DSDV Presentation

© Yufei ChengITTC

2009-10-28

Implementation of DSDV is NS-3

© 2005–2006 James P.G. Sterbenz

Yufei Cheng

Department of Electrical Engineering & Computer Science

Information Technology & Telecommunications Research Center

The University of Kansas

EECS 882 Presentation

[email protected]

DSDV Implementation

© Yufei ChengITTC

2009-10-28 DSDV implementation 2

DSDV implementationAbstract

This paper presents a routing protocol for ad-hoc network. The basic idea of the

design is to operate each mobile node as a specialized router, which periodically

advertises its view of interconnection topology to all other nodes within the

network. The author makes modification to Bellman Ford routing mechanism and

addresses the problem of looping properties.

The DSDV code in NS2 covers more detail about the routing protocol than the

paper, and I will include some corresponding code for core function of DSDV.

The presentation will also cover some differences between AODV and DSDV.

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DSDV implementation Outline

• Basic function of DSDV

• Comparison of AODV and DSDV

• Direction of future work for project

• Conclusion

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DSDV implementation




• Conclusion

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Overview of Routing Methods

• Link-State

• Distance-Vector

DSDV Implementation

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• Link-State

– Each node maintains view of cost for each link

– Periodically broadcast is used to keep updated

• Problem:

– View of the cost affected by delay, partitioned network, etc.

– Formation of routing loop

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• Distance-Vector (Distributed Bellman-Ford)

– Every node i maintains , for each destination x

– Treat k as next-hop if equals

– Each node broadcasts its estimate of shortest

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Core function of DSDV

• Route advertisements

• Route table entry

• Responding to topology changes

• Route selection

• Summary

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Core function of DSDVRoute Advertisements

• Route table entry tagged with sequence number

– Originated by destination

– In order to avoid forming loops

• Each node advertises routing table to neighbors

• Routing tables update periodically

– Deal with topology changes

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Core function of DSDVRoute Table Entry

• Data includes in the broadcast

– New sequence number

– Destination’s address

– Hops required to reach destination

– Sequence number received regarding that destination

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• The advertised table of MH4 (one node)

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• Broken links

– Detected directly or indirectly

– Described as a metric of ∞

– Later sequence number with a finite metric

• Triggers an immediate route update

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Core function of DSDVResponding to Topology Changes

• Two kinds of adjustments

(Between periodic advertisement)

– Full dump packets

• Contains all available routing updates

• Multiple NPDUs (network protocol data units) of size

• Transmitted infrequently when movement is seldom

– Incremental packets

• Contains only information since last full dump

• One NPDU of size

• Transmitted more frequently compared to full dump

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Core function of DSDVRoute Selection

• Two ways to decide new route

– Routes with later sequence number be preferred

– If same sequence number, the better metric be preferred

– Keep record of settling time of route-weighted average time that routes to a destination will fluctuate before receiving the route with best metric (Why?)

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Core function of DSDVRoute Selection

• Problem:

MH9 to MH2 has 12 hops, MH9

to MH6 has 11 hops, yet route

from MH2 arrives first, the route

information will fluctuate even

no movement has occurred

• Solution:

Delay the advertisement of such

routes by settling time

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• Conclusion

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• Proactive

– Contains all the active links in the table

– Calculate the shortest path

– Update table when node moves

– Immediately knows whether node is reachable or not

– Data is transmitted immediately

– High overheads

DSDV vs. AODVDSDV

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• Reactive

– Find route on demand

– Cache request from other nodes

– No static overhead

– Can not immediately transmit data

– Calculate the shortest path

DSDV vs. AODVAODV

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Direction of Future Work

• Dig into AODV NS-3 codes and know how it works

• Cut off AODV functions and leave a clean work place

• Push DSDV functions in piece by piece

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Direction of Future WorkWork Load Distribution

• Yufei: Routing

– Have a clear view of both DSDV and AODV functions

(partly finished)

– Transfer the core part of routing protocol

• Hemanth: Packet & Table

– Understand P & T of both DSDV and AODV

– Make sure they could be realized smoothly

• Chris: Queue & Neighbor

– Understand Q & N of both DSDV and AODV

– Make sure they could be realized smoothly

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Conclusion

• DSDV relies on periodic advertisement to keep routing table updated, it is effective for creating ad-hoc networks for small population of mobile nodes

• AODV is on-demand routing protocol and does not require node to contain complete list of routes

• The implementation of DSDV will base on the code of AODV in NS-3

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References

• “Highly Dynamic Destination-Sequenced Distance-Vector Routing (DSDV) for Mobile Computers”, Charles E. Perkins, Pravin Bhagwat

• “Ad-hoc On-Demand Distance Vector Routing”, Charles E. Perkins, Elizabeth M. Royer

DSDV Presentation

Documents

Transcript of DSDV Presentation