Improve Contents Synchronous Situation of CDN using Partial Mirror Server

1
Improve Contents Synchronous Situation of CDN
using Partial Mirror Server

• Muneyuki Iwasa
• Graduate School of Information Science, Kyushu
  Sangyo University

2
Outline

• 1.Background
• 2.Purpose of this study
• 3.Proposal
• 4.Related work
• 5.Future works
• 6.Conclusion

3
Background load balancing

• Client-server model has a problem that over load
  of servers and networks
• ?Some servers can not provide their service
  because of the over load
• Load balancing technology
• Multiple servers
• Servers are distributed in wide area

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Background -CDN

• CDN(Contents Delivery Network)
• Contents are delivered by multiple surrogate
  servers
• Video streaming services, Software distribution
  services
• Mirror server
• Deliver contents to users

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Background -CDN
Enlarged size
copies and synchronize
copies all contents
delivers contents
synchronous situation becomes worse
Does not hold contents
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Purpose of this study

• Problem
• Mirror server does not hold contents at CDN

Improve contents synchronous situation of CDN
using partial mirror server
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Define some Term

• Original contents
• the whole contents that an origin of distribution
  offers
• Package
• a part of original contents
• Mirror
• doing synchronization of contents
• Full mirror
• to mirror whole original contents
• Server selection
• to select the best server from mirror servers

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Partial Mirror Server

• has a small part of original contents
• A unit of mirroring is a package
• reduction mirroring contents

The synchronous situation can improve
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Conventional CDN Model
Each mirror server does full mirror
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Proposal Model
Each partial mirror servers may do mirror par
package
connect to partial mirror server holding contents
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Navigation Method to Partial Mirror Server

• Connect to partial mirror server holding contents
  that a user wants
• Use DNS
• Scalable
• Convenience for users

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Navigation using DNS

• Hostname including the package name
• include the name of package which the mirror
  server holds
• Hostname list must be announced that the user can
  use
• make links to each mirror servers on some Web site

A user can connect to one of the partial mirror
server which holds contents that the user needed
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Example(1/4) ? conventional

• Assume mirror servers of FreeBSD
• FreeBSDs packages
• source code
• ISO image for installation
• compiled applications
• Hostname
• www.example.ne.jp
• The hostname of the mirror server which has whole
  contents of FreeBSD

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Example(2/4) ? conventional
source code ISO image applications
source code ISO image applications
source code ISO image applications
source code ISO image applications
www.example.ne.jp
www.example.ne.jp
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Example(3/4) ? proposal

• Want source code
• source.freebsd.example.ne.jp has the source code
  of FreeBSD
• Want ISO image for installation
• iso.frebsd.example.ne.jp has the ISO image for
  installation of FreeBSD
• Want compiled application
• application.freebsd.example.ne.jp has the
  compiled application of FreeBSD

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Example(4/4) ? proposal
source code ISO image applications
ISO image
applications
source code ISO image
The host has ISO image for installation
The host has compiled application
iso.frebsd.example.ne.jp
application.frebsd.example.ne.jp
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Advantage of this Method

• Easy to integrate with the existing system
• Base on DNS
• Practical and convenient
• Simple hostname
• Integrate with the existing server selection
  system
• Existing server selection methods
• Selection by routing information
• Selection by the synchronous state of contents

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Disadvatage of this Method

• Management of hostnames
• Whenever the number of mirror packages increases,
  the host names increases
• Consider about link site

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Related work

• Server selection technique using DNS to the
  server group of a partial mirror
• master thesis of the Kochi University of
  Technology in 2003
• Uses s hostname including the directory
  information of file and file name that needed
• Example hostname
• README.Audio.GNUinfo.GNU.pub.server.ring
• gcc-g---2.95.tar.gz.gcc-2.95.gcc.GNU.pub.ring.kiku
  ken.org
• Problem of this technique
• Complexity of hostname
• Not practical
• Hard to integrate with the existing system

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Future Work

• Implement the prototype system of the proposal
  method
• Use Tenbin for prototype system
• Do some experiment in local environment
• Apply the proposal method to the Ring Server
  System
• Do some experiments in a real environment
• Study about fusion of this method and the other
  existing server selection method

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Conclusion

• Background
• CDN is used widely
• Contents synchronous situation of the mirror
  server turns worse with the enlargement of
  contents is expected in future
• Purpose of this study
• Improve the contents synchronous situation of CDN
• Develop the operation technique of the partial
  mirror server which is practical conventionally
• Improvement of contents synchronous situation is
  tried by providing partial mirror service of CDN
  for user
• Future work
• Implement the prototype system of the proposal
  method and do some experiment

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Tenbin

• DNS based Server Selection Mechanism
• DNS name resolution as selection policy
• Example of a selection policy
• data-transfer rate
• round-trip-time
• load state of server
• Easy to integrate with the existing system

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Ring Server

• One of famous and largest distributed file server
  in Japan
• Collects free software and provides download
  service
• More than 20 servers distributed in wide area
• Server Selection Mechanisms
• round robin, by routing information
• Each mirror servers are managed by each
  organization voluntary
• Contents Synchronous Problem