Post on 14-Dec-2015
The Economics of Transit and Peering Interconnections in the
InternetAmogh Dhamdhere (CAIDA/UCSD)
amogh@caida.orgWith
Constantine Dovrolis (Georgia Tech)Pierre Francois (Univ. catholique de Louvain)
Kc Claffy (CAIDA)
04/18/23 1
Outline
• Motivation
• ITER: A computational model of interdomain interconnection
• Modeling the transition from the “old” to the “new” Internet
• Modeling complex interdomain relationships: value-based peering
• Ongoing Work
04/18/23 The Economics of Transit and Peering Interconnections 2
[CoNEXT 2010, to appear]
[ITC 2010, NANOG 49]
[NSF NETSE grant, 2010-2013]
The Internet Ecosystem
• >30,000 autonomous networks independently operated and managed
• The “Internet Ecosystem”– Different types of networks– Interact with each other and with “environment”
• Network interactions– Localized, in the form of bilateral contracts– Competitive (customer-provider), symbiotic (peering)
• Distributed optimizations by each network
04/18/23 3The Economics of Transit and Peering Interconnections
High Level Questions
• How does the Internet ecosystem evolve?
• What is the Internet heading towards?– Topology– Economics– Performance
• Which interconnection strategies of networks optimize their profits, costs and performance?
• How do these strategies affect the global Internet?
04/18/23 4The Economics of Transit and Peering Interconnections
Economics of the Internet Ecosystem
04/18/23 5The Economics of Transit and Peering Interconnections
Source: Cisco
Source: Arbor Networks
Source: William Norton
Source: IAB
Economics of the Internet Ecosystem
How do we make sense of all this?
04/18/23 6The Economics of Transit and Peering Interconnections
Economically-principled models
• Objective: understand the structure and dynamics of the Internet ecosystem from an economic perspective
• Capture interactions between network business relations, internetwork topology, routing policies, and resulting interdomain traffic flow
• Create a scientific basis for modeling Internet interconnection and dynamics based on empirical data
04/18/23 7The Economics of Transit and Peering Interconnections
Previous Work
• “Descriptive”– Match graph properties
e.g. degree distribution
• Homogeneity– Nodes and links all the
same
• Game theoretic, analytical– Restrictive assumptions
• Little relation to real-world data
04/18/23 8
• “Bottom-up”– Model the actions of
individual networks
• Heterogeneity– Networks with different
incentives, link types
• Computational– As much realism as
possible
• Parameterize/validate using real data
The Economics of Transit and Peering Interconnections
Outline
• Motivation
• ITER: A computational model of interdomain interconnection
• Modeling the transition from the “old” to the “new” Internet
• Modeling complex interdomain relationships: value-based peering
• Ongoing Work
04/18/23 The Economics of Transit and Peering Interconnections 9
The ITER Model
Agent-based computational model to answer “what-if” questions about Internet evolution
Inputs: According to the best available data… Network types based on business function Peer/provider selection methods Geographical constraints Pricing/cost parameters Interdomain traffic matrix
Output: Equilibrium internetwork topology, traffic flow, per-network fitness
1004/18/23 The Economics of Transit and Peering Interconnections
The ITER approach
11
InterdomainTM
Traffic flow
Interdomain topology
Per-ASfitness
Cost/priceparameters
Routing
Providerselection
Peer selection
Compute equilibrium: no network has the incentive to change its providers/peers
Measure topological and economic properties of equilibrium e.g., path lengths, which providers are profitable, who peers with whom
04/18/23 The Economics of Transit and Peering Interconnections
Why Study Equilibria?
• The Internet is never at equilibrium, right?– Networks come and go, traffic patterns change,
pricing/cost structures change, etc….
• Studying equilibria tells us what’s the best that networks could do under certain traffic/economic conditions, and what that means for the Internet as a whole
• If those conditions change, we need to re-compute equilibria
04/18/23 12The Economics of Transit and Peering Interconnections
ITER: Network Types
• Enterprise Customers (EC)– Stub networks at the edge, e.g. Georgia Tech
• Transit Providers– Provide Internet transit– Regional in scope (STP), e.g. Comcast– “Tier-1” or global (LTP), e.g., AT&T
• Content Providers (CP)– Major sources of content, e.g. Google
04/18/23 13The Economics of Transit and Peering Interconnections
ITER: Provider and Peer Selection
• Provider selection– Choose providers based on customer cone size– Good measure of the “size” of a provider– Used by commercial products, e.g., Renesys
• Peer selection strategies– Peer based on total traffic handled– Approximates the “equality” of two ISPs
04/18/23 14The Economics of Transit and Peering Interconnections
ITER: Economics, Routing and Traffic Matrix
• Realistic transit, peering and operational costs– Transit prices based on data from NANOG
• BGP-like routing policies– No-valley, prefer customer, prefer peer routing policy
• Traffic matrix– Heavy-tailed content popularity and consumption by sinks
– client-server traffic: from CPs to ECs
– peer-to-peer traffic: between ECs
04/18/23 15The Economics of Transit and Peering Interconnections
Computing Equilibrium
• Situation where no network has the incentive to change its connectivity
• Too complex to find analytically: Solve computationally
• Computation– Proceeds iteratively, networks “play” in sequence– Compute routing, traffic flow, AS fitness– Repeat until no player has incentive to move
04/18/23 16The Economics of Transit and Peering Interconnections
Properties of the equilibrium
• Is equilibrium always reached?– Yes, in most cases
• Is the equilibrium unique?– No, can depend on playing sequence
• Multiple runs with different playing sequence– Per-network properties vary widely across runs– Macroscopic properties show low variability
04/18/23 17The Economics of Transit and Peering Interconnections
Outline
• Motivation
• ITER: A computational model of interdomain interconnection
• Modeling the transition from the “old” to the “new” Internet
• Modeling complex interdomain relationships: value-based peering
• Ongoing Work
04/18/23 The Economics of Transit and Peering Interconnections 18
[CoNEXT 2010, to appear]
Recent Trends: Arbor Networks Study
• The Old Internet (late 90s – 2007)
• Content providers generated small fraction of total traffic
• Content providers were mostly local
• Peering was restrictive
• The New Internet (2007 onwards)
• Content providers generate large fraction of total traffic
• Content providers are present everywhere
• Peering is more open
“Internet Interdomain Traffic”, Labovitz et al., Sigcomm 2010
04/18/23 19The Economics of Transit and Peering Interconnections
Plugging into ITER
• Simulate two instances of ITER: “Old” and “New” Internet
• Change three parameters– Fraction of traffic sourced by CPs– Geographical spread of CPs– Peering openness
• Compute equilibria for these two instances– Compare topological, economic properties
04/18/23 The Economics of Transit and Peering Interconnections 20
ITER Sims: End-to-end Paths
• End-to-end paths weighted by traffic are shorter in the “new Internet”
04/18/23 The Economics of Transit and Peering Interconnections 21
ITER Sims: Traffic Transiting Transit Providers
• Traffic bypasses transit providers
• More traffic flows directly on peering links
• Implication: Transit providers lose money!
• Content providers get richer
04/18/23 The Economics of Transit and Peering Interconnections 22
ITER Sims: Peering in the New Internet
• Transit providers need to peer strategically in the “new” Internet
• Peering with large Content Providers benefits transit providers in the new Internet
• Try to attract traffic by peering with CPs
04/18/23 The Economics of Transit and Peering Interconnections 23
Outline
• Motivation
• ITER: A computational model of interdomain interconnection
• Modeling the transition from the “old” to the “new” Internet
• Modeling complex interdomain relationships: value-based peering
• Ongoing Work
04/18/23 The Economics of Transit and Peering Interconnections 24
[ITC 2010, NANOG 49]
Complex Interdomain Relationships
• So far, we considered customer-provider and settlement-free peering links
• Customer-provider: customer pays provider
• Settlement-free peering: No payments
• A whole spectrum of relationships somewhere in between – paid peering
• “To peer or not to peer?” “To peer or not to peer, at what price?”
04/18/23 25The Economics of Transit and Peering Interconnections
To Peer or Not to Peer, at What Price?
26
AA BB
Should I peer with B? make
Should it be settlement-free or
paid-peering?What price would B be
willing to offer (or accept) ?
???
04/18/23 The Economics of Transit and Peering Interconnections
Value Based Peering
Price based on the “value” of the link
For a network, define the notion of “fitness” f = revenue – interconnect costs – backhaul cost
Value of the link is the difference in fitness with and without the link
V = fwith - fwithout
Revenue and costs could change on peering/depeering
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What Affects Peering Value?
• Interconnect cost changes: Avoid a transit provider
• Backhaul cost changes: Peering link changes how traffic is routed in a network
• Revenue changes: Attract/lose traffic due to new peering link
28
AA BB
TT
$$$
$$$ $$$
04/18/23 The Economics of Transit and Peering Interconnections
The Fair Peering Price
An oracle knows VA
and VB
Oracle must decide the price for peering
Fair price is (VA-V
B)/2
29
The fair price equalizes the benefit that A and B see from the link
AA BB
VA VB
(VA-VB)/2
04/18/23 The Economics of Transit and Peering Interconnections
Why Peer at the Fair Price? Peering with the fair price is optimal
Both networks see better fitness by peering at the fair price
Peering with the fair price is stable No network has the incentive to unilaterally depeer the
other network Unique Nash Equilibrium
Optimal and stable as long as VA+V
B > 0
Either VA or VB can be negative, as long as total is positive For cost-benefit peering, both VA and VB must be positive
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Some Hard Questions..
Value-based peering is fair, optimal and stable. But is there an incentive to be fair?
How do networks estimate peering value?
What if networks lie about peering value?
What happens if everyone uses value-based peering?
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ITER Results: Value-based Peering
Higher density of peering links with value-based peering Shorter end-to-end paths Links that are not allowed with traffic-ratio or cost-
benefit peering are possible with value-based peering
Payment direction: Content providers end up paying large transit providers, get paid by smaller transit providers This could be happening already!
3204/18/23 The Economics of Transit and Peering Interconnections
Outline
• Motivation
• ITER: A computational model of interdomain interconnection
• Modeling the transition from the “old” to the “new” Internet
• Modeling complex interdomain relationships: value-based peering
• Ongoing Work
04/18/23 The Economics of Transit and Peering Interconnections 33
[NSF NETSE grant, Aug 2010-2013]
Ongoing Work
• Strategy selection by ISPs– Model how networks dynamically change their
provider/peer selection strategies– What is the best possible strategy for different
network types?
• Managing the cost of network traffic– Model traffic related-costs for ISPs– Support peering decisions, capacity upgrades,
differential pricing models
04/18/23 The Economics of Transit and Peering Interconnections 34
[A. Lodhi, A. Dhamdhere, C. Dovrolis]
[M. Motiwala, A. Dhamdhere, N. Feamster, A. Lakhina]
Avoiding “garbage-in, garbage-out”
• Models are only as good as the data you provide as input
• How do we get the best possible data to parameterize ITER-like models?
• What data do we need?– Interdomain traffic patterns– Peering policies– Geographical presence of networks– Cost/pricing structures
04/18/23 35The Economics of Transit and Peering Interconnections
Measuring Interdomain Traffic
• We don’t really know how much traffic each pair of networks exchanges!
• Measure qualitative properties of the interdomain TM from different vantage points
04/18/23 36The Economics of Transit and Peering Interconnections
GT GT
A A B B
Internet
Internet
Netflow
Measuring Interdomain Traffic
• We don’t really know how much traffic each pair of networks exchanges!
• Measure qualitative properties of the interdomain TM from different vantage points
04/18/23 37The Economics of Transit and Peering Interconnections
C C A A
B B
ISP ISPNetflow
Measuring Interdomain Traffic
• We need data from as many vantage points as possible!
• Currently working with GEANT, SWITCH, Georgia Tech
• Let us know if you can help!
04/18/23 38The Economics of Transit and Peering Interconnections
C C A A
B B
ISP ISPNetflow
Summary
• We need realistic, economically-principled models to make sense of the Internet ecosystem
• We developed ITER, a computational model of interdomain interconnection
• We are working on better parameterization and validation using real-world measurements
• We need your help and feedback!
04/18/23 The Economics of Transit and Peering Interconnections 39
Thanks!amogh@caida.org
www.caida.org/~amogh
04/18/23 40The Economics of Transit and Peering Interconnections
References
• “The Internet is Flat: Modeling the Transition from a Transit Hierarchy to a Peering Mesh”– A. Dhamdhere, C. Dovrolis [CoNEXT 2010]
• “A Value-based Framework for Internet Peering Agreements”– A. Dhamdhere, C. Dovrolis, P. Francois [ITC 2010]
• “The Economics of Transit and Peering Interconnections in the Internet”– C. Dovrolis, K. Claffy, A. Dhamdhere [NSF NETSE 2010-2013]
04/18/23 41The Economics of Transit and Peering Interconnections
Network actions
• Networks perform their actions sequentially
• Can observe the actions of previous networks– And the effects of those actions on traffic flow and
economics
• Network actions in each move– Pick set of preferred providers– Evaluate each existing peering link– Try to create new peering links
04/18/23 43The Economics of Transit and Peering Interconnections
Three Factors
• Fraction of traffic sourced by CPs
• Geographical presence of CPs
• Peering openness• All three factors need to
change to see the differences between the “old” and “new” Internet
04/18/23 The Economics of Transit and Peering Interconnections 44
Peering Requirements
Laundry list of conditions that networks specify as requirements for (settlement-free) peering Traffic ratios, minimum traffic, backbone capacity,
geographical spread …
Heuristics to find networks for which it makes sense to exchange traffic for “free” But when it comes to paid peering.. What is the right price? Who should pay whom?
Are these heuristics always applicable? Mutually beneficial peering links may not be formed
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Peering Uncertainty – Current Peers
46
AA BB
Why is B still a settlement-free peer?
Does B benefit more than me? make Should I demand
payment? Should I depeer?
04/18/23 The Economics of Transit and Peering Interconnections
Negative Peering Value
47
A A B B
fA: $50k $60k fB: $100k $95k
VB=-$5kVA=$10k
$7.5k
$52.5k $102.5k
04/18/23 The Economics of Transit and Peering Interconnections
Modeling the Internet Ecosystem
• Networks select providers and peers to optimize an objective function• E.g., Profit, performance…
• What are the effects of provider and peer selection strategies on the involved networks?
• What are the global, long-term effects of these strategies on the whole Internet?• Topology, traffic flow, economics, performance (path lengths)
• E.g., Can we predict what would happen if (fair) paid-peering becomes the common case?
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Measuring Peering Value
How do A and B measure VA and VB?
With Peering trials: Collect: netflow, routing data Know: topology, costs, transit providers
With peering trials, A and B can measure their own value for the peering link (VA and VB) reasonably well
Hard for A to accurately measure VB (and vice versa)
4904/18/23 The Economics of Transit and Peering Interconnections
Hiding peering value
Assume true VA+ V
B > 0 and V
B> V
A
A should get paid (VB - V
A )/2
If A estimates VB correctly, and claims its peering value is VL, where VL << VA
B is willing to pay more: (VB - V
L )/2
If A doesn’t estimate VB correctly, and VL+ V
B < 0, the
peering link is not feasible! A loses out on any payment
Does the risk of losing out on payment create an incentive to disclose the true peering value?
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Peering Policies
• What peering policies do networks use? How does this depend on network type?
• Do they peer at IXPs? How many IXPs are they present at?
• PeeringDB: Public database where ISPs volunteer information about business type, traffic volumes, peering policies
• Collecting peeringDB snapshots periodically • Goal is to study how peering policies evolve
04/18/23 51The Economics of Transit and Peering Interconnections