tomography-based overlay network monitoring and its applications
DESCRIPTION
Tomography-based Overlay Network Monitoring and its Applications. Yan Chen. Joint work with David Bindel, Brian Chavez, Hanhee Song, and Randy H. Katz UC Berkeley. Overlay Network Operation Center. End hosts. topology. measurements. Problem Formulation. - PowerPoint PPT PresentationTRANSCRIPT
Tomography-based Overlay Network Monitoring and its
Applications
Joint work with David Bindel, Brian Chavez, Hanhee Song, and Randy H. Katz
UC Berkeley
Yan Chen
Problem FormulationGiven n end hosts on an overlay network and
O(n2) paths, how to select a minimal subset of paths to monitor so that the loss rates/latency of all other paths can be inferred.
• Key idea: select a basis set of k paths that completely describe all O(n2) paths (k «O(n2)) – Select and monitor k linearly independent paths to
compute the loss rates of basis set– Infer the loss rates of all other paths
End hosts
Overlay Network Operation Center
topology
measurements
1 2
1
2 3
1’
Real links (solid) and overlaypaths (dotted) going through them
Virtualization
Virtual links
1’ 2’
1
2
3
1’2’
4
k =1
k = 2
k = 3
3’
4’
Intuition through Topology Virtualization
1
1 2
12
3
• Virtual links: minimal path segments whose loss rates uniquely identified
• Can fully describe all paths
5
Efficiency and Adaptation
• Internet has moderate hierarchical structure [TGJ+02]
• For reasonably large n, (e.g., 100), k = O(nlogn)
• Tolerant to topology measurement errors• Incremental topology change detection and
update of monitoring paths– End host join/leave– Routing changes
Areas and Domains# of
hosts
US (40)
.edu 33
.org 3
.net 2
.gov 1
.us 1
Interna-tional (11)
Europe (6)
France 1
Sweden 1
Denmark 1
Germany 1
UK 2
Asia (2)Taiwan 1
Hong Kong 1
Canada 2
Australia 1
Experiments on Planet Lab
• 51 hosts, each from different organizations– 51 × 50 = 2,550 paths
• Simultaneous loss rate measurement– 300 trials– In each trial, send a 40-
byte UDP pkt to every other host
• Simultaneous topology measurement– Traceroute
• Experiments: 6/24 – 6/27– 100 experiments in peak
hours
• Loss rate distribution
• Accuracy– On average k = 872 out of 2550– Absolute error |p – p’|:
• Average 0.0027 for all paths, 0.0057 for lossy paths
– Small relative error and good lossy path inference
• Topology measurement error tolerance– On average 245 out of 2550 paths have no or
incomplete routing information– No router aliases resolved
lossrate
[0, 0.05)
lossy path [0.05, 1.0] (4.1%)
[0.05, 0.1) [0.1, 0.3) [0.3, 0.5) [0.5, 1.0) 1.0
% 95.9% 15.2% 31.0% 23.9% 4.3% 25.6%
Tomography-based Overlay Monitoring Results
Performance Improvement with Overlay
• With single-node relay• Loss rate improvement
– Among 10,980 lossy paths:– 5,705 paths (52.0%) have loss rate reduced by 0.05 or more– 3,084 paths (28.1%) change from lossy to non-lossy
• Throughput improvement– Estimated with
– 60,320 paths (24%) with non-zero loss rate, throughput computable
– Among them, 32,939 (54.6%) paths have throughput improved, 13,734 (22.8%) paths have throughput doubled or more
• Implications: use overlay path to bypass congestion or failures
lossraterttthroughput
5.1
SERVER
OVERLAY RELAYNODE
OVERLAY NETWORKOPERATION CENTER
CLIENT
3. Network congestion /failure
4. Detect congestion /failure
2. Register trigger
7. Skip-free streamingmedia recovery
6. Setup New Path
1. Setupconnection
5. Alert +New Overlay Path
X
UC Berkeley
UC San Diego
Stanford
HP Labs
Adaptive Overlay Streaming Media
• Implemented with Winamp client and SHOUTcast server• Congestion introduced with a Packet Shaper• Skip-free playback: server buffering and rewinding• Total adaptation time < 4 seconds
Pros and Cons About Planet Lab
+ Easy batch processing via SSH- No root privileges
– Many measurement tools don’t work!
- Limited tools– Only ping and traceroute– but people are adding more, like scriptroute
- Linux-only platform– New applications (multiplayer games, live
media) are mostly on Windows platform
- Limited programming language choices– Only C/C++ and perl, no Java
Backup Slides
Adaptive Streaming Media Architecture
Client 1
MEDIASOURCE
SERVER
SHOUTcastServer
Buffering Layer
Clie
nt 1
Clie
nt 2
Clie
nt 3
Clie
nt 4
FromSHOUTcast
server
Calculated
concatenationpoint
BU
FF
ER
ByteCounter
Client 2
Client 3
Client 4
INTERNET
Triggering /alert + new path
OVERLAY RELAY NODE
RELAY
Overlay Layer
Path Management
TCP/IP Layer
RELAY
CLIENT
Winamp client
TCP/IP Layer
Overlay Layer
Internet
Path Management
Winamp Video/Audio Filter
Byte Counter
TCP/IP Layer
OVERLAY NETWORKOPERATION CENTER