Finding Alternate Paths in the Internet:A Survey of Techniques for End-to-End Path Discovery
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paper_title: Delayed Internet routing convergence

paper_content:

This paper examines the latency in Internet path failure, failover, and repair due to the convergence properties of interdomain routing. Unlike circuit-switched paths which exhibit failover on the order of milliseconds, our experimental measurements show that interdomain 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 fluctuations formed during the operation of the border gateway protocol (BGP) path selection process on the 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 interdomain routing faults, we describe several unexpected properties of convergence and show that the measured upper bound on Internet interdomain 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.
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paper_title: Improving the Reliability of Internet Paths with One-hop Source Routing

paper_content:

Recent work has focused on increasing availability in the face of Internet path failures. To date, proposed solutions have relied on complex routing and path-monitoring schemes, trading scalability for availability among a relatively small set of hosts. ::: ::: This paper proposes a simple, scalable approach to recover from Internet path failures. Our contributions are threefold. First, we conduct a broad measurement study of Internet path failures on a collection of 3,153 Internet destinations consisting of popular Web servers, broad-band hosts, and randomly selected nodes. We monitored these destinations from 67 PlanetLab vantage points over a period of seven days, and found availabilities ranging from 99.6% for servers to 94.4% for broadband hosts. When failures do occur, many appear too close to the destination (e.g., last-hop and end-host failures) to be mitigated through alternative routing techniques of any kind. Second, we show that for the failures that can be addressed through routing, a simple, scalable technique, called one-hop source routing, can achieve close to the maximum benefit available with very low overhead. When a path failure occurs, our scheme attempts to recover from it by routing indirectly through a small set of randomly chosen intermediaries. ::: ::: Third, we implemented and deployed a prototype one-hop source routing infrastructure on PlanetLab. Over a three day period, we repeatedly fetched documents from 982 popular Internet Web servers and used one-hop source routing to attempt to route around the failures we observed. Our results show that our prototype successfully recovered from 56% of network failures. However, we also found a large number of server failures that cannot be addressed through alternative routing. ::: ::: Our research demonstrates that one-hop source routing is easy to implement, adds negligible overhead, and achieves close to the maximum benefit available to indirect routing schemes, without the need for path monitoring, history, or a-priori knowledge of any kind.
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paper_title: Bandwidth-Aware Routing in Overlay Networks

paper_content:

In the absence of end-to-end quality of service (QoS), overlay routing has been used as an alternative to the default best effort Internet routing. Using end-to-end network measurement, the problematic parts of the path can be bypassed, resulting in improving the resiliency and robustness to failures. Studies have shown that overlay paths can give better latency, loss rate, and TCP throughput. Overlay routing also offers flexibility as different routes can be used based on application needs. There have been very few proposals of using bandwidth as the main metric of interest, which is of great concern in media applications. We introduce our scheme BARON (Bandwidth-Aware Routing in Overlay Networks) that utilizes capacity between the end hosts to identify viable overlay paths and measures available bandwidth to select the best route. We propose our path selection approaches, and using the measurements between 174 PlanetLab nodes and over 13,189 paths, we evaluate the usefulness of overlay routes in terms of bandwidth gain. Our results show that among 658,526 overlay paths, 25% have larger bandwidth than their native IP routes, and over 86% of (source, destination) pairs have at least one overlay route with larger bandwidth than the default IP routes. We also present the effectiveness of BARON in preserving the bandwidth requirement over time for a few selected Internet paths.
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paper_title: Exploiting internet route sharing for large scale available bandwidth estimation

paper_content:

Recent progress in active measurement techniques has made it possible to estimate end-to-end path available bandwidth. However, how to efficiently obtain available bandwidth information for the N2 paths in a large N-node system remains an open problem. While researchers have developed coordinate-based models that allow any node to quickly and accurately estimate latency in a scalable fashion, no such models exist for available bandwidth. In this paper we introduce BRoute--a scalable available bandwidth estimation system that is based on a route sharing model. The characteristics of BRoute are that its overhead is linear with the number of end nodes in the system, and that it requires only limited cooperation among end nodes. BRoute leverages the fact that most Internet bottlenecks are on path edges, and that edges are shared by many different paths. It uses AS-level source and sink trees to characterize and infer path-edge sharing in a scalable fashion. In this paper, we describe the BRoute architecture and evaluate the performance of its components. Initial experiments show that BRoute can infer path edges with an accuracy of over 80%. In a small case study on Planetlab, 80% of the available bandwidth estimates obtained from BRoute are accurate within 50%.
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paper_title: Dynamic Overlay Routing Based on Available Bandwidth Estimation: A Simulation Study

paper_content:

Dynamic overlay routing has been proposed as a way to enhance the reliability and performance of IP networks. The major premise is that overlay routing can bypass congestion, transient outages, or suboptimal paths, by forwarding traffic through one or more intermediate overlay nodes. In this paper, we perform an extensive simulation study to investigate the performance of dynamic overlay routing. In particular, we leverage recent work on available bandwidth (avail-bw) estimation, and focus on overlay routing that selects paths based on avail-bw measurements between adjacent overlay nodes. First, we compare two overlay routing algorithms, reactive and proactive, with shortest-path native routing. We show that reactive routing has significant benefits in terms of throughput and path stability, while proactive routing is better in providing flows with a larger safety margin (''headroom''), and propose a hybrid routing scheme that combines the best features of the previous two algorithms. We then examine the effect of several factors, including network load, traffic variability, link-state staleness, number of overlay hops, measurement errors, and native sharing effects. Some of our results are rather surprising. For instance, we show that a significant measurement error, even up to 100% of the actual avail-bw value, has a negligible impact on the efficiency of overlay routing.
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paper_title: Backup path allocation based on a correlated link failure probability model in overlay networks

paper_content:

Communication reliability is a desired property in computer networks. One key technology to increase the reliability of a communication path is to provision a disjoint backup path. One of the main challenges in implementing this technique is that two paths that are disjoint at the IP or overlay layer may share the same physical links. As a result, although we may select a disjoint backup path at the overlay layer one physical link failure may cause the failure of both the primary and the backup paths. In this paper we propose a solution to address this problem. The main idea is to take into account the correlated link failure at the overlay layer More precisely, our goal is to find a route for the backup path to minimize the joint path failure probability between the primary and the backup paths. To demonstrate the feasibility of our approach, we perform extensive evaluations under both single and double link failure models. Our results show that, in terms of robustness, our approach is near optimal and is up to 60% better than no backup path reservation and is up to 30% better than using the traditional shortest disjoint path algorithm to select the backup path.
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paper_title: How to Select a Good Alternate Path in Large Peer-to-Peer Systems?

paper_content:

When multiple paths are available between communicating hosts, application quality can be improved by switching among them to always use the best one. The key to such an approach is the availability of diverse paths, i.e., paths with uncorrelated performance. A promising approach for implementing the necessary path diversity is to leverage the capabilities of peer-to-peer systems. Peer-to-peer systems are attractive not only because their many participating nodes can act as relays for others, and therefore offer a large number of different alternate paths, but also because their distributed operation can facilitate the deployment of the required functionality. However, these advantages come at a cost, as the sheer number of alternate path choices they offer creates its own challenge. In particular, because not all choices are equally good, it is necessary to develop mechanisms for easily and rapidly identifying relay nodes that yield good alternate paths. This paper is about the formulation and evaluation of such mechanisms in the context of large peerto-peer systems. Our goal is to devise techniques that for any given destination allow nodes to quickly select a candidate relay node with as small a cost as possible in terms of how much information they need to store or process. We combine several heuristics that rely only on local routing information, and validate the resulting solution by comparing it to a number of benchmark alternatives. This comparison is carried out using both topology data from RouteView/RIPE and PlanetLab nodes, and through measurements across a large set of PlanetLab nodes.
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paper_title: On the constancy of internet path properties

paper_content:

Many Internet protocols and operational procedures use measurements to guide future actions. This is an effective strategy if the quantities being measured exhibit a degree of constancy: that is, in some fundamental sense, they are not changing. In this paper we explore three different notions of constancy: mathematical, operational, and predictive. Using a large measurement dataset gathered from the NIMI infrastructure, we then apply these notions to three Internet path properties: loss, delay, and throughput. Our aim is to provide guidance as to when assumptions of various forms of constancy are sound, versus when they might prove misleading.
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paper_title: Traceroute probe method and forward IP path inference

paper_content:

Several traceroute probe methods exist, each designed to perform better in a scenario where another fails. This paper examines the effects that the choice of probe method has on the inferred forward IP path by comparing the paths inferred with UDP, ICMP, and TCP-based traceroute methods to (1) a list of routable IP addresses, (2) a list of known routers, and (3) a list of well-known websites. We further compare methods by examining seven months of macroscopic Internet topology data collected by CAIDA's Archipelago infrastructure. We found significant differences in the topology observed using different probe methods. In particular, we found that ICMP-based traceroute methods tend to successfully reach more destinations, as well as collect evidence of a greater number of AS links. UDP-based methods infer the greatest number of IP links, despite reaching the fewest destinations. We hypothesise that some per-flow load balancers implement different forwarding policies for TCP and UDP, and run a specific experiment to confirm this hypothesis.
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paper_title: Practical Issues of Statistical Path Monitoring in Overlay Networks with Large, Rank-Deficient Routing Matrices

paper_content:

A conventional form of vehicle axle suspension comprises on each side of a vehicle-a leaf spring pack and a shock absorber system. A height control system may also be included. According to this invention the leaf spring pack is replaced by a single leaf spring and a pair of air springs. The opposite ends of the single leaf spring are shackled to the existing shackle attachments and their vehicle frame mounts. Midway between its ends the single leaf spring is connected to the adjacent axle end by the existing spring-to-axle attachment components. In order to compensate for the difference in thicknesses of leaf spring pack and the single leaf spring at their midpoints, a spacer having a vertical thickness equal to the difference in the thicknesses is mounted on top of the single thickness spring at the axle. Air spring support brackets are symmetrically mounted on the chassis frame member on opposite sides of the axle. The upper end of each air spring is attached to one of the brackets and the lower end of each air spring is attached to the single leaf spring. Preferably a-height control system is provided on each side so as to maintain the chassis at a predetermined level. Except for the single leaf spring and the spacer, the other components may be of the type used in conventional leaf spring pack suspensions.
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paper_title: Using Type-of-Relationship (ToR) Graphs to Select Disjoint Paths in Overlay Networks

paper_content:

Routing policies used in the Internet can be restrictive, limiting communication between source-destination pairs to one path, when often better alternatives exist. To avoid route flapping, recovery mechanisms may be dampened, making adaptation slow. Unstructured overlays have been widely proposed to mitigate the issues of path and performance failures in the Internet by routing through an indirect-path via overlay peer(s). Choice of alternate-paths in overlay networks is a challenging issue. Ensuring both availability and performance guarantees on alternate paths requires aggressive monitoring of all overlay paths using active probing; this limits scalability when the number of overlay-paths becomes large. An alternate technique to select an overlay-path is to bias its selection based on physical disjointness criteria to bypass the failure on primary-path. In this paper, we show how type-of-relationship (ToR)-Graphs can be used to select maximally-disjoint overlay-paths.
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paper_title: Heuristics for Internet map discovery

paper_content:

Mercator is a program that uses hop-limited probes-the same primitive used in traceroute-to infer an Internet map. It uses informed random address probing to carefully exploring the IP address space when determining router adjacencies, uses source-route capable routers wherever possible to enhance the fidelity of the resulting map, and employs novel mechanisms for resolving aliases (interfaces belonging to the same router). This paper describes the design of these heuristics and our experiences with Mercator, and presents some preliminary analysis of the resulting Internet map.
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paper_title: Detection, Understanding, and Prevention of Traceroute Measurement Artifacts

paper_content:

Traceroute is widely used, from the diagnosis of network problems to the assemblage of internet maps. Unfortunately, there are a number of problems with traceroute methodology, which lead to the inference of erroneous routes. This paper studies particular structures arising in nearly all traceroute measurements. We characterize them as ''loops'', ''cycles'', and ''diamonds''. We identify load balancing as a possible cause for the appearance of false loops, cycles, and diamonds, i.e., artifacts that do not represent the internet topology. We provide a new publicly available traceroute, called Paris traceroute, which, by controlling the packet header contents, provides a truer picture of the actual routes that packets follow. We performed measurements, from the perspective of a single source tracing towards multiple destinations, and Paris traceroute allowed us to show that many of the particular structures we observe are indeed traceroute measurement artifacts.
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paper_title: Backup path allocation based on a correlated link failure probability model in overlay networks

paper_content:

Communication reliability is a desired property in computer networks. One key technology to increase the reliability of a communication path is to provision a disjoint backup path. One of the main challenges in implementing this technique is that two paths that are disjoint at the IP or overlay layer may share the same physical links. As a result, although we may select a disjoint backup path at the overlay layer one physical link failure may cause the failure of both the primary and the backup paths. In this paper we propose a solution to address this problem. The main idea is to take into account the correlated link failure at the overlay layer More precisely, our goal is to find a route for the backup path to minimize the joint path failure probability between the primary and the backup paths. To demonstrate the feasibility of our approach, we perform extensive evaluations under both single and double link failure models. Our results show that, in terms of robustness, our approach is near optimal and is up to 60% better than no backup path reservation and is up to 30% better than using the traditional shortest disjoint path algorithm to select the backup path.
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paper_title: Interdomain Traffic Engineering with BGP

paper_content:

Traffic engineering is performed by means of a set of techniques that can be used to better control the flow of packets inside an IP network. We discuss the utilization of these techniques across interdomain boundaries in the global Internet. We first analyze the characteristics of interdomain traffic on the basis of measurements from three different Internet service providers and show that a small number of sources are responsible for a large fraction of the traffic. Across interdomain boundaries, traffic engineering relies on a careful tuning of the route advertisements sent via the border gateway protocol. We explain how this tuning can be used to control the flow of incoming and outgoing traffic, and identify its limitations.
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paper_title: Managing a portfolio of overlay paths

paper_content:

In recent years, several architectures have been proposed and developed for supporting streaming applications that take advantage of multiple paths through the network simultaneously. We consider the problem of computing a set of paths and the relative amounts of data conveyed through them in order to provide the desired level of performance for data streams. Given the expectation, variance, and covariance of an appropriate metric of interest for overlay links, we attempt to solve the underlying resource allocation problem by applying methods used in managing a finance portfolio. We observe that the flow allocation problem requires constrained application of these methods, and we discuss the tractability of enforcing the constraints. We finally present some simulation results to evaluate the effectiveness of our proposed techniques.
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paper_title: On characterizing BGP routing table growth

paper_content:

The sizes of the BGP routing tables have increased by an order of magnitude over the last six years. This dramatic growth of the routing table can decrease the packet forwarding speed and demand more router memory space. In this paper, we explore the extent that various factors contribute to the routing table size and characterize the growth of each contribution. We begin with measurement study using routing tables of Oregon Route Views server to determine the contributions of multi-homing, load balancing, address fragmentation, and failure to aggregate to routing table size. We find that the contribution of address fragmentation is the greatest and is three times that of multi-homing or load balancing. The contribution of failure to aggregate is the least. Although multi-homing and load balancing contribute less to routing table size than address fragmentation does, we observe that the contribution of multi-homing and that of load balancing grow faster than the routing table does and that the load balancing has surpassed multihoming becoming the fastest growing contributor. Moreover, we find that both load balancing and multi-homing contribute to routing table growth by introducing more prefixes of length greater than 17 but less than 25, which is the fastest growing class of prefixes. Next, we compare the growth of the routing table to the expanding of IP addresses that can be routed and conclude that the growth of routable IP addresses is much slower than that of routing table size. Last, we demonstrate that our findings based on the view derived from the Oregon server are accurate through evaluation using additional 15 routing tables collected from different locations in the Internet.
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paper_title: R-BGP: Staying Connected in a Connected World

paper_content:

Many studies show that, when Internet links go up or down, the dynamics of BGP may cause several minutes of packet loss. The loss occurs even when multiple paths between the sender and receiver domains exist, and is unwarranted given the high connectivity of the Internet. ::: ::: Our objective is to ensure that Internet domains stay connected as long as the underlying network is connected. Our solution, R-BGP works by pre-computing a few strategically chosen failover paths. R-BGP provably guarantees that a domain will not become disconnected from any destination as long as it will have a policy-compliant path to that destination after convergence. Surprisingly, this can be done using a few simple and practical modifications to BGP, and, like BGP, requires announcing only one path per neighbor. Simulations on the AS-level graph of the current Internet show that R-BGP reduces the number of domains that see transient disconnectivity resulting from a link failure from 22% for edge links and 14% for core links down to zero in both cases.
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paper_title: Best-path vs. multi-path overlay routing

paper_content:

Time-varying congestion on Internet paths and failures due to software, hardware, and configuration errors often disrupt packet delivery on the Internet.Many aproaches to avoiding these problems use multiple paths between two network locations. These approaches rely on a path-independence assumption in order to work well; i.e., they work best when the problems on different paths between two locations are uncorrelated in time.This paper examines the extent to which this assumption holds on the Internet by analyzing 14 days of data collected from 30 nodes in the RON testbed. We examine two problems that manifest themselves---congestion-triggered loss and path failures---and find that the chances of losing two packets between the same hosts is nearly as high when those packets are sent through an intermediate node (60%) as when they are sent back-to-back on the same path (70%). In so doing, we also compare two different ways of taking advantage of path redundancy proposed in the literature: mesh routing based on packet replication, and reactive routing based on adaptive path selection.
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paper_title: Exploiting routing redundancy via structured peer-to-peer overlays

paper_content:

Structured peer-to-peer overlays provide a natural infrastructure for resilient routing via efficient fault detection and precomputation of backup paths. These overlays can respond to faults in a few hundred milliseconds by rapidly shifting between alternate routes. In this paper, we present two adaptive mechanisms for structured overlays and illustrate their operation in the context of Tapestry, a fault-resilient overlay from Berkeley. We also describe a transparent, protocol-independent traffic redirection mechanism that tunnels legacy application traffic through overlays. Our measurements of a Tapestry prototype show it to be a highly responsive routing service, effective at circumventing a range of failures while incurring reasonable cost in maintenance bandwidth and additional routing latency.
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paper_title: MIRO: multi-path interdomain routing

paper_content:

The Internet consists of thousands of independent domains with different, and sometimes competing, business interests. However, the current interdomain routing protocol (BGP) limits each router to using a single route for each destination prefix, which may not satisfy the diverse requirements of end users. Recent proposals for source routing offer an alternative where end hosts or edge routers select the end-to-end paths. However, source routing leaves transit domains with very little control and introduces difficult scalability and security challenges. In this paper, we present a multi-path inter-domain routing protocol called MIRO that offers substantial flexiility, while giving transit domains control over the flow of traffic through their infrastructure and avoiding state explosion in disseminating reachability information. In MIRO, routers learn default routes through the existing BGP protocol, and arbitrary pairs of domains can negotiate the use of additional paths (bound to tunnels in the data plane) tailored to their special needs. MIRO retains the simplicity of BGP for most traffic, and remains backwards compatible with BGP to allow for incremental deployability. Experiments with Internet topology and routing data illustrate that MIRO offers tremendous flexibility for path selection with reasonable overhead.
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paper_title: Improving the Reliability of Internet Paths with One-hop Source Routing

paper_content:

Recent work has focused on increasing availability in the face of Internet path failures. To date, proposed solutions have relied on complex routing and path-monitoring schemes, trading scalability for availability among a relatively small set of hosts. ::: ::: This paper proposes a simple, scalable approach to recover from Internet path failures. Our contributions are threefold. First, we conduct a broad measurement study of Internet path failures on a collection of 3,153 Internet destinations consisting of popular Web servers, broad-band hosts, and randomly selected nodes. We monitored these destinations from 67 PlanetLab vantage points over a period of seven days, and found availabilities ranging from 99.6% for servers to 94.4% for broadband hosts. When failures do occur, many appear too close to the destination (e.g., last-hop and end-host failures) to be mitigated through alternative routing techniques of any kind. Second, we show that for the failures that can be addressed through routing, a simple, scalable technique, called one-hop source routing, can achieve close to the maximum benefit available with very low overhead. When a path failure occurs, our scheme attempts to recover from it by routing indirectly through a small set of randomly chosen intermediaries. ::: ::: Third, we implemented and deployed a prototype one-hop source routing infrastructure on PlanetLab. Over a three day period, we repeatedly fetched documents from 982 popular Internet Web servers and used one-hop source routing to attempt to route around the failures we observed. Our results show that our prototype successfully recovered from 56% of network failures. However, we also found a large number of server failures that cannot be addressed through alternative routing. ::: ::: Our research demonstrates that one-hop source routing is easy to implement, adds negligible overhead, and achieves close to the maximum benefit available to indirect routing schemes, without the need for path monitoring, history, or a-priori knowledge of any kind.
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paper_title: Source selectable path diversity via routing deflections

paper_content:

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.
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paper_title: Improving the Reliability of Internet Paths with One-hop Source Routing

paper_content:

Recent work has focused on increasing availability in the face of Internet path failures. To date, proposed solutions have relied on complex routing and path-monitoring schemes, trading scalability for availability among a relatively small set of hosts. ::: ::: This paper proposes a simple, scalable approach to recover from Internet path failures. Our contributions are threefold. First, we conduct a broad measurement study of Internet path failures on a collection of 3,153 Internet destinations consisting of popular Web servers, broad-band hosts, and randomly selected nodes. We monitored these destinations from 67 PlanetLab vantage points over a period of seven days, and found availabilities ranging from 99.6% for servers to 94.4% for broadband hosts. When failures do occur, many appear too close to the destination (e.g., last-hop and end-host failures) to be mitigated through alternative routing techniques of any kind. Second, we show that for the failures that can be addressed through routing, a simple, scalable technique, called one-hop source routing, can achieve close to the maximum benefit available with very low overhead. When a path failure occurs, our scheme attempts to recover from it by routing indirectly through a small set of randomly chosen intermediaries. ::: ::: Third, we implemented and deployed a prototype one-hop source routing infrastructure on PlanetLab. Over a three day period, we repeatedly fetched documents from 982 popular Internet Web servers and used one-hop source routing to attempt to route around the failures we observed. Our results show that our prototype successfully recovered from 56% of network failures. However, we also found a large number of server failures that cannot be addressed through alternative routing. ::: ::: Our research demonstrates that one-hop source routing is easy to implement, adds negligible overhead, and achieves close to the maximum benefit available to indirect routing schemes, without the need for path monitoring, history, or a-priori knowledge of any kind.
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paper_title: Network sensitivity to hot-potato disruptions

paper_content:

Hot-potato routing is a mechanism employed when there are multiple (equally good) interdomain routes available for a given destination. In this scenario, the Border Gateway Protocol (BGP) selects the interdomain route associated with the closest egress point based upon intradomain path costs. Consequently, intradomain routing changes can impact interdomain routing and cause abrupt swings of external routes, which we call hot-potato disruptions. Recent work has shown that hot-potato disruptions can have a substantial impact on large ISP backbones and thereby jeopardize the network robustness. As a result, there is a need for guidelines and tools to assist in the design of networks that minimize hot-potato disruptions. However, developing these tools is challenging due to the complex and subtle nature of the interactions between exterior and interior routing. In this paper, we address these challenges using an analytic model of hot-potato routing that incorporates metrics to evaluate network sensitivity to hot-potato disruptions. We then present a methodology for computing these metrics using measurements of real ISP networks. We demonstrate the utility of our model by analyzing the sensitivity of a large AS in a tier~1 ISP network.
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paper_title: Source selectable path diversity via routing deflections

paper_content:

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.
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paper_title: The Rich-Club Phenomenon In The Internet Topology

paper_content:

We show that the Internet topology at the autonomous system (AS) level has a rich-club phenomenon. The rich nodes, which are a small number of nodes with large numbers of links, are very well connected to each other. The rich-club is a core tier that we measured using the rich-club connectivity and the node-node link distribution. We obtained this core tier without any heuristic assumption between the ASs. The rich-club phenomenon is a simple qualitative way to differentiate between power law topologies and provides a criterion for new network models. To show this, we compared the measured rich-club of the AS graph with networks obtained using the Baraba/spl acute/si-Albert (BA) scale-free network model, the Fitness BA model and the Inet-3.0 model.
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paper_title: Algebra-Based Scalable Overlay Network Monitoring: Algorithms, Evaluation, and Applications

paper_content:

Overlay network monitoring enables distributed Internet applications to detect and recover from path outages and periods of degraded performance within seconds. For an overlay network with n end hosts, existing systems either require O(n2) measurements, and thus lack scalability, or can only estimate the latency but not congestion or failures. Our earlier extended abstract [Y. Chen, D. Bindel, and R. H. Katz, "Tomography-based overlay network monitoring," Proceedings of the ACM SIGCOMM Internet Measurement Conference (IMC), 2003] briefly proposes an algebraic approach that selectively monitors k linearly independent paths that can fully describe all the O(n2) paths. The loss rates and latency of these k paths can be used to estimate the loss rates and latency of all other paths. Our scheme only assumes knowledge of the underlying IP topology, with links dynamically varying between lossy and normal. In this paper, we improve, implement, and extensively evaluate such a monitoring system. We further make the following contributions: i) scalability analysis indicating that for reasonably large n (e.g., 100), the growth of k is bounded as O(n log n), ii) efficient adaptation algorithms for topology changes, such as the addition or removal of end hosts and routing changes, iii) measurement load balancing schemes, iv) topology measurement error handling, and v) design and implementation of an adaptive streaming media system as a representative application. Both simulation and Internet experiments demonstrate we obtain highly accurate path loss rate estimation while adapting to topology changes within seconds and handling topology errors.
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paper_title: The paths toward IPv6 multihoming

paper_content:

A powder metallurgical method of producing metal bodies using spherical powder, produced by inert gas atomization, from magnetizable material with a particle size distribution closely approximating the so called Fuller curve for maximum density packing of spherical particles. Said powder is magnetized and filled into a form, which may take place before or after magnetization, said mixed and magnetized powder then sintered in said form with the exclusion of air, to produce a sintered body without communicating porosity.
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paper_title: MIRO: multi-path interdomain routing

paper_content:

The Internet consists of thousands of independent domains with different, and sometimes competing, business interests. However, the current interdomain routing protocol (BGP) limits each router to using a single route for each destination prefix, which may not satisfy the diverse requirements of end users. Recent proposals for source routing offer an alternative where end hosts or edge routers select the end-to-end paths. However, source routing leaves transit domains with very little control and introduces difficult scalability and security challenges. In this paper, we present a multi-path inter-domain routing protocol called MIRO that offers substantial flexiility, while giving transit domains control over the flow of traffic through their infrastructure and avoiding state explosion in disseminating reachability information. In MIRO, routers learn default routes through the existing BGP protocol, and arbitrary pairs of domains can negotiate the use of additional paths (bound to tunnels in the data plane) tailored to their special needs. MIRO retains the simplicity of BGP for most traffic, and remains backwards compatible with BGP to allow for incremental deployability. Experiments with Internet topology and routing data illustrate that MIRO offers tremendous flexibility for path selection with reasonable overhead.
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paper_title: Path-Computation-Element-Based Architecture for Interdomain MPLS/GMPLS Traffic Engineering: Overview and Performance

paper_content:

The Path Computation Element Working Group at the Internet Engineering Task Force is chartered to specify a PCE-based architecture for the path computation of interdomain MPLS- and GMPLS-based traffic engineered label switched paths. In this architecture, path computation does not occur at the head-end LSR, but on another path computation entity that may not be physically located on the head-end LSR. This method is greatly different from the traditional "per-domain" approach to path computation. This article presents analysis and results that compare performance of the PCE architecture with the current state-of-the-art approach. Detailed simulations are undertaken on varied and realistic scenarios where preliminary results show several performance benefits from the deployment of PCE. To provide a complete overview of significant development taking place in this area, milestones and progress at the IETF PCE WG are also discussed.
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paper_title: An evaluation of IP-based fast reroute techniques

paper_content:

Today, IP-based networks are used to carry all types of traffic, from the traditional best-effort Internet access to traffic with much more stringent requirements such as realtime voice or video services and Virtual Private Networks. Some of those services have strong requirements in terms of restoration time in case of failure. When a link or a router fails in an IP network, the routers adjacent to the failing ressource must react by distributing new routing information to allow each router of the network to update its routing table. A realistic estimate of the convergence time of a tuned intradomain routing protocol in a large network is a few hundred of milliseconds [1]. For some mission critical services like voice or video over IP, achieving a restoration time in the order of a few tens of milliseconds after a failure is important [2]. In this paper, we first present several techniques that can be used to achieve such a short restoration time. While most of the work on fast restoration has focussed on MPLS-based solutions [2], recent work indicate that fast restoration techniques can be developed also for pure IP networks. Recently, the RTGWG working group of the IETF started to work actively on this problem and several fast reroute techniques are being discussed. However, as of today, no detailed evaluation of the various proposed IP-based fast reroute techniques has been published. The goal of this short paper is to firstly provide a brief overview of fast restoration techniques suitable for pure IP networks, in section 2. Then, in section 3, we evaluate by simulation how many links can be protected by each technique in large ISP networks based on their actual topology. This coverage is an important issue as some techniques cannot protect all links from failures.
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paper_title: Exploring the performance benefits of end-to-end path switching

paper_content:

This paper explores the feasibility of improving the performance of end-to-end data transfers between different sites through path switching. Our study is focused on both the logic that controls path switching decisions and the configurations required to achieve sufficient path diversity. Specifically, we investigate two common approaches offering path diversity - multi-homing and overlay networks - and investigate their characteristics in the context of a representative wide-area testbed. We explore the end-to-end delay and loss characteristics of different paths and find that substantial improvements can potentially be achived by path switching, especially in lowering end-to-end losses. Based on this assessment, we develop a simple path-switching mechanism capable of realizing those performance improvements. Our experimental study demonstrates that substantial performance improvements are indeed achievable using this approach.
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paper_title: On characterizing BGP routing table growth

paper_content:

The sizes of the BGP routing tables have increased by an order of magnitude over the last six years. This dramatic growth of the routing table can decrease the packet forwarding speed and demand more router memory space. In this paper, we explore the extent that various factors contribute to the routing table size and characterize the growth of each contribution. We begin with measurement study using routing tables of Oregon Route Views server to determine the contributions of multi-homing, load balancing, address fragmentation, and failure to aggregate to routing table size. We find that the contribution of address fragmentation is the greatest and is three times that of multi-homing or load balancing. The contribution of failure to aggregate is the least. Although multi-homing and load balancing contribute less to routing table size than address fragmentation does, we observe that the contribution of multi-homing and that of load balancing grow faster than the routing table does and that the load balancing has surpassed multihoming becoming the fastest growing contributor. Moreover, we find that both load balancing and multi-homing contribute to routing table growth by introducing more prefixes of length greater than 17 but less than 25, which is the fastest growing class of prefixes. Next, we compare the growth of the routing table to the expanding of IP addresses that can be routed and conclude that the growth of routable IP addresses is much slower than that of routing table size. Last, we demonstrate that our findings based on the view derived from the Oregon server are accurate through evaluation using additional 15 routing tables collected from different locations in the Internet.
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paper_title: Improved BGP convergence via ghost flushing

paper_content:

Labovitz et al. (2001) and Labovitz et al. (2000) noticed that sometimes it takes border gateway protocol (BGP) a substantial amount of time and messages to converge and stabilize following the failure of some node in the Internet. In this paper, we suggest a minor modification to BGP that eliminates the problem pointed out and substantially reduces the convergence time and communication complexity of BGP. Roughly speaking, our modification ensures that bad news (the failure of a node/edge) propagate fast, while good news (the establishment of a new path to a destination) propagate somewhat slower. This is achieved in BGP by allowing withdrawal messages to propagate with no delay as fast as the network forward them, while announcements propagate as they do in BGP with a delay at each node of one minRouteAdver (except for the first wave of announcements). As a by product of this work, a new stateless mechanism to overcome the counting to infinity problem is provided, which compares favorably with other known stateless mechanisms (in RIP and IGRP).
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paper_title: Source selectable path diversity via routing deflections

paper_content:

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.
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paper_title: Internet connectivity at the AS-level: an optimization-driven modeling approach

paper_content:

Two ASs are connected in the Internet AS graph only if they have a business "peering relationship." By focusing on the AS subgraph ASPC whose links represent provider-customer relationships, we develop a new optimization-driven model for Internet growth at the ASPC level. The model's defining feature is an explicit construction of a novel class of intuitive, multi-objective, local optimizations by which the different customer ASs determine in a fully distributed and decentralized fashion their "best" upstream provider AS. Key criteria that are explicitly accounted for in the formulation of these multi-objective optimization problems are (i) AS-geography, i.e., locality and number of PoPs within individual ASs; (ii) AS-specific business models, abstract toy models that describe how individual ASs choose their "best" provider; and (iii) AS evolution, a historic account of the "lives" of individual ASs in a dynamic ISP market. We show that the resulting model is broadly robust, perforce yields graphs that match inferred AS connectivity with respect to a number of different metrics, and is ideal for exploring the impact of new peering incentives or policies on AS-level connectivity.
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paper_title: A distributed approach to topology-aware overlay path monitoring

paper_content:

Path probing is essential to maintain an efficient overlay network topology. However, the cost of complete probing can be as high as O(n/sup 2/), which is prohibitive in large-scale overlay networks. Recently we proposed a method that trades probing overhead for inference accuracy in sparse networks such as the Internet. The method uses physical path information to infer path quality for all of the n/spl times/(n-1) overlay paths, while actually probing only a subset of the paths. We propose and evaluate a distributed approach to implement this method. We describe a minimum diameter, link-stress bounded overlay spanning tree, which is used to collect and disseminate path quality information. All nodes in the tree collaborate to infer the quality of all paths. Simulation results show this approach can achieve a high-level of inference accuracy while reducing probing overhead and balancing link stress on the spanning tree.
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paper_title: Improving multipath reliability in topology-aware overlay networks

paper_content:

Use of multiple paths between node pairs can enable an overlay network to bypass Internet link failures. Selecting high quality primary and backup paths is challenging, however. To maximize communication reliability, an overlay multipath routing protocol must account for both the failure probability of a single path and link sharing among multiple paths. We propose a practical solution that exploits physical topology information and end-to-end path quality measurement results to select high quality path pairs. Simulation results show the proposed approach is effective in achieving higher multipath reliability in overlay networks at reasonable communication cost.
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paper_title: On the cost-quality tradeoff in topology-aware overlay path probing

paper_content:

Path probing is essential to maintaining an efficient overlay network topology. However, the cost of a full-scale probing is as high as O(n/sup 2/), which is prohibitive in large-scale overlay networks. Several methods have been proposed to reduce probing overhead, although at a cost in terms of probing completeness. In this paper, an orthogonal solution is proposed that trades probing overhead for estimation accuracy in sparse networks such as the Internet. The proposed solution uses network-level path composition information (for example, as provided by a topology server) to infer path quality without full-scale probing. The inference metrics include latency, loss rate and available bandwidth. This approach is used to design several probing algorithms, which are evaluated through analysis and simulation. The results show that the proposed method can significantly reduce probing overhead while providing hounded quality estimations for all n /spl times/ (n - 1) overlay paths. The solution is well suited to medium-scale overlay networks in the Internet. In other environments, it can be combined with extant probing algorithms to further improve performance.
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paper_title: Characterizing selfishly constructed overlay routing networks

paper_content:

We analyze the characteristics of overlay routing networks generated by selfish nodes playing competitive network construction games. We explore several networking scenarios - some simplistic, others more realistic - and analyze the resulting Nash equilibrium graphs with respect to topology, performance, and resilience. We find a fundamental tradeoff between performance and resilience, and show that limiting the degree of nodes is of great importance in controlling this balance. Further, by varying the cost function, the game produces widely different topologies; one parameter in particular - the relative cost between maintaining an overlay link and increasing the path length to other nodes - can generate topologies with node-degree distributions whose tails vary from exponential to power-law. We conclude that competitive games can create overlay routing networks satisfying very diverse goals.
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paper_title: Comparing the structure of power-law graphs and the Internet AS graph

paper_content:

In this work we devise algorithmic techniques to compare the interconnection structure of the Internet AS graph with that of graphs produced by topology generators that match the power-law degree distribution of the AS graph. We are guided by the existing notion that nodes in the AS graph can be placed in tiers with the resulting graph having an hierarchical structure. Our techniques are based on identifying graph nodes at each tier, decomposing the graph by removing such nodes and their incident edges, and thus explicitly revealing the interconnection structure of the graph. We define quantitative metrics to analyze and compare the decomposition of synthetic power-law graphs with the Internet-AS graph. Through experiments, we observe qualitative similarities in the decomposition structure of the different families of power-law graphs and explain any quantitative differences based on their generative models. We believe our approach provides insight into the interconnection structure of the AS graph and finds continuing applications in evaluating the representativeness of synthetic topology generators.
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paper_title: The Rich-Club Phenomenon In The Internet Topology

paper_content:

We show that the Internet topology at the autonomous system (AS) level has a rich-club phenomenon. The rich nodes, which are a small number of nodes with large numbers of links, are very well connected to each other. The rich-club is a core tier that we measured using the rich-club connectivity and the node-node link distribution. We obtained this core tier without any heuristic assumption between the ASs. The rich-club phenomenon is a simple qualitative way to differentiate between power law topologies and provides a criterion for new network models. To show this, we compared the measured rich-club of the AS graph with networks obtained using the Baraba/spl acute/si-Albert (BA) scale-free network model, the Fitness BA model and the Inet-3.0 model.
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paper_title: Race Conditions in Coexisting Overlay Networks

paper_content:

By allowing end hosts to make independent routing decisions at the application level, different overlay networks may unintentionally interfere with each other. This paper describes how multiple similar or dissimilar overlay networks could experience race conditions, resulting in oscillations (in both route selection and network load) and cascading reactions. We pinpoint the causes for synchronization and derive an analytic formulation for the synchronization probability of two overlays. Our model indicates that the probability of synchronization is non-negligible across a wide range of parameter settings, thus implying that the ill effects of synchronization should not be ignored. Using the analytical model, we find an upper bound on the duration of traffic oscillations. We also show that the model can be easily extended to include a large number of co-existing overlays. We validate our model through simulations that are designed to capture the transient routing behavior of both the IP- and overlay-layers. We use our model to study the effects of factors such as path diversity (measured in round trip times) and probing aggressiveness on these race conditions. Finally, we discuss the implications of our study on the design of path probing process in overlay networks and examine strategies to reduce the impact of race conditions.
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paper_title: Brocade: Landmark Routing on Overlay Networks

paper_content:

Recent work such as Tapestry, Pastry, Chord and CAN provide efficient location utilities in the form of overlay infrastructures. These systems treat nodes as if they possessed uniform resources, such as network bandwidth and connectivity. In this paper, we propose a systemic design for a secondaryoverlay of super-nodes which can be used to deliver messages directly to the destination's local network, thus improving route efficiency. We demonstrate the potential performance benefits by proposing a name mapping scheme for a Tapestry-Tapestry secondary overlay, and show preliminary simulation results demonstrating significant routing performance improvement.
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paper_title: Drafting behind Akamai (travelocity-based detouring)

paper_content:

To enhance web browsing experiences, content distribution networks (CDNs) move web content "closer" to clients by caching copies of web objects on thousands of servers worldwide. Additionally, to minimize client download times, such systems perform extensive network and server measurements, and use them to redirect clients to different servers over short time scales. In this paper, we explore techniques for inferring and exploiting network measurements performed by the largest CDN, Akamai; our objective is to locate and utilize quality Internet paths without performing extensive path probing or monitoring.Our contributions are threefold. First, we conduct a broad measurement study of Akamai's CDN. We probe Akamai's network from 140 PlanetLab vantage points for two months. We find that Akamai redirection times, while slightly higher than advertised, are sufficiently low to be useful for network control. Second, we empirically show that Akamai redirections overwhelmingly correlate with network latencies on the paths between clients and the Akamai servers. Finally, we illustrate how large-scale overlay networks can exploit Akamai redirections to identify the best detouring nodes for one-hop source routing. Our research shows that in more than 50% of investigated scenarios, it is better to route through the nodes "recommended" by Akamai, than to use the direct paths. Because this is not the case for the rest of the scenarios, we develop lowoverhead pruning algorithms that avoid Akamai-driven paths when they are not beneficial.
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paper_title: Characterizing selfishly constructed overlay routing networks

paper_content:

We analyze the characteristics of overlay routing networks generated by selfish nodes playing competitive network construction games. We explore several networking scenarios - some simplistic, others more realistic - and analyze the resulting Nash equilibrium graphs with respect to topology, performance, and resilience. We find a fundamental tradeoff between performance and resilience, and show that limiting the degree of nodes is of great importance in controlling this balance. Further, by varying the cost function, the game produces widely different topologies; one parameter in particular - the relative cost between maintaining an overlay link and increasing the path length to other nodes - can generate topologies with node-degree distributions whose tails vary from exponential to power-law. We conclude that competitive games can create overlay routing networks satisfying very diverse goals.
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paper_title: Practical Issues of Statistical Path Monitoring in Overlay Networks with Large, Rank-Deficient Routing Matrices

paper_content:

A conventional form of vehicle axle suspension comprises on each side of a vehicle-a leaf spring pack and a shock absorber system. A height control system may also be included. According to this invention the leaf spring pack is replaced by a single leaf spring and a pair of air springs. The opposite ends of the single leaf spring are shackled to the existing shackle attachments and their vehicle frame mounts. Midway between its ends the single leaf spring is connected to the adjacent axle end by the existing spring-to-axle attachment components. In order to compensate for the difference in thicknesses of leaf spring pack and the single leaf spring at their midpoints, a spacer having a vertical thickness equal to the difference in the thicknesses is mounted on top of the single thickness spring at the axle. Air spring support brackets are symmetrically mounted on the chassis frame member on opposite sides of the axle. The upper end of each air spring is attached to one of the brackets and the lower end of each air spring is attached to the single leaf spring. Preferably a-height control system is provided on each side so as to maintain the chassis at a predetermined level. Except for the single leaf spring and the spacer, the other components may be of the type used in conventional leaf spring pack suspensions.
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paper_title: Exploiting routing redundancy via structured peer-to-peer overlays

paper_content:

Structured peer-to-peer overlays provide a natural infrastructure for resilient routing via efficient fault detection and precomputation of backup paths. These overlays can respond to faults in a few hundred milliseconds by rapidly shifting between alternate routes. In this paper, we present two adaptive mechanisms for structured overlays and illustrate their operation in the context of Tapestry, a fault-resilient overlay from Berkeley. We also describe a transparent, protocol-independent traffic redirection mechanism that tunnels legacy application traffic through overlays. Our measurements of a Tapestry prototype show it to be a highly responsive routing service, effective at circumventing a range of failures while incurring reasonable cost in maintenance bandwidth and additional routing latency.
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paper_title: Race Conditions in Coexisting Overlay Networks

paper_content:

By allowing end hosts to make independent routing decisions at the application level, different overlay networks may unintentionally interfere with each other. This paper describes how multiple similar or dissimilar overlay networks could experience race conditions, resulting in oscillations (in both route selection and network load) and cascading reactions. We pinpoint the causes for synchronization and derive an analytic formulation for the synchronization probability of two overlays. Our model indicates that the probability of synchronization is non-negligible across a wide range of parameter settings, thus implying that the ill effects of synchronization should not be ignored. Using the analytical model, we find an upper bound on the duration of traffic oscillations. We also show that the model can be easily extended to include a large number of co-existing overlays. We validate our model through simulations that are designed to capture the transient routing behavior of both the IP- and overlay-layers. We use our model to study the effects of factors such as path diversity (measured in round trip times) and probing aggressiveness on these race conditions. Finally, we discuss the implications of our study on the design of path probing process in overlay networks and examine strategies to reduce the impact of race conditions.
---
paper_title: Interdomain traffic engineering in a locator/identifier separation context

paper_content:

The Routing Research Group (RRG) of the Internet Research Task Force (IRTF) is currently discussing several architectural solutions to build an interdomain routing architecture that scales better than the existing one. The solutions family currently being discussed concerns the addresses separation into locators and identifiers, LISP being one of them. Such a separation provides opportunities in terms of traffic engineering. In this paper, we propose an open and flexible solution that allows an ISP using identifier/locator separation to engineer its interdomain traffic. Our solution relies on the utilization of a service that transparently ranks paths using cost functions. We implement a prototype server and demonstrate its benefits in a LISP testbed.
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paper_title: On characterizing BGP routing table growth

paper_content:

The sizes of the BGP routing tables have increased by an order of magnitude over the last six years. This dramatic growth of the routing table can decrease the packet forwarding speed and demand more router memory space. In this paper, we explore the extent that various factors contribute to the routing table size and characterize the growth of each contribution. We begin with measurement study using routing tables of Oregon Route Views server to determine the contributions of multi-homing, load balancing, address fragmentation, and failure to aggregate to routing table size. We find that the contribution of address fragmentation is the greatest and is three times that of multi-homing or load balancing. The contribution of failure to aggregate is the least. Although multi-homing and load balancing contribute less to routing table size than address fragmentation does, we observe that the contribution of multi-homing and that of load balancing grow faster than the routing table does and that the load balancing has surpassed multihoming becoming the fastest growing contributor. Moreover, we find that both load balancing and multi-homing contribute to routing table growth by introducing more prefixes of length greater than 17 but less than 25, which is the fastest growing class of prefixes. Next, we compare the growth of the routing table to the expanding of IP addresses that can be routed and conclude that the growth of routable IP addresses is much slower than that of routing table size. Last, we demonstrate that our findings based on the view derived from the Oregon server are accurate through evaluation using additional 15 routing tables collected from different locations in the Internet.
---
paper_title: Delayed Internet routing convergence

paper_content:

This paper examines the latency in Internet path failure, failover, and repair due to the convergence properties of interdomain routing. Unlike circuit-switched paths which exhibit failover on the order of milliseconds, our experimental measurements show that interdomain 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 fluctuations formed during the operation of the border gateway protocol (BGP) path selection process on the 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 interdomain routing faults, we describe several unexpected properties of convergence and show that the measured upper bound on Internet interdomain 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.
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paper_title: MIRO: multi-path interdomain routing

paper_content:

The Internet consists of thousands of independent domains with different, and sometimes competing, business interests. However, the current interdomain routing protocol (BGP) limits each router to using a single route for each destination prefix, which may not satisfy the diverse requirements of end users. Recent proposals for source routing offer an alternative where end hosts or edge routers select the end-to-end paths. However, source routing leaves transit domains with very little control and introduces difficult scalability and security challenges. In this paper, we present a multi-path inter-domain routing protocol called MIRO that offers substantial flexiility, while giving transit domains control over the flow of traffic through their infrastructure and avoiding state explosion in disseminating reachability information. In MIRO, routers learn default routes through the existing BGP protocol, and arbitrary pairs of domains can negotiate the use of additional paths (bound to tunnels in the data plane) tailored to their special needs. MIRO retains the simplicity of BGP for most traffic, and remains backwards compatible with BGP to allow for incremental deployability. Experiments with Internet topology and routing data illustrate that MIRO offers tremendous flexibility for path selection with reasonable overhead.
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Title: Finding Alternate Paths in the Internet: A Survey of Techniques for End-to-End Path Discovery

Section 1: INTRODUCTION
Description 1: Introduce the problem of suboptimal routing in the Internet, the importance of alternate paths, and outline various scenarios where alternate paths can improve end-to-end QoS.

Section 2: CRITERIA FOR SELECTING ALTERNATE PATHS
Description 2: Discuss the performance metrics and criteria for selecting alternate paths, such as latency, throughput, packet loss, and path disjointness.

Section 3: Monitoring Paths Based on Performance
Description 3: Explain the methodologies for dynamic path monitoring and ranking alternate paths based on performance metrics.

Section 4: Disjoint Paths
Description 4: Describe the strategies for selecting the most disjoint paths to avoid shared points of failure and ensure reliable data delivery.

Section 5: Multi-path routing
Description 5: Explore the concept of multi-path routing and its application in improving data transmission reliability through techniques such as Forward Error Correction (FEC).

Section 6: USES OF ALTERNATE PATHS
Description 6: Classify the methods of realizing alternate paths, including detour routing, routing deflections, and back-up route construction.

Section 7: Detour Routing
Description 7: Detail the use of intermediate nodes to create detours around faulty primary paths, highlighting frameworks like Resilient Overlay Networks (RONs).

Section 8: Routing Deflections
Description 8: Discuss how routers can make localized deflection decisions to find alternate paths around failed links.

Section 9: Back-up Routes
Description 9: Describe the techniques for constructing backup routes with specific QoS parameters and the process of Fast ReRoute (FRR) setup both inter-domain and intra-domain.

Section 10: OPEN RESEARCH ISSUES
Description 10: Identify and discuss ongoing research challenges in multi-homing, modifying underlay routing mechanisms, and using alternate paths in Resilient Overlay Networks.

Section 11: CONCLUSIONS AND PROPOSALS FOR FUTURE DIRECTIONS OF RESEARCH
Description 11: Summarize the survey findings, the effectiveness of current approaches, and propose areas for future research, especially emphasizing deployment of Resilient Overlay Networks and security concerns in underlay routing modifications.