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 2 Internet Topology Discovery 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 3 Internet Topology Discovery

4. 4 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 Internet

5. Once the graph is built, one can study its characteristics Essential to design, implement, protect, and operate underlying network 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 Motivation on Internet Topology Measurement 5 Internet Topology Discovery Lumenta Jan 06

6. 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 Internet Topology Measurement 6 Internet Topology Discovery Lumenta Jan 06CAIDA Jan 08CAIDA 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 7 Internet Topology Discovery

8. 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... Internet Topology Measurement Topology Collection 8 Internet Topology Discovery

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

10. Internet Topology Measurement How to collect Internet Topology Discovery 10

11. Direct probing Indirect probing A DBC Internet Topology Measurements Probing IP B TTL=64 IP B IP D TTL=64 IP D Vantage Point A DBC IP B IP D TTL=2IP D TTL=1 IP C 11 Internet Topology Discovery

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 S DABC Destination Internet Topology Measurement Topology Collection (traceroute) TTL=1 IP A TTL=2 IP B TTL=3 IP C TTL=4 IP D Vantage Point 12 Internet Topology Discovery

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

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

15. Internet Topology Measurement Topology Collection Internet2 backbone 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 S L U K C H A W N e d f 15 Internet Topology Discovery

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 16 Internet Topology Discovery

17. 17 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 Topology Data Collecting Platforms - I Internet Topology Discovery

18. 18 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... Topology Data Collecting Platforms - II Internet Topology Discovery

19. 19... 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 Topology Data Collecting Platforms - III Internet Topology Discovery

20. 20 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 Topology Collecting Platforms - IV Internet Topology Discovery

21. 21 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 Topology Collecting Platforms - V Internet Topology Discovery

22. 22 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 Topology Collecting Platforms - VI Internet Topology Discovery

23. 23 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 Topology Collecting Platforms - VII Internet Topology Discovery

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 24 Internet Topology Discovery

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

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

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 27 Internet Topology Discovery

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

29. 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 Alias Resolution.5.33.18.13.7 Denver 29 Internet Topology Discovery

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

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 1. Ignore all ICMP packets 2. ICMP rate-limiting 3. Ignore ICMP when congested 4. Filter ICMP at border 5. Private IP address 31 Internet Topology Discovery UK C N L HA W S x y z Sampled network x y z S U L C A W Resulting network

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

33. 33 Genuine Subnet Resolution Problem Subnet resolution Identify IP addresses that are connected over the same medium Improve the quality of resulting topology map IP2 IP3 IP1 IP2IP3 IP1 Internet Topology Discovery (observed topology)(inferred topology)(underlying topology) CD AB CD AB CD AB CD AB

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 34 Internet Topology Discovery

35. Questions ? Internet Topology Discovery 35