Embed Size (px)
Citation preview
1
COACS: A Cooperative and AdaptiveCaching System for MANETs
Hassan Artail, Member, IEEE, Haidar Safa, Member, IEEE, Khaleel Mershad,Zahy Abou-Atme, Student Member, IEEE, and Nabeel Sulieman, Student Member, IEEE
IEEE TRANSACTIONS ON MOBILE COMPUTING, VOL. 7, NO. 8, AUGUST 2008
Present: I-Wei TingDate: Sep. 17, 2008
Manuscript received 8 June 2006; revised 12 Mar. 2007; accepted 23 Jan.2008; published online 28 Jan. 2008.
2
Outline Related work
Data discovery under ICP (Internet Cache Protocol)
Proposed protocol Election of Query Nodes (QN, Proxy) in MANETs
Life time, Battery, Bandwidth, Memory Data discovery phase Management of the QN and Caching Node
Performance Evaluation Analysis
3
Internet Cache Protocol The ICP protocol was designed to be lightweight in order to minimize r
ound-trip time between caches. It is intended for unreliable but quick connections, using short time-outs before a cache starts to retrieve an object on its own. UDP is commonly used as delivery protocol.
The ICP protocol is described in RFC 2186, its application to hierarchical web caching in RFC 2187.
Web proxies that support ICP include: Squid cache Microsoft Proxy Cisco Content Engine ProxySG
4
Internet Cache Protocol (1/6)
A
BC D
FE G
S
sibling
sibling
Server
Client
How to find a data object (web page)?
Case 1
5
Internet Cache Protocol (2/6)
A
BC D
FE G
S
sibling
sibling
Server
Client
Case 2
1 2
6
Internet Cache Protocol (3/6)
A
BC D
FE G
S
sibling
sibling
Server
Client
Case 3
1
2 2
3
4
7
Internet Cache Protocol (4/6)
A
BC D
FE G
S
sibling
sibling
Server
Client
Case 4
1
2 2
3 4
5
8
Internet Cache Protocol (5/6)
A
BC D
FE G
S
sibling
sibling
Server
Client
Case 5
1
2 2
3
4 4
5
6
7
9
Internet Cache Protocol (6/6)
A
BC D
FE G
S
sibling
sibling
Server
Client
Case 6
1
2 2
3
4 4
5 6
7
8
10
Property Comparison
Internet MANETs
Entity Specific nodes
(Proxy server)
Any nodes
Location Fixed Mobility
Leave/Join Not frequent Frequent
Protocol Overhead Less Much
11
Election of Query Nodes (1/6)
A
BC D
FE G
S
RN:Requesting Node
Initial: No QD (Query Directory; Proxy server)
Each RN only cache its requested data object. Then, query index is sent to the nearest QD
12
Election of Query Nodes (2/6)
A
BC D
FE G
S
RN:Requesting Node
Find out the first QD (Query Directory; Proxy server)
COACS Score Packet (CSP)
Traverse all nodes in the networks sequentially(need to adopt routing table, DSDV)
13
Election of Query Nodes (3/6)
A
BC D
FE G
S
RN:Requesting Node
Send QD Assignment PacketTo the E (highest score)
14
Election of Query Nodes (4/6)
A
BC D
FE G
S
RN:Requesting Node
Find out Other QDs based on the # of QDs and score
QD1
15
Election of Query Nodes (5/6)
A
BC D
FE G
S
RN:Requesting Node
QD1QD1 find other QDs(ex:3) high. score
ACK:OK
ACK:OK
16
Election of Query Nodes (6/6)
QD1 E
QD2 S
QD3 D
A
BC D
FE G
S
QD1
QD Information packet
Broadcast QD list to all nodes
17
Data discovery phase
QD1 E
QD2 S
QD3 D
A
BC D
FE G
RN:Requesting Node
K
S
18
Case 1: QD E has an entry for the query
A
BC D
FE G
RN:Requesting Node
K
S
19
Case 2: QD forwards the request to the nearest QD
QD1 E
QD2 S
QD3 D
QD1 E
QD2 S
QD3 D
A
BC D
FE G
S
RN:Requesting Node
QD1 E
QD2 S
QD3 D
K
20
Management of QD and CN A new QD is added to the system when a query needs to be cached b
ut no QD agreed to cache it. The last QD to receive the caching request will initiate a CSP
When a QD receives a query and related CN is offline Delete associated entries and forward the query to the original serv
er
CN offline QD detect and remove related entries
Lookup routing table (proactive routing)QD ack CN periodically (on-demand routing)
QD offline First node detect
Run “add a new QD”
21
Packet types
22
Comments Node join
The available caching space can not be utilized efficiently
23
Simulation parameters1000m*1000m
Nodes: 100Cache size: 200KbTrans. Range: 100mDSDV routing protocolRandom Waypoint mobility modelSpeed:0.01~2, 10~20 m/sQuery interval: 10 seconds
DB: 10,000 items, 10Kb/item
Number of QD nodes: 7
24
25
26
Analysis
1. Expected Number of Hops between Two Nodes E[H] = 0.521 * (a/r)
expected minimum number of hops between any two nodes in the network,
Ex: rectangular topology a=1000m2, r=250m, 0.521*4=2.084
2. Expected Number of Hops within the System of Query Directories
27
Analysis 3. Expected Number of Hops to the External Network
4. Query Directory Access and Delay
Tin: the delay for transmitting packets between nodes inside the networkTout: the delay for accessing a node outside the network (data source)
28
Analysis
5. Determining the Maximum Number of Query Directories
29
Analysis
6. Load Balancing on Query Directories
