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GroCoca: Group-based Peer-to-Peer Cooperative Caching in Mobile Environment

Authors: Chi-Yin Chow, Hong Va Leong, and Alvin T. S. ChanPresent: I-Wei Ting

IEEE Journal on Selected Areas in Communications, Vol. 25, NO. 1, January 2007

Department of Computer Science and Information Engineering National Cheng Kung University, Taiwan R.O.C.

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Mobile P2P environments

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Mobile P2P environments

Local Cache Hit

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Mobile P2P environments

Global Cache Hit

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Mobile P2P environments

Global Cache Miss

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Related works Cooperative CAching scheme (COCA)

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Similarity Measurement in Mobility Patterns

mobile host i,j weight

m0

m0

mj

mi

Two-dimensional weighted averageDistance matrix (WADM)

Stored in MSS

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Similarity Measurement in Data Access Patterns

Two-dimensional access similarity matrix (ASM)

Stored in MSS

m0

m0

mj

mi

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How to find Tightly-Coupled Group (TCG)?

MSS

AB

C

D

Case 1: data request

Case 2: update its location

Check two tables

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11

12

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How to reduce the unnecessary search process?

Data signature Cache signature Peer signature Search signature

MSS

B CD

A

? ?

?

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Bloom Filter

1

1

1

1

1

bits

h1( )h2( )h3( )h4( )…hk( )

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Data signature

0

1

0

1

1

0

1

0

0

1

bits

h1( )h2( )h3( )h4( )…hk( )

URL, Keyword,Integral identifierAttribute value

Data signature

Data object:

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Peer signature

1

1

0

1

1

1

1

1

0

1

1

1

0

1

1

0

1

1

0

1

1

0

0

0

1

1

1

0

0

1

superimpose

Cache sig. of peer A Cache sig. of peer B Peer signature

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Search signature When an MH encounters a local cache miss, it generates a data signat

ure for the required data item, called search signature.

It also computes a peer signature by superimposing the peers’ cache signatures maintained in the local cache.

The data signature is then compared with the peer signature by performing a bitwise AND operation on them.

If the result is zero, it indicates that no peer caches the required data item, so the MH bypasses the Peer Cache layer and requests the data item from the MSS.

If the result is the same as the search signature, the neighboring peers are likely to cache the data item, so the MH broadcasts the request to them.

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Cache exchange protocol

MSS

A

B

Cache Sig. Request

Cache Sig. Reply

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Cooperative cache management

Local cache miss Search signature is true

Send request to its peer (If global cache hit)

• From TCG member

• Not cache and update the TTL (Time-To-Live)

• From Non-TCG member

• Cache and update the TTL

Search signature is false

Send request to MSS

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Client Disconnection Handling Protocol

Each MH maintains a list, OutstandSigList, to record members not yet turned in their cache signatures.

MSS

AB

12

34

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Average latency under different cache size

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Server request ratio under different cache size

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Global cache ratio under different cache size

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Power consumption under different cache size