregular networks are truly incrementally scalable and have potential to be reconfigured to adapt to the dynamics of network traffic conditions.

Efficient routing in optical networks

Abstract: This paper studies the problem of dedicating routes to connections in optical networks. In optical networks, the vast bandwidth available in an optical fiber is utilized by partitioning it into several channels, each at a different optical wavelength. A connection between two nodes is assigned a specific wavelength, with the constraint that no two connections sharing a link in the network can be assigned the same wavelength. This paper considers optical networks with and without switches, and different types of routing in these networks. It presents optimal or near-optimal constructions of optical networks in these cases and algorithms for routing connections, specifically permutation routing for the networks constructed here.

Congestion-oriented shortest multipath routing

Abstract: We present a framework for the modeling of multipath routing in connectionless networks that dynamically adapt to network congestion. The basic routing protocol uses a short-term metric based on hop-by-hop credits to reduce congestion over a given link, and a long-term metric based on end-to-end path delay to reduce delays from a source to a given destination. A worst-case bound on the end-to-end path delay is derived under three architectural assumptions: each router adopts weighted fair queueing (or packetized generalized processor sharing) service discipline on a per destination basis, a permit-bucket filter is used at each router to regulate traffic flow on a per destination basis, and all paths are loop free. The shortest multipath routing protocol regulates the parameters of the destination-oriented permit buckets and guarantees that all portions of a multipath are loop free.

A fault-tolerant routing strategy in hypercube multicomputers

Abstract: We investigate fault-tolerant routing which aims at finding feasible minimum paths in a faulty hypercube. The concept of unsafe node and its extension are used in our scheme. A set of stringent criteria is proposed to identify the possibly bad candidates for forwarding a message. As a result, the number of such undesirable nodes is reduced without sacrificing the functionality of the mechanism. Furthermore, the notion of degree of unsafeness for classifying the unsafe nodes is introduced to facilitate the design of efficient routing algorithms which rely on having each node keep the states of its nearest neighbors. We show that a feasible path of length no more than the Hamming distance between the source and the destination plus four can always be established by the routing algorithm as long as the hypercube is not fully unsafe. The issue of deadlock freeness is also addressed in this research. More importantly, another fault-tolerant routing algorithm, which requires only a constant of five virtual networks in wormhole routing to ensure the property of deadlock freeness for a hypercube of any size, is presented in this paper.

SVC routing in network with static routing tables

Abstract: A method is disclosed for establishing a switched virtual circuit in a digital network having network nodes with static routing tables. The static routing tables contain at least primary and alternate routing data. When a node is unable to forward a call over its outgoing primary route due to congestion or physical failure and its alternate route is the same as the route on which a call setup request arrived, it clears the call at that node and sends a crankback message to the preceding node, which responds to the crankback message to attempt to dynamically re-route the call over the alternate route stored in the routing table of the preceding node. If the attempt is unsuccessful, it sends the message back to the next preceding node and so on.

Memory requirement for routing in distributed networks

Abstract: In this paper, we deal with the compact routing problem on distributed networks, that is implementing routing schemes that use a minimum memory size on each node. We prove that for every shortest path routing scheme, for any constant e, O < c < 1, and for every integer d such that 3 ~ d < En, there exists a n-node network of maximum degree d that locally requires @(n log d) bits of memory on El(n) nodes. This optimal lower bound means that whatever you choose the routing scheme (interval routing, boolean routing, prefix routing, . ..). there exists a network on which one can not do better than routing tables.

Method and system of forwarding calls in a remote access call forwarding service of a telephone system

Abstract: A remote access call forwarding method and system adapted for an Advanced Intelligent Network to forward a call incoming to a subscriber's telephone number in response to a routing destination number if the routing destination number does not correspond to a blocked destination identifier retrieved from a database. Further, a search to a subscriber profile unique to each subscriber is provided, the subscriber profile containing valid routing destination numbers previously validated to which the calls incoming to the subscriber have previously been forwarded. Thus, calls are forwarded in response to the routing destination number when the routing destination number matches a valid destination number found in the subscriber profile.

Mobile network geographic address translation

Abstract: The present invention is a system and method of providing the information necessary for geographically-based mobile services by translating public geographic information to corresponding mobile network structure. When an indication of a geographic area is received, the indication is translated to an indication of a portion of the mobile network corresponding to the geographic area and an indication of the service is transmitted to the indicated portion of the mobile network. In a preferred embodiment, a broadcast message is transmitted over a mobile network to a plurality of mobile stations within a geographic area. When the system receives a message to be broadcast and an indication of the geographic area of the broadcast, the indication of the geographic area is translated to an indication of a portion of the mobile network corresponding to the geographic area. The message is then transmitted to the indicated portion of the mobile network.

Call routing in an atm switching network

Abstract: A routing scheme for an ATM switching network includes a plurality of switching nodes, each of which includes individual storage for storing routing messages for each outgoing link. A call at a source node is routed through one possible routing path which requires only one or two links to complete a connection to a destination node. In such case, one of the routing paths is selected based on link state information concerning only the possible routing paths. If the call requires a route path which includes three or more links to the destination node, the source node performs a predefined sequential routing to its neighboring node before the neighboring node negotiates with selected intermediate nodes for a connection involving two links. The routing messages stored at each node are processed independently and simultaneously by each node. The main requirement is that routing decisions must be based on true link-state information. A protocol is devised for fast and efficient bulk processing while avoiding potential deadlocks.

A hybrid approach to vehicle routing using neural networks and genetic algorithms

Abstract: A competitive neural network model and a genetic algorithm are used to improve the initialization and construction phase of a parallel insertion heuristic for the vehicle routing problem with time windows. The neural network identifies seed customers that are distributed over the entire geographic area during the initialization phase, while the genetic algorithm finds good parameter settings in the route construction phase that follows. Computational results on a standard set of problems are also reported.

Routers connecting LANs through public network

Abstract: A router includes a routing table containing flags each representing a public-network side or a LAN side. A path for a received packet is determined such that the packet is forwarded to the next node through the LAN according to the next node address when the flag corresponding to the specified destination represents the LAN side, and the packet is forwarded to the next node through the public network according to the next node address when the flag represents the public network side. When a change of the routing information sets is monitored, the routing table is searched for the second router having the flag representing the public network side and then the changed routing information sets are transmitted to the second router.

Dead reckoning routing of packet data within a network of nodes having generally regular topology

Abstract: A packet is routed by “dead reckoning” on a network having a generally regular topology. The packet is received at a node where a local routing decision is made. The packet is output in a direction selected according to the routing decision. The packet carries in addition to a destination address a directional flag indicating explicitly the preferred direction of onward travel and the routing decision is made using this flag. Several flags may be used, corresponding to different dimensions of the network.

Graph based analysis of 2-D FPGA routing

Abstract: In this paper, we study the two-dimensional FPGA, Xilinx-like routing architectures and present the first known computational complexity results for them. The routing problem is formulated as a two-dimensional interval packing problem and is proved to be NP-complete with or without doglegs. Next, we consider other routing structures obtained from the industrial one by arbitrarily changing switch box connection topology while maintaining the same connection flexibility. There is an exponentially large number of such routing structures. We further prove that there does not exist a better routing architecture among the members of this large domain. In addition, we prove that there is no constant bound on the mapping ratio of a track number required by a detailed routing to a global routing channel density for the studied architectures. Finally, we show two directions of changing the routing architectures which yield polynomial time mapping solutions and constant bounded mapping ratios. Our theoretical analysis is intended to give some insight to, and understanding of this new routing problem's fundamental properties.

Adaptive source routing in multistage interconnection networks

Abstract: We describe the adaptive source routing (ASR) method which is a first attempt to combine adaptive routing and source routing methods. In ASR, the adaptivity of each packet is determined at the source processor. Every packet can be routed in a fully adaptive or partially adaptive or non-adaptive manner, all within the same network at the same time. We evaluate and compare performance of the proposed adaptive source routing networks and oblivious routing networks by simulations. We also describe a route generation algorithm that determines maximally adaptive routes in multistage networks.

Method of routing in an asynchronous transfer mode network

Abstract: A novel method of routing and performing autoconfiguration in an ATM network is disclosed. The method simplifies the configuration and routing for ATM networks having a relatively large number of nodes. Networks are constructed in hierarchical fashion in the form of branches and trees and assigned network address prefixes in accordance with their location in the network. Network nodes periodically exchange identification information permitting both switches on either side of a link to be aware of who they are connected to. Each node registers a network address and its associated significant length for each of its neighbors on each of its links. A node performs routing by comparing the destination address against each of its registered addresses for all its links. The routing method takes advantage of the network address prefix to ensure that the routing proceeds in the correct direction towards the destination and does not enter a tree or a branch that does not contain the destination. In addition, each node performs load balancing at each point in the routing process. A node can generate crankback messages if the routing leads to a dead end.

Performance comparison of static routing and dynamic routing in low-Earth orbit satellite networks

Abstract: We compare the performance of two routing schemes for LEO satellite networks through simulation. The two routing schemes represent static and dynamic routing for the case where the LEO satellite network is modeled as a finite state automaton (FSA). Each state in this FSA modeling corresponds to an equal-length interval within the period of the LEO satellite network. Modeling the LEO satellite network in this way allows us to consider the LEO satellite network as if it is a fixed topology network within each state. The routing table for the static routing is fixed within each state whereas that for the dynamic routing is updated continuously according to the shortest-path algorithm. The simulation results show that the static routing performs better in terms of newly initiated call blocking than the dynamic one. The results also show that the static routing gives lower ongoing call blocking probabilities than the dynamic counterpart since the former's pre-computed routing table is less susceptible to the abrupt topological change during a state transition.

A theory of wormhole routing in parallel computers

Abstract: Virtually all theoretical work on message routing in parallel computers has dwelt on packet routing: messages are conveyed as packets, an entire packet can reside at a node of the network, and a packet is sent from the queue of one node to the queue of another node until its reaches its destination. A trend in multicomputer architecture, however, is to use wormhole routing. In wormhole routing a message is transmitted as a contiguous stream of bits, physically occupying a sequence of nodes/edges in the network. Thus, a message resembles a worm burrowing through the network. In this paper we give theoretical analyses of simple wormhole routing algorithms, showing them to be nearly optimal for butterfly and mesh connected networks. Our analysis requires initial random delays in injecting messages to the network. We report simulation results suggesting that the idea of random initial delays may have an impact beyond theoretical analysis.

Design of wavelength-routed optical networks for circuit switched traffic

Abstract: We consider the problem of routing and assignment of wavelength (RAW) in wavelength-routed optical networks. Given a set of requests for all-optical connections (or lightpaths), the problem is to find wavelength-continuous routes from the source nodes to their respective destination nodes. Since the number of wavelengths available per link is limited, lightpaths cannot be established between every source-destination node pairs. Moreover, a common wavelength might not be available on all the segments of a chosen route. Thus, routing and wavelength assignment are to be considered concurrently for the best possible performance. Several heuristic algorithms have already been proposed for the RAW problem, however, most of these algorithms are based on the traditional model of circuit-switched networks where the routing and wavelength assignment steps are decoupled. A new RAW scheme is developed which unifies the routing and wavelength assignment subproblems. This unified approach is found to yield significantly better solutions to the RAW problem than the earlier ones. The paper also introduces an analytical model for predicting the average number of lightpaths requests a given physical network can support.

Dynamic routing of real-time virtual circuits

Abstract: Future integrated services networks, such as ATM networks, will support diverse services, including the guaranteed real-time service required by many applications such as voice and video. To support such services, virtual circuit (VC) routing algorithms are often proposed. Typically, the source maintains a view of the network, and uses this view to select a path to the destination. A request is then made to setup a real-time VC over this path through resource reservations. The request is blocked if the requested resources are not available. These VC routing algorithms are usually evaluated individually in terms of steady-state performance measures. In this paper, we compare several VC routing schemes in terms of instantaneous measures using a time-dependent evaluation method. Our results show that a routing scheme which defines the cost of a path as the sum of measured link utilizations yields more stable behavior and lower VC blocking probability over a wide range of workload parameters and network configurations than other traditional schemes.

Throughput properties of a queueing network with distributed dynamic routing and flow control

Abstract: A queueing network with arbitrary topology, state dependent routing and flow control is considered. Customers may enter the network at any queue and they are routed through it until they reach certain queues from which they may leave the system. The routing is based on local state information. The service rate of a server is controlled based on local state information as well. A distributed policy for routing and service rate control is identified that achieves maximum throughput. The policy can be implemented without knowledge of the arrival and service rates. The importance of flow control is demonstrated by showing that, in certain networks, if the servers cannot be forced to idle, then no maximum throughput policy exists when the arrival rates are not known. Also a model for exchange of state information among neighboring nodes is presented and the network is studied when the routing is based on delayed state information. A distributed policy is shown to achieve maximum throughput in the case of delayed state information. Finally, some implications for deterministic flow networks are discussed.

Congestion control in asynchronous, high-speed wormhole routing networks

Abstract: High-speed networks use lightweight protocols and a simple switch architecture for achieving higher speeds. A lightweight switching technique for local area and campus environments is wormhole routing, in which the head of a packet (worm), upon arriving at an intermediate switch, is immediately forwarded to the next switch on the path. Thus, the packet, like a worm, may stretch across several intermediate switches and links. Wormhole routing networks provide low latency. However, they are particularly prone to congestion, thus requiring careful flow control. The authors consider high-speed, asynchronous, unslotted wormhole routing networks. For such networks, two different flow control mechanisms are compared and contrasted, namely, backpressure flow control and deflection routing (with local input rate control). With backpressure, in order to maintain deadlock-free routing, either up/down routing or shortest path routing with virtual channels is assumed. With deflection routing, to avoid livelocks, worm alignment (delayed deflection) is performed at the switches. It is shown via simulation that the throughput performance of the two schemes is comparable (except for up/down routing). The authors also discuss the tradeoffs with respect to the complexity of hardware, routing protocols and buffer requirements. The authors further examine the role of input rate control at the hosts to overcome unbounded delays typical of deflection routing, and show it is possible to achieve lower average number of hops and transit delays by employing suitable input rate control policies.

Modeling location management in personal communications services

Abstract: Location management refers to accessing and maintaining user information for call routing purposes. This paper presents a realistic modeling framework for evaluating the performance of location management schemes in PCS networks. The framework captures complex human behaviors and has been validated through analysis of actual call and mobility data. Simulation results, showing the performance of IS-41, are presented.