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Router-level Internet Topology Mapping

Router-level Internet Topology Mapping. By Talha OZ. Outline. Introduction Internet Topology Collection Basic Techniques Some Measurement Projects & Platforms Issues in Topology Collection Issues in Topology Construction Resolving Anonymous Routers Resolving Alias IP Addresses

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Router-level Internet Topology Mapping

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  1. Router-level Internet Topology Mapping By Talha OZ

  2. Outline • Introduction • Internet Topology Collection • Basic Techniques • Some Measurement Projects & Platforms • Issues in Topology Collection • Issues in Topology Construction • Resolving Anonymous Routers • Resolving Alias IP Addresses • Resolving Genuine Subnets • Summary My stress on this presentation Will be explained in detail in the next presentation

  3. Outline • Introduction • Internet as a Complex Network • Motivations on Internet Topology Measurement • Internet Topology Collection • Basic Techniques • Some Measurement projects & platforms • Issues in Topology Collection • Issues in Topology Construction • Resolving Anonymous Routers • Resolving Alias IP Addresses • Resolving Genuine Subnets • Summary

  4. Internet • Web of interconnected networks • Grows with no central authority • Autonomous Systems optimize local communication efficiency • The building blocks are engineered and studied in depth • Global entity has not been characterized • Most real world complex-networks have non-trivial properties. • Global properties can not be inferred from local ones • Engineered with large technical diversity • Range from local campuses to transcontinental backbone providers

  5. Motivation on Internet Topology Measurement • Once the graph is built, one can study its characteristics • Essential to design, implement, protect, and operate underlyingnetwork technologies, protocols, services, and applications • Capture graph’s theoretic resilience to failure or say something about its efficiency for routing • Realistic simulation environment for developed products • Comprehend spreading of worms/viruses (Burch and Cheswick’s proposal) • Improve QoS for the multimedia content • Where to store the data in replicated servers distributed across the internet • ISPs are not willing to share their topology information Lumenta Jan 06

  6. Internet Topology Measurement • Types of Internet topology maps • Autonomous System (AS) level maps • Point of presence (PoP) level • Router level maps • IP interface level • A router level Internet map consists of • Nodes: End-hosts and routers • Links: Point-to-point or multi-access links • Router level Internet topology discovery • A process of identifying nodes and links among them Lumenta Jan 06 CAIDA Jan 08 CAIDA Jan 00

  7. Outline • Introduction • Internet Topology Collection • Basic Techniques • Some Measurement projects & platforms • Issues in Topology Collection • Issues in Topology Construction • Resolving Anonymous Routers • Resolving Alias IP Addresses • Resolving Genuine Subnets • Summary

  8. Internet Topology MeasurementTopology Collection • Internet topology measurement studies • Involves topology collection / construction / analysis • How to collect ? • Work on IP layer, leverage header information • IETF’s RFCs determine the behavior of the nodes • Send ICMP, UDP, TCP packets and wait ... • Ideal case and issues ...

  9. Internet Topology MeasurementTopology Collection – Who sets the rules ? • IETF The Internet Engineering Task Force (IETF) develops and promotes Internet standards • RFC An Internet Standard is a special Request for Comments (RFC) or set of RFCs. • http://tools.ietf.org/html/rfc792

  10. Internet Topology MeasurementHow to collect

  11. Direct probing Indirect probing Internet Topology MeasurementsProbing IPB IPD Vantage Point IPB TTL=64 IPD TTL=64 B C D A IPB IPC Vantage Point B C D IPD TTL=1 IPD TTL=2 A

  12. Probe packets are carefully constructed to elicit intended response from a probe destination traceroute probes all nodes on a path towards a given destination TTL-scoped probes obtain ICMP error messages from routers on the path ICMP messages includes the IP address of intermediate routers as its source Merging end-to-end path traces yields the network map Internet Topology MeasurementTopology Collection (traceroute) IPB IPA IPC IPD Vantage Point Destination TTL=1 TTL=4 TTL=2 TTL=3 A B C D S

  13. Internet Topology Measurement:Background Internet2 backbone S s.3 s.2 s.2 n.1 n.3 n.3 N c.2 w.2 w.1 u.1 c.1 W C c.3 w.3 w.3 u.2 U c.4 k.1 k.2 K u.3 l.1 k.3 Trace to NY a.1 a.2 l.2 L A l.3 l.3 a.3 a.3 h.2 Trace to Seattle H h.3 h.1 h.4 h.4 h.4 d

  14. Internet Topology Measurement:Background s.1 f e S s.3 n.2 s.2 n.1 n.3 N c.2 w.2 w.1 c.1 u.1 W C c.3 w.3 u.2 U c.4 k.1 k.2 K u.3 l.1 k.3 a.1 a.2 l.2 L A l.3 a.3 h.2 H h.3 h.1 h.4 d

  15. Internet Topology MeasurementTopology Collection f Internet2 backbone e S N C W U K L A H • Traces • d - H - L - S - e • d - H - A - W - N - f • e - S - L - H - d • e - S - U - K - C - N - f • f - N - C - K- H - d • f - N - C - K - U - S - e d

  16. Outline • Introduction • Internet Topology Collection • Basic Techniques • Some measurement projects & platforms • Issues in Topology Collection • Issues in Topology Construction • Resolving Anonymous Routers • Resolving Alias IP Addresses • Resolving Genuine Subnets • Summary

  17. Topology Data Collecting Platforms - I • PlanetLab • Currently consists of 1020 nodes at 483 sites • Since the beginning of 2003, 1000+ researchers develop new technologies for • distributed storage • network mapping • peer-to-peer systems • distributed hash tables • query processing • CAIDA (Cooperative Association for Internet Data Analysis) • Provides tools and analyses promoting the engineering and maintenance of a robust, scalable global Internet infrastructure. • San Diego Supercomputer Center @ UCSD

  18. Topology Data Collecting Platforms - II • Macroscopic Topology Measurements (Skitter project) by CAIDA • characterize macroscopic connectivity and performance of the Internet • allow various topological and geographical representations at multiple levels of aggregation granularity • provide a valuable input for empirically-based modeling of the Internet behavior and properties • Skitter, developed by CAIDA • skitter measurement tool reads a file of destinations and writes a file of traceroute paths • ...

  19. Topology Data Collecting Platforms - III • ... • ICMP traceroutes are used • RTTs are also stored • 24 monitors around the world • 970K common destination, IPv4 addresses • Scamper does the similar thing for IPv6 • Archipelago (Ark) is the evolution of the skitter infrastructure, by CAIDA • skitter monitors • skitter measurement tool • an internal web server for distributing destination lists • a file storage server for collecting traces from monitors

  20. Topology Collecting Platforms - IV • The Distributed Internet Measurements and Simulations (DIMES) • Model of SETI@home • Counts more than 20,343 agents scattered over five continents • “What we ask is not so much your CPU or bandwidth (which we hardly consume), but rather, your location.” • iPlane • Measuring the Internet: performs traceroutes from various VPs -- PlanetLab nodes and traceroute servers -- to construct a router interface-level atlas of the Internet. • Clustering interfaces into PoPs • Measuring link attributes • Opportunistic measurements • Route prediction

  21. Topology Collecting Platforms - V • Rocketfuel tries to get the picture of the ISPs • Number of required probes is decreased • directed probing • path reduction (ingress & egress) • Alias resolution • Router identification and annotation (DNS and ISP naming) • Report on properties of maps from ten diverse ISPs : • Size of POPs • Distribution of router outdegree • Inter-domain peering structure

  22. Topology Collecting Platforms - VI • Scriptroute allows everyone to measure from several VPs • Proposes remote measurement execution on PlanetLab nodes • RPT tool avoids retracing paths • TTM, developed by RIPE NCC • Full mesh between roughly a hundred monitors • One-way delay, packet loss, and bandwidth are also stored • Atlas is based on “source-routed IPv6 traceroute” • probe engine, topology constructor, topology verifier, interactive visualization program

  23. Topology Collecting Platforms - VII • TCP Sidecar • a technique and associated API for embedding measurement probes into non-measurement TCP streams • avoids abuse reports and allows measurements to tunnel through NATs and behind firewalls • Augment traceroute (TR) probes with IP Record Route option (RR) • DipZoom (Deep Internet Performance Zoom) • Focused, on-demand Internet measurements • Offers a matchmaking service which uses P2P concepts to bring together experimenters in need of measurements with external measurement providers. • DipZoom participants offer measurements for the benefit of being able to access measurements offered by other participants

  24. Outline • Introduction • Internet Topology Collection • Basic Techniques • Some measurement projects & platforms • Issues in Topology Collection • Issues in Topology Construction • Resolving Anonymous Routers • Resolving Alias IP Addresses • Resolving Genuine Subnets • Summary

  25. Issues in Topology CollectionIssues I • Forward & primary paths • Asymmetric routing • miss out on backup paths • Unbiased Sampling • Traceroute & load balancer (Paris traceroute) • MPLS (TTL reduction) • Misconfigurated network elements

  26. Issues in Topology Collection Issues II • Third-party address (multi homing) • Redundancy • intra-monitor redundancy • inter-monitor redundancy • DDoS • Responsiveness • ICMP echo request • TCP syn • UDP port unreachable

  27. Outline • Introduction • Internet Topology Collection • Basic Techniques • Some measurement projects & platforms • Issues in Topology Collection • Issues in Topology Construction • Resolving Alias IP Addresses • Resolving Anonymous Routers • Resolving Genuine Subnets • Summary

  28. Issues in Topology Construction - I at Router Level • Alias Resolution • Iffinder • Ally • DNS based method • Graph based method • Analytical IP Alias Resolution (APAR) • Record route option

  29. Alias Resolution .33 • Each interface of a router has an IP address. • A router may respond with different IP addresses to different queries. • Alias Resolution is the process of grouping the interface IP addresses of each router into a single node. • Inaccuracies in alias resolution may result in a network map that • includes artificial links/nodes • misses existing links .5 .18 Denver .7 .13

  30. Issues in Topology Construction - II at Router Level • Anonymous Router Resolution • Basic heuristics [Bilir 05] & [Xin 06] • Graph minimization approach [Yao 03] • ISOMAP based dimensionality reduction approach [Xin 06] • Graph based induction

  31. Anonymous Router Resolution Problem Anonymous routers do not respond to traceroute probes and appear as a  in path traces Same router may appear as a  in multiple traces. Anonymous nodes belonging to the same router should be resolved. Anonymity Types Ignore all ICMP packets ICMP rate-limiting Ignore ICMP when congested Filter ICMP at border Private IP address U K N S C z y W H A L x Sampled network C z U S W y L A Resulting network x

  32. Issues in Topology Construction - III at Router Level • Genuine Subnet Resolution • Inferring Subnets in Router-level Topology Collection Studies [Gunes 07]

  33. Genuine Subnet ResolutionProblem Subnet resolution Identify IP addresses that are connected over the same medium Improve the quality of resulting topology map A A B B C C D D IP1 IP1 IP2 IP3 IP2 IP3 A A B B C C D D (underlying topology) (observed topology) • (inferred topology)

  34. Summary • Introduction • Internet as a Complex Network • Motivations on Internet Topology Measurement • Internet Topology Collection • Basic Techniques • Some Measurement Projects & Platforms • Issues in Topology Collection • Issues in Topology Construction • Resolving Anonymous Routers • Resolving Alias IP Addresses • Resolving Genuine Subnets

  35. Questions ?

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