Optimized Link State Routing Protocol for Ad Hoc Networks

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Optimized Link State Routing Protocol for Ad Hoc

Networks

Philippe Jacquet, Paul Muhlethaler, Thomas Clausen, Anis Laouiti, Amir

Qayyum, Laurent Viennot

To cite this version:

Philippe Jacquet, Paul Muhlethaler, Thomas Clausen, Anis Laouiti, Amir Qayyum, et al.. Optimized

Link State Routing Protocol for Ad Hoc Networks. Multi Topic Conference, 2001. IEEE INMIC 2001,

2001, Lahore, Pakistan. pp.62 - 68, �10.1109/INMIC.2001.995315�. �inria-00471622�

for Ad Ho Networks

P. Ja quet, P. Muhlethaler, T. Clausen, A. Laouiti,A. Qayyum, L. Viennot



Hiper omProje t,INRIARo quen ourt,BP105, 78153LeChesnayCedex,Fran e

Abstra t: In this paper we propose and

dis uss anoptimizedlink stateroutingproto ol,

namedOLSR, formobilewirelessnetworks. The

proto ol isbasedonthelinkstatealgorithmand it is proa tive (or table-driven) in nature. It employsperiodi ex hange of messagesto main-taintopologyinformationofthenetworkatea h node. OLSRis anoptimization overapurelink state proto ol as it ompa ts the size of

infor-mation sent in the messages, and furthermore,

redu es the number of retransmissions to ood

these messagesin entirenetwork. For this pur-pose, theproto ol usesmultipointrelaying te h-niquetoeÆ ientlyande onomi ally oodits on-trolmessages. Itprovidesoptimalroutesinterms ofnumber ofhops, whi h areimmediately avail-ablewhenneeded. Theproposedproto olisbest suitableforlargeanddenseadho networks.

keywords: routing proto ol, link state

pro-to ol,proa tiveor table-driven proto ol, mobile wirelessnetworks,adho networks

1 Introdu tion

With theadventofnewte hnologiesandthe de-mandfor exibilityandeaseinworking

environ-ment, the use of mobile wireless omputing is

growingfast. Besides their use, mobile wireless networksare assumedto growin size too. They an fun tion in independent groups, ontaining

some tens of nodes up to several hundreds of

nodes. As thenetwork sizein reases,itbe omes ommonforthenodestobedispersedinalarger area than the radio range of individual nodes. Under su h onditions, one has to employ rout-ing te hniquessu h that the outof range nodes

may ommuni ate with ea h other via

interme-diate nodes. This problem of routing in mobile adho networksisourfo usofdis ussionin this paper,andaproto olisproposedasasolution.



[Philippe.Ja quet, Paul.Muhlethaler, Thomas.Clausen, Anis.Laouiti, Amir.Qayyum, Laurent.Viennot℄inria. fr

Designissuesfordevelopingaroutingproto ol for wireless environment with mobility are very dierentandmore omplexthanthosefor wired

networks with stati nodes. Major problems in

mobileadho networksare(a)limitedbandwidth and (b) high rate of topologi al hanges. Thus thegoalforaroutingproto olis tominimizeits ontroltraÆ overheadwhileatthesametime,it shouldbe apableofrapidlyadaptingtolink

fail-ures and additions aused by node movements.

It implies, therefore, that the routing proto ol shouldworkinadistributedmanneranditshould beselfstartingandselforganizing. The possibil-ityofadho networkstogrowinsizetohavelarge diameters bringswith itthe s alingupproblem, possibility of loops in the routes, and in onsis-ten yofinformationindierentpartsofthe net-work. Moreover,theexisten e of uni-dire tional links isareal hallengeforroutingproto ols.

2 Rea tive versus proa tive

routing approa h

Dierentroutingproto olstrytosolvethe prob-lem of routingin mobile adho networks in one way orthe other. In rea tiverouting approa h, aroutingproto oldoesnottaketheinitiativefor nding a route to a destination, until it is re-quired. Theproto olattemptsto dis overroutes only \on-demand" by ooding its query in the network. This type of proto ols redu es ontrol traÆ overheadatthe ostofin reasedlaten yin ndingtheroutetoadestination. Theexamples of this kindof proto olsare AODV[9℄, DSR [5℄

and TORA [7℄. On the other hand, proa tive

proto olsarebasedonperiodi ex hange of on-trol messages. Somemessagesaresentlo allyto

enable a node to know its lo al neighborhood,

and some messages are sent in entire network

whi hpermittoex hangetheknowledgeof

topol-ogy among all the nodes of the network. The

proa tive proto ols immediately provide the re-quired routes when needed,at the ostof

band-of topology. The examples of this kind of

pro-to ols areDSDV [8℄, STAR [2℄ and TBRPF [6℄.

Some proto ols use a mixture of the two

te h-niques, i.e., they keep routes available for some destinations allthetime, but dis overroutesfor otherdestinationsonlywhenrequired. [3℄ analy-sessomeroutingproto olsforadho networks.

3 OLSR (Optimized Link

State Routing) proto ol

3.1 Overview

Wepropose aproa tiveroutingproto ol for mo-bileadho networks,whi hwe allasOptimized LinkStateRouting(OLSR).Theproto ol inher-itsthestabilityofthelinkstatealgorithm. Dueto itsproa tivenature,ithasanadvantageofhaving theroutesimmediatelyavailablewhenneeded. In apurelinkstateproto ol,allthelinkswith neigh-bornodesarede laredandare oodedin the en-tirenetwork. OLSR proto ol is an optimization ofapurelinkstateproto olformobileadho net-works. First,it redu es thesize of ontrol pa k-ets: insteadofalllinks,itde laresonlyasubset oflinks withitsneighborswhoareitsmultipoint relaysele tors(seeSe tion3.2). Se ondly,it min-imizes oodingofthis ontroltraÆ byusingonly thesele tednodes, alledmultipointrelays,to dif-fuseitsmessagesinthenetwork. Onlythe multi-point relays of a node retransmit its broad ast

messages. This te hnique signi antly redu es

the number of retransmissions in a ooding or

broad astpro edure [10,12℄.

Apartfrom normalperiodi ontrol messages, theproto oldoesnotgenerateextra ontrol traf- inresponsetolinkfailuresandadditions. The proto ol keepstheroutesfor allthedestinations inthenetwork,hen eitisbene ial forthe

traf- patterns where a large subset of nodes are

ommuni atingwithea hother,andthe[sour e, destination℄ pairs are also hanging with time. Theproto olisparti ularlysuitableforlargeand dense networks, as the optimization done using themultipoint relaysworks wellin this ontext.

More dense and large a network is, more

opti-mizationis a hievedas ompared to thenormal link statealgorithm.

The proto ol is designed to work in a

om-pletelydistributedmannerandthusdoesnot de-penduponany entralentity. Theproto oldoes

messages: ea h node sends its ontrol messages periodi ally, and an therefore sustain a loss of

some pa kets from time to time, whi h happens

veryoften in radio networks due to ollisionsor other transmission problems. The proto ol also does not need an in-order delivery of its mes-sages: ea h ontrolmessage ontainsasequen e numberofmostre entinformation,thereforethe re-orderingatthere eivingend annotmakethe oldinformationinterpretedasthere entone.

OLSR proto ol performs hop by hop routing,

i.e. ea hnodeusesitsmostre entinformationto route apa ket. Therefore, when anode is mov-ing, its pa kets an be su essfully delivered to it,ifitsspeedissu hthatitsmovement ouldbe followed in its neighborhood, at least. The pro-to olthussupportsanodalmobilitythat anbe tra ed throughits lo al ontrol messages, whi h dependsuponthefrequen yofthese messages.

3.2 Multipoint relays

The idea of multipoint relays [1℄ is to minimize the oodingof broad astpa ketsin thenetwork byredu ingdupli ateretransmissionsinthesame region. Ea h node in the network sele ts a set of nodes in its neighborhood, whi h retransmits itspa kets. Thissetofsele tedneighbornodesis alledthemultipointrelays(MPRs)ofthatnode.

The neighbors of any node N whi h are not in

itsMPR set,read andpro essthepa ketbut do notretransmitthebroad astpa ketre eivedfrom node N. Forthis purpose, ea h node maintains a set of itsneighbors whi h are alled the MPR Sele tors of thenode. Every broad astmessage

oming from these MPR Sele tors of a node is

assumed toberetransmittedbythat node. This set an hange over time, whi h is indi ated by thesele tornodesintheirHELLOmessages(see Se tion 4.1).

Ea h node sele ts its multipoint relay set

among its one hop neighbors in su h a manner

that the set overs(in terms of radio range) all

the nodes that are two hops away. The

multi-pointrelaysetofnodeN, alledMPR (N),isan arbitrarysubsetoftheneighborhoodofN whi h satises the following ondition: every node in

the twohopneighborhood ofN must havea

bi-dire tionallinktowardMPR (N). Thesmalleris themultipointrelayset, themoreoptimalis the routingproto ol. Figure 1showsthe multipoint relaysele tionaroundnodeN.

N

retransmitting

nodes or

multipoint relays

Figure 1: Multipointrelays

OLSRproto olreliesonthesele tionof multi-pointrelays,and al ulatesitsroutestoallknown destinationsthroughthesenodes,i.e. MPRnodes aresele tedasintermediatenodesinthepath. To implementthiss heme,ea hnodeinthenetwork periodi ally broad asttheinformation aboutits one-hopneighborswhi hhavesele teditasa mul-tipointrelay. Uponre eiptofthisMPRSele tors' information,ea hnode al ulatesandupdatesits routestoea hknowndestination. Therefore,the routeisasequen eofhopsthroughthemultipoint relaysfrom sour etodestination.

Multipoint relays are sele ted among the one hop neighbors with abi-dire tionallink. There-fore, sele ting the route through multipoint re-laysautomati allyavoidstheproblemsasso iated withdatapa kettransferonuni-dire tionallinks. Su hproblemsmay onsistofgettingan a knowl-edgmentfordatapa ketsatea hhopwhi h an-notbere eivedifthereisauni-dire tionallinkin thesele tedroute.

4 Proto ol fun tioning

4.1 Neighbor sensing

Ea h node must dete tthe neighbornodes with

whi hithasadire tandbi-dire tionallink. The

un ertainties over radio propagation may make

somelinksuni-dire tional. Consequently,alllinks mustbe he kedinbothdire tionsinordertobe onsideredvalid.

To a omplish this, ea h node periodi ally

broad asts its HELLO messages, ontaining the

information about its neighbors and their link status. These ontrol messages are transmitted inthebroad astmode. Thesearere eivedbyall one-hop neighbors, but they are not relayed to

 thelistofaddressesoftheneighborstowhi h thereexists avalidbi-dire tionallink;

 the list of addresses of the neighbors whi h

are heardbythis node (a HELLO hasbeen

re eived)but thelink isnotyetvalidatedas bi-dire tional: ifanodendsitsownaddress inaHELLOmessage,it onsidersthelinkto thesendernodeasbi-dire tional.

Remark: ThelistofneighborsintheHELLO

message an be partial, the rule being that all neighbornodes are ited at least on e within a predened refreshingperiod.

These HELLO messages permit ea h node to

learn the knowledge of its neighbors up to two hops. Onthebasisofthisinformation,ea hnode performs the sele tion of its multipoint relays. These sele tedmultipointrelaysareindi atedin

theHELLO messageswiththelinkstatus MPR.

Onthere eptionofHELLO messages,ea hnode

an onstru t its MPR Sele tor table with the

nodeswhohavesele teditasamultipointrelay.

Intheneighbortable,ea hnodere ordsthe in-formationaboutitsonehopneighbors,thestatus ofthelinkwiththeseneighbors,andalistoftwo hop neighborsthat these onehop neighbors give a ess to. Thelink status anbeuni-dire tional,

bi-dire tional or MPR.The link status as MPR

implies that the link with the neighbor node is bi-dire tional ANDthat node is alsosele ted as amultipointrelaybythislo alnode. Ea hentry in the neighbortable has an asso iated holding time, upon expiry of whi h it is no longer valid

andhen eremoved.

The neighbor table also ontains a sequen e

number value whi h spe ies the most re ent

MPR set that thelo al nodekeepingthis neigh-bortable hassele ted. Everytimeanodesele ts orupdatesitsMPR set,this sequen enumberis in rementedtoahighervalue.

4.2 Multipoint relay sele tion

Ea h node of the network sele ts independently

its own set of multipoint relays. The MPR set

is al ulated in amanner to ontaina subsetof one hop neighbors whi h oversall the twohop neighbors,i.e., the unionof theneighborsets of

all MPRs ontains the entire two hop neighbor

dire tionallink nodesfoundin theHELLO mes-sagesre eivedby thisnode(this two-hop neigh-borinformationis storedin the neighbortable).

The MPR set need not be optimal, however it

shouldbesmallenoughtoa hievethebenetsof multipointrelays. Bydefault, themultipoint re-layset an oin idewiththewhole neighborset. This will be the ase at network initialization. Onepossiblealgorithmforsele tingtheseMPRs ispresentedin[11℄,whi hisanalysedin [13℄and [10℄,andimprovedin[12℄.

Multipoint relaysof agivennode arede lared

in the subsequent HELLOs transmitted by this

node, sothat theinformation rea hesthe multi-pointrelaysthemselves. Themultipointrelayset isre- al ulatedwhen:

 a hange in the neighborhood is dete ted

when either a bi-dire tional link with a

neighbor is failed, or a new neighbor with abi-dire tionallinkisadded;or

 a hange in the two-hop neighbor set with

bi-dire tionallink isdete ted.

With information obtained from the HELLO

messages,ea h nodealso onstru tits MPR Se-le tortable,in whi h itputs theaddresses ofits onehop neighbornodes whi h hassele ted itas amultipoint relayalong with the orresponding

MPRsequen enumberofthatneighbornode. A

sequen e number is also asso iated to theMPR

Sele tor table whi h spe ies that the MPR Se-le tor table is most re ently modied with that

sequen e number. A nodeupdates its MPR

Se-le torseta ordingtotheinformationitre eives

in the HELLO messages, and in rementthis

se-quen enumberonea hmodi ation.

4.3 MPR information de laration

In order to build the intra-forwarding database neededforroutingpa kets,ea hnodebroad asts spe i ontrolmessages alledTopology Control

(TC) messages. TC messagesareforwardedlike

usual broad ast messagesin the entire network. This te hnique is similar to the link state

te h-nique used in ARPANET, but it takes

advan-tage of MPRs whi h enable a better s alability ofintra-forwarding [4℄.

ATCmessageissentperiodi allybyea hnode in the network to de lare its MPR Sele tor set, i.e., the message ontains the list of neighbors

pointrelay. The sequen e numberasso iated to thisMPR Sele torsetisalsoatta hedtothelist. The list of addresses an be partial in ea h TC message, butparsingmust be ompletewithin a ertain refreshing period. (In [1℄, the list of ad-dressesismandatorilyexhaustive). The informa-tiondiusedinthenetworkbytheseTCmessages willhelpea hnodetobuilditstopologytable. A nodewhi hhasanemptyMPRSele torset, i.e., nobodyhassele teditasamultipointrelay,may notgenerateanyTCmessage.

The interval between the transmission of two

TC messages depends upon whether the MPR

Sele torset is hangedornot,sin e thelast TC

message transmitted. When a hange o urs in

theMPR Sele torset,thenextTC messagemay

be sent earlier that the s heduled time, but af-tersomepre-spe iedminimuminterval,starting from thetime the last TC messagewas sent. If thismu htimehasalreadyelapsed,thenextTC

message may be transmitted immediately. All

subsequentTCmessagesaresentwiththenormal default interval for sending TC messages, until theMPR Sele torsetis hangedagain.

Ea hnodeofthenetworkmaintainsatopology table, in whi h it re ordsthe information about

the topology of the network obtained from the

TC messages. A nodere ordsinformation about

themultipointrelaysofothernodesinthistable. Based on this information, the routing table is al ulated. An entry in the topology table on-sistsofanaddressofa(potential)destination(an

MPR Sele torin the re eived TC message),

ad-dressofalast-hopnodetothatdestination

(orig-inator of the TC message) and the

orrespond-ing MPR Sele tor set sequen e number (of the

sendernode). Itimpliesthatthedestinationnode anberea hedin thelast hopthroughthis last-hopnode. Ea htopologyentryhasanasso iated holdingtime,uponexpiryofwhi hitisnolonger valid andhen eremoved.

Upon re eipt of a TC message, the following

proposed pro edure may be exe uted to re ord

theinformationin thetopologytable:

1. Ifthereexistsomeentryinthetopologytable

whose last-hop address orresponds to the

originatoraddressoftheTCmessageandthe

MPR Sele tor sequen e numberin that

en-try is greater than the sequen e number in the re eived message, then no further pro- essing ofthis TC messageisdoneand itis silentlydis arded( ase: pa ketre eivedout oforder).

whose last-hop address orresponds to the originatoraddressoftheTCmessageandthe MPRSele torsequen enumberinthatentry is smaller thanthe sequen e number in the re eived message, then that topology entry isremoved.

3. For ea h of the MPR Sele tor address

re- eivedintheTCmessage:

 Ifthereexistsomeentryinthetopology table whose destination address

orre-sponds to the MPR Sele tor address

and the last-hop addressof that entry orrespondstotheoriginatoraddressof theTCmessage,thentheholdingtime ofthatentryisrefreshed.

 Otherwise, a new topology entry is

re ordedin thetopologytable.

4.4 Routing table al ulation

Ea h node maintains a routing table whi h

al-lowsittoroutethepa ketsforotherdestinations

in the network. The nodes whi h re eive a TC

message parse and store some of the onne ted

pairs of form [last-hop,node℄ where\nodes" are theaddressesfoundin theTCmessagelist. The routingtableisbuiltfromthisdatabaseby tra k-ingthe onne tedpairsinades endingorder. To ndapathfrom agivenorigintoaremotenode R, onehas to nd a onne tedpair (X,R), then a onne ted pair (Y,X), and so forth until one ndsa nodeY in theneighborsetof theorigin. Figure2explainsthis pro edureofsear hingthe [last-hop,destination℄ pairsin thetopology table to get a omplete, onne ted route from sour e to destination. In order to restri t to optimal paths, the forwardingnodes will sele t only the onne tedpairsontheminimalpath. This

sele -tion anbedone dynami allyand with minimal

storagefa ilities. Thesequen enumbersareused todete t onne tedpairswhi hhavebeen invali-datedbyfurthertopology hanges. The informa-tion ontained in the intra-forwarding database (topologytable),whi hhasnotbeenrefreshedis dis arded. Seese tion5formoredetails.

The route entries in the routing table onsist ofdestination address,next-hopaddress,and es-timateddistan e to destination. Theentries are re ordedin thetable for ea h destination in the

network for whi h the route is known. All the

destinationsforwhi htherouteisbrokenor par-tiallyknownarenotenteredin thetable.

T_last --- T_dest

T_last --- T_dest

T_last --- T_dest

T_last --- T_dest

Dest

Source

Figure2: Buildingaroutefromtopologytable

The routingtable isbased ontheinformation ontainedintheneighbortableandthetopology table. Therefore,ifanyofthesetablesis hanged, the routing table is re- al ulated to update the route information aboutea h knowndestination inthenetwork. Thetableisre- al ulatedwhena hangein theneighborhood isdete ted on ern-ing abi-dire tional link or when aroute to any destinationisexpired(be ausethe orresponding topologyentryisexpired). There- al ulationof thisroutingtabledoesnotgenerateortriggerany pa kets to be transmitted, neither in the entire network,norin theone-hopneighborhood.

The following proposed pro edure may be

ex-e uted to al ulate (or re- al ulate) the routing table :

1. All theentriesofroutingtableareremoved.

2. The new entries are re orded in the table

starting with one hop neighbors (h = 1) as destination nodes. For ea h neighborentry intheneighbortable,whoselinkstatusisnot uni-dire tional,anewrouteentryisre orded in the routing table where destination and next-hop addresses are both set to address oftheneighboranddistan eissetto1.

3. Then the new route entries for destination

nodes h+1hops away are re orded in the

routing table. The following pro edure is

exe uted for ea h value of h, starting with

h = 1and in rementing it by 1 ea h time.

The exe ution will stop if no new entry is re ordedinaniteration.

 Forea htopologyentryintopology ta-ble, if its destination address does not orresponds to destination address of

any route entry in the routing table

AND its last-hop address orresponds

to destination addressof aroute entry

with distan e equal to h, then a new

route entry is re orded in the routing table where:

dressin topologytable;

{ next-hop is set to next-hop of the

route entry whose destination is

equalto above-mentioned last-hop address;and

{ distan eissetto h+1.

4. After al ulatingtheroutingtable,the topol-ogy table entries whi h are notused in al- ulatingtheroutesmayberemoved,ifthere isaneedto savememoryspa e. Otherwise, theseentriesmayprovidemultipleroutes.

5 Performan e analysis

5.1 Route optimality

Themain problem isto showthat the introdu -tion of a multipoint relay set as asubset of the neighbor set does not destroy the onne tivity propertiesofthenetwork.

Let us take the following model: we onsider

a network made up of a set of nodes and a set

of valid links. This network an be seen as an inter onne tion graph. Wedene theusual

dis-tan e d(X;Y) whi h gives the minimal number

of hops between node X and node Y. We also

dene d

F

(X;Y)as theminimal numberof hops, providing that the intermediate relay nodes are forwarders. We annoti ethatd

F

doesnotdene

a distan e when some nodes are non-forwarders

be ausetriangleinequality ouldbenotsatised every time. Inthe following, we onsider asafe network:i.e. d

F

(X;Y)<1forallpairsofnodes

X andY.

By denition of link validity and sin e the

HELLO messagesareperiodi allyretransmitted, the neighbor sensing and the ele tion of multi-pointrelay nodes anbeperformed withoutany parti ularproblem, ex ept ifmobile nodesmove fasterthan HELLOinterval. Inthefollowingwe suppose that every node has a multipoint relay set that oversitstwohop neighborset. Wedo notneed toassume optimalityof themultipoint relayset.

The last operation is topology information

broad ast. Ifforanynodeitsmultipointrelayset oin ideswithitsneighborset,thentheTC mes-sagebroad astwillrea hanynodein a straight-forwardway. Inthis ase theminimalpath toa

remotenode re eivedviaTC messageswouldbe

tain the appropriate information. Our point is thatthispropertyremainsvalidwhenmultipoint relaysetsarestri tsubsetsofneighborsets.

Wedene foranygivennodetheset of multi-pointrelaysofrank0asthenodeitselfandtheset of multipoint relays of rank 1as the multipoint relaysetitself. Letusdenethesetofmultipoint relays of rank k+1,for k integer, asthe union ofmultipointrelaysetofallnodeselementofthe multipoint relay set of rank k. In other words,

ea h element M

k

of the multipoint relay set of

rank k of a node X an be rea hed via a path

XM 1 :::M k where M 1 is multipointrelay of X, andM i+1 ismultipointrelayofM i .

Theorem 1 If for two nodes X and Y,

d F

(X;Y) = k+1, for k integer, then Y is at distan e1fromthe multipointrelaysetofrankk of X.

Proof : Byre ursion.

The proposition is valid for k= 0and k =1,

by denition of the multipoint relay set. We

suppose the proposition valid for k, and let us

assume a node Y su h that d

F

(X;Y) = k +

2. Therefore there exists an optimal valid path

XF 1 :::F k F k +1 Y wheretheF i

sareallforwarder

nodes. We have d F (X;F k +1 ) = k +1, there-fore F k +1

is at distan e 1 from the multipoint

relay set of rank k. Let M

k

be the element of themultipointrelaysetofrankkofX su hthat d F (M k ;F k +1 )=1;therefore d F (M k ;Y)=2and Y belongstothetwohopneighborsetofM

k . Let M

k +1

bethemultipointrelayofM k whi h overs Y: d(M k +1 ;Y)=1. Sin eM k +1 belongs to the multipointrelaysetofrankk+1thetheoremis proved.

5.2 Broad ast performan e

Theorem2 For allpairs of nodesX and Y,X

generatingandtransmittingabroad astpa ketP, Y re eivesa opy of P.

Proof : Byreversedre ursion.

We suppose that transmissions are error free but aresubje tto arbitrary nite delays. Let k be the losest distan e to Y from whi h a opy of pa ketP hasbeeneventually(re)transmitted. Weshallprovethat k=1.

2)fromY,whi hhasretransmittedP. There ex-istsamultipointrelayF

0

ofFwhi hisatdistan e k 1ofY. Tobe onvin ed: weimagineapathof length k from F to Y: F;F 1 ;F 2 :::F k 1 ;Y and we take for F 0

the multipoint relay of F whi h oversF

2 ).

Sin eF 0

re eiveda opyofPthersttimefrom F(thepriortransmittersarene essarilytwo-hops

away from F

0

), therefore F 0

will automati ally forwardP: pa ketP willberetransmittedat

dis-tan ek 1fromY. Thetheoremisproved.

Notethat ifthetransmissionsareproneto er-rors,thenthereisnoguaranteeof orre tpa ket re eption by the intended destination. But this isa ommonproblemto allunreliable ommuni- ationsnetworkswhi hneedupperlayerre overy pro edure.

6 Con lusions

Formobilewirelessnetworks,theperforman eof aroutingproto ol is oupledwith manyfa tors, like the hoi e of physi al te hnology, link layer behavior,et . Theoverallbehaviorofaproto ol spe ies its working domain for whi h it ould besuitable. OLSR proto ol isproa tiveor table driven in nature, hen eit favors the networking ontext where this all-time-kept information is usedmoreandmore,andwhererouterequestsfor newdestinationsareveryfrequent. Theproto ol also goes in favor of the appli ations whi h do notallowlongdelays in transmittingdata

pa k-ets. OLSR proto ol is adapted to the network

whi his dense,and where the ommuni ationis assumedtoo urfrequentlybetweenalarge num-berofnodes.

Referen es

[1℄ ETSISTC-RES10Committee.Radio

Equip-mentandSystems: HighPerforman eRadio

Lo al Area Network (HIPERLAN) Type1,

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