Study of Cluster Based Routing Protocol

in Mobile Ad-hoc Networks

Submitted By :Sudhansu Sekhar Dash

CSE-D, 8th Semester 1011012190

Guided By :Ms. Nibedita JagadevAssistant ProfessorDept. of CSE

Discussion OutlineIntroduction• What are MANETs ?• Features of MANETs

Routing ProtocolsCluster Based Routing Protocol• Concept of Clustering• Cluster Formation

Mechanisms in CBRP• Routing Process• Route Discovery• Route Reply• Route Error Detection• Local Route Repair

Features Of CBRPConclusionReferences

Introduction A Mobile Ad hoc Network (MANET) is a dynamically

changing, infrastructure less network of wireless and mobile nodes.

Features : Dynamic Topology : Nodes are mobile & are

independent of one another. Limited Bandwidth : Available bandwidth of the

links is limited, leading to multi-hop transmission of data.

Limited Power : Due to the lack of any fixed infrastructure, available power is low.

Applications: Military Operations Search & Rescue Disaster Mitigation

Routing ProtocolsRouting

Protocols in

MANETs

Proactive Routing

Reactive Routing

Hybrid Routing

Presence of Updated Routes in the Routing Table.

Ex : DSDV

On-demand Discovery of Routes.

Ex : AODV

Uses the features of both proactive & reactive routing

Ex : ZRP

Concept Of Clustering

Clustering is a process that divides the network into interconnected sub-structures called clusters.

Each cluster has a cluster-head as a coordinator within the sub-structure, which acts as a medium for data transfer between the nodes.

Cluster heads communicate with each other by using gateway nodes.

The Gateway node has two or more cluster heads as its neighbors or— when the clusters are disjoint—at least one cluster head and another gateway node.

Cluster Based Routing Protocol

Figure 1 : Different States in which a Node can Exist

Cluster Formation

• A node elects itself as the cluster head if it has the lowest/highest ID in its neighborhood. (Lowest-Id Heuristic)

Identifier-based

Clustering

• The node, which has the most neighbor nodes, is elected as the cluster head.(Highest Degree Heuristic)

Connectivity-

based Clusterin

g

Cluster formation takes place using two mechanisms :

Continued… The CBRP uses a variation of the lowest-ID algorithm, which

is an identifier-based algorithm.

Each node uses a neighbor table. Information stored in a neighbor table are : o Unique Node IDso Role in the cluster (i.e. Cluster head or Member node)o Status of the link to that node

(Unidirectional/Bidirectional).

The neighbor table is maintained by periodically broadcasting HELLO messages. A HELLO message contains information about a node’s state, its neighbor table and its cluster adjacency table.

Mechanisms in CBRPA. Routing Process :

CBRP uses two data structures to support the routing process:1) The Cluster Adjacency Table (CAT) - The CAT stores information about neighboring clusters, i.e. whether the links are bi-directional or unidirectional.2) The Two-Hop Topology Database - The two-hop topology database contains all nodes that are at most two hops away.

The routing process works in two steps:1) Discovery of a route from a source node ‘S’

to a destination node ‘D’.2) Actual transmission of the data packets.

B. Route Discovery • In CBRP only cluster heads are flooded with route

request package (RREQ). Gateway nodes receive the RREQs and forward them to the next cluster head.

• Initially, the source node ‘S’ broadcasts a RREQ with unique ID containing the address of the destination node ‘D’.

• When a node ‘N’ receives a RREQ it does the following:a) If ‘N’ is Gateway Node -> Forwards the RREQ to

the next Cluster head ‘C’.

b)If ‘N’ is Cluster Head -> Checks whether ‘D’ is a neighbor or is two-hops away from it. It then sends the RREQ to ‘D’. Else broadcasts it to the neighboring Cluster head.

[3]

[3,1,8,11]

1

2

4

5 6 7

8

9

10

11

3 (S)

11 (D)

[3,1]

[3,1,6]

[3,1,8]

Example :Source Node-[3]Destination Node-[11]Route Discovered- [3,1,8,11]

C. Route Reply If the RREQ reaches the destination node ‘D’, it

contains the path called as “loose source route”, [S,C1,C2,...,Ck,D].

‘D’ sends a Route Reply message (RREP) back to S using the reversed loose source route [D, Ck,...,C1,S], i.e. RREP is sent back to source along reversed loose source route of cluster heads.

Every time a cluster head receives this RREP it computes a strict source route, which then consists only of nodes that form the shortest path within each cluster.

Example :Source Node-[3]Destination Node-[11]Loose Source Route of RREP- [11,8,1,3]Strict Source Route of RREP- [11,9,4,3]

1

2

4

5 6 7

8

9

10

3

11

3 (S)

11 (D)

[11][11,9]

[11,9,4]

[11,9,4,3]

Example :Source Node-[3]Destination Node-[11]Loose Source Route of RREP- [11,8,1,3]Strict Source Route of RREP- [11,9,4,3]

1

2

4

5 6 7

8

9

10

3

11

3 (S)

11 (D)

D. Route Error Detection After determining the route, source routing is used

for actual packet transmission.A forwarding node sends a Route Error Message

(ERR) to packet source if the next hop in source route is unreachable.

1

2

4

5 6 7

8

9

10

3

11

3 (S)

11 (D)

Example:

Source route header of datapacket: [3,4,9,11]

Route error (ERR)down link: [9->11]

E. Local Route Repair Objective

Increase Packet Delivery Ratio. Save Route Rediscovery flooding traffic. Reduce overall route acquisition delay.

A forwarding node repairs a broken route using its 2-hop-topology information and then modifies the source route header accordingly.

Destination node sends a Gratuitous Route Reply to inform source of the modified route.

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2

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5 6 7

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9

10

3

11

3 (S)

11 (D)

Example :Source route header of DataPacket : [3,4,9,11]

Route error (ERR)down link : [9->11]

1

2

4

5 6 7

8

9

10

3

11

3 (S)

11 (D)

Example :Source route header of DataPacket : [3,4,9,11]

Modified source route:[3,4,9,8,11]

1

2

4

5 6 7

8

9

10

3

11

3 (S)

11 (D)

Example :Source route header of DataPacket : [3,4,9,11]

Gratuitous route reply :[3,4,9,8,11]

Features of CBRP Advantages:

Clustering approach minimizes on-demand route discovery traffic and routing overhead.

Uses “local repair” mechanism to reduce route acquisition delay and new route re-discovery traffic.

Increases the packet delivery ratio to a great extent.

Disadvantages: With increase in cluster size, the overhead per packet

increases due to source routing. Every node of the route has to be stored in the routed

packet. So the packet size rises proportional to the path length of the route.

The transmission time increases with increase in cluster size and path length of the route.

Conclusion Ad hoc networks, play a critical role in places where a

wired (central) connection is neither available nor economical to build, such as law enforcement operations, battle field communications, disaster recovery situations, and so on.

Such situations demand a network where all the nodes are potentially mobile and communication must be supported untethered between any two nodes.

The Cluster Based Routing Protocol (CBRP), which is a robust and scalable routing protocol provides these functionalities with better efficiency than the existing proactive and reactive protocols.

References[1] Tim Daniel Hollerung. The Cluster-Based Routing Protocol, PP.5-8, Winter Semester 2003/2004. hollerung.org/daniel/en/studies/the-cluster-based-routing-protocol/pdf[2] M. Rezaee, M. Yaghmaee. Cluster based Routing Protocol for Mobile Ad Hoc Networks. www.dcc.ufla.br/infocomp/artigos/v8.1/art05.pdf[3]Mainak Chatterjee, Sajal K. Das & Damla Turgut. WCA: A Weighted Clustering Algorithm for Mobile Ad Hoc Networks. Published in Cluster Computing, Vol-5, PP.193–204, Year- 2002 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.8.5353&rep=rep1&type=pdf[4] http://en.wikipedia.org/wiki/List_of_ad_hoc_routing_protocols[5] Mingliang Jiang. CBRP: A cluster-based routing protocol for mobile ad hoc networks. www.comp.nus.edu.sg/˜tayyc/cbrp/hon.ppt.[6]Mukesh Kumar, Rahul Rishi, D.K. Madan. Comparative Analysis of CBRP, DSR, AODV Routing Protocol in MANET. Published in (IJCSE) International Journal on Computer Science and Engineering Vol. 02, No. 09, Year-2010, PP.2853-2858