interdomain routing as social choice l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Interdomain Routing as Social Choice PowerPoint Presentation
Download Presentation
Interdomain Routing as Social Choice

Loading in 2 Seconds...

play fullscreen
1 / 41

Interdomain Routing as Social Choice - PowerPoint PPT Presentation


  • 103 Views
  • Uploaded on

Interdomain Routing as Social Choice. Ronny R. Dakdouk, Semih Salihoglu, Hao Wang, Haiyong Xie, Yang Richard Yang Yale University IBC ’ 06. Outline. Motivation A social choice model for interdomain routing Implications of the model Summary & future work. Motivation.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Interdomain Routing as Social Choice' - sylvie


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
interdomain routing as social choice

Interdomain Routing as Social Choice

Ronny R. Dakdouk, Semih Salihoglu, Hao Wang, Haiyong Xie, Yang Richard Yang

Yale University

IBC’06

outline
Outline
  • Motivation

A social choice model for interdomain routing

  • Implications of the model
  • Summary & future work
motivation
Motivation
  • Importance of Interdomain Routing
    • Stability
      • excessive churn can cause router crash
    • Efficiency
      • routes influence latency, loss rate, network congestion, etc.
  • Why policy-based routing?
    • Domain autonomy: Autonomous System (AS)
    • Traffic engineering objectives: latency, cost, etc.
slide4
BGP
  • The de facto interdomain routing protocol of the current Internet
  • Support policy-based, path-vector routing
    • Path propagated from destination
    • Import & export policy
    • BGP decision process selects path to use
      • Local preference value
      • AS path length
      • and so on…
policy interactions could lead to oscillations

2 1 0

2 0

2

4

0

3 2 0

3 0

1 3 0

1 0

3

3

1

Policy Interactions Could Lead to Oscillations

The BAD GADGET example:

- 0 is the destination

- the route selection policy of each AS is to prefer its counter clock-wise neighbor

Policy interaction causes routing instability !

previous studies
Previous Studies
  • Policy Disputes (Dispute Wheels) may cause instability [Griffien et al. ‘99]
  • Economic/Business considerations may lead to stability [Gao & Rexford ‘00]
  • Design incentive-compatible mechanisms [Feigenbaum et al. ‘02]
  • Interdomain Routing for Traffic Engineering [Wang et al. ‘05]
what s missing
What’s Missing
  • Efficiency (Pareto optimality)
  • Previous studies focus on BGP-like protocols
    • Increasing concern about extension of BGP or replacement (next-generation protocol)
    • Need a systematic methodology
      • Identify desired properties
      • Feasibility + Implementation
  • Implementation in strategic settings
    • Autonomous System may execute the protocol strategically so long as the strategic actions do not violate the protocol specification!
our approach a black box view of interdomain routing
Our approach - A Black Box View of Interdomain Routing
  • An interdomain routing system defines a mapping (a social choice rule)
  • A protocol implements this mapping
  • Social choice rule + Implementation

AS 1 Preference

Interdomain Routing Protocol

AS 1 Route

.....

.....

AS N Preference

AS N Route

in this talk
In this Talk
  • A social choice model for interdomain routing
  • Implications of the model
    • Some results from literature
    • A case study of BGP from the social choice perspective
outline10
Outline
  • Motivation

A social choice model for interdomain routing

  • Implications of the model
  • Summary & future work
a social choice model for interdomain routing
A Social Choice Model for Interdomain Routing
  • What’s the set of players?
    • This is easy, the ASes are the players
  • What’s the set common of outcomes?
    • Difficulty
      • AS cares about its own egress route, possibly some others’ routes, but not most others’ routes
      • The theory requires a common set of outcomes
    • Solution
      • Use routing trees or sink trees as the unifying set of outcomes
routing trees sink trees
Routing Trees (Sink Trees)
  • Each AS i = 1, 2, 3 has a route to the destination (AS 0)
  • T(i) = AS i’s route to AS 0
  • Consistency requirement:
  • If T(i) = (i, j) P, then T(j) = P

A routing tree

realizable routing trees
Realizable Routing Trees
  • Not all topologically consistent routing trees are realizable
    • Import/Export policies
  • The common set of outcomes is the set of realizable routing trees
local routing policies as preference relations
Local Routing Policies as Preference Relations
  • Why does this work?
    • Example: The preference of AS i depends on its own egress route only, say, r1 > r2
    • The equivalent preference: AS i is indifferent to all outcomes in which it has the same egress route
    • E.g: If T1(i) = r1, T2(i) = r2, T3(i) = r2, then

T1 >i T2 =i T3

local routing policies as preference relations cont
Local Routing Policies as Preference Relations (cont’)
  • Not just a match of theory
  • Can express more general local policies
    • Policies that depend not only on egress routes of the AS itself, but also incoming traffic patterns
    • AS 1 prefers its customer 3 to send traffic through it, so T1 >1 T2
preference domains
Preference Domains
  • All possible combinations of preferences of individual ASes
    • Traditional preference domains:
      • Unrestricted domain
      • Unrestricted domain of strict preferences
    • Two special domains in interdomain routing
      • The domain of unrestricted route preference
      • The domain of strict route preference
preference domains cont
Preference Domains (cont’)
  • The domain of unrestricted route preference
    • Requires: If T1(i) = T2(i), then T1 =i T2
    • Intuition: An AS cares only about egress routes
  • The domain of strict route preference
    • Requires: If T1(i) = T2(i), then T1 =i T2
    • Also requires: if T1(i)  T2(i) then T1 i T2
    • Intuition: An AS further strictly differentiates between different routes
interdomain social choice rule scr
Interdomain Social Choice Rule (SCR)
  • An interdomain SCR is a correspondence:
  • F: R=(R1,...,RN)  P  F(R) A
  • F incorporates the criteria of which routing tree(s) are deemed “optimal”– F(R)
some desirable properties of interdomain routing scr
Some Desirable Properties of Interdomain Routing SCR
  • Non-emptiness
    • All destinations are always reachable
  • Uniqueness
    • No oscillations possible
  • Unanimity
  • (Strong) Pareto optimality
    • Efficient routing decision
  • Non-dictatorship
    • Retain AS autonomy
protocol as implementation
Protocol as Implementation
  • No central authority for interdomain routing
    • ASes execute routing protocols
  • Protocol specifies syntax and semantics of messages
    • May also specify some actions that should be taken for some events
    • Still leaves room for policy-specific actions <- strategic behavior here!
  • Therefore, a protocol can be modeled as implementation of an interdomain SCR
outline22
Outline
  • Motivation

A social choice model for interdomain routing

  • Implications of the model
  • Summary & future work
some results from literature
Some Results from Literature
  • On the unrestricted domain
    • No non-empty SCR that is non-dictatorial, strategy-proof, and has at least three possible routing trees at outcomes [Gibbard’s non-dominance theorem]
  • On the unrestricted route preference domain
    • No non-constant, single-valued SCR that is Nash-implementable
    • No strong-Pareto optimal and non-empty SCR that is Nash-implementable
a case study of bgp
A Case Study of BGP
  • Assumption 1: ASes follow the greedy BGP route selection strategy
  • Assumption 2: if T1(i) = T2(i) then either T1(i) or T2(i) can be chosen

AS 1 Preference

Routing Tree

BGP

.....

.....

AS N Preference

reverse engineering bgp
Reverse engineering BGP
  • Non-emptiness: X
  • Uniqueness: X
  • Unanimity: 
  • Strong Pareto Optimality:  only on strict route preference domain
  • Non-dictatorship: X
bgp is manipulable
BGP is manipulable!
  • If AS 1 and 3 follow the default BGP strategy, then AS 2 has a better strategy
    • If (3,0) is available, selects (2, 3, 0)
    • Otherwise, if (1, 0) is available, selects (2, 1, 0)
    • Otherwise, selects (2, 0)
    • The idea: AS 2 does not easily give AS 3 the chance of exploiting itself!
  • Comparison of strategies for AS 2 (AS 1, 3 follow default BGP strategy)
    • Greedy strategy: depend on timing, either (2, 1, 0) or (2, 3, 0)
    • The strategy above: always (2, 3, 0)
possibility of fixing bgp
Possibility of fixing BGP
  • BGP is (theoretically) Nash implementable (actually, also strong implementable)
  • But, only in a very simple game form
  • The problem: the simple game form may not be followed by the ASes
summary
Summary
  • Viewed as a black-box, interdomain routing is an SCR + implementation
  • Strategic implementation impose stringent constraints on SCRs
  • The greedy BGP strategy has its merit, but is manipulable
what s next
What’s next?
  • Design of next-generation protocol (the goal!)
    • Stability, optimality, incentive-compatible
    • Scalability
    • Scalability may serve as an aide (complexity may limit viable manipulation of the protocol)
  • What is a reasonable preference domain to consider?
  • A specialized theory of social choice & implementation for routing?
social choice rules scr
Social Choice Rules (SCR)
  • A set of players V = { 1,...,N }
  • A set of outcomes = { T1,…,TM }
  • Player i has its preference Ri over 
    • a complete, transitive binary relation
  • Preference profile R = (R1,…,RN)
    • R completely specifies the “world state”
preference domains34
Preference Domains
  • Preference domain P : a non-empty set of potential preference profiles
    • Why a domain? – The preference profile that will show up is not known in advance
  • Some example domains:
    • Unrestricted domain
    • Unrestricted domain of strict preferences
social choice rule scr
Social Choice Rule (SCR)
  • An SCR is a correspondence:
  • F: R=(R1,...,RN)  P  F(R) A
  • F incorporates the criteria of which outcomes are deemed “optimal”– F(R)
  • Some example criteria:
    • Pareto Optimal (weak/strong/indifference)
    • (Non-)Dictatorship
    • Unanimity
scr implementation
SCR Implementation
  • The designer of a SCR has his/her criteria of what outcomes should emerge given players’ preferences
  • But, the designer does not know R
    • Question: What can the designer do to ensure his criteria get satisfied?
scr implementation37
SCR Implementation
  • Implementation: rules to elicit designer’s desired outcome(s)
  • Game Form (M,g)
    • M: Available action/message for players (e.g, cast ballots)
    • g: Rules (outcome function) to decide the outcome based on action/message profile (e.g, majority wins)
scr implementation38
SCR Implementation
  • Given the rules, players will evaluate their strategies (e.g, vote one’s second favorite may be better, if the first is sure to lose)
  • Solution Concepts: predict players strategic behaviors
    • Given (M,g,R), prediction is that players will play action profiles S  A
scr implementation39
SCR Implementation
  • The predicted outcome(s)

OS(M,g,R) = { a  A |  m  S(M,g,R), s.t. g(m) = a }

  • Implementation: predicted outcomes satisfy criteria
  • OS(M,g,R) = F(R), for all R  P
protocol as implementation feasibility
Protocol as Implementation - Feasibility
  • Dominant Strategy implementation
  • Gibbard’s non-dominance theorem:
  • No dominant strategy implementation of non-dictatorial SCR w/ >= 3 possible outcomes on unrestricted domain
some results from literature41
Some Results from Literature
  • On the unrestricted route preference domain)
    • “Almost no” non-empty and strong Pareto optimal SCR can be Nash implementable
    • If we want a unique routing solution (social choice function, SCF), then only constant SCF can be Nash implementable
    • 2nd result does not hold on a special domain which may be of interest in routing context (counter-example, dictatorship)