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29.09.04 Dept. of Information Technology - Ghent University 2
Outline
• Multimedia Services = New Requirements
• Current state of the Internet
• Overlay Networks
• Algorithms
• Evaluation
• Conclusion
29.09.04 Dept. of Information Technology - Ghent University 3
Multimedia Services
• Internet For Multimedia:
- Video Conferencing
- Voice Over IP (VOIP)• Skype
- Video On Demand
- Multiplayer Gaming • Xbox Live• MMORPG
VOIP Video Conferencing Video On Demand
29.09.04 Dept. of Information Technology - Ghent University 4
New Services = New Requirements
• These new Services require more from the network than just connectivity
• Characteristics of Multimedia Services:- Time Critical - Loss Sensitive - Bandwidth Consuming- Sensitive to jitter
PESQ
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
0 10 20 30 40
Packet Loss
PESQ
29.09.04 Dept. of Information Technology - Ghent University 5
The Current Internet
• Provides CONNECTIVITY • ≠ QoS• Problems :
- Shortest Path Routing- Hot Potato Routing- QoS research:
• Intserv (scalability?) • Diffserv (ubiquitous deployment?)
E2E QoS ???
Need for a fast and efficient way to introduce QoS in the Internet…
29.09.04 Dept. of Information Technology - Ghent University 6
A New Player
uses network and services
USERS
Service Provider Service Provider
Overlay Provider
Builds a QoSplatform on top of the Internet
offers multimedia services to users
provides connectivity
29.09.04 Dept. of Information Technology - Ghent University 7
General Concept
• Place servers in the Internet• Monitor QoS metrics (delay, loss, throughput,…) • Select routes fulfilling the requirements of multimedia
connections
Overlay Server
Client
29.09.04 Dept. of Information Technology - Ghent University 8
Overlay Network Functionality
Overlay Server
Source DestinationIP Router
IP RouteOverlay Route
Bad IPLink
29.09.04 Dept. of Information Technology - Ghent University 9
Where to Place the Overlay Servers?
• Essential: location of overlay servers• This Paper: Server Placement Algorithms• Support as many connections as possible with a minimal number
of servers.• Assumptions:
- Link BW is known- Link Delay is known- E2E Internet path known- Overlay server can be placed anywhere in the network- Connection is rejected if QoS requirements are not met
NetworkAlgorithm Server
LocationConnections
29.09.04 Dept. of Information Technology - Ghent University 10
Optimal Algorithms
Input:
- Topology
- Link delay
- Link bw
- Demands
ILP Formulation:
Constraints:
- Connectivity Constraints
- Server Presence Constraints
- QoS Constraints
Variables:
- Connection Supported
- Server Present
- Link Used for a connection
Objective Function:
Maximize # connections,
Minimize # servers
Output:
- Connections
supported
- Servers placed
- Paths followed
29.09.04 Dept. of Information Technology - Ghent University 11
Heuristics
• BP heuristic: locations that are on optimal paths
• MSPP heuristic: locations that are on routes that meet connection requirements and that require a minimal number of overlay servers
• Random Placement
29.09.04 Dept. of Information Technology - Ghent University 12
EvaluationConnectionNetwork
Link Bandwidth:
U[10,40] Mbits/sec
Link Delay:
U[10,80] milliseconds
` `
Bandwidth:
5 Mbit/sec
Max Delay:
Min. Delay * 115%
End points:
Chosen at random
29.09.04 Dept. of Information Technology - Ghent University 13
Optimal Unicast Algorithm
50556065707580859095
100
1 5 9 13 17 21# Requested Connections
Acc
epta
nce
Rat
e (%
)
OverlayIP
Higher Acceptance Rate with Overlay Network
Acceptance Rate Decreases as network gets congested
29.09.04 Dept. of Information Technology - Ghent University 14
Number Of Servers
0
0,5
1
1,5
2
2,5
3
1 5 9 13 17 21
# Requested Connections
#Ser
vers
Req
uire
d
More Servers Have to be Placed to support more connections…
29.09.04 Dept. of Information Technology - Ghent University 15
5 Servers Placed, Heuristics
50556065707580859095
100
3 13 23 33 43 53 63 73 83
# Requested Connections
Acc
epta
nce
Rat
e (%
)
MSPPBPRandomIP
Random placement performs worse
Overlay will have increased acceptance rateConvergence as Network gets Congested
29.09.04 Dept. of Information Technology - Ghent University 16
Dependence on Number of Servers
50
55
60
65
70
75
80
85
90
95
100
3 13 23 33 43 53 63 73 83
# Requested Connections
Acc
epta
nce
Rat
e (%
)
MSPP (5 Servers)MSPP (4 Servers)MSPP (3 Servers)MSPP (2 Servers)MSPP (1 Server)IP
More Servers = Higher Acceptance Rate
Convergence as Network gets Congested
29.09.04 Dept. of Information Technology - Ghent University 17
Larger Topology (5 servers placed)
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1 5 9 13 17 21 25 29
# Requested Connections
Acc
epta
nce
Rat
e (%
)
MSPPBPRandomIP
29.09.04 Dept. of Information Technology - Ghent University 18
Multicast Results: All algorithms
0102030405060708090
100
1 5 9 13 17
# Requested Connections
Acc
epta
nce
Rat
e (%
)
ILP MSPPBP RandomIP-Multicast IP-UnicastPredicted ILP
Increased Acceptance Rate
Random Placement Outperformed
29.09.04 Dept. of Information Technology - Ghent University 19
Multicast Results: Number of Servers
0102030405060708090
100
3 7 11 15 19
# Requested Connections
Acc
epta
nce
Rat
e (%
)
MSPP (5 Servers) MSPP (4 Servers)MSPP (3 Servers) MSPP (2 Servers)MSPP (1 Server) IP-Unicast
More Servers = Higher Acceptance Rate
29.09.04 Dept. of Information Technology - Ghent University 20
Conclusion
• Overlay network as a way to introduce QoS…- Better QoS- More connections supported
(more than 20% for 10 connections in 16 node topology)
• Placement is not trivial (Random placement is outperformed significantly)
• More Servers results in higher acceptance rate• Analogous conclusions for multi- and unicast case and
for different sizes of the test network
29.09.04 Dept. of Information Technology - Ghent University 21
Questions?
Questions?
