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ISMA Winter 2001 Workshop - Talk Abstracts
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Talk Title and PresenterAbstract
Route Views Update
Joel Jaeggli and
David Meyer

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The University of Oregon Route Views service (www.routeviews.orgi) is widely used both for operational purposes by ISPs as well as a source of data for Internet researchers. The server currently has EBGP multi-hop peerings service providers at 42 points around the world, carries more than 1.6M paths, and has averaged more than 1800 connections per day. We discuss how routeviews data has been put to use, and outline some of the things that could help the sustainability of services of this kind. New elements since the earlier talk at NANOG23 entitled "Trends and Dynamics in BGP" include a discussion of current and projected storage requirements, ongoing migration to zebra bgpd, and continued legacy data format archiving.
RIPE NCC Measurement Infrastructure Update
Henk Uijterwaal

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Part 1 of the talk will discuss recent development in the TTM and RIS infrastructure and new features interesting for people analyzing the data.

Part 2 will be recent analysis of TTM and RIS data. Topics (TTM): Jitter/IP Delay Variations, Bandwidth measurements, Long term trends in the delays, RIS: growth of routing table. And more.

Growth of Public Internet Exchanges over Time
Bill Woodcock, and
Bob Arasmith

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This is a short presentation of data and analysis surrounding the rate of growth which public Internet exchange facilities (peering points) experience over time. There is a commonly-held belief that exchange points begin with a small number (2-3) of initial participants, followed by straight-line growth up to a magic "critical mass" threshold, followed by exponential growth up to the maximum carrying capacity of the facility and its switch fabric. We hope to be able to either corroborate or refute this belief upon completion of our analysis, which we will present at ISMA. Principal investigator: Bill Woodcock, research director, Packet Clearing House. Co-author: Bob Arasmith, research associate, Packet Clearing House.
Global Routing Instabilities during Code Red II and Nimda Worm Propagation
Andy Ogielski

slides (PDF)

I will present the latest results following the work published at http://www.renesys.com/funding/bgp_instability/(link no longer available). This work was performed jointly with James Cowie of Renesys.
Detection of Routing Loops in Packet Traces and Analysis of Their Impact
Sue Moon

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Changes in routing information are propagated by various routing protocols. Transient inconsistency between router states exists as part of the normal routing protocol operation. As a result, a routing loop is conformed, and some packets might be bounced back and forth until the inconsistency is resolved. If the reachability to many destination addresses is affected by the inconsistency, it is likely that many packets are affected.

In this work, we present a methodology to detect routing loops as they manifest in the packet traces. Then we study the causes behind the routing incidents, and classify them by identifiable causes. As a final step, we analyse the impact of routing loops on the network traffic in terms of delay, loss, and bandwidth.

A study of BGP misconfigurations
Ratul Mahajan

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We present preliminary results from a new study of BGP misconfiguration. In the talk, we focus on two kinds of misconfigurations. The first is accidental origination of routes. It includes not only origination of routes owned by the ISP itself, but also address space hijacks. The second is route leaks, exporting routes not consistent with the ISP's policy. We talk about our methodology, results based on an email survey, and the underlying causes of these misconfigurations.
On the performance characteristics of BGP routing decisions
Mike Lloyd

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We describe a data collection infrastructure which accumulates BGP feeds along with performance data on a wide variety of end points. We then show some of the results we have generated by correlating these data sources. Specifically, we analyze the frequency with which BGP's unmodified decision process selects suboptimal forwarding paths. We also investigate the dynamic properties of observed performance differences.
Load Balancing Traffic in a BGP Environment Using On-line Simulation and Dynamic NAT Techniques
Shivkumar Kalyanaraman

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We focus on two problems in this talk: a) outbound load-balancing using BGP LOCAL_PREF settings aided by online simulation and b) inbound load balancing in a multihomed stub AS environment using dynamic NAT.

Outbound: The outbound load-balancing problem is posed as a constrained multi-criterion optimization problem, with objectives such as utilization of outbound links, cost, as_path length and reliability of outbound paths. This optimization problem here can be modeled as a classical ``bin packing'' problem, which is NP-hard. A new "Recursive Random Search (RRS)" algorithm, which has been designed for general black-box optimization problems, has been used to find a approximate solution for this problem. We first identify a number of ``hot'' prefixes, then we use RRS algorithm to search for a ``optimal'' routing for these prefixes such that the objective function is minimized. Then we implement these routes by setting the local preference for these prefixes on BGP routers.

Inbound: Multihomed Stub AS's advertise a good share of the more-specific prefixes which cause instability and increase global routing table sizes. Many of these are more-specifics proxy advertised to achieve inbound load balancing goals. We are investigating an alternative solution using dynamic NAT coordinated between edge boxes at the stub AS which would remove the need to advertise these more-specifics. In effect, the load balancing problem is re-cast as a dynamic public address assignment problem to the internal nodes that contribute to a large fraction of inbound traffic. This solution will not work for transit ASs that use full public addressing.
Edge vs. core time delay of propagation
Avi Freedman

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A study of the real-world delay in propagation for prefixes with changing associated BGP attributes. We examine, for ASs that Akamai has BGP sessions with, prefixes with changing attributes, and examine how long it takes in practice for those changes (i.e. origin or AS_PATH padding, prefix introduction or prefix withdrawl) to propagate. We classify networks by 'core' or 'edge' (less than 20 non-customer connections to another AS) as an initial taxonomy, and compare time for changes to propagate to core vs. edge ASs. We further classify edge networks by degree of multihomed connectivity and present similar data.
Analysis of RIPE/RIS Project's BGP Data: CIDR at Work
Cengiz Alaettinoglu

slides (PDF)

We analyze the BGP messages collected by the RIPE-NCC Routing Information Service. The data has been collected for about two years. It is much richer than the daily snapshots often used in analysis and helps us address more detailed questions than simply table size growth. For example, we can show the effectiveness of CIDR aggregation, or account for multi-homing and inter-domain traffic engineering more accurately.

In short, we find that the routing table size growth is not exponential, CIDR is doing very well, and churn is decreasing. Most of the churn is due to the loss and re-establishment of BGP peerings, as well as policy misconfigurations (leaking routes, etc).

Internet stability amid change
Andre Broido and
k claffy

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We analyze the RouteViews BGP routing tables sampled with a granularity ranging from 6 months for data measured in 1997-2001 to 2 hours for data from the end of 2001. We study the globally routed prefixes (those present in the majority of backbone tables) and categorize them as:
  • standalone -- only one entry in tables for this prefix's address range
  • root -- a least specific route, but more specific routes cover part of this prefix's address range
  • subset -- a more specific route, less specific routes also include this prefix.

Using these distinctions, we find that changes in global routing system are not adequately captured by bulk measures like total number of prefixes in a table. This is due to the net change representing a sum total of commensurable contibutions of opposite sign, so that the total variation is not the difference, but rather the sum of their magnitudes. This phenomenon partly explains the fact that most measures of routing system complexity demonstrate slow growth, dynamic equilibrium and/or decrease for the second half of the year 2001.

Comparison of end-to-end distance measurement metrics
Brad Huffaker

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While several methods currently exist for estimating the end-to-end distance between Internet hosts, I present a novel technique for comparing the distance metrics underlying different techniques. Analysis of a set of baseline comparisons of different distance metrics serves as a first step towards evaluating the utility of each current or proposed distance estimation method. Individual metrics provide dissimilar levels of predictive value for particular application types. However, high computational overhead may negate the benefits of measuring distance using an application's optimal distance metric. For this study we chose four existing metrics: previously seen round trip time (RTT); geographical distance; autonomous system (AS) path length; and IP path length.
Characterizing Resource Location in the Internet
Mark Crovella

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I will report on recent work studying the geographic location of nodes and links in router-level Internet graphs.
Measuring Provider Path Diversity from traceroute Data: Work in Progress
Krishna Nayak

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With many Internet hosts today being multi-homed, it is important to consider the path-diversity between providers. By collecting traceroute data through all available providers, we uncover convergence points between different providers' paths to determine which combination of providers could produce the most diversity across the Internet "middle mile". Our initial study involved four providers with points of presence in San Jose, CA, and a random selection of 46,089 active prefixes identified using netflow. In this talk, we will describe our initial study, correlate results with active TCP probe data, and attempt to make general statements about provider diversity based on these data.
Towards Capturing Representative AS-Level Internet Topologies
Hyunseok Chang

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Recent studies concerning the Internet connectivity at the AS level have attracted considerable attention. These studies have exclusively relied on the BGP data from Oregon route-views to derive some unexpected and intriguing results. There has been anecdotal evidence and an intuitive understanding among researchers in the field that BGP-based AS-level topology is not complete, however, as far as we know, there has been no systematic study on quantifying the completeness of AS-level topologies. By augmenting the Oregon route-views data sets with BGP summary information from a large number of Internet Looking Glass sites and with routing policy information from Internet Routing Registry (IRR) databases, we find that (1) a significant number of existing AS connections remain hidden from most BGP routing tables, (2) the AS connections to tier-1 ASs are in general more easily observed than those to non tier-1 ASs, and (3) there are at least about 25--50% more AS connections in the Internet than commonly-used BGP-derived AS maps reveal (but only about 2% more ASs). Finally, we validate the newly-found connectivity by identifying physically-adjacent ASs, and comment on how our findings can be interpreted to capture more representative AS-level topologies.
Estimating Router ICMP Generation Times
Ramesh Govindan, and
Vern Paxson

slides (PDF)

As a consequence of layering in the Internet protocol suite, ICMP responses provide the only available general mechanism for attaining visibility into the Internet's internal packet dynamics. Measurement tools such as pathchar (and the related clink and pchar) and treno both send large numbers of TTL-limited packets in order to analyze the delays between the transmissions of the packets and the receipt of the corresponding ICMP replies. There are two significant difficulties with analyzing such timing, however. The first is that the ICMP reply might not be generated in a timely fashion at a router; in particular, ICMP generation at routers might be relegated to the "slow" path. A second difficulty with analyzing timing based on ICMP replies is that responses from different routers might follow different paths. In this talk, we discuss a technique for measuring a router's ICMP generation time (specifically for Time Exceeded TE messages) using only end-system measurements, and discuss an analysis of a preliminary set of measurements made using the NIMI measurement infrastructure.
Statistical Reconstruction of Largest Contributors to Network Traffic
Valery Kanevsky

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The topic of this work is the issue of assessment of consistency of statistical inference from the sampling of network traffic. Network management depends on extensive data acquisition, processing, and analysis. One aspect of such analysis is sample-based allocation of the traffic along a variety of observable features/attributes (e.g, volume, protocol, source, destination), and selection of subsets of features that contribute to a significant portion of the total traffic. We present a statistical foundation that provides a confidence level to support such selection by addressing the following question: How confident can one be to infer "large" contributors from a sample of a limited size and how does confidence level depend on sample size?

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