Showing papers on "Routing protocol published in 1993"

RSVP: a new resource ReSerVation Protocol

Abstract: A resource reservation protocol (RSVP), a flexible and scalable receiver-oriented simplex protocol, is described. RSVP provides receiver-initiated reservations to accommodate heterogeneity among receivers as well as dynamic membership changes; separates the filters from the reservation, thus allowing channel changing behavior; supports a dynamic and robust multipoint-to-multipoint communication model by taking a soft-state approach in maintaining resource reservations; and decouples the reservation and routing functions. A simple network configuration with five hosts connected by seven point-to-point links and three switches is presented to illustrate how RSVP works. Related work and unresolved issues are discussed. >

A survey of wormhole routing techniques in direct networks

Abstract: Several research contributions and commercial ventures related to wormhole routing, a switching technique used in direct networks, are discussed. The properties of direct networks are reviewed, and the operation and characteristics of wormhole routing are discussed in detail. By its nature, wormhole routing is particularly susceptible to deadlock situations, in which two or more packets may block one another indefinitely. Several approaches to deadlock-free. routing, along with a technique that allows multiple virtual channels to share the same physical channel, are described. In addition, several open issues related to wormhole routing are discussed. >

Packet Routing in Dynamically Changing Networks: A Reinforcement Learning Approach

Abstract: This paper describes the Q-routing algorithm for packet routing, in which a reinforcement learning module is embedded into each node of a switching network. Only local communication is used by each node to keep accurate statistics on which routing decisions lead to minimal delivery times. In simple experiments involving a 36-node, irregularly connected network, Q-routing proves superior to a nonadaptive algorithm based on precomputed shortest paths and is able to route efficiently even when critical aspects of the simulation, such as the network load, are allowed to vary dynamically. The paper concludes with a discussion of the tradeoff between discovering shortcuts and maintaining stable policies.

Cyclic transfer algorithms for multivehicle routing and scheduling problems

Abstract: This paper investigates the application of a new class of neighborhood search algorithms—cyclic transfers—to multivehicle routing and scheduling problems. These algorithms exploit the two-faceted decision structure inherent to this problem class: First, assigning demands to vehicles and, second, routing each vehicle through its assigned demand stops. We describe the application of cyclic transfers to vehicle routing and scheduling problems. Then we determine the worst-case performance of these algorithms for several classes of vehicle routing and scheduling problems. Next, we develop computationally efficient methods for finding negative cost cyclic transfers. Finally, we present computational results for three diverse vehicle routing and scheduling problems, which collectively incorporate a variety of constraint and objective function structures. Our results show that cyclic transfer methods are either comparable to or better than the best published heuristic algorithms for several complex and important ...

Loop-free routing using diffusing computations

Abstract: A family of distributed algorithms for the dynamic computation of the shortest paths in a computer network or internet is presented, validated, and analyzed. According to these algorithms, each node maintains a vector with its distance to every other node. Update messages from a node are sent only to its neighbors; each such message contains a distance vector of one or more entries, and each entry specifies the length of the selected path to a network destination, as well as an indication of whether the entry constitutes an update, a query, or a reply to a previous query. The new algorithms treat the problem of distributed shortest-path routing as one of diffusing computations, which was first proposed by Dijkstra and Scholten (1980). They improve on a number of algorithms introduced previously. The new algorithms are shown to converge in finite time after an arbitrary sequence of link cost or topological changes, to be loop-free at every instant, and to outperform all other loop-free routing algorithms previously proposed from the standpoint of the combined temporal, message, and storage complexities. >

How bad is naive multicast routing

Abstract: In previous approaches to routing multicast connections in networks, the emphasis has been on the source transmitting to a fixed set of destinations (the multicast group). There are some applications where destinations will join and leave the multicast group. Under these conditions, computing an 'optimal' spanning tree after each modification may not be the best way to proceed. An alternative is to make modest alterations to an existing spanning tree to derive a new one. An extreme, though nonoptimal, variation of this is to use minimal cost source to destination routing for each destination, effectively ignoring the existing multicast tree. The authors examine just how nonoptimal these trees are in random general topology networks and conclude that they are worse by only a small factor. The factor is reduced still further if a hierarchy is imposed on the random network to give a more realistic model. >

Routing device utilizing an ATM switch as a multi-channel backplane in a communication network

Abstract: A data communications network providing for a multiport router and providing for use of an asynchronous transfer mode (ATM) switch or the like as a routing backplane or packet switching engine. A router front end formats ATM cells including providing routing information in the cell header. The routing information may comprise, for example, a destination port identifier in the VPI field of the cell header. The ATM switch then switches the cell from an input port, coupled with the router front end to an output port based on the routing information. The ATM switch may also translate the routing information to provide source identification information to the destination. In a described embodiment, the multiport router is used as a backplane bus in a network concentrator.

System for extending network resources to remote networks

Abstract: A system for interconnecting networks transparently extends the multiprotocol routing functionality of a router across a communication link to a remote LAN, while requiring a device on the remote LAN which operates independent of the higher layer protocol suites. A boundary router, having a local routing interface coupled to the first network, and a remote routing interface coupled to the communication link, provides the higher level protocol suite services for routing frames of data to terminals in the first and second networks. A routing adapter extends the remote routing interface of the boundary router transparently across the communication link to the second network.

A comparison of adaptive wormhole routing algorithms

Abstract: Improvement of message latency and network utilization in torus interconnection networks by increasing adaptivity in wormhole routing algorithms is studied. A recently proposed partially adaptive algorithm and four new fully-adaptive routing algorithms are compared with the well-known e-cube algorithm for uniform, hotspot, and local traffic patterns. Our simulations indicate that the partially adaptive north-last algorithm, which causes unbalanced traffic in the network, performs worse than the nonadaptive e-cube routing algorithm for all three traffic patterns. Another result of our study is that the performance does not necessarily improve with full-adaptivity. In particular, a commonly discussed fully-adaptive routing algorithm, which uses 2n virtual channels per physical channel of a k-ary n-cube, performs worse than e-cube for uniform and hotspot traffic patterns. The other three fully-adaptive algorithms, which give priority to messages based on distances traveled, perform much better than the e-cube and partially-adaptive algorithms for all three traffic patterns. One of the conclusions of this study is that adaptivity, full or partial, is not necessarily a benefit in wormhole routing.

A mobile networking system based on internet protocol(IP)

Abstract: Due to advances in wireless communication technology there is a growing demand for providing continuous network access to the users of portable computers, regardless of their location. Existing network protocols cannot meet this requirement since they were designed with the assumption of a static network topology where hosts do not change their location over time. Based on IP's Loose Source Route option, we have developed a scheme for providing transparent network access to mobile hosts. Our scheme is easy to implement, requires no changes to the existing set of hosts and routers, and achieves optimal routing in most cases. An outline of the proposed scheme is presented and a reference implementation is described.

Message routing in a multiprocessor computer system

Abstract: A parallel processing computer system having an improved architecture for communication of information between nodes. The computer system of the present invention comprises at least three nodes; each of the three nodes for processing information. Each of the nodes comprises a routing means for routing information between nodes. The routing means allow reservation of a route through the network of nodes. Messages may then be transmitted from an origin node to a destination node over the reserved route. Use of a route reservation system reduces requirements for buffering of information at intermediate nodes on a route, improves message passing latency and increases node-to-node bandwidth. The present invention teaches communication of messages between nodes in a synchronous manner.

The Message Flow Model for Routing in Wormhole-Routed Networks

Abstract: In this paper, we introduce a new approach to deadlock-free routing in wormhole-routed networks called the message flow model. We first establish the necessary and sufficient condition for deadlock-free routing based on the analysis of the message flow on each channel. We then show how to use the model to prove that a given adaptive routing algorithm is deadlock-free. Finally, we use the method to de? velop new, efficient adaptive routing algorithms for 2D meshes and hypercubes.

Adaptive Deadlock-Free Routing in Multicomputers Using Only One Extra Virtual Channel

Abstract: We present three protocols defin ing the relationship between messages and the chan nel resources requested: request-then-hold, requestthen wait, and request-then-relinquish. Based on the three protocols, we develop an adaptive deadlockfree routing algorithm called the SP routing. The SP routing uses shortest paths and is fully-adaptive, so messages can be routed via any of the shortest paths from the source to the destination. Since it is a minimal or shortest routing, the SP routing guar antees the freedom of livelocks. The SP routing is not limited to a specific network topology. The main requirement for an applicable network topology is that there exists a deterministic, minimal, deadlock-free routing algorithm. Most ex isting network topologies are equipped with such an algorithm. In this paper, we present an adaptive deadlock-free routing agorithm for n-dimensional meshes by using the SP routing. The hardware re quired by the SP routing uses only one extra virtual channel as compared to the deterministic routing.

Routing multipoint connections using virtual paths in an ATM network

Abstract: The point-to-multipoint routing problem is studied for an asynchronous transfer mode (ATM) network that uses virtual paths (VPs). ATM networks with asymmetric and symmetric VPs are considered, and the performance factors studied are bandwidth and establishment and switching costs. A VP with intermediate exit, where a node that performs VP switching can copy the switched packets for the local destination, is proposed and studied. Mathematical formulations of multicast routing problems are presented, and heuristics for finding a low cost multicast routing tree, based on the transshipment simplex algorithm, are developed. >

An Efficient Timing-Driven Global Routing Algorithm

Abstract: In this paper, we propose an efficient timing-driven global routing algorithm. Unlike other conventional global routing techniques, interconnection delays are modeled and included during routing and rerouting process in order to minimize the routing area as well as to satisfy timing constraint. The timing-driven global routing problem is formulated as a multiterminal, multicommodity flow problem with integer flows and additional timing constraint. Two efficient timing-driven Steiner tree approach and one Steiner tree improving approach have been used to create initial routing results and reroute trees respectively. The algorithm has been implemented and the experimental results are quite promising.

Integration of security in network routing protocols

Abstract: There are two sources of threats to secure operation of routing protocols in networks. The first source of threats is subverted routers that legitimately participate in a routing protocol. The second source of threats is intruders which may illegally attempt to interfere in routing protocols by masquerading as routers. In this paper, we first analyse the security requirements of network routing protocols and then discuss the necessary measures which can be adopted to make the operation of these protocols secure.

Minimax open shortest path first routing algorithms in networks supporting the SMDS service

Abstract: Two quasi-static minimax open shortest path first (OSPF) routing algorithms in networks supporting the Switched Multi-megabit Data Service (SMDS) are presented and compared. In OSPF routing, the network is modeled as a graph and each link is associated with a nonnegative arc weight. A shortest path spanning tree is calculated for each origin to carry both the individually addressed and the group addressed (multicast) traffic. The OSPF routing protocol is adopted as a major part of the default inter-switching system interface (ISSI) routing algorithm for SMDS networks where arc weights are inversely proportional to the aggregate link set capacities. The problem of choosing a set of link set metrics is considered so that the maximum link utilization factor is minimized in an SMDS network. The problem is formulated as a nonlinear mixed integer programming problem. >

An analytical model for wormhole routing in multicomputer interconnection networks

Abstract: The communication performance of the interconnection network is critical in a multicomputer system. Wormhole routing has been known to be more efficient than the traditional circuit switching and packet switching. To evaluate wormhole routing, a queueing-theoretic analysis is used. This paper presents a general analytical model for wormhole routing based on very basic assumptions. The model is used to evaluate the routing delays in hypercubes and meshes. Delays calculated are compared against those obtained from simulations, and these comparisons show that the model is within a reasonable accuracy. >

Dynamics of internet routing information

Abstract: The Internet is a complex mesh of networks that use a common suite (TCP/IP) of networking protocols. A key feature of the Internet is that all of these constituent networks are interconnected, thereby providing system wide communication. The magnitude and pattern of the flow of routing information directly represents the connectivity stability of the Internet. The NSFNET backbone network provides transit services to a large portion of the global Internet and maintains routing tables reflecting this current connectivity. These routing tables are constantly updated based on information received by the attached networks. This paper investigates the dynamics of routing information flow as presented to the NSFNET backbone network.

Unslotted deflection routing in all-optical networks

Abstract: When nodes of a communication network have identical input- and output-link capacities, it is possible to use as few as one packet buffer per link, if one is willing to deflect-or misroute-a subset of simultaneously arriving fixed-length packets from preferred to alternate output links. This scheme, known as deflection routing, can achieve very fast packet switching in regular networks and has been proposed as the basic routing and switching protocol of several all-optical networks. The performance models of deflection-routing networks that have appeared in the literature have assumed that time is slotted and packets arrive at nodes on time-slot boundaries. In practice, however, slotted operation is difficult to implement in all-optical networks. The present authors evaluate by simulation the performance of deflection routing in unslotted networks. The evaluations show a surprising degradation of throughput in unslotted deflection routing networks, compared to slotted networks, and reveal situations where severe congestion occurs. To overcome these limitations they propose the use of specific control mechanisms in unslotted networks that allow one to eliminate congestion and to improve substantially the network throughput. >

An Efficient Multilayer MCM Router Based on Four-Via Routing

Abstract: In this paper, we present an efficient multilayer general area router, named V4R, for MCM and dense PCB designs. It uses no more than four vias to route every net and yet produces high quality routing solutions. It combines global routing and detailed routing in one step and produces high quality detailed routing solutions directly from the given netlist and module placement. As a result, V4R is independent of net ordering, runs much faster, and uses far less memory compared to other multilayer general area routers. Experimental results show that V4R outperforms both the 3D maze router and the SLICE router significantly.

A new theory of deadlock-free adaptive multicast routing in wormhole networks

Abstract: A theory for the design of deadlock-free adaptive routing algorithms for wormhole networks has been proposed previously. This theory supplies the sufficient conditions for an adaptive routing algorithm to be deadlock-free, even when there are cyclic dependencies between channels. Also, two design methodologies have been proposed. Multicast communication refers to the delivery of the same message from one source node to an arbitrary number of destination nodes. Two multicast wormhole routing methods have been presented previously for multicomputers with 2D-mesh and hypercube topologies. This paper develops the theoretical background for the design of deadlock-free adaptive multicast routing algorithms for wormhole networks. Some basic definitions and two theorems are proposed, developing conditions to verify that an adaptive multicast routing algorithm is deadlock-free, even when there are cyclic dependencies between channels. As an example, the multicast routing algorithms presented previously are extended, so that they can take advantage of the alternative paths offered by the network. >

Open shortest path first (OSPF) routing protocol simulation

Abstract: Open Shortest Path First (OSPF) is a dynamic, hierarchical routing protocol designed to support routing in TCP/IP networks. A simulation of the OSPF Election Protocol shows three results: (1) The Designated Router (DR) can be elected in constant time. (2) If a router has a limited number of input buffers, a competition for buffers between the Election and the Flooding Protocols increases the election time and causes an oscillatory behavior.At each router, the Router-ID of the DR continuously changes causing instability. (3) In the worst case, when the DR and the BDR fail at the same time, the DR-agreement-time is bounded above by twice the HelloInterval. A simulation of the OSPF Flooding Protocol, using 20, 50 and 80 router point-to-point networks, shows three results: (1) For the 50 router network, as link speed exceeds 4000 Kbps, the probability of overflowing the input buffers increases causing retransmissions. The increase in bootup-convergence-time from retransmissions is bounded by two and three times the RxmtInterval for link speeds of 4000 to 6000 Kbps and above 50 Mbps respectively. The increase in the bootup-convergence-time is due to large number of unacknowledged flooding packets received within RxmtInterval. (2) For 20 and 50 router networks, the input buffer size has little impact on the bootup-convergence-time. For the 80 router network, a small change in the input buffer size drastically changes the bootup-convergence-time. (3) Reducing the value of the RxmtInterval lowers the bootup-convergence-time at high link speeds.

Integrating security in inter-domain routing protocols

Abstract: Network routing protocols work in a vulnerable environment. Unless protected by appropriate security measures, their operation can be easily subverted by intruders capable of modifying, deleting or adding false information in routing updates. This paper first analyses threats to the secure operation of inter-domain routing protocols, and then proposes various counter measures to make these protocols secure against external threats.

Deadlock-free fault-tolerant routing in injured hypercubes

Abstract: Wormhole routing with the e-cube algorithm is an excellent solution for deadlock-free interprocess communication in healthy hypercubes. However, it does not work for injured hypercubes where some nodes and/or links are faulty. The authors propose a new deadlock-free routing scheme in an injured hypercube with the wormhole routing capability. All previously proposed schemes suggest the use of virtual channels to avoid the cycle of resource dependency. By contrast, the authors' scheme is based on the re-establishment of a routing path to the destination, but it does not always yield a shortest path between the source and destination. The proposed routing scheme uses either wormhole routing or staged routing, depending on the availability of one or more healthy (n-2)-cubes within an injured n-cube. >

Dispersity routing on ATM networks

Abstract: Dispersity routing is defined. It is combined with random access and fast circuit set-up and tear-down to put bursty data on an asynchronous transfer mode (ATM) network. This approach makes the storage in the network independent of the message length. This approach is evaluated assuming that the propagation delay may be more than the message transmission time. It is shown that the efficiency improves as the number of channels on each path increases, and that dispersity routing makes it reasonable to use the strategy on networks with a small number of channels per path. Dispersity routing requires networks with multiple paths between many of the nodes. This characteristic is also required for many adaptive routing strategies. A class of networks is proposed in which the fraction of nodes with multiple paths, and the number of multiple paths between nodes, can be controlled. These networks provide a platform for evaluating multiple path strategies. >

Dynamic routing in multiparented networks

Abstract: The authors investigate some of the consequences for dynamic routing schemes of dual- and multiparented networks, in which a call can enter (or leave) the network at two or more points. In particular, they compare bounds on the performance of optimal dynamic routing strategies which respectively ignore and utilize the multiparented structure, and show that simple schemes, easily implemented and analyzed, are able to achieve most of the additional advantages allowed to dynamic routing schemes by multiparenting. The robust behavior of these schemes under traffic mismatches as well as multiple link or node failure events is illustrated. >

Chaotic routing: design and implementation of an adaptive multicomputer network router

Abstract: A crucial component of a massively parallel multicomputer is the interconnection network which links all of the nodes of the computer together This network provides the primary method of communication between the hundreds or thousands of processing nodes and is, thus, critical to the successful operation of the multicomputer Current state-of-the-art interconnection networks use simple, oblivious routing techniques which achieve very good performance when loading is light, but do not perform well in the presence of non-uniform congestion or faults Chaotic routing, a non-minimal adaptive routing technique, provides a mechanism which takes into account the presence of congestion and faults when choosing a path for a message and can, thus, achieve better performance Chaotic routing is shown to be applicable to all finite-sized networks of bounded degree with bi-directionally connected links A design for a chaotic router is presented which includes both the features of virtual cut-through routing and the advantages of internal non-blocking buffering This design allows messages to follow minimum-latency paths when network loading is light, and provides sufficient buffering to ensure high throughput when the network is heavily loaded The resulting design is compared with other minimal and non-minimal adaptive designs, as well as with oblivious routing Chaotic routing is shown to be superior to most other adaptive designs due to its lower design complexity, and simulations are used to compare it with oblivious and deflection routing The simulations show that, for mesh-connected networks, chaotic routing performs only slightly better than oblivious routing However, for torus- and hypercube-connected networks, chaotic routing is superior to oblivious and deflection routing, achieving much higher throughput and lower latency To demonstrate the feasibility of chaotic routing, a prototype chaos router chip is presented This chip, fabricated in 12$\mu$m CMOS, implements a two-dimensional chaos router The chip, in simulations, operates at 66MHz, with the speed being limited only by the speed at which the 5V CMOS pads can be switched Thus, the chip should operate at the same clock speed as oblivious routers using the same technology, giving an equivalent bandwidth capability

Improving the routing and addressing of IP

Abstract: Simple mechanisms for introducing hierarchy into the interdomain routing system, making it practical to route a truly large Internet, are described. It is shown that addresses need to be assigned along network topological lines to maximise the reduction in routing overhead. Simplifying the mechanisms for changing hot addresses makes it possible to renumber a network so that it has a topologically significant address when the site changes position within the routing system. These proposals make it possible to significantly increase the utilization of addresses and extend the time the Internet can use the Internet Protocol (IP) Version 4. >

A protocol for route establishment and packet forwarding across multidomain internets

Abstract: Internetworks that are global in scale, contain multiple administrative domains, and support a range of services present special requirements for routing. Multiple administrative domains introduce the need for policy-sensitive routing. Service heterogeneity intensifies the requirement for type of service (TOS) routing, as well as other protocol support for handling a range of services, from datagrams to multimedia streams. Key concepts and protocols developed as part of the interdomain policy routing (IDPR) architecture are summarized. Emphasis is placed on the route installation and packet forwarding mechanisms because they are critical to protocol performance and differ significantly from current practice in datagram wide area networks. >