109 Peer-to-Peer Peer-to-Peer (P2P) [5]. P2P P2P P2P P2P [10] [11], [12] [4] For an efficient contents sharing by a lot of network users, various kind

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1 109 Peer-to-Peer Peer-to-Peer (P2P) [5]. P2P P2P P2P P2P [10] [11], [12] [4] For an efficient contents sharing by a lot of network users, various kinds of content replication strategies in pure Peer-to-Peer (P2P) networks have been researched recently[5]. Although the total amount of consumed storage capacity tends to become enlarged in P2P information sharing systems in general, reducing storage resource consumption is very important for diminishing the total cost of contents sharing especially in hybrid P2P, because an index server can readily identify the shared content items locations and that is why the network load for contents searching is much lower than that in pure P2P networks and storage cost sometimes becomes dominant part of the total cost. From this point of view, we have proposed some effective content replication strategies in hybrid P2P[10] [11], however, the effectiveness of them in the case where the capacity of each replica varies by its original content item has not investigated sufficiently. There existed a problem of users convenience degradation as well caused by unavoidable eliminations of some content items in the network because there is a limitation of the peers storage capacities in reality. In order to solve the problem, we also have proposed an improved scheme which repeats content relocations[12] [4], however, the effectiveness of the relocations has not clearly been verified yet. Accordingly in this paper, we evaluate the replication scheme which tries to relocate overflowed content items to other peers repeatedly in the condition that each capacity of content item varies, and at the same time, we introduce a mechanism to control the number of times of content relocations and discuss the effectiveness of the wasted processes reduction. Efficient Shared Content Replication-Relocation Strategy in Hybrid Peer-to-Peer Networks. Shinji Sugawara, Yusuke Inoue, Yutaka Ishibashi,, Graduate School of Engineering, Nagoya Institute of Technology. Katsunori Yamaoka,, Graduate School of Engineering, Tokyo Institute of Technology., Vol.29, No.2 (2012),pp [ ] Peer-to-Peer (P2P) [15] [8][6][7]. P2P

2 110 P2P ( ) () ( ) P2P P2P 1 P2P [16][13][14][9]. 2 P2P P2P 1 P2P 2 P2P [4] 5. Related Work P2P CDN [4][10][11][12] [3]. [4] P2P

3 Vol. 29 No. 2 May (1) (2) P2P ( ) (3) ( ) (4) (5) (6) () (7) 1 (8) 3 (i) A B A (ii) A B A (iii) I. ( ) II. III. ( ) P2P BA [2]

4 112 3 [4] (1) (iv)(e), (v) H th ( 1 ). N mov(> 0, ) 3 (1) (i) (ii) (iii) (ii) ( ) (v) 1 H th =2 2 (iii) (iv) (iii) ( ) (a) 1 (b) C (c) (a), (b) (d) C (e) (v) (v)

5 Vol. 29 No. 2 May N mov > 0 N mov 1 (v) N mov =0 < > ( ) 3 3 ( ) 4 (2) ( ) (i) (ii) C (iii) (i), (ii) C (iv) C < > 4 r P d P r A S(A) A B ( )

6 H(A, B)( H(A, A) =0) A a( ) R(A, a) i, j, C, C i S(A) S(A) S(P r) 1 i C C i C i (3) a H th NH a th, a Nref a Nref/N a H a th B Nref/N a H a th Nref/N a H a th 4. 1 E (1) E = W 1 E N + W 2 E S + W 3 E L (1) E N ( ) ( ) E S E L ( ), W 1,W 2,W 3 E P2P P2P

7 Vol. 29 No. 2 May BA ( 2, =1, =3) H th 1 3 B (0.1 ) BA BA [2] ( ), 2 Peer-to-Peer 2 ( µ =6.0, σ 2 =1) ( µ =6.0, σ 2 =4) ( 6.0) ( 2, =1, =3) LFU(Least Frequently Used)[1] N mov 1 2 λ req =0.5 λ mov =0.1 1 BA (Preferential Attachment)[2]

8 ( µ =3, σ 2 =1) 2 Zipf ( (2) ), 4 1 W 1 =10 W 2 =1 W 3 =10 2 W 1 =1 W 2 =10 W 3 =10 3 W 1 =10 W 2 =1 W 3 =50 4 W 1 =1 W 2 =10 W 3 = ( 1). 3 1 ( 2). (2) Zipf 1 (2) N 1 N k P k (1 k N) P k = k 1 (2) N n 1 n=1 1 W 1,W 2,W W 3 ( 1, 3), ( 2, 4) W 2 ( 1, 3) ( ) 3, [5] ERCT[12] [11]( ) I. () II. ERCT (Expanded RCT) H th ERCT (1) (2) (1) H th (1) (3) (4) (3)

9 Vol. 29 No. 2 May (4) III. () [11] N mov = N mov =1H th,b H th B 2 Zipf 6, E ERCT, H th 1 H th =1 ERCT, B 0.1 ERCT, 2 ERCT, ERCT ERCT ERCT H th ERCT 6 2 Zipf 1, Zipf 3, 4 LFU 3 1 1

10 Zipf (σ 2 =1) 1, Zipf 1, Zipf (σ 2 =4) 1, 2 4 ERCT, 2 2 ERCT, , 2 3, , , 2 2 Zipf ( 6) 3, Zipf 12 H th B N mov =1 2 N mov =1 2

11 Vol. 29 No. 2 May Zipf (N mov =0 ) (N mov =1) N mov [4] ( 2) [4] 2 Zipf ( 6) ( /0 ) 1 4 [4]

12 [4] , ,

Vol. 29 No. 2 May 2012 121 [ 1 ] Arlitt, M., Cherkasova, L., Illey, J., Friendrich, R. and Jin, T: Evaluating content management techniques for web proxy caches, in Proc.

Kurc, A. R., Raz, D. and Shavitt, Y.: Constrained mirror placement on the internet, IEEE Journal on Selected Areas in Communications, Vol. 20, No. 7(2002), pp. 1369 1382. [ 4 ] Inoue, Y., Sugawara, S.

455 465. [ 5 ] Lv, Q., Cao, P., Cohen, E., Li, K. and Shenker, S.: Search and replication in unstructured peer-topeer networks, in Proc.

13 Vol. 29 No. 2 May [ 1 ] Arlitt, M., Cherkasova, L., Illey, J., Friendrich, R. and Jin, T: Evaluating content management techniques for web proxy caches, in Proc. of the 2nd Workshop on Internet Server Performance, May [2] BarabásiA.andAlbert,R.: Emergenceofscaling in random networks, Science, (1999), pp [ 3 ] Cronin, E., Jamin, S., Jin, C. Kurc, A. R., Raz, D. and Shavitt, Y.: Constrained mirror placement on the internet, IEEE Journal on Selected Areas in Communications, Vol. 20, No. 7(2002), pp [ 4 ] Inoue, Y., Sugawara, S. and Ishibashi, Y.: Efficient content replication strategy for data sharing considering storage capacity restriction in hybrid Peer-to-Peer networks, IEICE Trans. Commun., Vol. E94-B, No. 2 (2011), pp [ 5 ] Lv, Q., Cao, P., Cohen, E., Li, K. and Shenker, S.: Search and replication in unstructured peer-topeer networks, in Proc. of 16th ACM International Conference on Supercomputing (ICS 02), [ 6 ] Ratnasamy, S., Francis, P., Handley, R. and Karp, R.: A scalable content-addressable network, in Proc. of the 2001 conference on applications, technologies, architectures, and protocols for computer communications, 2001, pp [ 7 ] Stoica, I., Morris, R., Kaashoek, M. F. and Balakrishnan, H.: Chord : A scalable peer-to-peer lookup service for internet applications, in Proc. of the Conference of the ACM Special Interest Group on Data Communication (SIGCOMM 01), 2001, pp [ 8 ] Sunaga, H., Hoshiai, T. Kamei, S. and Kimura, S.: Technical trends in P2P-based communications. IEICE Trans. Commun., Vol. E87-B, No. 10 (2004), pp [ 9 ] Yazti, D. Z., Kalogeraki, V. and Gunopulos, D.: Information retrieval techniques for peer-topeer networks, Computing in Science and Engineering, Vol. 6, No. 4 (2004), pp [10] : P2P No. B-7-17, [11] : P2P, No. IN , [12] : P2P, No. NS , [13] : P2P, No. IN , 2005, pp [14] : P2P, DEWS2004, No. 1-C-02, [15] :P2P Web, IIJ Internet Infrastructure Review, Vol. 8 (2010), pp [16] : Peer-to-Peer, Web IPSJ Symposium Series, Vol. 1, No. 16, 2005, pp IEEE, ACM NTT University of South Florida IEEE ACM

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P2P P2P Winny 3 P2P 15 20 P2P 1 P2P, i

26 P2P Reduction of search packets by sharing peer information in P2P communication 1175073 2015 2 27 P2P P2P Winny 3 P2P 15 20 P2P 1 P2P, i Abstract Reduction of search packets by sharing peer information