1. CS 4700 / CS 5700 Network Fundamentals Lecture 16: IXPs (The Underbelly of the Internet) Revised 3/23/2015

2.  Emerging Internet Trends  Internet Exchange Points (IXPs) Outline 2

3. The Internet as a Natural System 3  You’ve learned about the TCP/IP Internet  Simple abstraction: Unreliable datagram transmission  Various layers  Ancillary services (DNS)  Extra in-network support  So what does the Internet look like?

4. What does the Internet look like? 4

5. 5

6. Characterization challenges 6  Limited measurements and models can hint at it  Traceroute does not give us a complete view  Gao-Rexford (policy routing) doesn’t capture everything  What is the Internet actually being used for?  Emergent properties impossible to predict from protocols  Requires measuring the network  Constant evolution makes it a moving target

7. How is the Internet used? 7

8. 8

9. Measuring the capital-I Internet* 9  Measuring the Internet is hard  Significant previous work on  Router and AS-level topologies  Individual link / ISP traffic studies  Synthetic traffic demands  But limited “ground-truth” on inter-domain traffic  Most commercial arrangements under NDA  Significant lack of uniform instrumentation *Mainly borrowed stolen from Labovitz 2010

10. Conventional Wisdom (i.e., lies) 10  Internet is a global scale end-to-end network  Packets transit (mostly) unmolested  Value of network is global addressability /reachability  Broad distribution of traffic sources / sinks  An Internet “core” exists  Dominated by a dozen global transit providers (tier 1)  Interconnecting content, consumer and regional providers

11. Traditional view 11

12. Does this still hold? 12  Emergence of ‘hyper giant’ services  How much traffic do these services contribute?  Hard to answer!  Reading: Labovitz 2010 tries to look at this.

13. How do we validate/improve this picture? 13  Measure from  110+ ISPs / content providers  Including 3,000 edge routers and 100,000 interfaces  And an estimated ~25% all inter-domain traffic  Do some other validation  Extrapolate estimates with fit from ground-truth data  Talk with operators

14. Where is traffic going? 14  Increasingly: Google and Comcast  Tier 1 still has large fraction, but large portion of it is to Google!  Why?  Consolidation of traffic  Fewer ASes responsible for more of the traffic

15. Why is this happening? 15

16. Transit is dead! Long live the eyeball! 16  Commoditization of IP and Hosting / CDN  Drop of price of wholesale transit  Drop of price of video / CDN  Economics and scale drive enterprise to “cloud”  Consolidation  Bigger get bigger (economies of scale)  e.g., Google, Yahoo, MSFT acquisitions  Success of bundling / Higher Value Services – Triple and quad play, etc.  New economic models  Paid content (ESPN 3), paid peering, etc.  Difficult to quantify due to NDA / commercial privacy  Disintermediation  Direct interconnection of content and consumer  Driven by both cost and increasingly performance

17. New applications + ways to access them 17

18. The shift from hierarchy to flat Local Access Provider Local Access Provider Regional Access Provider Regional Access Provider AT&T Sprint Verizon Regional Access Provider Regional Access Provider Tier 1 ISPs (settlement free peering) Tier 2 ISPs Tier 3 ISPs Local Access Provider Local Access Provider Businesses/consumers $ $ $ $ $ $ $$$$

19. The shift from hierarchy to flat Local Access Provider Local Access Provider Regional Access Provider Regional Access Provider AT&T Sprint Verizon Regional Access Provider Regional Access Provider Tier 1 ISPs (settlement free peering) Tier 2 ISPs Tier 3 ISPs Local Access Provider Local Access Provider Businesses/consumers $ IXP$ $

20. A more accurate model? 20

21. How do ASes connect? 21  Point of Presence (PoP)  Usually a room or a building (windowless)  One router from one AS is physically connected to the other  Often in big cities  Establishing a new connection at PoPs can be expensive  Internet eXchange Points (IXP)  Facilities dedicated to providing presence and connectivity for large numbers of ASes  Many fewer IXPs than PoPs  Economies of scale

22. IXPs Definition 22  Industry definition (according to Euro-IX) A physical network infrastructure operated by a single entity with the purpose to facilitate the exchange of Internet traffic between Autonomous Systems The number of Autonomous Systems connected should be at least three and there must be a clear and open policy for others to join. https://www.euro-ix.net/what-is-an-ixp

23. IXPs worldwide 23 https://prefix.pch.net/applications/ixpdir/

24. Inside an IXP 24  Connection fabric  Can provide illusion of all-to-all connectivity  Lots of routers and cables  Also a route server  Collects and distributes routes from participants

25. Structure 25 IXPs offer connectivity to ASes enable peering

26. Inside an IXP 26

27. IXPs – Publicly available information 27

28. How much traffic is at IXPs?* 28  We don’t know for sure!  Seems to be a lot, though.  One estimate: 43% of exchanged bytes are not visible to us  Also 70% of peerings are invisible *Mainly borrowed stolen from Feldmann 2012

29. Revised model 2012+ 29

30. Exercise answers 30  EDNS  Client identifier can be embedded in query IP address Location Prefix …  CDN now knows more about where a client is located, instead of just knowing where its LDNS server is

31. Exercise answers (2) 31  Peering at an IXP  Good Closer to other ISPs (performance) Lower cost to other ISPs (peering)  Bad How much does it cost to get there? How much does it cost to stay there? What if I’m a tier 1? 

32. Exercise answers (3) 32  Remote peering  How is this different than BGP? First of all: the good is that you don’t have to be physically present at the IXP! BGP: You forward your announcement to your provider, it decides how to announce it from there BGP only cares about the next hop Can’t establish settlement-free link over a 2-hop path Remote peering: You have direct control over how your announcements are forwarded to other IXP participants