Showing papers on "Static routing published in 1996"

Quality-of-service routing for supporting multimedia applications

Abstract: Several new architectures have been developed for supporting multimedia applications such as digital video and audio. However, quality-of-service (QoS) routing is an important element that is still missing from these architectures. In this paper, we consider a number of issues in QoS routing. We first examine the basic problem of QoS routing, namely, finding a path that satisfies multiple constraints, and its implications on routing metric selection, and then present three path computation algorithms for source routing and for hop-by-hop routing.

An efficient routing protocol for wireless networks

Abstract: We present the Wireless Routing Protocol (WRP). In WRP, routing nodes communicate the distance and second-to-last hop for each destination. WRP reduces the number of cases in which a temporary routing loop can occur, which accounts for its fast convergence properties. A detailed proof of correctness is presented and its performance is compared by simulation with the performance of the distributed Bellman-Ford Algorithm (DBF), DUAL (a loop-free distance-vector algorithm) and an Ideal Link-state Algorithm (ILS), which represent the state of the art of internet routing. The simulation results indicate that WRP is the most efficient of the alternatives analyzed.

The PIM architecture for wide-area multicast routing

Abstract: The purpose of multicast routing is to reduce the communication costs for applications that send the same data to multiple recipients. Existing multicast routing mechanisms were intended for use within regions where a group is widely represented or bandwidth is universally plentiful. When group members, and senders to those group members, are distributed sparsely across a wide area, these schemes are not efficient; data packets or membership report information are occasionally sent over many links that do not lead to receivers or senders, respectively. We have developed a multicast routing architecture that efficiently establishes distribution trees across wide area internets, where many groups will be sparsely represented. Efficiency is measured in terms of the router state, control message processing, and data packet processing, required across the entire network in order to deliver data packets to the members of the group. Our protocol independent multicast (PIM) architecture: (a) maintains the traditional IP multicast service model of receiver-initiated membership, (b) supports both shared and source-specific (shortest-path) distribution trees, (c) is not dependent on a specific unicast routing protocol, and (d) uses soft-state mechanisms to adapt to underlying network conditions and group dynamics. The robustness, flexibility, and scaling properties of this architecture make it well-suited to large heterogeneous internetworks.

A novel distributed routing protocol to support ad-hoc mobile computing

Abstract: This paper presents a new, simple and bandwidth-efficient distributed routing protocol for ad-hoc mobile networks. Unlike the conventional distributed routing algorithms, our protocol does not attempt to consistently maintain routing information in every node. In an ad-hoc mobile network where mobile hosts are acting as routers and where routes are made inconsistent by mobile host movements, we employ a new associativity-based routing scheme where a route is selected based on nodes having associativity states that imply periods of stability. In this manner, the routes selected are likely to be long-lived and hence there is no need to restart frequently, resulting in higher attainable throughput. The association property also allows the integration of ad-hoc routing into a BS-oriented wireless LAN environment, providing fault tolerance in times of base station (BS) failures. The protocol is free from loops, deadlock and packet duplicates and has scalable memory requirements. Simulation results obtained reveal that shorter and better routes can be discovered during route re-constructions.

The Vehicle Routing Problem with Time Windows Part II: Genetic Search

Abstract: This paper is the second part of a work on the application of new search techniques for the vehicle routing problem with time windows. It describes GENEROUS, the GENEtic ROUting System, which is based on the natural evolution paradigm. Under this paradigm, a population of solutions evolves from one generation to the next by “mating” parent solutions to form new offspring solutions that exhibit characteristics inherited from their parents. For this vehicle routing application, a specialized methodology is devised for merging two vehicle routing solutions into a single solution that is likely to be feasible with respect to the time window constraints. Computational results on a standard set of test problems are reported, and comparisons are provided with other heuristics.

End-to-end routing behavior in the internet

Abstract: The large-scale behavior of routing in the Internet has gone virtually without any formal study, the exception being Chinoy's analysis of the dynamics of Internet routing information [Ch93]. We report on an analysis of 40,000 end-to-end route measurements conducted using repeated "traceroutes" between 37 Internet sites. We analyze the routing behavior for pathological conditions, routing stability, and routing symmetry. For pathologies, we characterize the prevalence of routing loops, erroneous routing, infrastructure failures, and temporary outages. We find that the likelihood of encountering a major routing pathology more than doubled between the end of 1994 and the end of 1995, rising from 1.5% to 3.4%. For routing stability, we define two separate types of stability, "prevalence" meaning the overall likelihood that a particular route is encountered, and "persistence," the likelihood that a route remains unchanged over a long period of time. We find that Internet paths are heavily dominated by a single prevalent route, but that the time periods over which routes persist show wide variation, ranging from seconds up to days. About 2/3's of the Internet paths had routes persisting for either days or weeks. For routing symmetry, we look at the likelihood that a path through the Internet visits at least one different city in the two directions. At the end of 1995, this was the case half the time, and at least one different autonomous system was visited 30% of the time.

The Cray T3E Network: Adaptive Routing in a High Performance 3D Torus

Abstract: This paper describes the interconnection network used in the Cray T3E multiprocessor. The network is a bidirectional 3D torus with fully adaptive routing, optimized virtual channel assignments, integrated barrier synchronization support and considerable fault tolerance. The routers are built with LSI’s 500K ASIC technology with custom transmitters/ receivers driving low-voltage differential signals at 375 MHz, for a link data payload capacity of approximately 500 MB/s.

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.

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.

Digital network including early packet discard mechanism with adjustable threshold

Abstract: A computer network includes a plurality of routing nodes, each routing node being connected to selected ones of the other routing nodes and at least some of the routing nodes being connected to one of a plurality of packet sources or one of a plurality of packet destinations. Each routing node routes packets that are generated by the packet sources to respective ones of the packet destinations, each packet including a plurality of serially-transmitted cells. At least some of the routing nodes, in response to detection of a selected degree of congestion, enable an "early packet discard control arrangement," in which they discards cells which they receive which are related to packets for which they did not receive a cell prior to enabling the early packet discard control arrangement. The routing nodes periodically adjust the degree of congestion at which they will activate the early packet discard mechanism in relation to information corresponding to rates of reception and transmission of cells over a selected period of time prior thereto.

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.

Proxies for anonymous routing

Abstract: Using traffic analysis, it is possible to infer who is talking to whom over a public network. This paper describes a flexible communications infrastructure, called onion routing, which is resistant to traffic analysis. Onion routing lies just beneath the application layer, and is designed to interface with a wide variety of unmodified Internet services by means of proxies. Onion routing has been implemented on a Sun Solaris 2.4; in addition, proxies for World Wide Web browsing (HTTP), remote logins (RLOGIN), e-mail (SMTP) and file transfers (FTP) have been implemented. Onion routing provides application-independent, real-time and bi-directional anonymous connections that are resistant to both eavesdropping and traffic analysis. Applications making use of onion routing's anonymous connections may (and usually should) identify their users over the anonymous connection. User anonymity may be layered on top of the anonymous connections by removing identifying information from the data stream. Our goal is anonymous connections, not anonymous communication. The use of a packet-switched public network should not automatically reveal who is talking to whom; this is the traffic analysis that onion routing complicates.

Automatic layout standard cell routing

Abstract: A method of interconnecting transistors and other devices in order to optimize area of a layout of a cell while honoring performance constraints (1502) and enhancing yield starts with a prerouting step (152) that routes adjacent transistors using diffusion wiring (1506), routes power and ground nets (1508), routes aligned gates (1510), routes all remaining aligned source/drain nets as well as any special nets (1512). Next, all of the remaining nets are routed using an area based router (1408). Nets are order based on time criticality or net topology (1602). A routing grid is assigned for all the layers to be used in routing (1604). An initial coarse routing is performed (1606). Wire groups are assigned to routing layers (1608). Routing is improved and vias are minimized (1610). A determination is then made whether the routing solution is acceptable (1612). If the routintg solution is not acceptable, the routing space is expanded and routing costs and via costs are modifyied to improve the routing solution. Finally, the best routing solution is picked (1414).

Virtual trees routing protocol for an ATM-based mobile network

Abstract: The present invention is a system and method for routing cells in a wireless communications network, wherein the communications network includes a plurality of switching nodes and the cells are routed according to destination-rooted virtual path identifier (VPI) trees. The present invention includes a routing protocol for determining preestablished VPI trees rooted at each destination node. The routing protocol manages the routes of these trees, while ensuring that there are at least two VPI trees from each source to each destination for reliability reasons, and that each destination node has multiple VPI trees for load-balancing reasons. The routing protocol includes an off-line procedure for the determination of the initial VPI trees. In order to handle changes in network traffic and conditions, the routing protocol updates the routes of the VPI trees in a dynamic and distributed fashion. These update procedures are triggered by congestion, link/node failures and link/node additions.

Digital signature protection of the OSPF routing protocol

Abstract: The routing protocols used to disseminate routing information throughout the Internet are not protected from intruders or faulty router participants. This paper reports on work in progress to protect the OSPF routing protocol through the use of cryptography, specifically, digital signatures. The routing information is signed with an asymmetric cryptographic algorithm, allowing each router recipient to check the source and integrity of the information. This paper discusses the fundamental issues in security of routing protocols, reviews the basics of OSPF operation, describes the proposed design and discusses remaining vulnerabilities.

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.

System for generating explicit routing advertisements to specify a selected path through a connectionless network to a destination by a specific router

Abstract: A system for providing explicit routing functions in a connectionless network. A specific router selects a path through the connectionless network to a destination. Explicit routing advertisements are generated by the specific router and contain information regarding the selected path. Routing state is installed according to information contained in the explicit routing advertisements. The explicit routing advertisements are forwarded to each next hop router. Each next hop router installs routing state, generates the explicit routing advertisement, and forwards the explicit routing advertisement to further propagate the routing information.

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.

Method of and system for call routing compliant with international regulatory routing requirements

Abstract: A method of and system for routing switched termination telephone calls in accordance with international routing requirements and with consideration of available network capacity. A call is received at a switch of an international carrier. The switch sends a query identifying the first country as the country of origin for the call and the second country as the country of termination for the call to a service control point of the international carrier. The service control point determines from the query that the call is an international call and sends a request for a routing translation to a regulatory routing platform of the international carrier. The regulatory routing platform determines an optimal route for the call in accordance with international regulatory routing requirements.

On the nucleolus of the basic vehicle routing game

Abstract: In the vehicle routing cost allocation problem the aim is to find a good cost allocation method, i.e., a method that according to specified criteria allocates the cost of an optimal route configuration among the customers. We formulate this problem as a co-operative game in characteristic function form and give conditions for when the core of the vehicle routing game is nonempty. One specific solution concept to the cost allocation problem is the nucleolus, which minimizes maximum discontent among the players in a co-operative game. The class of games we study is such that the values of the characteristic function are obtained from the solution of a set of mathematical programming problems. We do not require an explicit description of the characteristic function for all coalitions. Instead, by applying a constraint generation approach, we evaluate information about the function only when it is needed for the computation of the nucleolus.

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.