Slides by Yong Liu1, Deep Medhi2, and Michał Piro3
-
Upload
clement-ross -
Category
Documents
-
view
218 -
download
0
description
Transcript of Slides by Yong Liu1, Deep Medhi2, and Michał Piro3
1
Slides byYong Liu1, Deep Medhi2, and Michał Pióro3
1Polytechnic University, New York, USA2University of Missouri-Kansas City, USA
3Warsaw University of Technology, Poland & Lund University, Sweden
October 2007
Routing, Flow, and Capacity Design in Communication and Computer
NetworksChapter 8:
Fair Networks
2
Outline Fair sharing of network resource
Max-min Fairness
Proportional Fairness
Extension
3
Fair Networks Elastic Users:
demand volume NOT fixed greedy users: use up resource if any, e.g. TCP competition resolution?
Fairness: how to allocate available resource among network users. capacitated design: resource=bandwidth uncapacitated design: resource=budget
Applications rate control, bandwidth reservation link dimensioning
4
Max-Min Fairness: definiation Lexicographical Comparison
a n-vector x=(x1,x2, …,xn) sorted in non-decreasing order (x1≤x2 ≤ …≤ xn) is lexicographically greater than another n-vector y=(y1,y2, …,yn) sorted in non-decreasing order if an index k, 0 ≤k ≤n exists, such that xi =yi, for i=1,2,…,k-1 and xk >yk
(2,4,5) >L (2,3,100) Max-min Fairness: an allocation is max-min fair if its
lexicographically greater than any feasible allocation
Uniqueness?
5
Other Fairness MeasuresProportional fairness [Kelly, Maulloo & Tan, ’98] A feasible rate vector x is proportionally fair if for every
other feasible rate vector y
Proposed decentralized algorithm, proved propertiesGeneralized notions of fairness [Mo & Walrand,
2000] -proportional fairness: A feasible rate vector x is
fair if for any other feasible rate vector y
Special cases: : proportional fairness : max-min fairness
0)(
i
iii x
xyw
0)(
i
iii x
xyw
),( p
1
6
Capacitated Max-Min Flow Allocation
Fixed single path for each demand
Proposition: a flow allocation is max-min fair if for each demand d there exists at least one bottle-neck, and at least on one of its bottle-necks, demand d has the highest rate among all demands sharing that bottle-neck link.
7
Max-min Fairness Example
Max-min fair flow allocation sessions 0,1,2: flow rate of 1/3 session 3: flow rate of 2/3
C=1 C=1
Session 1Session 2 Session 3
Session 0
8
Max-Min Fairness: other definitions Definition1: A feasible rate vector is
max-min fair if no rate can be increased without decreasing some s.t.
Definition2: A feasible rate vector is an optimal solution to the MaxMin problem iff for every feasible rate vector with , for some user i, then there exists a user k such that and
9
How to Find Max-min Fair Allocation?
Idea: equal share as long as possible Procedure
1. start with 0 rate for all demand2. increase rate at the same speed for all
demands, until some link saturated3. remove saturated links, and demands using
those links4. go back to step 2 until no demand left.
10
Max-min Fair Algorithm
11
Max-min Fair Example
B
CA
link rate: AB=BC=1, CA=2
demand 1,2,3 =1/3 demand 4 =2/3
demand 5=4/3
12
Extended MMF lower and upper bound on demands weighted demand rate
13
Extended MMF: algorithm
14
Deal with Upper Bound Add one auxiliary virtual link with link
capacity wdHd for each demand with upper bound Hd
15
MMF with Flexible Paths one demand can take multiple paths max-min over aggregate rate for each demand potentially more fair than single-path only more difficult to solve
16
Uncapacitated Problem Max-min fair sharing of budget Formulation
17
Uncapacitated Problem max-min allocation
all demands have the same rate each demand takes the shortest path
proof?
18
Proportional Fairness Proportional Fairness [Kelly, Maulloo & Tan,
’98] A feasible rate vector x is proportionally fair if for every
other feasible rate vector y
formulation
0)(
i
iii x
xyw
19
Linear Approximation of PF
20
Extended PF Formulation
21
Uncapacitated PF Design maximize network revenue minus
investment