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Study on Adaptation of CDN Request-Routing

to Scalable 　 Conference System

Toshiyuki KAWASAKI* 　　 Koji OKAMURA*** Graduate School of Information Science and

Electrical Engineering (ISEE), Kyushu University** Computing and Communications Center,

Kyushu University

Aug 28,2003

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１． Background

２． Goal and approach

３． Evaluation

４． Consideration

５． Conclusion

Contents

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• H.323 conference system is popular– Remote conference

– Remote medical care

– Remote education

• H.323– Standard of video conference

on IP networks

• MCU（Multipoint Control Unit）– Enable multipoint conference

– Mixing the video and audio streams

Host A Host B

Host A Host B

Host C Host D

１． Background － H.323 conference system

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1 ． Background － Overload of MCU

• Problem of H.323 multipoint conference systemWhen hosts (participants) increase ・・・

MCU may become overload　→ load sharing is needed MCU

←overload

• Existing method of load sharing– Distribute the load to several MCUs

When more hosts increase　 → MCUs may become overload after all

Lack of scalability for the number of hosts

←overload

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Proposal method • Don’t use any MCUs

• Hosts connect with each other

• Hosts play a role of MCUs– Hosts distribute load – increase of hosts 　　

　 　→ increase of MCUs

２． Goal and approach － Load Sharing by Hosts

Obtain scalability for the number of hosts

Existing method

Proposal method

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• Problem of the multipoint conference system without MCU– Each host should select the host which it connects with.

• Existing method– ALM ( Application Level Multicast)

• Multicast on logical network (overlay network)• Hosts play the role of multicast router on logical network.

２． Goal and approach － Application Level Multicast

Lobby server

New host

Entry

IP address list

Make links

AS1AS2

Make high cost links between ASs

Overlay network

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２． Goal and approach － ORIO and CDN Request Routing

• Proposal method ORIO（ Optimal Routing Inter Organization）– Using CDN Request-Routing

• CDN （ Content Delivery Network ）– Network of severs to distribute content efficiently– Load sharing by using many surrogates

• Request Routing– Select the optimal surrogate for the clients– Tell clients their optimal surrogates

Origin server

surrogate surrogatesurrogate surrogate

client clientclientclientclientclient

Redirection server

contents

request

select

notify

notifyDeliverycontents

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• Process of participation at ORIO– Request Routing using DNS

• Prepare DNS to redirect requests.• New participants write the certain host name for participation into the packets destination address.• DNS tell the optimal hosts IP address at name resolution.

　→ Connected with its optimal host automatically

２． Goal and approach － Request routing using DNS

New host

DNS server

conference.ac.jp （ host name ）133.x.x.xxx

133.x.x.xxx （ IP address ）

select

connect

AS 1

AS 3

AS 2

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３． Evaluation － Evaluation Environment

• Evaluation standard– Maximum network load

• Comparing with the method using ALM

• Experimental Network– SuperSINET– The number of ASs is １８– The number of hosts per ASs is 64

• Environment– Speakers※ 　１、 Hosts※ １～２

５６• Change distribution of hosts• Change the number of active AS

– Speakers 　１～１２８、 Hosts１２８

Experimental Network （ SuperSINET ）

Simulation based evaluation using network simulator “NS２”

※Speakers = the number of source hosts, hosts = the number of destination hosts

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３． Evaluation － simulation under the 3 distribution of hosts

• Speakers １ , Hosts １～２５６– Distribute hosts to 6 ASs– Measure under the 3 distrib

ution of hosts• Concentrate at 1 area• Concentrate at 2 areas• Concentrate at 3 areas

• Result– the increase amount of network load is decreasing as the number

of participants increase

　　→ Scalability to the number of hosts.

– ORIO is better than ALM at load sharing

Maximum use of bandwidth (kbps)

The number of hosts

1 area (ORIO) 2 area (ORIO)

3 area (ORIO)

1 area (ALM)

2 area (ALM)

3 area (ALM)

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3.Evaluation － Change the number of ASs

• Speakers1,Hosts １～２５６– Changing the number of A

Ss which hosts belong to• Select hosts from 6 ASs

• Select hosts from 12 ASs

• Select hosts from 18 ASs

• Result– ORIO is better than ALM at load sharing

– ORIO’s efficiency of load sharing become worse when the number of AS is small ( hosts per AS is big).

　　→　 Policy of routing within AS should be improved.

The number of hosts

Maximum use of bandwidth (kbps)

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3.Evaluation － Speakers

• Change the number of Speakers 　　　　　　　　　　　　　　　　　　 Speakers １～１２８　　　　Hosts １２８– Select hosts randomly

• Result– Network load increase linearly at both ORIO and ALM.

　→ Don’t provide scalability in this case.

　　　 The number of speakers should be limited.

Maximum use of bandwidth (Mbps)

The number of speakers

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• ORIO provide more efficient load sharing than ALM

• Possible reason・ ALM uses logical network for routing,

but ORIO doesn’t use it.

In ALM, there are two restrictions in receiving streams

• Receivable only from its neighbors on the overlay network

• Receivable only from its upstream hosts

４． Consideration － Efficiency of ORIO and restriction of ALM

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• Receivable only from its neighbors on the overlay network

• Receivable only from its upstream hosts→ Promote the concentration of the load

４． Consideration － restriction of ALM

Router Router

Host B

Concentrate the loadConcentrate the load

Host B

Speaker Speaker

Host A Host A

Host C Host C

Not neighbor

Can’t use thislink though it is useful

router router

Host B

Concentrate the loadConcentrate the load

Host B

speaker speaker

Host A Host A

Host C Host C

B is not A’s upstream host(B’s delay is bigger than A)

Can’t use thislink though it is useful

delay5ms

delay10ms

delay7ms

delay7ms

delay10ms

delay5ms

delay9ms

delay9ms

delay7ms

delay7ms

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• Existing multipoint conference system– MCU easily become overload

• Method of load sharing– Any MCU is not used– Hosts play a role of MCUs instead

• The system which tells the hosts their connection partner is required– CDN Request-Routing

• Result– Prove the scalability of ORIO

• Future work– Adding the function which support the hosts exi

ting process– Improve the policy of routing within AS

５． Conclusion