topology mapping
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Topology Mapping. Bo Sheng Sept. 15. Outline. Overview Solutions LTM ACE Problems and discussion Conclusion. Introduction. Topology mapping Mismatch between overlay and physical infrastructure Topology optimization. Introduction. Traffic problem Facts - PowerPoint PPT PresentationTRANSCRIPT
Topology Mapping
Bo Sheng
Sept. 15
Outline
Overview Solutions
LTM ACE
Problems and discussion Conclusion
Introduction
Topology mapping Mismatch between overlay and physical
infrastructure Topology optimization
Introduction
Traffic problem Facts
95% of any pairs of Gnutella nodes are within 7 hops 50,000 nodes generate 1G/second, 330T/month
Reasons Blind flooding
Cycles, merge of multiple paths, neighbors exchange Topology problem
Multiple times over a physical link
Introduction
Perfect match
S S
Network infrastructure Overlay network
Introduction
Mismatch
S S
N1
N2
N3
Network infrastructure Overlay network
23
4
5
52
4
Topology Mismatch
Problems Randomly choosing neighbors Logically close, but physically far away
S PN1 N2
Topology Mismatch
Problems Unnecessary traffic
Inefficient utilization of bandwidth Only 2%~5% Gnutella connections link nodes within a
single AS (autonomous system) More than 40% Gnutella nodes are located within top 10
AS Delayed response
Do we need long-distance neighbors?
Topology Mismatch
Solutions to traffic problem Selective flooding Topology optimization
Avoid cycles Mapping
For each message, how many times it is delivered over a single physical link?
Performance Metrics
Traffic cost Search scope Response time Overhead
Approaches
Location-aware Topology Matching (LTM), INFOCOM 2004
Adaptive Connection Establishment (ACE), ICDCS 2004
LTM
Three main operations1. TTL-2-detector flooding
Message format Short Source IP& timestamp Long Source IP& timestamp, TTL1 IP& timesta
mp d(i,S,v)
Link cost
S N1IP(S),T(S)
IP(S),T(S)N2
IP(N1),T(N1)
d(i,S,1) d(i,S,0)
LTM
Three main operations2. Low productive connection cutting
1. Case1: P receives d(i,S,1) and d(i,S,0)
S
P
N
will-cut list
LTM
Three main operations2. Low productive connection cutting
2. Case2: P receives multiple d(i,S,0)
S
P
N1
N2
LTM
Three main operations2. Low productive connection cutting
3. Case3: P receives one d(i,S,1) and multiple d(i,S,0)
S
P
N1
N2
cut list
LTM
Three main operations3. Source peer probing
S
P
N1
LTM
S
P
N1
N2
Step2.case2 S
P
N1
Step3
LTM
S
P
N1
N2
S
P
N1
N2
Step2.case2Step2.case3
Step2.case1
Step2.case3
LTM
S
P
N1
S
P
N1
Step2.case1Step3
LTM
States
Case1
Step3
Case3
Case2
LTM
Performance Traffic Search scope Overhead
ACE
Step1: Probe link costs with neighbors Build neighbor cost table Exchange neighbors cost table with neighbors
ACE
Step2: Create a minimum spanning tree among each
peer and its neighbors
S
E
F
G
414
15
620
S
E
F
G
414
6
ACE
Step3: Replace neighbors
S
E
F
G
414
6
H
Case1: SH<SG
Case2: GH>SH>SG
Case3: SH>SG,SH>GH
ACE
Depth of optimization (h-neighbor closure)
10 1520
12 148
7
A
B
C
D
E
A->B=10A->D=15
B->E=8D->E=14
E->C=7E->D=14
Total:68
ACE
2-neighbor closure
10 1520
12 148
A
B
C
D
E
A
B
C
D
E7
A->B=10B->E=8E->C=7E->D=14
Total:39
Discussion
Measurement Link cost is not accurate
Link cutting and cycles Heuristic to theoretical support
f (Pn,Tn)=?
Conclusion
Importance Effectiveness vs. cost Future work