LSWA Youth Advisory Committee Meeting Agenda

Analysis of peering strategy
adoption by transit providers in
the Internet
Aemen Lodhi 
(Georgia Tech)
Amogh Dhamdhere 
(CAIDA)
Constantine Dovrolis 
(Georgia Tech)
1
 
Simula Research, May 30, 2012
3/1/2025
Outline
Background
Motivation & Objective
Approach: the GENESIS model
Results
Adoption of peering strategies
Impact on economic fitness
Who loses? Who gains?
Alternative peering strategies
Conclusion
2
3/1/2025
Pretty picture of the Internet
3
3/1/2025
Background
The Internet consists of ~40,000
networks
Each independently operated and managed
Called “Autonomous Systems” (ASes)
Various types: 
transit, content, access, enterprise
Distributed, decentralized interactions
between ASes
Transit link: 
Customer pays provider
Settlement-free peering link: 
Exchange
traffic for free
4
3/1/2025
Background
5
Enterprise
customer
Transit
Provider
Transit
Provider
Enterprise
customer
Content
Provider
Content
Provider
Tier-1
network
Tier-1
network
Tier-1
network
The Internet again..less pretty
3/1/2025
Motivation: Existing peering
environment
Increasing fraction of interdomain traffic
flows over peering links
*
How are transit providers responding?
6
Transit
Provider
Content
Provider/CDN
Access
ISP/Eyeballs
3/1/2025
Motivation: Existing peering
environment
Peering strategies of ASes in the Internet
   (source: PeeringDB 
www.peeringdb.com
)
Transit Providers peering openly ?
7
3/1/2025
Objective
Why are so many transit providers peering
openly?
What gives them the incentive to do so?
What is the impact on their economic
fitness?
Which transit providers lose/gain?
Are their any alternative peering
strategies?
8
3/1/2025
The model: 
GENESIS
*
Agent based interdomain network formation
model
Incorporates
Geographic constraints in provider/peer selection
Interdomain traffic matrix
Public & Private peering
Realistic peering costs, transit costs, transit revenue
9
3/1/2025
The model: 
GENESIS
*
Fitness = Transit Revenue – Transit Cost – Peering cost
Objective: Maximize economic fitness
Optimize connectivity through peer and
transit provider selection
Choose the peering strategy that
maximizes fitness
3/1/2025
10
Peering strategies
11
Networks must be co-located in order to
establish a peering link
Restrictive
: Peer only if the internetwork
would otherwise be partitioned
Selective
: Peer only with networks of
“similar size”
Use total traffic volume of potential peers as
proxy for size
Open
: Agree to peer with any co-located
network
3/1/2025
Peering strategy adoption
Strategy update in each round
Enumerate all available strategies
Estimate fitness with the connectivity
that results from each strategy
Choose the one which gives maximum
fitness
12
3/1/2025
Execution of a sample path
13
1
2
N
 
Iteration
1.
Depeering
2.
Peering
3.
Transit provider selection
4.
Peering strategy update
1.
Depeering
2.
Peering
3.
Transit provider selection
4.
Peering strategy update
1.
Depeering
2.
Peering
3.
Transit provider selection
4.
Peering strategy update
1
2
N
 
Iteration
Time
 
No exogenous changes
Networks have no foresight
Networks do not co-ordinate
 
Continues until every network has played,
but none has changed its peering strategy
3/1/2025
Scenarios
 
*Stubs always use Open
Without-open
Selective
Restrictive
With-open
Selective
Restrictive
Open
vs.
3/1/2025
14
RESULTS
15
3/1/2025
Strategy adoption by transit
providers
16
3/1/2025
Strategy adoption by transit
providers
17
Attraction towards Open peering not uniform
Less attractive for large transit providers
3/1/2025
Impact of Open peering on
cumulative fitness
Cumulative fitness reduced in all simulations
70% providers have lower fitness
18
3/1/2025
Impact of Open peering on individual
fitness
Some providers lose significantly due to open peering
19
3/1/2025
An Open peering environment
x
y
z
w
v
Save transit
costs
But your
customers are
doing the same!
Affects:
Transit Cost
Transit Revenue
Peering Cost
3/1/2025
20
Why gravitate towards Open
peering?
x
y
z
w
Options for
x?
Y peering openly
x adopts Open
peering
Not isolated
decisions!!
Y reduced
transit traffic
and revenue
for X!!
X recovers
some of its
transit traffic
3/1/2025
21
Some Game Theory (finally..)
Analyzed a simplified model game-
theoretically
Only two providers, co-located, no economies of
scale, each has single customer
With complete information about each other’s
payoffs, providers choose Selective peering
In the absence of complete information, Open
peering is the “risk-dominant” strategy
22
3/1/2025
Quantifying traffic stealing
Contention metric: Quantify traffic stealing
effect
23
x
y
z
w
No
contention
Maximum
Contention
3/1/2025
Contention and fitness
Cumulative fitness of transit providers decreases
as traffic stealing becomes more prevalent
24
3/1/2025
Avoid fitness loss?
vs.
Lack of coordination
No incentive to unilaterally withdraw from
peering with peer’s customer
Sub-optimal equilibrium
3/1/2025
25
Traffic volume and customer
cone size
Traffic stealing seems to be the root
cause of fitness loss
Let’s classify providers based on how
likely they are to steal traffic and have
their traffic stolen by peers
See what happens to different classes
3/1/2025
26
Classification of transit providers
Classification of transit providers
Traffic volume, Customer cone size
27
3/1/2025
Who loses? Who gains?
28
3/1/2025
Who loses? Who gains?
Who gains: Small customer cone small traffic volume
Cannot peer with large providers using Selective
Little transit revenue loss
Who loses: Large customer cone large traffic volume
Can peer with large transit providers with Selective
Customers peer extensively
3/1/2025
29
Alternatives: Open peering variants
Do not peer with immediate customers of peer
(Direct Customer Forbiddance DCF)
Do not peer with any AS in the customer tree of
peer (All Customer Forbiddance ACF)
30
DCF
x
y
z
w
v
ACF
3/1/2025
Open peering variants: Fitness
Collective fitness with DCF approaches Selective
Selective
Open
DCF
ACF
3/1/2025
31
Why the improvement with DCF?
No traffic “stealing” by peers
Aggregation of peering traffic over fewer links
(economies of scale !!)
Less pressure to adopt Open peering
32
Open peering variants: Fitness
3/1/2025
These rules cannot be enforced!
What happens if some networks decide to cheat at the
eqilibrium? i.e., is the DCF equilibrium stable?
Tit-for-tat equibrium
Genetic algorithm
What if some networks never agree to DCF? Can these
networks cause the system to gravitate towards Open
peering?
Coaalition games
Shapley value
Open peering variants: Open
questions
3/1/2025
33
Gravitation towards Open peering is a
network effect for transit providers (79%
adopt Open peering)
Economically motivated strategy selection
Myopic decisions
Lack of coordination
Extensive Open peering by transit
providers in the network results in
collective loss
34
Conclusion
3/1/2025
Effect on the fitness of transit providers
is not uniform
Small transit providers gain
Large transit providers lose
Coordination is required to mitigate losses
Not peering with customers of peers can
avoid fitness loss
35
Conclusion
3/1/2025
Thank you
 
36
3/1/2025
Motivation
Traffic ratio requirement for peering?
   (source: PeeringDB 
www.peeringdb.com
)
37
3/1/2025
Traffic components
 
Traffic
consumed in the
AS
 
Transit traffic = Inbound traffic – Consumed traffic
same as
Transit traffic = Outbound traffic – Generated traffic
38
Autonomous system
Inbound traffic
Traffic transiting
through the AS
Traffic generated
within the AS
Outbound traffic
3/1/2025
Customer-Provider traffic
comparison – PeeringDB.com
39
Traffic carried by
the AS
3/1/2025
Customer-Provider traffic
comparison
2500 customer-provider pairs
90% pairs: Customer traffic
significantly less than provider traffic
9.5% pairs: Customer traffic larger
than provider traffic (difference less
than 20%)
0.05% pairs: Customer traffic
significantly larger than provider
traffic
40
3/1/2025
Geographic presence & constraints
41
Link formation
across
geography not
possible
Regions
corresponding
to unique IXPs
Peering link at top
tier possible
across regions
Geographic
overlap
3/1/2025
Logical Connectivity
42
3/1/2025
Traffic Matrix
Traffic for ‘
N
’ size network represented
through an 
N * N  
matrix
Illustration of traffic matrix for a 4 AS
network
Traffic sent by AS 0
to other ASes in the
network
Traffic received by
AS 0 from other
ASes in the network
Intra-domain traffic
not captured in the
model
 
 
 
Generated traffic
 
 
 
Consumed traffic
43
3/1/2025
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  1. Analysis of peering strategy adoption by transit providers in the Internet Aemen Lodhi (Georgia Tech) Amogh Dhamdhere (CAIDA) Constantine Dovrolis (Georgia Tech) Simula Research, May 30, 2012 3/1/2025 1

  2. Outline Background Motivation & Objective Approach: the GENESIS model Results Adoption of peering strategies Impact on economic fitness Who loses? Who gains? Alternative peering strategies Conclusion 3/1/2025 2

  3. Pretty picture of the Internet 3/1/2025 3

  4. Background The Internet consists of ~40,000 networks Each independently operated and managed Called Autonomous Systems (ASes) Various types: transit, content, access, enterprise Distributed, decentralized interactions between ASes Transit link: Customer pays provider Settlement-free peering link: Exchange traffic for free 3/1/2025 4

  5. The Internet again..less pretty Tier-1 network Tier-1 network $$ Tier-1 network $$ Transit Provider Transit Provider $$ $$ $$ Enterprise customer Enterprise customer Content Provider Content Provider 3/1/2025 5

  6. Motivation: Existing peering environment Increasing fraction of interdomain traffic flows over peering links* How are transit providers responding? Transit Provider Access ISP/Eyeballs Content Provider/CDN 3/1/2025 6

  7. Motivation: Existing peering environment Peering strategies of ASes in the Internet (source: PeeringDB www.peeringdb.com) Transit Providers peering openly ? 3/1/2025 7

  8. Objective Why are so many transit providers peering openly? What gives them the incentive to do so? What is the impact on their economic fitness? Which transit providers lose/gain? Are their any alternative peering strategies? 3/1/2025 8

  9. The model: GENESIS* Agent based interdomain network formation model Incorporates Geographic constraints in provider/peer selection Interdomain traffic matrix Public & Private peering Realistic peering costs, transit costs, transit revenue 3/1/2025 9

  10. The model: GENESIS* Fitness = Transit Revenue Transit Cost Peering cost Objective: Maximize economic fitness Optimize connectivity through peer and transit provider selection Choose the peering strategy that maximizes fitness 3/1/2025 10

  11. Peering strategies Networks must be co-located in order to establish a peering link Restrictive: Peer only if the internetwork would otherwise be partitioned Selective: Peer only with networks of similar size Use total traffic volume of potential peers as proxy for size Open: Agree to peer with any co-located network 3/1/2025 11

  12. Peering strategy adoption Strategy update in each round Enumerate all available strategies Estimate fitness with the connectivity that results from each strategy Choose the one which gives maximum fitness 3/1/2025 12

  13. Execution of a sample path No exogenous changes Networks have no foresight Networks do not co-ordinate Continues until every network has played, but none has changed its peering strategy 1. Depeering 2. Peering 3. Transit provider selection 1. Depeering 2. Peering 3. Transit provider selection 4. Peering strategy update 4. Peering strategy update 1. Depeering 2. Peering 3. Transit provider selection 4. Peering strategy update Iteration Iteration 1 2 1 2 N N Time 3/1/2025 13

  14. Scenarios Without-open Selective Restrictive With-open Selective Restrictive Open vs. *Stubs always use Open 3/1/2025 14

  15. RESULTS 3/1/2025 15

  16. Strategy adoption by transit providers 100 Percentage of transit providers 90 80 70 60 50 Restrictive Selective Open 40 30 20 10 0 Without-open With -open Conservative Non-conservative Scenarios 3/1/2025 16

  17. Strategy adoption by transit providers Attraction towards Open peering not uniform Less attractive for large transit providers 3/1/2025 17

  18. Impact of Open peering on cumulative fitness Cumulative fitness reduced in all simulations 70% providers have lower fitness 3/1/2025 18

  19. Impact of Open peering on individual fitness Some providers lose significantly due to open peering 3/1/2025 19

  20. An Open peering environment Affects: Transit Cost Transit Revenue v Save transit costs Peering Cost x y But your customers are doing the same! z w 3/1/2025 20

  21. Why gravitate towards Open peering? Options for x? Y reduced transit traffic and revenue for X!! some of its transit traffic x adopts Open peering x y X recovers Not isolated decisions!! Y peering openly z w, traffic passes through x z w z w, z y, traffic bypasses x 3/1/2025 21

  22. Some Game Theory (finally..) Analyzed a simplified model game- theoretically Only two providers, co-located, no economies of scale, each has single customer With complete information about each other s payoffs, providers choose Selective peering In the absence of complete information, Open peering is the risk-dominant strategy 3/1/2025 22

  23. Quantifying traffic stealing Contention metric: Quantify traffic stealing effect No Maximum x y contention Contention z w 3/1/2025 23

  24. Contention and fitness Cumulative fitness of transit providers decreases as traffic stealing becomes more prevalent 3/1/2025 24

  25. Traffic volume and customer cone size Traffic stealing seems to be the root cause of fitness loss Let s classify providers based on how likely they are to steal traffic and have their traffic stolen by peers See what happens to different classes 3/1/2025 26

  26. Classification of transit providers Classification of transit providers Traffic volume, Customer cone size 3/1/2025 27

  27. Who loses? Who gains? 3/1/2025 28

  28. Who loses? Who gains? Who gains: Small customer cone small traffic volume Cannot peer with large providers using Selective Little transit revenue loss Who loses: Large customer cone large traffic volume Can peer with large transit providers with Selective Customers peer extensively 3/1/2025 29

  29. Alternatives: Open peering variants Do not peer with immediate customers of peer (Direct Customer Forbiddance DCF) Do not peer with any AS in the customer tree of peer (All Customer Forbiddance ACF) x y x y w z w v DCF z ACF 3/1/2025 30

  30. Open peering variants: Fitness Selective Open DCF ACF Collective fitness with DCF approaches Selective 3/1/2025 31

  31. Open peering variants: Fitness Why the improvement with DCF? No traffic stealing by peers Aggregation of peering traffic over fewer links (economies of scale !!) Less pressure to adopt Open peering 3/1/2025 32

  32. Open peering variants: Open questions These rules cannot be enforced! What happens if some networks decide to cheat at the eqilibrium? i.e., is the DCF equilibrium stable? Tit-for-tat equibrium Genetic algorithm What if some networks never agree to DCF? Can these networks cause the system to gravitate towards Open peering? Coaalition games Shapley value 3/1/2025 33

  33. Conclusion Gravitation towards Open peering is a network effect for transit providers (79% adopt Open peering) Economically motivated strategy selection Myopic decisions Lack of coordination Extensive Open peering by transit providers in the network results in collective loss 3/1/2025 34

  34. Conclusion Effect on the fitness of transit providers is not uniform Small transit providers gain Large transit providers lose Coordination is required to mitigate losses Not peering with customers of peers can avoid fitness loss 3/1/2025 35

  35. Thank you 3/1/2025 36

  36. Motivation Traffic ratio requirement for peering? (source: PeeringDB www.peeringdb.com) 3/1/2025 37

  37. Traffic components Inbound traffic Traffic consumed in the AS Traffic generated within the AS Traffic transiting through the AS Autonomous system Transit traffic = Inbound traffic Consumed traffic same as Transit traffic = Outbound traffic Generated traffic Outbound traffic 3/1/2025 38

  38. Customer-Provider traffic comparison PeeringDB.com Traffic carried by the AS 3/1/2025 39

  39. Customer-Provider traffic comparison 2500 customer-provider pairs 90% pairs: Customer traffic significantly less than provider traffic 9.5% pairs: Customer traffic larger than provider traffic (difference less than 20%) 0.05% pairs: Customer traffic significantly larger than provider traffic 3/1/2025 40

  40. Peering link at top tier possible across regions overlap Geographic presence & constraints Geographic Link formation across geography not possible Regions corresponding to unique IXPs 3/1/2025 41

  41. Logical Connectivity 3/1/2025 42

  42. Traffic Matrix Traffic for N size network represented through an N * N matrix Illustration of traffic matrix for a 4 AS network Traffic sent by AS 0 to other ASes in the network Intra-domain traffic not captured in the model Generated traffic = G x V ) ( 0 t t t t 01 02 03 N Traffic received by AS 0 from other ASes in the network = x i i , 0 t xi 0 10 Consumed traffic 0 t 20 N = , 0 0 t = ( ) V x t 30 C ix i i x 3/1/2025 43

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