Showing papers on "Routing table published in 2006"

MaxProp: Routing for Vehicle-Based Disruption-Tolerant Networks

Abstract: Disruption-tolerant networks (DTNs) attempt to route network messages via intermittently connected nodes. Routing in such environments is difficult because peers have little information about the state of the partitioned network and transfer opportunities between peers are of limited duration. In this paper, we propose MaxProp, a protocol for effective routing of DTN messages. MaxProp is based on prioritizing both the schedule of packets transmitted to other peers and the schedule of packets to be dropped. These priorities are based on the path likelihoods to peers according to historical data and also on several complementary mechanisms, including acknowledgments, a head-start for new packets, and lists of previous intermediaries. Our evaluations show that MaxProp performs better than protocols that have access to an oracle that knows the schedule of meetings between peers. Our evaluations are based on 60 days of traces from a real DTN network we have deployed on 30 buses. Our network, called UMassDieselNet, serves a large geographic area between five colleges. We also evaluate MaxProp on simulated topologies and show it performs well in a wide variety of DTN environments.

Pipelined packet switching and queuing architecture

Abstract: An architecture for a line card in a network routing device is provided. The line card architecture provides a bi-directional interface between the routing device and a network, both receiving packets from the network and transmitting the packets to the network through one or more connecting ports. In both the receive and transmit path, packets processing and routing in a multi-stage, parallel pipeline that can operate on several packets at the same time to determine each packet's routing destination is provided. Once a routing destination determination is made, the line card architecture provides for each received packet to be modified to contain new routing information and additional header data to facilitate packet transmission through the switching fabric. The line card architecture further provides for the use of bandwidth management techniques in order to buffer and enqueue each packet for transmission through the switching fabric to a corresponding destination port. The transmit path of the line card architecture further incorporates additional features for treatment and replication of multicast packets.

Virtual ring routing: network routing inspired by DHTs

Abstract: This paper presents Virtual Ring Routing (VRR), a new network routing protocol that occupies a unique point in the design space. VRR is inspired by overlay routing algorithms in Distributed Hash Tables (DHTs) but it does not rely on an underlying network routing protocol. It is implemented directly on top of the link layer. VRR provides both raditional point-to-point network routing and DHT routing to the node responsible for a hash table key.VRR can be used with any link layer technology but this paper describes a design and several implementations of VRR that are tuned for wireless networks. We evaluate the performance of VRR using simulations and measurements from a sensor network and an 802.11a testbed. The experimental results show that VRR provides robust performance across a wide range of environments and workloads. It performs comparably to, or better than, the best wireless routing protocol in each experiment. VRR performs well because of its unique features: it does not require network flooding or trans-lation between fixed identifiers and location-dependent addresses.

DyXY: a proximity congestion-aware deadlock-free dynamic routing method for network on chip

Abstract: A novel routing algorithm, namely dynamic XY (DyXY) routing, is proposed for NoCs to provide adaptive routing and ensure deadlock-free and livelock-free routing at the same time.A new router architecture is developed to support the routing algorithm.Analytical models based on queuing theory are developed for DyXY routing for a two-dimensional mesh NoC architecture,and analytical results match very well with the simulation results.It is observed that DyXY routing can achieve better performance compared with static XY routing and odd-even routing.

Evaluating Mobility Pattern Space Routing for DTNs

Abstract: Because a delay tolerant network (DTN) can often be partitioned, routing is a challenge. However, routing benefits considerably if one can take advantage of knowledge concerning node mobility. This paper addresses this problem with a generic algorithm based on the use of a high-dimensional Euclidean space, that we call MobySpace, constructed upon nodes' mobility patterns. We provide here an analysis and a large scale evaluation of this routing scheme in the context of ambient networking by replaying real mobility traces. The specific MobySpace evaluated is based on the frequency of visits of nodes to each possible location. We show that routing based on MobySpace can achieve good performance compared to that of a number of standard algorithms, especially for nodes that are present in the network a large portion of the time. We determine that the degree of homogeneity of node mobility patterns has a high impact on routing. And finally, we study the ability of nodes to learn their own mobility patterns.

ROFL: routing on flat labels

Abstract: It is accepted wisdom that the current Internet architecture conflates network locations and host identities, but there is no agreement on how a future architecture should distinguish the two. One could sidestep this quandary by routing directly on host identities themselves, and eliminating the need for network-layer protocols to include any mention of network location. The key to achieving this is the ability to route on flat labels. In this paper we take an initial stab at this challenge, proposing and analyzing our ROFL routing algorithm. While its scaling and efficiency properties are far from ideal, our results suggest that the idea of routing on flat labels cannot be immediately dismissed.

Longest prefix matching using bloom filters

Abstract: We introduce the first algorithm that we are aware of to employ Bloom filters for longest prefix matching (LPM). The algorithm performs parallel queries on Bloom filters, an efficient data structure for membership queries, in order to determine address prefix membership in sets of prefixes sorted by prefix length. We show that use of this algorithm for Internet Protocol (IP) routing lookups results in a search engine providing better performance and scalability than TCAM-based approaches. The key feature of our technique is that the performance, as determined by the number of dependent memory accesses per lookup, can be held constant for longer address lengths or additional unique address prefix lengths in the forwarding table given that memory resources scale linearly with the number of prefixes in the forwarding table. Our approach is equally attractive for Internet Protocol Version 6 (IPv6) which uses 128-bit destination addresses, four times longer than IPv4. We present a basic version of our approach along with optimizations leveraging previous advances in LPM algorithms. We also report results of performance simulations of our system using snapshots of IPv4 BGP tables and extend the results to IPv6. Using less than 2 Mb of embedded RAM and a commodity SRAM device, our technique achieves average performance of one hash probe per lookup and a worst case of two hash probes and one array access per lookup.

Fast IP Network Recovery Using Multiple Routing Configurations

Abstract: As the Internet takes an increasingly central role in our communications infrastructure, the slow convergence of routing protocols after a network failure becomes a growing problem. To assure fast recovery from link and node failures in IP networks, we present a new recovery scheme called Multiple Routing Configurations (MRC). MRC is based on keeping additional routing information in the routers, and allows packet forwarding to continue on an alternative output link immediately after the detection of a failure. Our proposed scheme guarantee s recovery in all single failure scenarios, using a single mechanism to handle both link and node failures, and without knowing the root cause of the failure. MRC is strictly connectionless, and assumes only destination based hop-by-hop forwarding. It can be implemented with only minor changes to existing solutions. In this paper we present MRC, and analyze its performance with respect to scalability, backup path lengths, and load distribution after a failure.

Design and Analysis of Distributed Algorithms

Abstract: Preface. 1. Distributed Computing Environments. 1.1 Entities. 1.2 Communication. 1.3 Axioms and Restrictions. 1.3.1 Axioms. 1.3.2 Restrictions. 1.4 Cost and Complexity. 1.4.1 Amount of Communication Activities. 1.4.2 Time. 1.5 An Example: Broadcasting. 1.6 States and Events. 1.6.1 Time and Events. 1.6.2 States and Configurations. 1.7 Problems and Solutions (). 1.8 Knowledge. 1.8.1 Levels of Knowledge. 1.8.2 Types of Knowledge. 1.9 Technical Considerations. 1.9.1 Messages. 1.9.2 Protocol. 1.9.3 Communication Mechanism. 1.10 Summary of Definitions. 1.11 Bibliographical Notes. 1.12 Exercises, Problems, and Answers. 1.12.1 Exercises and Problems. 1.12.2 Answers to Exercises. 2. Basic Problems And Protocols. 2.1 Broadcast. 2.1.1 The Problem. 2.1.2 Cost of Broadcasting. 2.1.3 Broadcasting in Special Networks. 2.2 Wake-Up. 2.2.1 Generic Wake-Up. 2.2.2 Wake-Up in Special Networks. 2.3 Traversal. 2.3.1 Depth-First Traversal. 2.3.2 Hacking (). 2.3.3 Traversal in Special Networks. 2.3.4 Considerations on Traversal. 2.4 Practical Implications: Use a Subnet. 2.5 Constructing a Spanning Tree. 2.5.1 SPT Construction with a Single Initiator: Shout. 2.5.2 Other SPT Constructions with Single Initiator. 2.5.3 Considerations on the Constructed Tree. 2.5.4 Application: Better Traversal. 2.5.5 Spanning-Tree Construction with Multiple Initiators. 2.5.6 Impossibility Result. 2.5.7 SPT with Initial Distinct Values. 2.6 Computations in Trees. 2.6.1 Saturation: A Basic Technique. 2.6.2 Minimum Finding. 2.6.3 Distributed Function Evaluation. 2.6.4 Finding Eccentricities. 2.6.5 Center Finding. 2.6.6 Other Computations. 2.6.7 Computing in Rooted Trees. 2.7 Summary. 2.7.1 Summary of Problems. 2.7.2 Summary of Techniques. 2.8 Bibliographical Notes. 2.9 Exercises, Problems, and Answers. 2.9.1 Exercises. 2.9.2 Problems. 2.9.3 Answers to Exercises. 3. Election. 3.1 Introduction. 3.1.1 Impossibility Result. 3.1.2 Additional Restrictions. 3.1.3 Solution Strategies. 3.2 Election in Trees. 3.3 Election in Rings. 3.3.1 All the Way. 3.3.2 As Far As It Can. 3.3.3 Controlled Distance. 3.3.4 Electoral Stages. 3.3.5 Stages with Feedback. 3.3.6 Alternating Steps. 3.3.7 Unidirectional Protocols. 3.3.8 Limits to Improvements (). 3.3.9 Summary and Lessons. 3.4 Election in Mesh Networks. 3.4.1 Meshes. 3.4.2 Tori. 3.5 Election in Cube Networks. 3.5.1 Oriented Hypercubes. 3.5.2 Unoriented Hypercubes. 3.6 Election in Complete Networks. 3.6.1 Stages and Territory. 3.6.2 Surprising Limitation. 3.6.3 Harvesting the Communication Power. 3.7 Election in Chordal Rings (). 3.7.1 Chordal Rings. 3.7.2 Lower Bounds. 3.8 Universal Election Protocols. 3.8.1 Mega-Merger. 3.8.2 Analysis of Mega-Merger. 3.8.3 YO-YO. 3.8.4 Lower Bounds and Equivalences. 3.9 Bibliographical Notes. 3.10 Exercises, Problems, and Answers. 3.10.1 Exercises. 3.10.2 Problems. 3.10.3 Answers to Exercises. 4. Message Routing and Shortest Paths. 4.1 Introduction. 4.2 Shortest Path Routing. 4.2.1 Gossiping the Network Maps. 4.2.2 Iterative Construction of Routing Tables. 4.2.3 Constructing Shortest-Path Spanning Tree. 4.2.4 Constructing All-Pairs Shortest Paths. 4.2.5 Min-Hop Routing. 4.2.6 Suboptimal Solutions: Routing Trees. 4.3 Coping with Changes. 4.3.1 Adaptive Routing. 4.3.2 Fault-Tolerant Tables. 4.3.3 On Correctness and Guarantees. 4.4 Routing in Static Systems: Compact Tables. 4.4.1 The Size of Routing Tables. 4.4.2 Interval Routing. 4.5 Bibliographical Notes. 4.6 Exercises, Problems, and Answers. 4.6.1 Exercises. 4.6.2 Problems. 4.6.3 Answers to Exercises. 5. Distributed Set Operations. 5.1 Introduction. 5.2 Distributed Selection. 5.2.1 Order Statistics. 5.2.2 Selection in a Small Data Set. 5.2.3 Simple Case: Selection Among Two Sites. 5.2.4 General Selection Strategy: RankSelect. 5.2.5 Reducing the Worst Case: ReduceSelect. 5.3 Sorting a Distributed Set. 5.3.1 Distributed Sorting. 5.3.2 Special Case: Sorting on a Ordered Line. 5.3.3 Removing the Topological Constraints: Complete Graph. 5.3.4 Basic Limitations. 5.3.5 Efficient Sorting: SelectSort. 5.3.6 Unrestricted Sorting. 5.4 Distributed Sets Operations. 5.4.1 Operations on Distributed Sets. 5.4.2 Local Structure. 5.4.3 Local Evaluation (). 5.4.4 Global Evaluation. 5.4.5 Operational Costs. 5.5 Bibliographical Notes. 5.6 Exercises, Problems, and Answers. 5.6.1 Exercises. 5.6.2 Problems. 5.6.3 Answers to Exercises. 6. Synchronous Computations. 6.1 Synchronous Distributed Computing. 6.1.1 Fully Synchronous Systems. 6.1.2 Clocks and Unit of Time. 6.1.3 Communication Delays and Size of Messages. 6.1.4 On the Unique Nature of Synchronous Computations. 6.1.5 The Cost of Synchronous Protocols. 6.2 Communicators, Pipeline, and Transformers. 6.2.1 Two-Party Communication. 6.2.2 Pipeline. 6.2.3 Transformers. 6.3 Min-Finding and Election: Waiting and Guessing. 6.3.1 Waiting. 6.3.2 Guessing. 6.3.3 Double Wait: Integrating Waiting and Guessing. 6.4 Synchronization Problems: Reset, Unison, and Firing Squad. 6.4.1 Reset /Wake-up. 6.4.2 Unison. 6.4.3 Firing Squad. 6.5 Bibliographical Notes. 6.6 Exercises, Problems, and Answers. 6.6.1 Exercises. 6.6.2 Problems. 6.6.3 Answers to Exercises. 7. Computing in Presence of Faults. 7.1 Introduction. 7.1.1 Faults and Failures. 7.1.2 Modelling Faults. 7.1.3 Topological Factors. 7.1.4 Fault Tolerance, Agreement, and Common Knowledge. 7.2 The Crushing Impact of Failures. 7.2.1 Node Failures: Single-Fault Disaster. 7.2.2 Consequences of the Single Fault Disaster. 7.3 Localized Entity Failures: Using Synchrony. 7.3.1 Synchronous Consensus with Crash Failures. 7.3.2 Synchronous Consensus with Byzantine Failures. 7.3.3 Limit to Number of Byzantine Entities for Agreement. 7.3.4 From Boolean to General Byzantine Agreement. 7.3.5 Byzantine Agreement in Arbitrary Graphs. 7.4 Localized Entity Failures: Using Randomization. 7.4.1 Random Actions and Coin Flips. 7.4.2 Randomized Asynchronous Consensus: Crash Failures. 7.4.3 Concluding Remarks. 7.5 Localized Entity Failures: Using Fault Detection. 7.5.1 Failure Detectors and Their Properties. 7.5.2 The Weakest Failure Detector. 7.6 Localized Entity Failures: Pre-Execution Failures. 7.6.1 Partial Reliability. 7.6.2 Example: Election in Complete Network. 7.7 Localized Link Failures. 7.7.1 A Tale of Two Synchronous Generals. 7.7.2 Computing With Faulty Links. 7.7.3 Concluding Remarks. 7.7.4 Considerations on Localized Entity Failures. 7.8 Ubiquitous Faults. 7.8.1 Communication Faults and Agreement. 7.8.2 Limits to Number of Ubiquitous Faults for Majority. 7.8.3 Unanimity in Spite of Ubiquitous Faults. 7.8.4 Tightness. 7.9 Bibliographical Notes. 7.10 Exercises, Problems, and Answers. 7.10.1 Exercises. 7.10.2 Problems. 7.10.3 Answers to Exercises. 8. Detecting Stable Properties. 8.1 Introduction. 8.2 Deadlock Detection. 8.2.1 Deadlock. 8.2.2 Detecting Deadlock: Wait-for Graph. 8.2.3 Single-Request Systems. 8.2.4 Multiple-Requests Systems. 8.2.5 Dynamic Wait-for Graphs. 8.2.6 Other Requests Systems. 8.3 Global Termination Detection. 8.3.1 A Simple Solution: Repeated Termination Queries. 8.3.2 Improved Protocols: Shrink. 8.3.3 Concluding Remarks. 8.4 Global Stable Property Detection. 8.4.1 General Strategy. 8.4.2 Time Cuts and Consistent Snapshots. 8.4.3 Computing A Consistent Snapshot. 8.4.4 Summary: Putting All Together. 8.5 Bibliographical Notes. 8.6 Exercises, Problems, and Answers. 8.6.1 Exercises. 8.6.2 Problems. 8.6.3 Answers to Exercises. 9. Continuous Computations. 9.1 Introduction. 9.2 Keeping Virtual Time. 9.2.1 Virtual Time and Causal Order. 9.2.2 Causal Order: Counter Clocks. 9.2.3 Complete Causal Order: Vector Clocks. 9.2.4 Concluding Remarks. 9.3 Distributed Mutual Exclusion. 9.3.1 The Problem. 9.3.2 A Simple And Efficient Solution. 9.3.3 Traversing the Network. 9.3.4 Managing a Distributed Queue. 9.3.5 Decentralized Permissions. 9.3.6 Mutual Exclusion in Complete Graphs: Quorum. 9.3.7 Concluding Remarks. 9.4 Deadlock: System Detection and Resolution. 9.4.1 System Detection and Resolution. 9.4.2 Detection and Resolution in Single-Request Systems. 9.4.3 Detection and Resolution in Multiple-Requests Systems. 9.5 Bibliographical Notes. 9.6 Exercises, Problems, and Answers. 9.6.1 Exercises. 9.6.2 Problems. 9.6.3 Answers to Exercises. Index.

Geographic routing without planarization

Abstract: We present a new geographic routing algorithm, Greedy Distributed Spanning Tree Routing (GDSTR), that finds shorter routes and generates less maintenance traffic than previous algorithms. While geographic routing potentially scales well, it faces the problem of what to do at local dead ends where greedy forwarding fails. Existing geographic routing algorithms handle dead ends by planarizing the node connectivity graph and then using the right-hand rule to route around the resulting faces. GDSTR handles this situation differently by switching instead to routing on a spanning tree until it reaches a point where greedy forwarding can again make progress. In order to choose a direction on the tree that is most likely to make progress towards the destination, each GDSTR node maintains a summary of the area covered by the subtree below each of its tree neighbors. While GDSTR requires only one tree for correctness, it uses two for robustness and to give it an additional forwarding choice. Our simulations show that GDSTR finds shorter routes than geographic face routing algorithms: GDSTR's stretch is up to 20% less than the best existing algorithm in situations where dead ends are common. In addition, we show that GDSTR requires an order of magnitude less bandwidth to maintain its trees than CLDP, the only distributed planarization algorithm that is known to work with practical radio networks.

Source selectable path diversity via routing deflections

Abstract: We present the design of a routing system in which end-systems set tags to select non-shortest path routes as an alternative to explicit source routes Routers collectively generate these routes by using tags as hints to independently deflect packets to neighbors that lie off the shortest-path We show how this can be done simply, by local extensions of the shortest path machinery, and safely, so that loops are provably not formed The result is to provide end-systems with a high-level of path diversity that allows them to bypass unde-sirable locations within the network Unlike explicit source routing, our scheme is inherently scalable and compatible with ISP policies because it derives from the deployed Internet routing We also sug-gest an encoding that is compatible with common IP usage, making our scheme incrementally deployable at the granularity of individual routers

Performance comparison of trust-based reactive routing protocols

Abstract: Ad hoc networks, due to their improvised nature, are frequently established in insecure environments and hence become susceptible to attacks. These attacks are launched by participating malicious nodes against different network services. Routing protocols, which act as the binding force in these networks, are a common target of these nodes. A number of secure routing protocols have recently been proposed, which make use of cryptographic algorithms to secure the routes. However, in doing so, these protocols entail a number of prerequisites during both the network establishment and operation phases. In contrast, trust-based routing protocols locate trusted rather than secure routes in the network by observing the sincerity in participation by other nodes. These protocols thus permit rapid deployment along with a dynamically adaptive operation, which conforms with the current network situation. In this paper, we evaluate the performance of three trust-based reactive routing protocols in a network with varying number of malicious nodes. With the help of exhaustive simulations, we demonstrate that the performance of the three protocols varies significantly even under similar attack, traffic, and mobility conditions. However, each trust-based routing protocol has its own peculiar advantage making it suitable for application in a particular extemporized environment.

A measurement study on the impact of routing events on end-to-end internet path performance

Abstract: Extensive measurement studies have shown that end-to-end Internet path performance degradation is correlated with routing dynamics. However, the root cause of the correlation between routing dynamics and such performance degradation is poorly understood. In particular, how do routing changes result in degraded end-to-end path performance in the first place? How do factors such as topological properties, routing policies, and iBGP configurations affect the extent to which such routing events can cause performance degradation? Answers to these questions are critical for improving network performance.In this paper, we conduct extensive measurement that involves both controlled routing updates through two tier-1 ISPs and active probes of a diverse set of end-to-end paths on the Internet. We find that routing changes contribute to end-to-end packet loss significantly. Specifically, we study failover events in which a link failure leads to a routing change and recovery events in which a link repair causes a routing change. In both cases, it is possible to experience data plane performance degradation in terms of increased long loss burst as well as forwarding loops. Furthermore, we find that common routing policies and iBGP configurations of ISPs can directly affect the end-to-end path performance during routing changes. Our work provides new insights into potential measures that network operators can undertake to enhance network performance.

Improving Lookup Performance Over a Widely-Deployed DHT

Abstract: During recent years, Distributed Hash Tables (DHTs) have been extensively studied through simulation and analysis. However, due to their limited deployment, it has not been possible to observe the behavior of a widely-deployed DHT in practice. Recently, the popular eMule file-sharing software incorporated a Kademlia-based DHT, called Kad, which currently has around one million simultaneous users. In this paper, we empirically study the performance of the key DHT operation, lookup, over Kad. First, we analytically derive the benefits of different ways to increase the richness of routing tables in Kademlia-based DHTs. Second, we empirically characterize two aspects of the accuracy of routing tables in Kad, namely completeness and freshness, and characterize their impact on Kad’s lookup performance. Finally, we investigate how the efficiency and consistency of lookup in Kad can be improved by performing parallel lookup and maintaining multiple replicas, respectively. Our results pinpoint the best operating point for the degree of lookup parallelism and the degree of replication for Kad.

Multilevel Routing With Redundant Via Insertion

Abstract: This brief presents an improved multilevel full-chip routing system which integrates the redundant via placement in the routing flow for yield and reliability enhancement. The system features a pre-coarsening stage which is equipped with fast congestion-driven L-pattern global router followed by detailed router. The L-pattern global routing benefits to the reduction of vias and thus relieves the burden of redundant via addition. In addition, a rvia-driven maze routing algorithm is also integrated in the system to improve the insertion of redundant vias. Finally a redundant via placement heuristic is adopted to enhance the completion rate. We have tested the system on a set of commonly used benchmark circuits and compared the results with a previous multilevel routing system. Besides much enhancement obtained in the aspect of redundant via placement, the system also obtains high routing completion rate, minimized total wire length and total number of vias in satisfactory runtime

On selfish routing in internet-like environments

Abstract: A recent trend in routing research is to avoid inefficiencies in network-level routing by allowing hosts to either choose routes themselves (e.g., source routing) or use overlay routing networks (e.g., Detour or RON). Such approaches result in selfish routing, because routing decisions are no longer based on system-wide criteria but are instead designed to optimize host-based or overlay-based metrics. A series of theoretical results showing that selfish routing can result in suboptimal system behavior have cast doubts on this approach. In this paper, we use a game-theoretic approach to investigate the performance of selfish routing in Internet-like environments based on realistic topologies and traffic demands in our simulations. We show that in contrast to theoretical worst cases, selfish routing achieves close to optimal average latency in such environments. However, such performance benefits come at the expense of significantly increased congestion on certain links. Moreover, the adaptive nature of selfish overlays can significantly reduce the effectiveness of traffic engineering by making network traffic less predictable.

Efficient and robust routing of highly variable traffic

Abstract: This thesis proposes two-phase routing as a capacity efficient and robust strategy for handling highly variable traffic. The scheme allows preconfiguration of the network such that all traffic patterns permissible within the network's natural ingress-egress capacity constraints can be routed with bandwidth guarantees without requiring detection of traffic changes in real-time or reconfiguring the network in response to it. The scheme routes traffic in two phases---traffic entering the network is sent from the source to a set of intermediate nodes in predetermined split ratios that depend on the intermediate nodes, and then from the intermediate nodes to the final destination. The scheme has the desirable properties of supporting static optical layer provisioning in IP-over-Optical networks and indirection in specialized service overlay models unlike previous approaches---like direct source-destination path routing---for handling variable traffic. This thesis represents the first comprehensive study, problem formulation, and algorithm design for many aspects of two-phase routing. Our contributions can be grouped into three broad parts. First, we consider the problems of minimum cost network design and maximum throughput network routing for the scheme. We give a simple solution for minimum cost network design. For maximum throughput network routing, we design linear programming based and combinatorial algorithms. We show how the algorithms can handle a, total cost constraint for maximum throughput two-phase routing. This can be used to solve the link capacitated version of minimum cost two-phase routing. We establish theoretical bounds on the resource requirements of two-phase routing under throughput and cost models with respect to the optimal scheme that is allowed to make the routing dynamically dependent on the current traffic matrix. We also generalize the traffic split ratios to depend not only on the intermediate nodes but also on source and destination of traffic and solve the corresponding optimization problems. Second, we consider making two-phase routing resilient to network failures. Two-phase routing in IP-over-Optical networks can be protected against router node failures through redistribution of traffic split ratio for the failed router node to other intermediate nodes. We propose two different schemes for provisioning the optical layer to handle router node failures. We develop linear programming formulations for both schemes and a fast combinatorial algorithm for the second scheme so as to maximize network throughput. Third, we consider the application of two-phase routing to multi-hop Wireless Mesh Networks (WMNs). These networks have recently been of much research interest due to their lowered need for wired infrastructure support and due to envisaged new applications like community wireless networks. We extend our optimization framework for maximum throughput two-phase routing in wired networks to handle routing and scheduling constraints that are peculiar to WMNs and arise from the requirement to handle radio transmit/receive diversity and the phenomenon of wireless link interference. We evaluate various aspects of two-phase routing on actual ISP topologies using the developed algorithms. For the WMN application, we use randomly generated WMN topologies for the evaluations. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.) (Abstract shortened by UMI.)

Rbridges: Base Protocol Specification

Abstract: RBridges provide the ability to have an entire campus, with multiple physical links, look to IP like a single subnet. The design allows for zero configuration of switches within a campus, optimal pair-wise routing, safe forwarding even during periods of temporary loops, and the ability to cut down on ARP/ND traffic. The design also supports VLANs, and allows forwarding tables to be based on RBridge destinations (rather than endnode destinations), which allows internal routing tables to be substantially smaller than in conventional bridge systems.

System and method for routing table computation and analysis

Abstract: Described is a system and method for determining routing information for a network link, the network link including a plurality of subnets, each subnet having the same routing information as the network link, storing the routing information as an entry in a routing table, determining subnet information for each of the plurality of subnets and storing the subnet information for each of the plurality of subnets in the entry. Methods of comparing and searching the subnet information are also described.

Segment-based routing: an efficient fault-tolerant routing algorithm for meshes and tori

Abstract: Computers get faster every year, but the demand for computing resources seems to grow at an even faster rate. Depending on the problem domain, this demand for more power can be satisfied by either, massively parallel computers, or clusters of computers. Common for both approaches is the dependence on high performance interconnect networks such as Myrinet, Infiniband, or 10 Gigabit Ethernet. While high throughput and low latency are key features of interconnection networks, the issue of fault-tolerance is now becoming increasingly important. As the number of network components grows so does the probability for failure, thus it becomes important to also consider the fault-tolerance mechanism of interconnection networks. The main challenge then lies in combining performance and fault-tolerance, while still keeping cost and complexity low. This paper proposes a new deterministic routing methodology for tori and meshes, which achieves high performance without the use of virtual channels. Furthermore, it is topology agnostic in nature, meaning it can handle any topology derived from any combination of faults when combined with static reconfiguration. The algorithm, referred to as segment-based routing (SR), works by partitioning a topology into subnets, and subnets into segments. This allows us to place bidirectional turn restrictions locally within a segment. As segments are independent, we gain the freedom to place turn restrictions within a segment independently from other segments. This results in a larger degree of freedom when placing turn restrictions compared to other routing strategies. In this paper a way to compute segment-based routing tables is presented and applied to meshes and tori. Evaluation results show that SR increases performance by a factor of 1.8 over FX and up*/down* routing.

FastRoute: a step to integrate global routing into placement

Abstract: Because of the increasing dominance of interconnect issues in advanced IC technology, placement has become a critical step in the IC design flow. To get accurate interconnect information during the placement process, it is desirable to incorporate global routing into it. However, previous global routers are computationally expensive. It is impractical to perform global routing repeatedly during placement. In this paper, we present an extremely fast and high-quality global router called FastRoute. In traditional global routing approaches, congestion is not considered during Steiner tree construction. So they have to rely on the time-consuming maze routing technique to eliminate routing congestion. Different from traditional approaches, we proposed a congestion-driven Steiner tree topology generation technique and an edge shifting technique to determine the good Steiner tree topologies and Steiner node positions. Based on the congestion-driven Steiner trees, we only need to apply maze routing to a small percentage of the two-pin nets once to obtain high quality global routing solutions. We also proposed a new cost function based on logistic function to direct the maze routing. Experimental results show that FastRoute generates less congested solutions in 132times and 64times faster runtimes than the state-of-the-art academic global routers Labyrinth (R. Kastner et al, 2000) and Chi Dispersion router (R. T. Hadsell and P. H. Madden, 2003), respectively. It is even faster than the highly-efficient congestion estimator FaDGloR (J. Westra and P. Groeneveld, 2005). The promising results make it possible to incorporate global routing directly into placement process without much runtime penalty. This could dramatically improve the placement solution quality. We believe this work will fundamentally change the way the EDA community look at and make use of global routing in the whole design flow

Routing calls in a network

Abstract: A method includes receiving a telephone number mapping query associated with a call. The method may also include generating routing information based on the query and forwarding the routing information to a control device. The routing information may indicate that processing associated with routing the call is to bypass a core portion of an Internet multimedia subsystem (IMS) when a calling party associated with the call does not invoke an IMS service, the called party associated with the call does not invoke an IMS service and the called party is not an IMS subscriber.

High-Throughput Multicast Routing Metrics in Wireless Mesh Networks

Abstract: The stationary nature of nodes in a mesh network has shifted the main design goal of routing protocols from maintaining connectivity between source and destination nodes to finding high-throughput paths between them. In recent years, numerous link-quality-based routing metrics have been proposed for choosing high-throughput paths for unicast protocols. In this paper we study routing metrics for high-throughput tree or mesh construction in multicast protocols. We show that there is a fundamental difference between unicast and multicast routing in how data packets are transmitted at the link layer, and accordingly there is a difference in how the routing metrics for each of these primitives are designed. We adapt certain routing metrics for unicast for high-throughput multicast routing and propose news ones not previously used for high-throughput. We then study the performance improvement achieved by using different link-quality-based routing metrics via extensive simulation and experiments on a mesh network testbed, using ODMRP as a representative multicast protocol. Our testbed experiment results show that ODMRP enhanced with linkquality routing metrics can achieve up to 17.5% throughput improvement as compared to the original ODMRP.

Layered routing in irregular networks

Abstract: Freedom from deadlock is a key issue in cut-through, wormhole, and store and forward networks, and such freedom is usually obtained through careful design of the routing algorithm. Most existing deadlock-free routing methods for irregular topologies do, however, impose severe limitations on the available routing paths. We present a method called layered routing, which gives rise to a series of routing algorithms, some of which perform considerably better than previous ones. Our method groups virtual channels into network layers and to each layer it assigns a limited set of source/destination address pairs. This separation of traffic yields a significant increase in routing efficiency. We show how the method can be used to improve the performance of irregular networks, both through load balancing and by guaranteeing shortest-path routing. The method is simple to implement, and its application does not require any features in the switches other than the existence of a modest number of virtual channels. The performance of the approach is evaluated through extensive experiments within three classes of technologies. These experiments reveal a need for virtual channels as well as an improvement in throughput for each technology class.

Energy Efficient Thermal Aware Routing Algorithms for Embedded Biomedical Sensor Networks

Abstract: One of the major applications of sensor networks in near future will be in the area of biomedical research. Implanted biosensor nodes are already being used for various medical applications. These in-vivo sensor networks collect different biometric data and communicate the data to the base station wirelessly. These sensor networks produce heat, as the nodes have to communicate among themselves wirelessly. The rise in temperature of the nodes due to communication should not be very high. A high temperature of the in-vivo nodes for a prolonged period might damage the surrounding tissues. In this paper, we propose a new routing algorithm that reduces the amount of heat produced in the network. In the simple form, the algorithm routes packets to the coolest neighbor without inducing routing loops. In the adaptive form, the algorithm uses mechanisms to adapt to topologies with low degree of connectivity and to switch to shortest path routing if a time threshold is exceeded. The proposed algorithm performs much better in terms of reducing the amount of heat produced, delay and power consumption compared to the shortest hop routing algorithm and a previously proposed Thermal Aware Routing Algorithm (TARA).

Routing with opportunistically coded exchanges in wireless mesh networks

Abstract: Network coding is known to improve network throughput by mixing information from different flows and conveying more information in each transmission. Recently there have been some proposals for applying network coding to wireless mesh networks leveraging the broadcast nature of wireless transmissions. These approaches exploit coding opportunities passively while forwarding packets but they do not proactively change routing of flows to create more coding opportunities. In this paper, we attempt to investigate the extent of performance gain possible when routing decisions are made with the awareness of coding. We first define the expected number of coded transmissions for a successful exchange of packets between two nodes through an intermediate node. We then formulate optimal routing with coding, given the topology and traffic, as a linear programming problem. We conduct a preliminary evaluation of coding-aware routing and show that it offers significant gain particularly when there are many long distance flows.

Cluster-Based Routing Protocols for Wireless Sensor Networks

Abstract: Routing technology at the network layer is pivotal in the architecture of wireless sensor networks. As an active branch of routing technology, cluster-based routing protocols excel in network topology management, energy minimization, data aggregation and so on. In this paper, cluster-based routing mechanisms for wireless sensor networks are analyzed. Cluster head selection, cluster formation and data transmission are three key techniques in cluster-based routing protocols. As viewed from the three techniques, recent representative cluster-based routing protocols are presented, and their characteristics and application areas are compared. Finally, the future research issues in this area are pointed out.

Biologically inspired self-adaptive multi-path routing in overlay networks

Abstract: In this paper we propose a multi-path routing scheme based on a biologically inspired attractor selection model. The advantage of this approach is that it is highly noise-tolerant and capable to operate in a very robust manner under varying environmental conditions. Further- more, the route selection is performed in accordance to

Network routing capacity

Abstract: We define the routing capacity of a network to be the supremum of all possible fractional message throughputs achievable by routing. We prove that the routing capacity of every network is achievable and rational, we present an algorithm for its computation, and we prove that every rational number in (0, 1] is the routing capacity of some solvable network. We also determine the routing capacity for various example networks. Finally, we discuss the extension of routing capacity to fractional coding solutions and show that the coding capacity of a network is independent of the alphabet used

Quantifying path exploration in the internet

Abstract: A number of previous measurement studies [10, 12, 17] have shown the existence of path exploration and slow convergence in the global Internet routing system, and a number of protocol enhancements have been proposed to remedy the problem [21, 15, 4, 20, 5]. However all the previous measurements were conducted over a small number of testing prefixes. There has been no systematic study to quantify the pervasiveness of BGP slow convergence in the operational Internet, nor there is any known effort to deploy any of the proposed solutions.In this paper we present our measurement results from identifying BGP slow convergence events across the entire global routing table. Our data shows that the severity of path exploration and slow convergence varies depending on where prefixes are originated and where the observations are made in the Internet routing hierarchy. In general, routers in tier-1 ISPs observe less path exploration, hence shorter convergence delays than routers in edge ASes, and prefixes originated from tier-1 ISPs also experience less path exploration than those originated from edge ASes. Our data also shows that the convergence time of route fail-over events is similar to that of new route announcements, and significantly shorter than that of route failures, which confirms our earlier analytical results [19]. In addition, we also developed a usage-time based path preference inference method which can be used by future studies of BGP dynamics.