Lecture 26: Internet Topology CS 765: Complex Networks

Web of interconnected networks 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

Internet Measurements Need for Internet measurements arises due to commercial, social, and technical issues Realistic simulation environment for developed products, Improve network management Robustness with respect to failures/attacks Comprehend spreading of worms/viruses Know social trends in Internet use Scientific discovery Scale-free (power-law), Small-world, Rich-club, Dissasortativity,… Topology collection is hard as ISPs do not share their internal topology info by default Complex networks are being analyzed for their growth mechanism and topological characteristics. Scale-free (Power-law) Small-world (6 degree of separation) Dissasortative mixing (degree-degree correlation) Rich-club phenomenon (tightly interconnected core)

Internet Topology Measurement CAIDA 2006

Internet Topology Measurement CAIDA 2006 5

Internet Topology Measurement

Internet Topology Measurement CAIDA 2006 7

Internet Topology Measurements Probing Direct probing Indirect probing IPB IPD Vantage Point IPB TTL=64 IPD TTL=64 B C D A A D B C Vantage Point IPB IPC IPD TTL=1 IPD TTL=2 http://www.caida.org/publications/animations/active_monitoring/traceroute.mpg 8

Internet Topology Measurement Topology Collection (traceroute) 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 IPA IPB IPC IPD Vantage Point Destination TTL=4 TTL=3 TTL=1 TTL=2 A B C D S 9

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

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

Topology Sampling Issues Sampling to discover networks Infer characteristics of the topology Different studies considered Effect of sample size [Barford 01] Sampling bias [Lakhina 03] Path accuracy [Augustin 06] Sampling approach [Gunes 07] Utilized protocol [Gunes 08] ICMP echo request TCP syn UDP port unreachable

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

Anonymous Router Resolution Problem Internet2 backbone f e S N C W U K L A H Traces d -  - L - S - e d -  - A - W -  - f e - S - L -  - d e - S - U -  - C -  - f f -  - C -  -  - d f -  - C -  - U - S - e d

Anonymous Router Resolution Problem K C N f L H A W e Traces d -  - L - S - e d -  - A - W -  - f e - S - L -  - d e - S - U -  - C -  - f f -  - C -  -  - d f -  - C -  - U - S - e d Sampled network d e f S U L C A W Resulting network

Graph Based Induction Common Structures x C y2 y1 y3  A x C y2 y1 y3  Parallel nodes A C x y D w F v E z  A C x y D w E z  D A w x C y E z  Clique Complete Bipartite Star Parallel *-substrings is equivalent to Initial Pruning Star is equivalent to neighbor matching A C x y D w F v E z  A C x y D w E z  D A w x C y E z 

Alias Resolution: .33 Each interface of a router has an IP address. .5 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

IP Alias Resolution Problem f S s.3 n.2 s.2 n.1 N n.3 c.2 u.1 c.1 w.1 w.2 C W u.2 c.3 U k.1 w.3 c.4 k.2 u.3 K k.3 l.1 l.2 a.1 L a.2 A l.3 a.3 h.2 H Traces d - h.4 - l.3 - s.2 - e d - h.4 - a.3 - w.3 - n.3 - f e - s.1 - l.1 - h.1 - d e - s.1 - u.1 - k.1 - c.1 - n.1 - f f - n.2 - c.2 - k.2 - h.2 - d f - n.2 - c.2 - k.2 - u.2 - s.3 - e h.3 h.1 h.4 d

IP Alias Resolution Problem K C N Sampled network f L H A W e d Sample map without alias resolution s.3 s.1 s.2 l.3 l.1 u.1 u.2 k.1 c.1 n.1 n.2 k.2 c.2 w.3 a.3 h.2 h.4 h.1 e d f n.3 Traces d - h.4 - l.3 - s.2 - e d - h.4 - a.3 - w.3 - n.3 - f e - s.1 - l.1 - h.1 - d e - s.1 - u.1 - k.1 - c.1 - n.1 - f f - n.2 - c.2 - k.2 - h.2 - d f - n.2 - c.2 - k.2 - u.2 - s.3 - e 19

Genuine Subnet Resolution Problem Alias resolution IP addresses that belong to the same router Subnet resolution IP addresses that are connected over the same medium IP2 IP3 IP4 IP1 IP6 IP5 IP1 IP1 IP2 IP3 IP2 IP3

Cheleby System Overview PlanetLab Vantage Points Traces x -  - L.2 - S.2 - y x -  - A.1 - W.1 -  - z y - S.1 - L.1 -  - x y - S.1 – U.1 -  - C.1 -  - z z -  - C.2 -  -  - x z -  - C.2 -  - U.2 - S.3 - y Initial Pruner (IP) Structural Graph Indexer (SGI) Raw Data SubNet Inferrer (SNI) U K C N L H A W S x y z Graph Based Induction (GBI) Analytical IP Alias Resolver v2 (APARv2), iffinder Network Topology http://cheleby.cse.unr.edu Cheleby: Subnet-Level Internet Topology

Exponents : -2.17, -2.02, -1.92, respectively Degree Distribution Exponents : -2.17, -2.02, -1.92, respectively Avr: -2.04 Cheleby: Subnet-Level Internet Topology

Interface Distribution Exponents : -2.71, -2.69, -2.74, respectively Avr: -2.71 Cheleby: Subnet-Level Internet Topology

Exponents : -3.42, 3.62, respectively Subnet Distribution Exponents : -3.42, 3.62, respectively Avr: -3.52 Nodes in Subnets Cheleby: Subnet-Level Internet Topology

Synthetic Topology Generation Network Size ID SD Generate Nodes Generate Subnets Heterogeneous Swap Calculate Degree Distribution based on DD Satisfies Subnet & Interface Distributions !!! no Match ? Final Topology yes Cheleby: Subnet-Level Internet Topology

Connectivity Analysis Relation between Interface Distribution and Number of Subnets Single connected component is feasible only when connectivity parameter <1 Feasible Region Cheleby: Subnet-Level Internet Topology

Autonomous System Level http://www.caida.org/publications/animations/active_monitoring/as_core.mpg