CS 4700 / CS 5700Network Fundamentals

Lecture 16: IXPs(The Underbelly of the Internet)

Revised 3/23/2015

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Emerging Internet Trends Internet Exchange Points

(IXPs)

Outline

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The Internet as a Natural System 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?

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What does the Internet look like?

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What does the Internet look like?

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Characterization challenges

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

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How is the Internet used?

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How is the Internet used?

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Measuring the capital-I Internet*

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

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Conventional Wisdom (i.e., lies) 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

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Traditional view

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Does this still hold?

Emergence of ‘hyper giant’ services

How much traffic do these services contribute?

Hard to answer! Reading: Labovitz 2010 tries to look at this.

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How do we validate/improve this picture?

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

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Where is traffic going?

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

Over time Google begins delivering YT’s trafficAs of 2009 Google is

6% of traffic

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Why is this happening?

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Transit is dead! Long live the eyeball! 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

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New applications + ways to access them

Fixed vs. Mobile Usage

The shift from hierarchy to flat

Local Access Provider

Regional Access Provider

AT&T

Sprint

Verizon

Regional Access Provider

Tier 1 ISPs(settlement free peering)

Tier 2 ISPs

Tier 3 ISPs

Local Access Provider

Businesses/consumers

$

$

$$

$

$

$$$

$

Money follows the arrows.

Autonomous systems (ASes) connect to each other based

on business relationships.

The shift from hierarchy to flat

Local Access Provider

Regional Access Provider

AT&T

Sprint

Verizon

Regional Access Provider

Tier 1 ISPs(settlement free peering)

Tier 2 ISPs

Tier 3 ISPs

Local Access Provider

Businesses/consumers

$IXP$$

Content provider no longer needs to pay for transit!More “eyeballs” less $$

Local Access Provider doesn’t have to pay for consumer access

to content!

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A more accurate model?

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How do ASes connect?

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

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IXPs Definition

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

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IXPs worldwide

https://prefix.pch.net/applications/ixpdir/

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Inside an IXP

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

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Structure

IXPs offer connectivity to ASes

enable peering

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Inside an IXP

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IXPs – Publicly available information

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How much traffic is at IXPs?*

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

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Revised model 2012+