M.c ppt

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INTRODUCTION

Routing is the process of selecting paths in a network

along which to send network traffic.

Routing directs packet forwarding,

the transit of logically addressed packets from their

source toward their ultimate destination through intermediate

nodes.

Packet is a formatted unit of

data.

-Pallavi Anand

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DSR

'Dynamic Source Routing' (DSR) is a routing protocol for wireless mesh

networks.

It divides the task of routing into two

separate problems.

Route Discovery

Route Maintenance

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1. ROUTE DISCOVERY

A node tries to discover a route to a destination if

it has to send something to this destination and

there is currently no known route.

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2. Route Maintenance

If a node is continuously sending packets via a route, it has to make

sure that the route is held upright. As soon as node detects problems with

the current route, it has to find an alternative.

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DSR eliminates all the periodic routing updates.

If a node needs to discover a route, it broadcasts a

route request with a unique identifier and the destination

address as parameters.

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3. Otherwise, the node appends its own address to a list of transverse hops in the packet and broadcast

this updated route request.

2. If the node recognizes its own address as destination, the request has reached the

target.

Any node that receives a route request does the

following.

1. If the node had already received

the request it drops the request packet.

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Using this approach, the route request collects a list of

addresses representing a possible path towards

the destination.

Request

Number

Destination

Address

Source

Address

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As soon as the request reaches the destination it can return the request packet containing the list to receiver

using this list in reverse order

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Dynamic Source Routing: Advantages

• Routes maintained only between nodes who need to

communicate

– reduces overhead of route maintenance

• Route caching can further reduce route discovery overhead

• A single route discovery may yield many routes to the

destination, due to intermediate nodes replying from local

caches

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DSR: Disadvantages

Packet header size grows with route length due to source routing

Flood of route requests may

potentially reach all nodes in the

network

Potential collisions between

route requests propagated by

neighboring nodes

Increased contention if too

many route replies come back

due to nodes replying using

their local cache

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