1. The Internet: A System of Interconnected Autonomous Systems
Mehmet Engin Tozal

2. The Internet The Internet
A global system of interconnected networks
Has already become a de-facto utility
Communication & Entertainment
Marketing & Administration
Collaboration & Citizen participation
Highly engineered
Globally distributed
Large scale complex system
Studying the structure of the Internet helps us to
Gain more insight into its topological features
Understand its operational characteristics
Enhance its communication infrastructure
Improve its reliability, resiliency and security

3. Autonomous Systems Autonomous System (AS)
A group of networks under a well defined protocol
Identified by unique AS number
Connected to each other through business relations
Customer-to-Provider (c2p)
Peer-to-Peer (p2p)
Sibling-to-Sibling (s2s)
The traffic in the Internet is routed according to the business relations among ASes

4. Autonomous Systems
Example AS-level Internet topology map

5. Autonomous Systems Taxonomy of ASes in the Internet
Stub, Tier-1, Tier-2, Tier-3, Transit, …
Ambiguous
Subjective
Unrealistic
Pole, Axial, Medial, Locus
Terminology from Geometry
Clear
Objective
Realistic
Traditionally the ASes are classified as …

6. Autonomous Systems
Taxonomy of ASes in the Internet

7. AS Analysis - Preliminaries

8. AS Analysis – Axial ASes
ClusterA: governments and government-related organizations
ClusterB: large scale IXPs and datacenters
ClusterC: small sized IXPs or ISPs that provide value-added services
ClusterD: pole ASes enabling global connectivity

9. AS Analysis – Medial ASes
The orbit of a medial AS is the length of the shortest c2p path(s) to any pole AS
O1 44%
O2 50%
O3,4 6%
O5 1 AS

10. AS Analysis – Medial ASes
Medial AS customers, providers and peers by orbits
Diversity in distributions
Kruskal-Wallis rank sum tests verify the differences in distributions by orbits
Mean and variability decrease as orbit increases
By using Kruskal-Wallis rank sum test we can decide whether the population distributions are identical without assuming them to follow the normal distribution

11. AS Analysis – Medial ASes
Medial ASes average peer links by country (top 25% ~ 92%)
Peering as a networking practice adopted at developed countries

12. AS Analysis – Locus ASes
Average hops to a pole AS via c2p links is 1.91
26% single hop
57% two hops
15% three hops
2% four/five hops
A shorter distance implies a better average performance

13. AS Analysis – Locus ASes
Locus ASes average distance to the pole ASes by country (top 25% ~ 94%)
Shorter distance implies better performance, on the average

14. Questions
Thank you!

15. Agenda The Internet Autonomous Systems (ASes)
AS Analysis – Preliminaries
AS Analysis – Axial ASes
AS Analysis – Pole Ases
AS Analysis – Medial Ases
AS Analysis – Locus ASes

16. AS Analysis - Preliminaries
AS-Relations Dataset (CAIDA)
Business relations
Oregon routeviews project
AS-Organizations Dataset (CIDR-Report)
Organization information
AS-to-country mappings
Large scale ISPs operate at multiple countries

17. AS Analysis – Pole ASes