Download An Overlay Scheme for Streaming Media Distribution

An Overlay Scheme for
Streaming Media Distribution
Using Minimum Spanning
Tree Properties
Journal of Internet Technology Volume
5(2004) No.4
Reporter：Wei-Zhi Chen
1
Outline
 Introduction
 Problem description-background work
 Architecture overview
 Simulation
 Conclusion
2
Introduction
 Real-time content delivery requires high
bandwidth availability and minimum jitter in
order to enhance user perceived quality.
 The primary goal of the simulation model
propose is to demonstrate the effectiveness
of the overlay scheme introduced for a large
number of users.
3
Problem description-background work
 As point to point connections lead to
excessive bandwidth consumption and server
overload, the multipoint delivery model seems
quite promising.
 Three major issues.



Group membership
Routing
Packet duplication
4
Problem description-background work
 Group membership
 A control protocol for the construction of
groups.
 An authentication mechanism for the potential
members of each group.
 Routing
 Construction and maintenance of the
distribution trees.
 Elimination of redundant traffic on the network.
 Packet duplication
5
Problem description-background work
 IP multicast


An architecture for multi-point packet delivery
at the network layer.
Suffer some problems



Scalability
Lack of effective access control polices.
No globally Inter-Domain multicast routing
protocol.
6
Problem description-background work
 Application layer multicast


Move functionality for multipoint data delivery
to the application layer for constructing overlay
network .
Deployment of overlay networks offers


Support different requirements
Better use of the network infrastructure without
need for changes.
7
Architecture overview
 Modules


NDM ( Network Distribution Manager)
SAS ( Streaming Access Servers )


The basic module of the architecture
At lowest level , a SAS is just a proxy : it forwards
incoming media streams to one or more clients.
8
The distribution architecture
9
Architecture overview
 Connection point decision
weightvalue  10 2  p2  101  p1  100  p0 …(1)
 Hierarchy level
10
Architecture overview
 Proximity


RTT( Round Trip Time )
WatchdogTimer is the maximum time allowed
for the experiment .
 Clients Served
Cl  10(1  clients / all _ cilents )
…(4)
11
Simulation
 Overlay tree construction

In order to construct an efficient overlay tree,
each SAS reports its existence to the NDM
node.
 G(V,E) V: the number of SAS nodes
E=N * (N-1)/2 edges
12
Simulation
 Distributed mini spanning tree algorithm


In the first phase, messages are exchanged
between all SAS nodes and measuring the
Round Trip Time( RTT ) between them.
In the second phase each SAS starts forming
a tree. At the end of distribution algorithm we
have a minimum weight spanning tree.
13
Simulation
 Scenario 1 ( client only )


SASs are assigned to transit nodes, and the
clients use only their knowledge about client
load on each SAS.
Stress which is an intuitive metric used in
overlay topologies to evaluate the quality of
the overlay tree built.
14
Simulation
15
Simulation( scenario 1)
16
Simulation( scenario 1)
17
Simulation( scenario 1)
18
Simulation
 Scenario 2 ( ping only )


We evaluate the system behavior using as
SAS selection criterion only the proximity
parameter.
RAP( Relative Average Delay Penalty ) is
reduced by 15%, but max stress is augment
from 25% to 40%
19
Simulation( scenario 2)
20
Simulation( scenario 2)
21
Simulation( scenario 2)
22
Simulation
 Scenario 3 ( formula only )



Merging ping information, client load and
hierarchy level.
RAP is reduced by 15%
Max stress is bigger than scenario 1 but is
smaller than scenario 2.
23
Simulation( scenario 3)
24
Simulation( scenario 3)
25
Conclusions
 RAP and average stress are reduced, since
the clients are connected to nearby SAS.
 In future plan, a more sophisticated
algorithm for SAS selection.
26