3. 404 Introduction Not Found.
●
「Webページの消失」をいかに防ぐか?
ex. Internet Archive (http://www.archive.org)
Internetをクローラにより自動巡回
-> 完全ではない
3
4. The number of web site
Netcraft「July 2011 Web Server Survay」
http://news.netcraft.com/archives/2011/07/08/july-2011-web-server-survey.html
They got responses from 357,292,065 sites!
4
5. The number of web site
Internetの世界は広大
-> ページは非常に高速に増加
-> 自動巡回だけでは収集しきれない
老舗レンタルサーバの撤退
Yahoo! GeoCities (http://www.geocities.com) 2009/10/24閉鎖
Infoseek isweb (http://isweb.www.infoseek.co.jp)
2010/11/01無料サーバ閉鎖、2012/05/01完全閉鎖
OTD BBS (http://www.otd.co.jp) 2011/06/30閉鎖
...
「Webページの消失」≒「Webページが持つ情報の消失」
-> Webページは遺すべき貴重な遺産
5
6. What is Peer to Peer(P2P)?
●
個々のピア(ノード)が対等
●
(ピュアP2P型では)中央サーバが存在しない
-> システムの大規模な拡張に耐えられる(scalability)
-> システムの障害に強い
6
14. Find and download file
Winny network
e
h
b d
g
a f
c
Query:
I want to get ”butterfly.jpg”.
If you know who have this file, please tell me their name:
Name: ________________________________________
Name: ________________________________________
Name: ________________________________________
Counter: 0
14
15. Find and download file
Winny network
e
h
b d
g
a f
c
Query:
I want to get ”butterfly.jpg”.
If you know who have this file, please tell me their name:
Name: ________________________________________
Name: ________________________________________
Name: ________________________________________
Counter: 0
15
16. Find and download file
Winny network
e
h
b: I don't know... d: I don't know...
g
a f
c: I don't know...
Query:
I want to get ”butterfly.jpg”.
If you know who have this file, please tell me their name:
Name: ________________________________________
Name: ________________________________________
Name: ________________________________________
Counter: 1
16
17. Find and download file
Winny network
e: I don't know...
h
b d
g: I know!
a f: I don't know...
c
Query:
I want to get ”butterfly.jpg”.
If you know who have this file, please tell me their name:
Name: _h______________________________________
Name: ________________________________________
Name: ________________________________________
Counter: 2
17
18. Find and download file
Winny network
Connect!
e
Transfer file!
h
b d
g
a f
c
Query:
I want to get ”butterfly.jpg”.
If you know who have this file, please tell me their name:
Name: _h______________________________________
Name: ________________________________________
Name: ________________________________________
Counter: 2
18