Showing papers on "Routing table published in 2000"

GPSR: greedy perimeter stateless routing for wireless networks

Abstract: We present Greedy Perimeter Stateless Routing (GPSR), a novel routing protocol for wireless datagram networks that uses the positions of routers and a packet's destination to make packet forwarding decisions. GPSR makes greedy forwarding decisions using only information about a router's immediate neighbors in the network topology. When a packet reaches a region where greedy forwarding is impossible, the algorithm recovers by routing around the perimeter of the region. By keeping state only about the local topology, GPSR scales better in per-router state than shortest-path and ad-hoc routing protocols as the number of network destinations increases. Under mobility's frequent topology changes, GPSR can use local topology information to find correct new routes quickly. We describe the GPSR protocol, and use extensive simulation of mobile wireless networks to compare its performance with that of Dynamic Source Routing. Our simulations demonstrate GPSR's scalability on densely deployed wireless networks.

Analysis of an Equal-Cost Multi-Path Algorithm

Abstract: Equal-cost multi-path (ECMP) is a routing technique for routing packets along multiple paths of equal cost. The forwarding engine identifies paths by next-hop. When forwarding a packet the router must decide which next-hop (path) to use. This document gives an analysis of one method for making that decision. The analysis includes the performance of the algorithm and the disruption caused by changes to the set of next-hops.

AODV-BR: backup routing in ad hoc networks

Abstract: Nodes in mobile ad hoc networks communicate with one another via packet radios on wireless multihop links. Because of node mobility and power limitations, the network topology changes frequently. Routing protocols therefore play an important role in mobile multihop network communications. A trend in ad hoc network routing is the reactive on-demand philosophy where routes are established only when required. Most of the protocols in this category, however, use a single route and do not utilize multiple alternate paths. We propose a scheme to improve existing on-demand routing protocols by creating a mesh and providing multiple alternate routes. Our algorithm establishes the mesh and multipaths without transmitting any extra control message. We apply our scheme to the Ad-hoc On-Demand Distance Vector (AODV) protocol and evaluate the performance improvements by simulation.

Fisheye state routing: a routing scheme for ad hoc wireless networks

Abstract: This paper presents a novel routing protocol for wireless ad hoc networks-fisheye state routing (FSR). FSR introduces the notion of multi-level fisheye scope to reduce routing update overhead in large networks. Nodes exchange link state entries with their neighbors with a frequency which depends on distance to destination. From link state entries, nodes construct the topology map of the entire network and compute optimal routes. Simulation experiments show that FSR is a simple, efficient and scalable routing solution in a mobile, ad hoc environment.

Delayed Internet routing convergence

Abstract: This paper examines the latency in Internet path failure, failover and repair due to the convergence properties of inter-domain routing. Unlike switches in the public telephony network which exhibit failover on the order of milliseconds, our experimental measurements show that inter-domain routers in the packet switched Internet may take tens of minutes to reach a consistent view of the network topology after a fault. These delays stem from temporary routing table oscillations formed during the operation of the BGP path selection process on Internet backbone routers. During these periods of delayed convergence, we show that end-to-end Internet paths will experience intermittent loss of connectivity, as well as increased packet loss and latency. We present a two-year study of Internet routing convergence through the experimental instrumentation of key portions of the Internet infrastructure, including both passive data collection and fault-injection machines at major Internet exchange points. Based on data from the injection and measurement of several hundred thousand inter-domain routing faults, we describe several unexpected properties of convergence and show that the measured upper bound on Internet inter-domain routing convergence delay is an order of magnitude slower than previously thought. Our analysis also shows that the upper theoretic computational bound on the number of router states and control messages exchanged during the process of BGP convergence is factorial with respect to the number of autonomous systems in the Internet. Finally, we demonstrate that much of the observed convergence delay stems from specific router vendor implementation decisions and ambiguity in the BGP specification.

Adaptive routing system and method for QOS packet networks

Abstract: A packet network employs routers that determine network routing based on quality of service (QoS) provisioning parameters and network topology information. QoS provisioning parameters are provided to each router from a network management database, and the network topology information is determined from a link state database of the router. The link state database may include network topology information collected by the router in accordance with the open shortest path protocol (OSPF). A network link, router, or other node failure initiates a new path-selection process. First, a temporary set of provisioning entries may be determined with a shortest path first (SPF) routing method. Then, the network packet flows may be classified into packet flows, real-time and non-real-time, and then as packet flows that require reserved bandwidth or that may be multiplexed. A multicommodity flow (MCF) routing method is then employed to determine an optimized set of candidate provisioning entries for the packet flows that may be multiplexed. The MCF routing method determines new routing for the packet flows based on QoS provisioning commitments as parameters. The MCF routing method determines the new routing based on an optimization criterion, such as maximized revenue. Once the new routing is determined, routing of network traffic is enabled by converting the provisioning entries into filter rules, which are then loaded into the packet classifier of the router.

Power-aware localized routing in wireless networks

Abstract: Two metrics where transmission power depends on distance between nodes, and a cost aware metric based on remaining battery power at nodes (assuming constant transmission power), together with corresponding non-localized shortest path routing algorithms, were recently proposed. We define a new power-cost metric based on the combination of both node's lifetime and distance based power metrics. We then propose power, cost, and power-cost GPS based localized routing algorithms, where nodes make routing decisions solely on the basis of location of their neighbors and destination. Power aware localized routing algorithm attempts to minimize the total power needed to route a message between a source and a destination. Cost-aware localized algorithm is aimed at extending battery's worst case lifetime. The combined power-cost algorithm attempts to minimize the total power needed and to avoid nodes with short remaining lifetime. We prove that these localized power, cost, and power-cost efficient routing algorithms are loop-free.

Multipath Issues in Unicast and Multicast Next-Hop Selection

Abstract: Various routing protocols, including Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (ISIS), explicitly allow "Equal-Cost Multipath" (ECMP) routing. Some router implementations also allow equal-cost multipath usage with RIP and other routing protocols. The effect of multipath routing on a forwarder is that the forwarder potentially has several next-hops for any given destination and must use some method to choose which next- hop should be used for a given data packet.

Network router search engine using compressed tree forwarding table

Abstract: Network routing apparatus employs multi-level tree data structures in a centralized routing table (144, 146, 148) and in distributed forwarding tables (150, 152, 154, 158, 160). Each level of each structure is associated with a different field of a network address appearing in received packets. Pointers in each structure are used to identify either an address of a next hop network, or a next-level tree to be examined for a next-hop address. An uncompressed tree routing table uses directly addressed trees in order to simplify the storage and retrieval of pointers, and the next-tree pointers directly identify next trees. Compressed tree forwarding tables are generated from the uncompressed routing table by reducing the number of pointers stored at one or more levels to substantially the number of unique next hop addresses associated with network addresses at that level. A single mapping table maps pointer values at one level to the locations of trees at the next level in the compressed trees. Next hop address lookup logic (50, 52, 76, 78) performs lookups in accordance with the structure of the compressed trees. Also, the lookup logic stores and selectively operates on multiple forwarding tables in order to provide support for virtual router operation.

Dynamic routing of bandwidth guaranteed tunnels with restoration

Abstract: This paper presents new algorithms for dynamic routing of restorable bandwidth-guaranteed paths. A straightforward solution for the restoration problem is to find two disjoint paths. However, this results in excessive resource usage for backup paths and does not satisfy the implicit service provider requirement of optimizing network resource utilization so as to increase the number of potential future demands that can be routed. We give an integer programming formulation for this problem which is new. Complete path routing knowledge is a reasonable assumption for a centralized routing algorithm. However, it requires maintenance of non-aggregated or per-path information which is not often desirable particularly when distributed routing is preferred. We show that a partial information scenario which uses only aggregated and not per-path information provides sufficient information for a suitably developed algorithm to be able to perform almost as well as the complete information scenario. In this partial information scenario the routing algorithm only knows what fraction of each link's bandwidth, is currently used by active paths, and is currently used by backup paths. Obtaining this information is feasible using proposed traffic engineering extensions to routing protocols. We formulate the dynamic restorable bandwidth routing problem in this partial information scenario and develop efficient routing algorithms. We compare there routing performance of this algorithm to a bound obtained using complete information. Our partial information-based algorithm performs very well and its performance in terms of the number of rejected requests is very close to the full information bound.

On inferring autonomous system relationships in the Internet

Abstract: Interdomain routing in the Internet is coordinated by the border gateway protocol (BGP). BGP allows each autonomous system (AS) to choose its own policy in selecting routes and propagating reachability information to others. These routing policies are constrained by the contractual commercial agreements between administrative domains. Such policies imply that connectivity alone can not fully characterize the structural properties of the Internet. We propose an augmented AS graph representation that classifies AS relationships into customer-to-provider, peer-to-peer, and sibling to-sibling relationships. We classify the types of routes that can appear in BGP routing tables based on the relationships between the ASs in the path and present heuristic algorithms that infer AS relationships from BGP routing tables. The algorithms are tested on publicly available BGP routing tables that contains dose to 1 million route entries. The algorithms infer that more than 90.5% of the connected AS pairs have customer-to-provider relationships, less than 1.5% of the connected AS pairs have sibling-to-sibling relationships, and less than 8% of the connected AS pairs have peer-to-peer relationships. We verify our inference results with AT&T internal information on its relationship with neighboring ASs. 99% of our inference results are confirmed by the AT&T internal information. We also verify our inferred sibling-to-sibling relationships with the information acquired from the WHOIS lookup service. More than half of our inferred sibling-to-sibling relationships are confirmed by the WHOIS lookup service. To the best of our knowledge this is the first attempt in understanding and inferring AS relationships in the Internet. We show evidence that some routing table entries stem from unusual AS relationships or router misconfiguration.

Network routing table using content addressable memory

Abstract: A routing table comprises routing table entries [230], a word line driver [92], prioritizer [100], and memory [106]. Each routing table entry [230] comprises content addressable memory (CAM) cells [220] and an entry masking circuit. The routing table looks up in parallel an entry matching an input network address, and outputs the search result in deterministic time. Only the bits specified by the masking circuit in each entry are compared when searching. If multiple entries match the input, the prioritizer [100] uses mask information from the masking circuits of the matching entries to select the best entry, e.g. the entry having the most matching bits.

Geographic routing for wireless networks

Abstract: Distributed shortest-path routing protocols for wired networks either describe the entire topology of a network or provide a digest of the topology to every router. They continually update the state describing the topology at all routers as the topology changes to find correct routes for all destinations. Hence, to find routes robustly, they generate routing protocol message traffic proportional to the product of the number of routers in the network and the rate of topological change in the network. Current ad-hoc routing protocols, designed specifically for mobile, wireless networks, exhibit similar scaling properties. It is the reliance of these routing protocols on state concerning all links in the network, or all links on a path between a source and destination, that is responsible for their poor scaling. We present Greedy Perimeter Stateless Routing (GPSR), a novel routing protocol for wireless datagram networks that uses the positions of routers and a packet's destination to make packet forwarding decisions. GPSR makes greedy forwarding decisions using only information about a router's immediate neighbors in the network topology. When a packet reaches a region where greedy forwarding is impossible, the algorithm recovers by routing around the perimeter of the region. By keeping state only about the local topology, GPSR scales better in per-router state than shortest-path and ad-hoc routing protocols as the number of network destinations increases. Under mobility's frequent topology changes, GPSR can use local topology information to find correct new routes quickly. We describe the GPSR protocol, and use extensive simulation of mobile wireless networks to compare its performance with that of Dynamic Source Routing. Our simulations demonstrate GPSR's scalability on densely deployed wireless networks.

On-demand routing in large ad hoc wireless networks with passive clustering

Abstract: This paper presents on-demand routing scalability improvements achieved using a "passive" clustering. Any on-demand routing typically requires some form of flooding. Clustering can dramatically reduce transmission overhead during flooding. In fact, by using clustering, we restrict the set of forwarding nodes during flood search and thus reduce the energy cost and traffic overhead of routing in dynamic traffic and topology environments. However existing "active" clustering mechanisms require periodic refresh of neighborhood information and tend to introduce quite a large amount of communication maintenance overhead. We introduce a passive clustering protocol scheme which is mostly supported/maintained by user data packets instead of explicit control packets. The passive scheme is consistent with the on-demand routing philosophy. Simulation results show significant performance improvements when passive clustering is used.

REUNITE: a recursive unicast approach to multicast

Abstract: We propose a new multicast protocol called REUNITE. The key idea of REUNITE is to use recursive unicast trees to implement multicast service. REUNITE does not use class D IP addresses. Instead, both group identification and data forwarding are based on unicast IP addresses. Compared with existing IP multicast protocols, REUNITE has several unique properties. First, only routers that are acting as multicast tree branching points for a group need to keep the multicast forwarding state of the group. All other non-branching-point routers simply forward data packets by unicast routing. In addition, REUNITE can be incrementally deployed in the sense that it works even if only a subset of the routers implement the protocol. Furthermore, REUNITE supports load balancing and graceful degradation such that when a router does not have resources (forwarding table entry, buffer space, processing power) to support additional multicast groups, the branching can be automatically migrated to other less-loaded routers. Finally, sender access control can be easily supported in REUNITE.

A framework for scalable global IP-anycast (GIA)

Abstract: This paper proposes GIA, a scalable architecture for global IP-anycast. Existing designs for providing IP-anycast must either globally distribute routes to individual anycast groups, or confine each anycast group to a pre-configured topological region. The first approach does not scale because of excessive growth in the routing tables, whereas the second one severely limits the utility of the service. Our design scales by dividing inter-domain anycast routing into two components. The first component builds inexpensive default anycast routes that consume no bandwidth or storage space. The second component, controlled by the edge domains, generates enhanced anycast routes that are customized according to the beneficiary domain's interests. We evaluate the performance of our design using simulation, and prove its practicality by implementing it in the Multi-threaded Routing Toolkit.

High performance switch fabric element and switch systems

Abstract: A high performance switch fabric element and flexible link interconnection topologies and frame addressing techniques therefor are disclosed. The fabric element, which may be a 16 port ASIC with internal steerable interconnection among all ports. The fabric element ports each have a unique local routing table, thereby avoiding the need for a global routing table for ports as is provided in the prior art. This also permits addressing and routing from port to port within the fabric element without need for look-up references from off the fabric element, thereby contributing to speed. The fabric element can be used in multiples interconnected by unique link interconnection techniques including cascade, mesh, microstaging, and combinations thereof. These link interconnection techniques provide unique switch topologies that permit high performance switching chassis or network box having a significantly larger number of ports than is achievable with the prior art techniques.

IP layer restoration and network planning based on virtual protection cycles

Abstract: We describe a novel restoration strategy called virtual protection cycles (p-cycles, patents pending) for extremely fast restoration in IP networks. Originally conceived for use in WDM and Sonet transport networks, we outline the adaption of the p-cycle concept to an IP environment. In an IP router-based network, p-cycles are implemented with virtual circuits techniques (such as an MPLS label switched path, or other means) to form closed logical loops that protect a number of IP links, or a node. In the event of failure, packets which would normally have been lost are encapsulated with a p-cycle IP address and reenter the routing table, which diverts them onto a protection cycle. They travel by normal forwarding or label switching along the p-cycle until they reach a node where the continuing route cost to the original destination is lower than that at the p-cycle entry node. Diverted packets are deencapsulated (dropped from the p-cycle) at that node and follow a normal (existing) route from there to their destination. Conventional routing protocols such as OSPF remain in place and operate as they do today, to develop a longer term global update to routing tables. Diversionary flows on the p-cycle inherently cease when the global routing update takes effect in response to the failed link or node. The p-cycle thus provides an immediate real-time detour, preventing packet loss, until conventional global routing reconvergence occurs. The aim of the paper is to explain the basic p-cycle concept and its adaptation to both link and node restoration in the IP transport layer, and to outline certain initial results on the problem of optimized design of p-cycle based IP networks.

Multicast routing with service-level guarantees between ingress egress-points in a packet network

Abstract: A packet network of interconnected nodes employs a method of routing with service-level guarantees to determine a path through the network for a requested multicast, label-switched path Each of the nodes includes one or more routers that forward packets based on a forwarding table constructed from a directed tree determined in accordance with the method of multicast routing with service-level guarantees. For a first implementation, a heuristic algorithm uses a scaling phase that iteratively adjusts a maximum arc capacity, determines the resulting tree for the iteration, and selects the tree as the routing tree that provides the “maximum” flow. For a second implementation, the heuristic algorithm computes maximum multicast flows and determines links in the network that are “critical” to satisfy future multicast routing requests. A multicast routing tree is selected such that provisioning the flows over its links “minimally interferes” with capacity of paths needed for future demands.

Online control of a multiprocessor computer system

Abstract: A control system using microprocessors for communicating through a LAN to control operation of processors and input and output subsystems (IO system) of a multi-processor computer system. Each processor includes memory, and an IO system comprising a plurality of busses. The processors are cabled together in a mesh arrangement so that messages can be transferred between any of the processors and delivered to memory associated with the destination processor, or an IO system associated with the destination processor, etc. The processors and IO system are mounted in a rack, and an IO system is associated with each processor. A rack may be hot swapped. In hot swapping, the microprocessor control system computes new routing tables for messages through the new cabling arrangement. Microprocessors, IO devices, and processor boards may be hot swapped.

Routing method for traffic load distribution in packet-switched network

Abstract: The present invention relates to a routing method for a traffic load distribution in a packet-switched network., which method includes a first step for computing an average cost between the start node and a plurality of nodes stored in a routing table and selecting a node having a cost lower than an average cost value K as a candidate of an intermediate node; a second step for randomly selecting one among the intermediate node candidates when a packet to be transmitted from the start node is generated and determining the selected node as an intermediate node of the packet; a third step for storing an information with respect to a path setting bit(b) a destination node address and intermediate node address in a header region of the packet and transmitting the packet to the intermediate node through the path of the lowest cost using the information stored in the routing table; and a fourth step for transmitting the packet to the destination node through the lowest cost path using the information stored in the routing table when the packet arrives at the intermediate node, for thereby diversifying data transmission path using an intermediate node address by providing an intermediate node address to a packet separately from a destination node address for thereby effectively distributing data traffic in a packet-switched network.

Scalable unidirectional routing with zone routing protocol (ZRP) extensions for mobile ad-hoc networks

Abstract: Ad-hoc networks consist of peer-to-peer communicating nodes that are highly mobile. As such, an ad-hoc network lacks infrastructure and the topology of the network changes dynamically. The task of routing data from a source to a destination in such a network is challenging. Several routing protocols have been proposed for wireless ad-hoc networks. Most of these protocols, however, pre-suppose the presence of bi-directional links between the nodes in the network. In reality the ad-hoc network may consist of heterogeneous nodes with different power capabilities and hence, different transmission ranges. When this is the case, a given node might be able to receive the transmission of another given node but might not be able to successfully transmit to the latter. Thus, unidirectional links are formed. Most of the current routing protocols are unsuitable for deployment when such unidirectional links are present. We consider a routing protocol called the zone routing protocol (ZRP) that has been proposed for wireless ad-hoc networks with bi-directional links. The zone routing protocol employs a hybrid proactive (table driven) and reactive (on-demand) methodology to provide scalable routing in the ad-hoc network. However, in the presence of unidirectional links some routes remain undiscovered if ZRP is used. We propose extensions to ZRP to support its deployment when unidirectional links are present. In particular, we propose a query enhancement mechanism that recursively builds partial routes to a destination. Simulation results show that even at a high mobility of 20 m/s, the queries resulting due to the enhancement mechanism result in the computation of valid routes more than 80% of the time. These results are valid even when a large number (40% of nodes have half the transmission range as that of the remaining nodes) of unidirectional links are present in the network.

Multi-service network switch with multiple virtual routers

Abstract: A physical network switch partitioned into a plurality of virtual routers (VRs) where each VR has allocated to it a set of resources and routing tables. The system resources are not tied to a particular network interface, allowing them to be flexibly partitioned among the various VRs. Each VR may also be partitioned into multiple virtual private networks (VPNs) for controlling access to certain portions of the VR. Access is controlled by filtering software that filters traffic directed to the VR based on criteria such as source and/or destination addresses.

Multi-service network switch

Abstract: A multi-service network switch capable of providing multiple network services from a single platform. The switch incorporates a distributed packet forwarding architecture where each of the various cards is capable of making independent forwarding decisions. The switch further allows for dynamic resource management for dynamically assigning modem and ISDN resources to an incoming call. The switch may also include fault management features to guard against single points of failure within the switch. The switch further allows the partitioning of the switch into multiple virtual routers where each virtual router has its own wet of resources and a routing table. Each virtual router is further partitioned into virtual private networks for further controlling access to the network. The switch's supports policy based routing where specific routing paths are selected based a domain name, a telephone number, and the like. The switch also provides tiered access of the Internet by defining quality of access levels to each incoming connection request. The switch may further support an IP routing protocol and architecture in which the layer two protocols are indepenent of the physical interface they run on. Furthermore, the switch includes a generic forwarding interface software for hiding the details of transmitting and receiving packets over different interface types.

Network fault detection and recovery

Abstract: A method of fault detection and recovery utilizes dual independent networks to provide fault-tolerance. These networks, a primary and alternate network, are utilized such that communications for a particular computer take place via that computer's preferred network by default. Faults are detected through the use of a heartbeat pinging mechanism to detect faults on the network itself and by periodic port integrity checks to detect port faults. The integrity of the non-default network and port are also periodically verified to assure effective fault recovery. Upon detection of a fault, a packet routing table in the detecting computer is altered to set the detecting computer's default network to the previously non-default network. Additionally, a new gateway packet is transmitted which allows other network computers to modify their routing tables to communicate with the detecting computer over its current default network.

Fault tolerant shared system resource with communications passthrough providing high availability communications

Abstract: A communications passthrough mechanism for high availability network communications between a shared system resource and clients of the system resource. The system resource includes a control/processing sub-system including multiple peer blade processors. A port of each blade processor is connected to each client/server network path and each client is connected to a corresponding port of each blade processor. Each blade processor includes a network fault detector exchanging beacon transmissions with other blade processors through corresponding blade processor ports and network paths. Each blade processor includes response generator responsive to a failure to receive a beacon transmission from a failed port of an other blade processor for redirecting the client communications to the failed port on the other blade processor to the corresponding port of the blade processor. A path manager in the blade processor is responsive to operation of the response generator for modifying the communications routing table to correspond with the redirection message to route the client communications to the failed port of the other blade processor to the other blade processor through the inter-processor communications link. Each blade processor may also include an inter-blade communications monitor for detecting a failure in the inter-processor communications link between the blade processor and another blade processor, reading the communications routing table to select a functional network communications path to a port of the other blade processor, and modifying the communications routing table to redirect inter-processor communications to the selected functional network communications path.

Predictable routing

Abstract: Predictable routing is the concept of using prespecified patterns to route a net. By doing this, we allow an more accurate prediction mechanism for metrics such as congestion and wirelength earlier in the design flow. Additionally, we can better plan the routes, insert buffers and perform wire sizing earlier. With comparable routing quality, we show that we can predictably route up to 80% of a selected subset of nets. Also, we introduce methods for finding a group of nets which can be predictably routed.

Method for network-aware clustering of clients in a network

Abstract: A method for clustering together network clients for guiding of placement of network servers is disclosed. A number of routing table prefix/netmask entries are aggregated and unified into a tubular format. The routing table entries may be converted into a singular format. A network server log is used to extract a number of client IP addresses which are compared to the entries within the unified routing table. A common prefix shared by a number of the client IP addresses and an entry in the unified routing table is determined and used to cluster the clients together in a client cluster. Network servers, such as proxy server, cache servers, content distribution servers and mirror server may be placed in the network according to the client clusters.

Energy-efficient transmission and routing protocols for wireless multiple-hop networks and spread-spectrum radios

Abstract: We describe link and network layer protocols that can conserve energy in store-and-forward packet radio networks. At the link layer, an adaptive-transmission protocol allows the radios to adjust the power in the transmitted signal and the information rate to respond to variations in interference and propagation loss. The network layer protocols are designed to account for the energy requirements of the alternative routes for each source-destination pair. Routing is accomplished using least-resistance routing (LRR) with a metric that includes a measure of the energy consumption.