Showing papers on "Routing protocol published in 1999"
25 Feb 1999
TL;DR: An ad-hoc network is the cooperative engagement of a collection of mobile nodes without the required intervention of any centralized access point or existing infrastructure and the proposed routing algorithm is quite suitable for a dynamic self starting network, as required by users wishing to utilize ad- hoc networks.
Abstract: An ad-hoc network is the cooperative engagement of a collection of mobile nodes without the required intervention of any centralized access point or existing infrastructure. We present Ad-hoc On Demand Distance Vector Routing (AODV), a novel algorithm for the operation of such ad-hoc networks. Each mobile host operates as a specialized router, and routes are obtained as needed (i.e., on-demand) with little or no reliance on periodic advertisements. Our new routing algorithm is quite suitable for a dynamic self starting network, as required by users wishing to utilize ad-hoc networks. AODV provides loop-free routes even while repairing broken links. Because the protocol does not require global periodic routing advertisements, the demand on the overall bandwidth available to the mobile nodes is substantially less than in those protocols that do necessitate such advertisements. Nevertheless we can still maintain most of the advantages of basic distance vector routing mechanisms. We show that our algorithm scales to large populations of mobile nodes wishing to form ad-hoc networks. We also include an evaluation methodology and simulation results to verify the operation of our algorithm.
11,360 citations
TL;DR: This paper proposes a distributed QoS routing scheme that selects a network path with sufficient resources to satisfy a certain delay (or bandwidth) requirement in a dynamic multihop mobile environment and can tolerate a high degree of information imprecision.
Abstract: In an ad hoc network, all communication is done over wireless media, typically by radio through the air, without the help of wired base stations. Since direct communication is allowed only between adjacent nodes, distant nodes communicate over multiple hops. The quality-of-service (QoS) routing in an ad hoc network is difficult because the network topology may change constantly, and the available state information for routing is inherently imprecise. In this paper, we propose a distributed QoS routing scheme that selects a network path with sufficient resources to satisfy a certain delay (or bandwidth) requirement in a dynamic multihop mobile environment. The proposed algorithms work with imprecise state information. Multiple paths are searched in parallel to find the most qualified one. Fault-tolerance techniques are brought in for the maintenance of the routing paths when the nodes move, join, or leave the network. Our algorithms consider not only the QoS requirement, but also the cost optimality of the routing path to improve the overall network performance. Extensive simulations show that high call admission ratio and low-cost paths are achieved with modest routing overhead. The algorithms can tolerate a high degree of information imprecision.
878 citations
21 Sep 1999
TL;DR: The protocol, termed ODMRP (on-demand multicast routing protocol), is a mesh-based, rather than a conventional tree-based multicast scheme and uses a forwarding group concept (only a subset of nodes forwards the multicast packets via scoped flooding).
Abstract: This paper presents a novel multicast routing protocol for mobile ad hoc wireless networks. The protocol, termed ODMRP (on-demand multicast routing protocol), is a mesh-based, rather than a conventional tree-based multicast scheme and uses a forwarding group concept (only a subset of nodes forwards the multicast packets via scoped flooding). It applies on-demand procedures to dynamically build routes and maintain multicast group membership. ODMRP is well suited for ad hoc wireless networks with mobile hosts where bandwidth is limited, topology changes frequently, and power is constrained. We evaluate ODMRP's scalability and performance via simulation.
795 citations
TL;DR: A large population of mobile stations that are interconnected by a multihop wireless network is considered, with the need to support multimedia communications, with low latency requirements for interactive traffic and quality-of-service (QoS) support for real-time streams (voice/video).
Abstract: We consider a large population of mobile stations that are interconnected by a multihop wireless network. The applications of this wireless infrastructure range from ad hoc networking (e.g., collaborative, distributed computing) to disaster recovery (e.g., fire, flood, earthquake), law enforcement (e.g., crowd control, search-and-rescue), and military (automated battlefield). Key characteristics of this system are the large number of users, their mobility, and the need to operate without the support of a fixed (wired or wireless) infrastructure. The last feature sets this system apart from existing cellular systems and in fact makes its design much more challenging. In this environment, we investigate routing strategies that scale well to large populations and can handle mobility. In addition, we address the need to support multimedia communications, with low latency requirements for interactive traffic and quality-of-service (QoS) support for real-time streams (voice/video). In the wireless routing area, several schemes have already been proposed and implemented (e.g., hierarchical routing, on-demand routing, etc.). We introduce two new schemes-fisheye state routing (FSR) and hierarchical state routing (HSR)-which offer some competitive advantages over the existing schemes. We compare the performance of existing and proposed schemes via simulation.
768 citations
TL;DR: The performance evaluations show that CEDAR is a robust and adaptive QoS routing algorithm that reacts quickly and effectively to the dynamics of the network while still approximating the performance of link-state routing for stable networks.
Abstract: We present CEDAR, a core-extraction distributed ad hoc routing algorithm for quality-of-service (QoS) routing in ad hoc network environments, CEDAR has three key components: (a) the establishment and maintenance of a self-organizing routing infrastructure called the core for performing route computations; (b) the propagation of the link-state of high bandwidth and stable links in the core through increase/decrease waves; and (c) a QoS-route computation algorithm that is executed at the core nodes using only locally available state. The performance evaluations show that CEDAR is a robust and adaptive QoS routing algorithm that reacts quickly and effectively to the dynamics of the network while still approximating the performance of link-state routing for stable networks.
716 citations
TL;DR: The core-assisted mesh protocol (CAMP) is introduced for multicast routing in ad hoc networks, which generalizes the notion of core-based trees introduced for internet multicasting into multicast meshes that have much richer connectivity than trees.
Abstract: The core-assisted mesh protocol (CAMP) is introduced for multicast routing in ad hoc networks. CAMP generalizes the notion of core-based trees introduced for internet multicasting into multicast meshes that have much richer connectivity than trees. A shared multicast mesh is defined for each multicast group; the main goal of using such meshes is to maintain the connectivity of multicast groups even while network routers move frequently, CAMP consists of the maintenance of multicast meshes and loop-free packet forwarding over such meshes. Within the multicast mesh of a group, packets from any source in the group are forwarded along the reverse shortest path to the source, just as in traditional multicast protocols based on source-based trees. CAMP guarantees that within a finite time, every receiver of a multicast group has a reverse shortest path to each source of the multicast group. Multicast packets for a group are forwarded along the shortest paths front sources to receivers defined within the group's mesh. CAMP uses cores only to limit the traffic needed for a router to join a multicast group; the failure of cores does not stop packet forwarding or the process of maintaining the multicast meshes.
680 citations
11 Oct 1999
TL;DR: An analytic modeling framework is developed to determine the relative frequency of query floods for various techniques and shows that while multipath routing is significantly better than single path routing, the performance advantage is small beyond a few paths and for long path lengths.
Abstract: Mobile ad hoc networks are characterized by multi-hop wireless links, absence of any cellular infrastructure, and frequent host mobility. Design of efficient routing protocols in such networks is a challenging issue. A class of routing protocols called on-demand protocols has recently attracted attention because of their low routing overhead. The on-demand protocols depend on query floods to discover routes whenever a new route is needed. Such floods take up a substantial portion of network bandwidth. We focus on a particular on-demand protocol, called dynamic source routing, and show how intelligent use of multipath techniques can reduce the frequency of query floods. We develop an analytic modeling framework to determine the relative frequency of query floods for various techniques. Results show that while multipath routing is significantly better than single path routing, the performance advantage is small beyond a few paths and for long path lengths. It also shows that providing all intermediate nodes in the primary (shortest) route with alternative paths has a significantly better performance than providing only the source with alternate paths.
630 citations
TL;DR: Two different schemes ("min searching" and "traffic adaptive") are introduced that allow individual nodes to identify and appropriately react to changes in network configuration, based only on information derived from the amount of received ZRP traffic.
Abstract: The zone routing protocol (ZRP) is a hybrid routing protocol that proactively maintains routes within a local region of the network (which we refer to as the routing zone). Knowledge of this routing zone topology is leveraged by the ZRP to improve the efficiency of a reactive route query/reply mechanism. The ZRP can be configured for a particular network through adjustment of a single parameter, the routing zone radius. We address the issue of configuring the ZRP to provide the best performance for a particular network at any time. Previous work has demonstrated that an optimally configured ZRP operates at least as efficiently as traditional reactive flood-search or proactive distance vector/link state routing protocols (and in many cases, much more efficiently). Adaptation of the ZIP to changing network conditions requires both an understanding of how the ZRP reacts to changes in network behavior and a mechanism to allow individual nodes to identify these changes given only limited knowledge of the network behavior. We demonstrate the effects of relative node velocity, node density, network span, and user data activity on the performance of the ZRP. We then introduce two different schemes ("min searching" and "traffic adaptive") that allow individual nodes to identify and appropriately react to changes in network configuration, based only on information derived from the amount of received ZRP traffic. Through test-bed simulation, we demonstrate that these radius estimation techniques can allow the ZRP to operate within 2% of the control traffic resulting from perfect radius estimation.
583 citations
TL;DR: Simulation results show that the location search scheme generates less overhead than the schemes based on flooding, and results confirm that the communication overhead for creating and maintaining the topology in the proposed protocol is smaller than that in the flat LSR protocol.
Abstract: A new global positioning system (GPS)-based routing protocol for ad hoc networks, called zone-based hierarchical link state (ZHLS) routing protocol, is proposed. In this protocol, the network is divided into nonoverlapping zones. Each node only knows the node connectivity within its zone and the zone connectivity of the whole network. The link state routing is performed on two levels: focal node and global zone levels. Unlike other hierarchical protocols, there is no cluster head in this protocol. The zone level topological information is distributed to all nodes. This "peer-to-peer" manner mitigates traffic bottleneck, avoids single point of failure, and simplifies mobility management. Since only zone ID and node ID of a destination are needed for routing, the route from a source to a destination is adaptable to changing topology. The zone ID of the destination is found by sending one location request to every zone. Simulation results show that our location search scheme generates less overhead than the schemes based on flooding. The results also confirm that the communication overhead for creating and maintaining the topology in the proposed protocol is smaller than that in the flat LSR protocol. This new routing protocol provides a flexible, efficient, and effective approach to accommodate the changing topology in a wireless network environment.
555 citations
TL;DR: This work proposes a bandwidth routing protocol for quality-of-service (QoS) support in a multihop mobile network and examines the system performance in various QoS traffic flows and mobility environments via simulation.
Abstract: The emergence of nomadic applications have generated much interest in wireless network infrastructures that support real-time communications. We propose a bandwidth routing protocol for quality-of-service (QoS) support in a multihop mobile network. The QoS routing feature is important for a mobile network to interconnect wired networks with QoS support (e.g., ATM, Internet, etc.). The QoS routing protocol can also work in a stand-alone multihop mobile network for real-time applications. This QoS routing protocol contains end-to-end bandwidth calculation and bandwidth allocation. Under such a routing protocol, the source (or the ATM gateway) is informed of the bandwidth and QoS available to any destination in the mobile network. This knowledge enables the establishment of QoS connections within the mobile network and the efficient support of real-time applications. In addition, it enables more efficient call admission control. In the case of ATM interconnection, the bandwidth information can be used to carry out intelligent handoff between ATM gateways and/or to extend the ATM virtual circuit (VC) service to the mobile network with possible renegotiation of QoS parameters at the gateway. We examine the system performance in various QoS traffic flows and mobility environments via simulation. Simulation results suggest distinct performance advantages of our protocol that calculates the bandwidth information. It is particularly useful in call admission control. Furthermore, "standby" routing enhances the performance in the mobile environment. Simulation experiments show this improvement.
552 citations
30 Aug 1999
TL;DR: A measurement-based study comparing the performance seen using the "default" path taken in the Internet with the potential performance available using some alternate path, finding that in 30-80% of the cases, there is an alternate path with significantly superior quality.
Abstract: The path taken by a packet traveling across the Internet depends on a large number of factors, including routing protocols and per-network routing policies. The impact of these factors on the end-to-end performance experienced by users is poorly understood. In this paper, we conduct a measurement-based study comparing the performance seen using the "default" path taken in the Internet with the potential performance available using some alternate path. Our study uses five distinct datasets containing measurements of "path quality", such as round-trip time, loss rate, and bandwidth, taken between pairs of geographically diverse Internet hosts. We construct the set of potential alternate paths by composing these measurements to form new synthetic paths. We find that in 30-80% of the cases, there is an alternate path with significantly superior quality. We argue that the overall result is robust and we explore two hypotheses for explaining it.
30 Aug 1999
TL;DR: This work presents an abstract model of BGP and uses it to define several global sanity conditions on routing policies that are related to BGP convergence/divergence, and shows that the complexity of statically checking it is either NP-complete or NP-hard.
Abstract: The Border Gateway Protocol (BGP) is the de facto inter-domain routing protocol used to exchange reachability information between Autonomous Systems in the global Internet. BGP is a path-vector protocol that allows each Autonomous System to override distance-based metrics with policy-based metrics when choosing best routes. Varadhan et al. [18] have shown that it is possible for a group of Autonomous Systems to independently define BGP policies that together lead to BGP protocol oscillations that never converge on a stable routing. One approach to addressing this problem is based on static analysis of routing policies to determine if they are safe. We explore the worst-case complexity for convergence-oriented static analysis of BGP routing policies. We present an abstract model of BGP and use it to define several global sanity conditions on routing policies that are related to BGP convergence/divergence. For each condition we show that the complexity of statically checking it is either NP-complete or NP-hard.
TL;DR: This paper analyze the use of on-demand behavior in routing protocols, focusing on its effect on the routing protocol's forwarding latency, overhead cost, and route caching correctness, drawing examples from detailed simulation of the dynamic source routing (DSR) protocol.
Abstract: A number of different routing protocols proposed for use in multihop wireless ad hoc networks are based in whole or in part on what can be described as on-demand behavior. By on-demand behavior, we mean approaches based only on reaction to the offered traffic being handled by the routing protocol. In this paper, we analyze the use of on-demand behavior in such protocols, focusing on its effect on the routing protocol's forwarding latency, overhead cost, and route caching correctness, drawing examples from detailed simulation of the dynamic source routing (DSR) protocol. We study the protocol's behavior and the changes introduced by variations on some of the mechanisms that make up the protocol, examining which mechanisms have the greatest impact and exploring the tradeoffs that exist between them.
21 Sep 1999
TL;DR: A novel soft state wireless hierarchical routing protocol-Hierarchical State Routing (HSR) is proposed, which keeps track of logical subnet movements using home agent concepts akin to Mobile IP.
Abstract: In this paper we present a hierarchical routing protocol in a large wireless, mobile network such as found in the automated battlefield or in extensive disaster recovery operations. Conventional routing does not scale well to network size. Likewise, conventional hierarchical routing cannot handle mobility efficiently. We propose a novel soft state wireless hierarchical routing protocol-Hierarchical State Routing (HSR). We distinguish between the "physical" routing hierarchy (dictated by geographical relationships between nodes) and "logical" hierarchy of subnets in which the members move as a group (e.g., company, brigade, battalion in the battlefield). HSR keeps track of logical subnet movements using home agent concepts akin to Mobile IP. A group mobility model is introduced and the performance of the HSR is evaluated through a detailed wireless simulation model.
31 Oct 1999
TL;DR: This paper introduces AMRIS, a new multicast routing protocol for ad hoc wireless networks designed to operate independently of underlying unicast protocols and the results reported are simulated with PARSEC.
Abstract: This paper introduces AMRIS, a new multicast routing protocol for ad hoc wireless networks. AMRIS (Ad hoc Multicast Routing protocol utilizing Increasing id-numberS) is designed to operate independently of underlying unicast protocols. The idea behind AMRIS is to dynamically assign every node (on demand) in a multicast session with an id-number. The ordering between id-numbers is used to direct the multicast flow, and the sparseness among them used for quick connectivity repair. A multicast delivery tree rooted at a special node called Sid joins up the nodes participating in the multicast session. The relationship between the id-numbers (and the nodes that own them) and Sid is that the id-numbers increase in numerical value as they radiate from Sid in the delivery tree. These id-numbers help the nodes dynamically leave and join a session, as well as adapt rapidly to changes in link connectivity (due to mobility etc.). Messages to repair a link breakage are confined to the region where it occurs. AMRIS is simulated with PARSEC and the results reported.
31 Oct 1999
TL;DR: Simulation results show that STAR is an order of magnitude more efficient than any topology-broadcast protocol, and four times moreefficient than ALP, which was the most efficient table-driven routing protocol based on partial link-state information reported to date.
Abstract: We present the source-tree adaptive routing (STAR) protocol and analyze its performance in wireless networks with broadcast radio links. Routers in STAR communicate to the neighbors their source routing trees either incrementally or in atomic updates. Source routing trees are specified by stating the link parameters of each link belonging to the paths used to reach every destination. Hence, a router disseminates link-state updates to its neighbors for only those links along paths used to reach destinations. Simulation results show that STAR is an order of magnitude more efficient than any topology-broadcast protocol, and four times more efficient than ALP, which was the most efficient table-driven routing protocol based on partial link-state information reported to date. The results also show that STAR is even more efficient than the dynamic source routing (DSR) protocol, which has been shown to be one of the best performing on-demand routing protocols.
01 Jan 1999
TL;DR: AntNet is an adaptive, distributed, mobile-agents-based algorithm which was inspired by recent work on the ant colony metaphor which is applied to a datagram network and compared with both static and adaptive state-of-the-art routing algorithms.
Abstract: This paper introduces AntNet, a new routing algorithm for communications networks. AntNet is an adaptive, distributed, mobile-agents-based algorithm which was inspired by recent work on the ant colony metaphor. We apply AntNet to a datagram network and compare it with both static and adaptive state-of-the-art routing algorithms. We ran experiments for various paradigmatic temporal and spatial tra c distributions. AntNet showed both very good performance and robustness under all the experimental conditions with respect to its competitors.
30 Aug 1999
TL;DR: This work presents a "near-optimal" routing framework that offers delays comparable to those of optimal routing and that is as flexible and responsive as single-path routing protocols proposed to date.
Abstract: The conventional approach to routing in computer networks consists of using a heuristic to compute a single shortest path from a source to a destination. Single-path routing is very responsive to topological and link-cost changes; however, except under light traffic loads, the delays obtained with this type of routing are far from optimal. Furthermore, if link costs are associated with delays, single-path routing exhibits oscillatory behavior and becomes unstable as traffic loads increase. On the other hand, minimum-delay routing approaches can minimize delays only when traffic is stationary or very slowly changing.We present a "near-optimal" routing framework that offers delays comparable to those of optimal routing and that is as flexible and responsive as single-path routing protocols proposed to date. First, an approximation to the Gallager's minimum-delay routing problem is derived, and then algorithms that implement the approximation scheme are presented and verified. We introduce the first routing algorithm based on link-state information that provides multiple paths of unequal cost to each destination that are loop-free at every instant. We show through simulations that the delays obtained in our framework are comparable to those obtained using the Gallager's minimum-delay routing. Also, we show that our framework renders far smaller delays and makes better use of resources than traditional single-path routing.
21 Sep 1999
TL;DR: MCEDAR is an extension to the CEDAR architecture and provides the robustness of mesh based routing protocols and the efficiency of tree based forwarding protocols and it decouples the control infrastructure from the actual data forwarding infrastructure.
Abstract: In this paper, we present the MCEDAR (multicast core extraction distributed ad hoc routing) multicast routing algorithm for ad hoc networks. MCEDAR is an extension to the CEDAR architecture and provides the robustness of mesh based routing protocols and the approximates the efficiency of tree based forwarding protocols. It decouples the control infrastructure from the actual data forwarding infrastructure. The decoupling allows for a very minimalistic and low overhead control infrastructure while still enabling very efficient data forwarding.
Book•
01 Jan 1999
TL;DR: Written by the inventor of many of the algorithms that make switching and routing robust and efficient, Interconnections, Second Edition offers an expert's insight into how and why networks operate as they do.
Abstract: Radia Perlman's Interconnections is recognized as a leading text on networking theory and practice. It provides authoritative and comprehensive information on general networking concepts, routing algorithms and protocols, addressing, and the mechanics of bridges, routers, switches, and hubs. This Second Edition is expanded and updated to cover the newest developments in the field, including advances in switching and bridge technology, VLANs, Fast Ethernet, DHCP, ATM, and IPv6. Additional new topics include IPX, AppleTalk, and DECnet. You will gain a deeper understanding of the range of solutions possible and find valuable information on protocols for which documentation is not readily available elsewhere.Written by the inventor of many of the algorithms that make switching and routing robust and efficient, Interconnections, Second Edition offers an expert's insight into how and why networks operate as they do. Perlman describes all of the major networking algorithms and protocols in use today in clear and concise terms, while exploring the engineering trade-offs that the different approaches represent.The book contains extensive coverage of such topics as: The spanning tree algorithm The differences between bridges, routers, and switches Virtual LANs (VLANs) and Fast Ethernet Addressing and packet formats for IP, IPv6, IPX, CLNP, AppleTalk, and DECnet Autoconfiguration of addresses; strategies in various protocol suites Routing protocols, including RIP, IS-IS, OSPF, PNNI, NLSP, and BGP Layer 3 multicast protocols, including IGMP, DVMRP, MOSPF, CBT, PIM, BGMP, Simple Multicast, and Express Sabotage-proof routing Protocol design folklore 0201634481B04062001
TL;DR: The inefficiencies in routing and transport protocols in the modern Internet are described and a prototype, called Detour, a virtual Internet is constructed, in which routers tunnel packets over the commodity Internet instead of using dedicated links.
Abstract: Despite its obvious success, the Internet suffers from end-to-end performance and availability problems. We believe that intelligent routers at key access and interchange points could improve Internet behavior by actively managing traffic. We describe the inefficiencies in routing and transport protocols in the modern Internet. We are constructing a prototype, called Detour, a virtual Internet, in which routers tunnel packets over the commodity Internet instead of using dedicated links.
30 Aug 1999
TL;DR: A new hybrid approach is introduced that performs dynamic routing of long-lived flows, while forwarding short- lived flows on static preprovisioned paths, which significantly outperforms traditional static and dynamic routing schemes, by reacting to fluctuations in network load without introducing route flapping.
Abstract: Internet service providers face a daunting challenge in provisioning network resources, due to the rapid growth of the Internet and wide fluctuations in the underlying traffic patterns. The ability of dynamic routing to circumvent congested links and improve application performance makes it a valuable traffic engineering tool. However, deployment of load-sensitive routing is hampered by the overheads imposed by link-state update propagation, path selection, and signaling. Under reasonable protocol and computational overheads, traditional approaches to load-sensitive routing of IP traffic are ineffective, and can introduce significant route flapping, since paths are selected based on out-of-date link-state information. Although stability is improved by performing load-sensitive routing at the flow level, flapping still occurs, because most IP flows have a short duration relative to the desired frequency of link-state updates. To address the efficiency and stability challenges of load-sensitive routing, we introduce a new hybrid approach that performs dynamic routing of long-lived flows, while forwarding short-lived flows on static preprovisioned paths. By relating the detection of long-lived flows to the timescale of link-state update messages in the routing protocol, route stability is considerably improved. Through simulation experiments using a one-week ISP packet trace, we show that our hybrid approach significantly outperforms traditional static and dynamic routing schemes, by reacting to fluctuations in network load without introducing route flapping.
TL;DR: It is shown by using both analysis and simulation methods that FPLC routing with the first-fit wavelength-assignment method performs much better than the alternate routing method in mesh-torus networks and in the NSFnet T1 backbone network (irregular topology).
Abstract: We present two dynamic routing algorithms based on path and neighborhood link congestion in all-optical networks. In such networks, a connection request encounters higher blocking probability than in circuit-switched networks because of the wavelength-continuity constraint. Much research has focused on the shortest-path routing and alternate shortest-path routing. We consider fixed-paths least-congestion (FPLC) routing in which the shortest path may not be preferred to use. We then extend the algorithm to develop a new routing method: dynamic routing using neighborhood information. It is shown by using both analysis and simulation methods that FPLC routing with the first-fit wavelength-assignment method performs much better than the alternate routing method in mesh-torus networks (regular topology) and in the NSFnet T1 backbone network (irregular topology). Routing using neighborhood information also achieves good performance when compared to alternate shortest-path routing.
05 Dec 1999
TL;DR: A new protocol, the flow oriented routing protocol (FORP), for routing real-time IPv6 flows in highly mobile ad hoc wireless networks with a new concept called "multi-hop handoff" to anticipate topological changes and perform rerouting, thus limiting the disruption of a flow due to the changing topology.
Abstract: In an ad hoc wireless network, mobile hosts are acting as routers and the network topology is constantly changing due to node mobility. The disruptions can cause serious degradation for real-time session. This paper describes a new protocol, the flow oriented routing protocol (FORP), for routing real-time IPv6 flows (e.g., voice and data) in highly mobile ad hoc wireless networks. A new concept called "multi-hop handoff" is introduced to anticipate topological changes and perform rerouting, thus limiting the disruption of a flow due to the changing topology. The performance of the proposed scheme is compared to other routing approaches.
21 Mar 1999
TL;DR: The Optimal Routing Table Constructor (ORTC) algorithm that is presented produces routing tables with roughly 60% of the original number of prefixes for large backbone routers.
Abstract: The Border Gateway Protocol (BGP) populates Internet backbone routers with routes or prefixes. We present an algorithm to locally compute (without any modification to BGP) equivalent forwarding tables that provably contain the minimal number of prefixes. For large backbone routers, the Optimal Routing Table Constructor (ORTC) algorithm that we present produces routing tables with roughly 60% of the original number of prefixes. The publicly available MaeEast database with 41315 prefixes reduces to 23007 prefixes when ORTC is applied. We present performance measurements on four publicly available databases and a formal proof that ORTC does produce the optimal set of routes.
21 Mar 1999
TL;DR: The network routing messages exchanged between core Internet backbone routers are examined to show that as a result of specific router vendor software changes suggested by earlier analysis, the volume of Internet routing updates has decreased by an order of magnitude.
Abstract: This paper examines the network routing messages exchanged between core Internet backbone routers. Internet routing instability, or the rapid fluctuation of network reachability information, is an important problem currently facing the Internet engineering community. High levels of network instability can lead to packet loss, increased network latency and time to convergence. At the extreme, high levels of routing instability have led to the loss of internal connectivity in wide-area, national networks. In an earlier study of inter-domain routing, we described widespread, significant pathological behaviour in the routing information exchanged between backbone service providers at the major US public Internet exchange points. These pathologies included several orders of magnitude more routing updates in the Internet core than anticipated, large numbers of duplicate routing messages, and unexpected frequency components between routing instability events. The work described in this paper extends our earlier analysis by identifying the origins of several of these observed pathological Internet routing behaviour. We show that as a result of specific router vendor software changes suggested by our earlier analysis, the volume of Internet routing updates has decreased by an order of magnitude. We also describe additional router software changes that can decrease the volume of routing updates exchanged in the Internet core by an additional 30 percent or more. We conclude with a discussion of trends in the evolution of Internet architecture and policy that may lead to a rise in Internet routing instability.
11 Oct 1999
TL;DR: This paper considers explicit routing algorithms for Internet traffic engineering and shows that the bifurcation case is NP-hard, and four heuristic schemes are proposed, the most sophisticated one being based on re-routing of split demands in the optimal solution of the bIfurcation cases.
Abstract: This paper considers explicit routing algorithms for Internet traffic engineering. Explicit routing is seen to be a much more capable solution for improving network utilization than the current destination-based routing and the multi-protocol label switching (MPLS) standard has made explicit routes implementable. ISP can now have fine granularity control over the traffic distribution across their backbones by carefully overlaying explicit routes over the physical network. The basic traffic engineering problem is how to set up explicit routes to meet bandwidth demands between the edge nodes of the network and at the same time to optimize the network performance. We model the traffic engineering problem as an optimization problem with the objective of minimizing congestion and maximizing potential for traffic growth. We present two mathematical formulations, one linear programming for the case of allowing demand bifurcation and one integer programming for the case of disallowing demand bifurcation. While the bifurcation case can be solved to optimality, we show that the non-bifurcation case is NP-hard. Four heuristic schemes are proposed for the non-bifurcation case, with the most sophisticated one being based on re-routing of split demands in the optimal solution of the bifurcation case. The performance of these heuristic schemes are tested in a large backbone topology. Our results show that shortest-path and minimum hop algorithms, although widely used in current routing protocols, perform poorly, white the re-routing approach performs best.
21 Mar 1999
TL;DR: The Core Assisted Mesh Protocol (CAMP) is introduced for multicast routing in ad hoc networks, which generalizes the notion of core-based trees introduced for internet multicasting into multicast meshes that have much richer connectivity than trees.
Abstract: The Core Assisted Mesh Protocol (CAMP) is introduced for multicast routing in ad hoc networks. CAMP generalizes the notion of core-based trees introduced for internet multicasting into multicast meshes that have much richer connectivity than trees. A shared multicast mesh is defined for each multicast group; the main goal of using such meshes is to maintain the connectivity of multicast groups even while network routers move frequently. CAMP consists of the maintenance of multicast meshes and loop-free packet forwarding over such meshes. Within the multicast mesh of a group, packets from any source in the group are forwarded along the reverse shortest path to the source, just as in traditional multicast protocols based on source-based trees. CAMP guarantees that, within a finite time, every receiver of a multicast group has a reverse shortest path to each source of the multicast group. Multicast packets for a group are forwarded along the shortest paths from sources to receivers defined within the group's mesh. CAMP uses cores only to limit the traffic needed for a router to join a multicast group; the failure of cores does not stop packet forwarding or the process of maintaining the multicast meshes.