presentation

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Introduction



What are Mobile Adhoc Networks (MANETs)?



Routing in MANETs

– Traditional algorithms not feasible

– Two main types of Protocol:

• Proactive / Table Driven (examples: DSDV,CGSR etc.)

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Destination Sequenced Distance Vector

Routing



Each node maintains a routing table determining next

hop for every other node

Destination

Next Hop

Metric

Seq #

2

1

4

2

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Destination Sequenced Distance Vector

Routing



Routing Table Management

– Periodic broadcasts / immediate broadcasts when topology changes

– Full Dump / Incremental dumps

– Broadcast starts with neighbors with metric equals to 1

– Neighbors increment the metric and rebroadcast to its neighbors. This Process continues until destination is reached. Destination updates its entries if its sequence number is less than new sequence number

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Cluster Head Gateway Switch Routing

(CSGR)



Nodes are organized as clusters with one node acting

as cluster head (CH)



Uses DSDV as underlying protocol



A gateway node is a node that is within

communication range of two/more CH



Packet sent by a node is first routed to its CH and

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Cluster Head Gateway Switch Routing

(CSGR)



Every node maintains cluster member table which

stores cluster heads of every destination that is

updated just like broadcasting in DSDV



In addition a routing table is also maintained by every

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Ad-hoc On-Demand Distance Vector Routing



Built on DSDV



Route Discovery

– RREQ packet is sent to neighbors to determine route to destination

– On receiving a packet, a node checks if it is the destination / if it knows the complete path to

destination. Failing to meet these two conditions, node will forward the packets to its neighbors

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Ad-hoc On-Demand Distance Vector Routing

– If packet reached destination or a node with fresh route, a reply is uni-casted

– As packet is going back, a forward entry is made into every intermediate node

– Used for symmetric links only



Route Maintenance

– If a node moves, its neighbor notices and propagates notification (RREP with infinite metric) to upstream

routers, upstream will notify to its upstream routers and so on until source is reached

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Ad-hoc On-Demand Distance Vector Routing



RFC 3561 –

http://www.ietf.org



Ad-hoc Support Library

http://aslib.sourceforge.net/

– Ad-hoc Support Library (ASL) is a user-space library which provides an API to facilitate implementation of routing protocols for wireless ad-hoc networks in Linux.

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Dynamic Source Routing



Based on Source Routing



Route cache maintains the path it is aware of



Route Discovery

– RREQ is sent to neighbors

– If intermediate nodes doesn’t know of the destination, it appends its own address to the packet and forwards the packet to its destination.

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Dynamic Source Routing

– If an intermediate node knows about the destination it appends its cached route to the packet route and

generates a RREP

– To return RREP, node checks if it has a path to source, it will use that route

– If symmetric routes are supported, node can reply by just reversing packet route

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Dynamic Source Routing



IETF Draft

http://www.monarch.cs.rice.edu/internet-drafts/draft-ie

tf-manet-dsr-01.txt



picoNet

http://piconet.sourceforge.net/

– API for Linux

– In development phase



Monarch Project

http://www.monarch.cs.rice.edu/dsr-impl.html

– DSR Implementation by Rice University

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Preemptive Ad-hoc On Demand Distance

Vector Routing



Two preemptive mechanisms

– Reschedule discovery in advance

• Reply packets contains information about life time of the newly discovered path

• Based on life time, a path discovery can be rescheduled

– Warning Messages

• When transfer time of packet to its neighbor is too high, that node is monitored

• If monitoring indicates this link is going to break, warning message is sent to the source

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Associativity-Based Routing



A new routing metric known as degree of association

stability



Each node sends periodically beacon messages to

neighbors



Associativity ticks is incremented for ever beacon

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Associativity-Based Routing



Route Discovery

– Node broadcasts a BQ message

– Nodes receiving this message appends append their address and associativity ticks with respect to

neighbors along with QoS information to message and forwards to destination

– Destination is then able to select the best route based on associativity ticks

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Signal Stability Routing



Selects routes based on signal strength



Two Cooperative Protocols:

– Dynamic Routing Protocols (DRP)

• Maintains Signal Stability Table (SST) and Routing Table (RT)

• SST records signal strength of neighboring nodes obtained by periodic beacons from link layer of each

neighboring nodes. Strength are recorded as weak/strong

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Signal Stability Routing

– Static Routing Protocol (SRP)

• SRP passes the packets up to the stack, if it is the intended destination

• Otherwise, it will forward the packet to next hop based on RT

• If no entry is found, route search process in initiated

• A node forwards a route requests only if they are received over a strong channel and have not processed previously

• Destination chooses the first arriving route-search packet to send back

• DRP then reverses the selected route and sends a route-reply message back to the initiator

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Summary and Conclusion



Different types of Routing Protocols for Ad hoc

networks are described



Proactive protocols have good throughput than

Reactive protocols, however proactive protocols have

more routing load



Presently different routing protocols are under study

by IETF MANET working group for evaluation and

standardization. These include:

– Ad hoc On-Demand Distance Vector Routing Protocol

– Dynamic Source Routing Protocol

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References



‘A Review of Current Routing Protocols for Ad Hoc

Mobile Wireless Networks’, Elizabeth M. Royer, Santa

Barbara, Chai-Keong Toh



‘Performance Evaluation of Routing Protocols for Ad

hoc Wireless Networks’, Azzedine Boukerche



‘Routing protocols For Mobile ad-hoc networks’ , Amit

Jain, Indian Institute of Technology, Kanpur



‘Request for Comments: 3561’, IETF MANET Working