maximizing user gain in multi-flow multicast streaming on overlay networks

Higashino Lab.Higashino Lab.Higashino Lab.Higashino Lab.

Maximizing User Gain Maximizing User Gain in Multi-flow Multicast in Multi-flow Multicast Streaming on Overlay Streaming on Overlay NetworksNetworks

Y.Nakamura, H.Yamaguchi and T.Higashino

Graduate School of Information Science and Technology,

Osaka University

FMUIT'06FMUIT'069 May 20069 May 2006 22


Research GoalResearch Goal Realizing Multi-party video conferencing systems

Many-to-many multicast application which consists of hundreds of users

User hosts exchange multiple video streams in real-time

Efficient use of bandwidth is required

Internet


Higashino Lab.Higashino Lab.Higashino Lab.Higashino Lab.Application Layer Multicast Application Layer Multicast (ALM)(ALM) ALM is multicast on overlay networks

End users act as multicast routers Does not require special hardware such as IP

multicast enable routers Application-specific routing protocols can be

designed More efficient than Unicast because a sender

does not need to send data to all receivers

Unicast A

B

C

S

D

A

B

C

S

D

ALM



Related worksRelated works Overcast ， CAN ， RMX

aiming at an efficient delivery of video stream in a large-scale group

HBM aiming at overlay network construction for the mobile terminal

Narada ， ALMI ， Yoid aiming at delivery of single video stream in small-scale group also target the conference application

Few research to deliver the two or more streams simultaneously and continuously for the video conferencing



Issues to be consideredIssues to be considered Each video uses some amount of bandwidth on overlay

networks→In delivering multiple video streams, they compete for bandwidth on overlay links

Users may have priority requirements to video streamse.g. users may prefer the speaker’s video than audience’s

video

Internet



Emma/QoSEmma/QoS New ALM protocol for multi-party communication systems

Users construct overlay network Each user sends its own video continuously and receives some of

other user hosts’ video streams on overlay networks Each user filters and adjusts the quality of streams and make

the space for a new requested stream

InternetOverlay Network

Red

Red



Overlay Network

New user joins the session by constructing the overlay link Measuring the delay with another user, and constructing the

overlay link with the number of appropriate users When the link is constructed, the link capacity (number of

streams that can be delivered) is negotiated and decided The participating users enhance the delivery routing tree The routing tree of the source user is constructed with the

shortest path tree by flooding

Overlay network Overlay network constructionconstruction

Underlying Network

D

A

B

E

C



Leaving failure managementLeaving failure management Many users frequently leave on

the overlay network Descendant node cannot recei

ve the stream We need guarantee the continu

ance delivery of the stream Need to make the stream ha

d delivered through the left node can immediately delivered from another node again

Each node knows the nodes can deliver the stream by periodical message

If neighbor node leaves, the node is immediately reconnected to one of them


Higashino Lab.Higashino Lab.Higashino Lab.Higashino Lab.Loss/Gain-based rate Loss/Gain-based rate adaptationadaptation Problem

Because of the restriction and a decrease of the link capacity, all requests of stream cannot be accepted

Solutions Simple way

When the stream cannot be delivered, all requests of the stream are not accepted

Narada When it is impossible to deliver the stream in the received rate in

each user, user reduces the rate of the stream so that it can be delivered

Emma/QoS Each user decides that it increases / reduces the rate of the stream

according to the value of the gain obtained by receiving the requested stream and cutting the rate of the delivering stream

Requests are accepted as many as possible



User gain functionUser gain function Every user defines for each stream

User gain is added when a unit of bandwidth is added to current receiving stream

We use utility function This function shows the priority of the us

er for each unit of bandwidthe.g. In the typical streaming, utility tends to

increase suddenly by the rate of a at least necessary quality, and to increase gradually in a rate increase after that

User gain is calculated by the difference of the following two values

Value on utility function of k-1 units Value on utility function of added k-th uni

t k denotes certain amount of bandwidthon the overlay links

Utility function

k-1 k

｝ User gain

Linear approximation



Protocol operationsProtocol operations Every node periodically

sends messages about user gain (negative gain) for each stream

Negative gain : Value of user gain lost in descendant nodes when a unit is deprived from delivering stream

Request message is transmitted calculating the optimal allocation of each unit

from user gain and a negative gain that increases by the request acceptance when requesting it

As a result, each user can know and decide which stream should be reduced

B

# of units of links is 3 ： Streams



Performance evaluationsPerformance evaluations We have

implemented a simulator of Emma/QoS simulated in a typical video conferencing scenario compared with Narada (one of the most popular ALMs)

We examined the following items Link stress : the number of copies of a single packet

delivered on a physical link Path stretch : the ratio of the sum of unicast hops of the

overlay links between two nodes to that on the shortest path on the underlying physical network

User satisfaction ratio : the ratio of the sum of user gain obtained by each node to that of user gains requested by the node

Variation of user gain



50

1 84

# of

use

rs

0

Emma/QoSNarada

1000

01 10 100

Emma/QoSNarada

Unicast

# of

phy

sica

l lin

ks

Link stress and path stretchLink stress and path stretch Compare with the performance of Narada

Narada assumes the delay between hosts to be optimizing metric and constructs mesh-like overlay network

On this overlay network Narada constructs shortest path tree Emma/QoS has better values than unicast

Maximum link stress is about 10th of the unicast The performance of Narada is not so quite different from that of Emm

a/QoS

Link Stress Path Stretch



0

50

100

150

200

250

0 0.2 0.45 0.6 0.8 0.88 0.89 0.9 1

satisfaction ratio

# of

req

uest

s

Emma/ QoSNaradaFCFS

Distribution of users’ Distribution of users’ satisfactionsatisfaction The ratio of the total gain of accepted requests to

that of all requests Requests not accepted at all is much smaller than

Narada and FCFS (First Come First Serve method) The admission control mechanism of Emma/QoS is useful

to video-conference systems



45

01 31

0

800Emma/QoSNarada

# of users

gain

(av

g.)

15

# of

use

rs

time

Variation of user gainVariation of user gain Emma/QoS achieves higher user gain than

Narada when users join/leave during the session when users’ preferences to stream s are

changed during the session



ConclusionConclusion We have proposed new ALM protocol called

Emma/QoS To avoid resource competition, we use utility-

based admission control in decentralized way From the experimental results

Higher satisfaction of users than a simple method Even though some users leave from or join to a

session, users’ satisfaction is kept high

maximizing user gain in multi-flow multicast streaming on overlay networks

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