Mitigation of Flooding Disruption Attacks in Hierarchical OLSR Networks

Transcription

1 Mitigtion o Flooing Disruption Attks in Hirrhil OLSR Ntworks Gimr Crvr, Mihl Bru, Joquin Gri-Alro n Evnglos Krnkis Shool o Computr Sin, Crlton Univrsity, K1S 5B6, Ottw, Ontrio, Cn Emil: {gvi,ru,krnkis}@ss.rlton. Institut Tlom, Tlom Brtgn, Csson-Svign, 35576, Frn Emil: joquin.gri-lro@m.org Astrt Th Hirrhil Optimiz Link Stt Routing (HOLSR) protool ws sign to improv slility o htrognous Moil A-Ho Ntworks (MANETs). HOLSR is riv rom th OLSR protool n implmnts Multipoint Rly (MPR) nos s looing mhnism or istriuting ontrol inormtion. Unlik OLSR, nos r orgniz in lustrs n implmnt Hirrhil Topology Control (HTC) mssgs or intr-lustr ommunitions. Nvrthlss, HOLSR ws sign without surity msurs. Thror, mishving no n t th topology mp quisition pross y intrrupting th looing o ontrol inormtion or isturing th MPR sltion pross. W prsnt txonomy o looing isruption ttks, tht t th topology mp quisition pross in HOLSR ntworks, n prvntiv mhnisms to mitigt th t o this kin o ttks. Kywors-HOLSR; surity; looing mhnisms; MPR; I. Introution Th Hirrhil Optimiz Link Stt Routing (HOLSR) [13] is protiv routing protool sign to improv slility o htrognous Moil A-Ho Ntworks (MANETs). HOLSR orgnizs th ntwork in logil lvls n istriuts th nos in lustrs. In vry lustr, it implmnts th mhnisms n lgorithms o th originl OLSR [4] to gnrt n to istriut ontrol tri inormtion. Nvrthlss, HOLSR ws sign without surity onrns n oth inhrits n nw surity thrts. In HOLSR, vry no must l to quir n urt topology mp to prsrv th onntivity in th ntwork. Thn, h no hs two min tsks to prorm: () to gnrt ontrol tri inormtion or () to rly tht inormtion on hl o othr nos. Thus, inormtion ontin in Hllo n Topology Control (TC) mssgs r us to lult optiml routs rom ny givn no to ny stintion within h lustr. Aitionlly, Hirrhil Topology Control (HTC) mssgs r implmnt to vrtis mmrship inormtion rom lustr to othr nos in highr lvls. Th or optimiztion o th protool is th sltion o Multipoint Rlys (MPRs) s looing mhnism or istriuting TC n HTC mssgs to ll lvls o th hirrhil rhittur. In HOLSR, topology mp quisition [7] is th ility o ny givn no to quir omplt viw o th ntwork onntivity (i.., routing tls) oring to thir topologil lvl in th ntwork. A no with n inomplt topologil mp is unl o lulting routing pths n orwring t. In this ontxt, mliious no is in s no tht intrrupts th looing o ontrol tri inormtion or os not oy th ruls o th protool to mintin th hirrhil rhittur. Topology mp quisition is t y mliious no tht prorms looing isruption ttk to intrrupt th propgtion o ontrol inormtion. This ttk n prorm y mishving no tht rports ithr ls intity (i.., intity spooing) or ls link (i.., link spooing) to prtur th propr sltion o th MPRs. Furthrmor, mliious no might not rly proprly ontrol tri inormtion on hl othr nos. Thus, th nos in th ntwork will not l o onstruting omplt mp o othr nos tth to its lustr or in lowr hirrhil lvls. Noti tht in som ss looing isruption ttks n prorm vn in sur HOLSR ntwork (.g., no os not orwr ontrol tri inormtion to sv nrgy). Aitionlly, i n ttk is tt, it is nssry to implmnt n iint mhnism to vrtis othr nos in th ntwork. In this oumnt, w nlyz

2 looing isruption ttks tht t th topology mp quisition pross in HOLSR ntworks. Aitionlly, w prsnt prvntiv mhnisms to mitigt th t o this kin o ttks. Lvl 3 B3 K3 I3 F3 In this ppr, w xplin th t o th looing isruption ttks in HOLSR ntworks, howvr othr hirrhil pprohs s on th OLSR protool tht implmnt th MPR mhnism to loo ontrol inormtion t oth intr-lustr n intr-lustr lvls, r lso t y th ttks tht w sri in Stion IV, or instn: lustr OLSR (C-OLSR) [12] propos y Ros t l., tr-s logil topology [2] to provi hirrhil routing prsnt y Blli, th Multi-lvl OLSR Routing using th Host n Ntwork Assoition (HNA) mssgs Extnsion (MORHE) [14] prsnt y Voorhn t l., hirrhil pproh whih lso uss HNA mssgs or oth intr-lustr n intr-lustr ommunition [1] y Ar t l. n lustring mhnism to mng n to istriut ryptogrphi kys in n OLSR ntwork [6] propos y Hjmi t l. Orgniztion o th ppr Stion II rviws th OLSR protool. HOLSR is sri in Stion III. Stion IV sris th looing isruption ttks in HOLSR ntworks. Stion V prsnts st o strtgis to mitigt th ttks. Exprimnts n rsults r prsnt in Stion VI. Finlly, onlusions r prsnt in Stion VII. II. Optimiz Link Stt Routing protool This stion prsnts n ovrviw o th originl OLSR protool. OLSR is protiv routing protool sign xlusivly or MANETs. Th or o th protool is th sltion, y vry no, o Multipoint Rly (MPR) sts mong thir on-hop symmtri nighors s mhnism to loo th ntwork with prtil link-stt inormtion. This thniqu minimizs th numr o tri ontrol mssgs loo in th ntwork, rus th siz o th mssgs n llows to onstrut optiml routs to vry stintion in th ntwork. Th link-stt inormtion is onstrut y vry no n involvs prioilly sning Hllo n TC mssgs. Th OLSR protool is hop-y-hop routing, i.., h routing tl lists, or vry rhl stintion, th rss o th nxt no long th pth to tht stintion. Evry no lrns out its on n two-hop nighors y prioilly gnrting n riving Hllo mssgs. Hllo mssgs r not rtrnsmitt urthr. Th MPR st is slt so tht vry two-hop nighor is rhl through, t lst, on MPR. Evry no rports th nos it hs slt s MPRs in its Hllo Mssgs. With this inormtion, th nos uil thir MPR sltor st, i.., th st o nos tht hv s- Lvl 2 Lvl 1 A2 Clustr C1.A Clustr C2.B Clustr C1.B A1 1 D2 3 B1 2 B2 4 C1 Clustr C3.B C2 Clustr C1.H 5 H2 H Clustr C1.C Clustr C2.F E2 9 E F2 13 Clustr C1.E 12 Clustr C1.G Figur 1. Exmpl o hirrhil rhittur with htrognous nos. lt givn no s n MPR. TC mssgs r gnrt xlusivly y th MPRs. A no tht hs n mpty MPR sltor st os not sn or rtrnsmit ny TC mssg. Th origintor o TC mssg vrtiss itsl s th lst hop to rh ll nos inlu in its sltor tl. This inormtion llows h no to onstrut n to mintin its topology tl [8]. Aitionlly, OLSR implmnts HNA n Multipl Intr Dlrtion (MID) mssgs. HNA mssgs r us to injt xtrnl routing inormtion into n OLSR ntwork n to provi onntivity to nos with non-olsr intrs. MID mssgs r us to lr th prsn o multipl intrs on no. HNA n MID r optionl n xlusivly rtrnsmitt y th MPRs. Thror, th sltion o th MPRs n th linkstt vrtismnt mhnism r ritil vulnrility trgts. III. Hirrhil OLSR MANETs r y ntur orm y htrognous vis n nos tht n join th ntwork without ollowing pritl pttrn. Furthrmor, slility is prolm in MANETS. Slility n in s th pity o th ntwork to just or to mintin its prormn vn i th numr o nos in th ntwork inrss [13]. OLSR is lt routing protool n th prormn o th protool tns to gr whn th numr o nos inrss u to highr numr o topology ontrol mssgs propgt through th ntwork. Th MPR mhnism is lol n thror vry sll. Howvr, th iusion y ll th nos in th ntwork o ll th link-stt inormtion is lss sll. For instn, in [11] Plm t. l., show tht OLSR hv goo rsults in trms o slility in ntworks with up to 70 nos, prrly with mort no sp n whr th numr o tri lows is G1 G2

3 lso mort. Howvr, OLSR s prormn rss in lrg htrognous ho ntworks. Aitionlly, OLSR os not irntit th pilitis o its mmr nos n, in onsqun, os not xploit nos with highr pilitis. Thus, HOLSR is n pproh sign to improv th slility o OLSR protool in lrg-sl htrognous ntworks. Th min improvmnts r rution in th mount o topology ontrol tri n iint us o high pity nos. HOLSR orgnizs th ntwork in hirrhil lustrs. This rhittur llows to ru th routing omputtionl ost, i.., in s link is rokn only nos insi th sm lustr hv to rlult thir routing tl whil nos in irnt lustrs r not t. In HOLSR, nos r orgniz oring to thir pitis. Th HOLSR ntwork rhittur is illustrt in Fig. 1. At lvl 1, w hv lowpility nos n on intr rprsnt y irls. Nos t th topology lvl 2 r quipp with up to two wirlss intrs, signt y squrs. Nos t lvl 2 mploy on intr to ommunit with nos t lvl 1. Nos t lvl 3, signt y tringls, rprsnt high-pity nos with up to thr wirlss intrs to ommunit with nos t vry lvl. Thus, in Fig. 1, no F3 rprsnts no F s intr t lvl 3. Th only rstrition or nos t lvls 2 n 3 is tht thy hv t lst on intr to ommunit with nos t lvls 2 or 3, rsptivly. For instn, in Fig. 1 no F hs two intrs n n ommunit with nos t lvls 2 n 3. No A hs lso two intrs n stlishs ommunition with nos t lvls 1 n 2. No D n just ommunit with nos t lvl 2. In th xmpl, th nottion us to nm th lustrs rlts th lvl o th lustr n th lustr h,.g., C1.A mns tht th lustr is t lvl 1 n th lustr h is no A. HOLSR llows ormtion o multipl lustrs n, unlik OLSR, HOLSR nos n xhng Hllo n TC mssgs xlusivly within h lustr. This onstrint rus th mount o tri inormtion rost to th ntir ho ntwork. A. Clustr Formtion Th topology ontrol inormtion twn lustrs is xhng vi spiliz HOLSR nos sign s lustr hs. Th sltion o lustr hs n lssiition o nos oring to thir pilitis r in t th strtup o th HOLSR pross. A lustr is orm y group o moil nos t th sm hirrhil lvl tht hv slt ommon lustr h. Nos n mov rom on lustr to nothr n ssoit with th nrst lustr h. Any no prtiipting in multipl topology lvls utomtilly oms th lustr h o th lowr-lvl lustr. In HOLSR, lustr h lrs its sttus n invits othr nos to join in y prioilly sning out Clustr ID Announmnt (CID) mssgs. Ths mssgs r trnsmitt in th sm pkt with Hllo mssgs using mssg grouping thniqu. This thniqu is implmnt to ru th numr o pkt trnsmissions. A CID mssg ontins two ils: lustr h tht rprsnts th intr rss o th origintor o th mssg, n istn whih is th istn in hops to th lustr h gnrting th mssg. Evry tim th lustr h gnrts CID mssg, it initilizs th il istn to zro. Th rivr no joins th lustr h n sns nw CID mssg. Th nw CID mssg inrss th vlu o th istn y on unit. This mhnism llows to invit othr nos to join th sm lustr. Th lustr ormtion pross is sri in mor til in [13]. B. Clustr H Mssg Exhng Th hirrhil rhittur must support th xhng o topology ontrol inormtion twn lustrs without introuing itionl ovrh. Thus, Hirrhil TC (HTC) mssgs r gnrt y th lustr h n us to trnsmit th mmrship inormtion o lustr to highr lvl nos. HTC orwring is nl y th MPRs n rstrit within lustr. Nos t th highst topology lvl hv ull knowlg o ll nos in th ntwork n thir routing tls r s lrg s thy woul in n OLSR ntwork. Howvr, in lowr lvls, th siz o th routing tl o vry no is rstrit to th siz o th lustr n it is smllr thn in OLSR. For instn, in Fig. 1 th lustr h A gnrts n HTC mssg or th intr A2 (lvl 2) nnouning tht nos 1, 2 n A1 r mmrs o its lustr t lvl 1. Th mssg is rly to ll nos t th sm lvl. Thn, no B gnrts n HTC mssg or th intr B3 (lvl 3) vrtising tht nos 1, 2, 3, 4, 5, 7, 8, A1, B1, C1 (t lvl 1) n A2, B2, C2, D2 (t lvl 2) r mmrs o its lustr. C. Topology Control Propgtion Nos in h lustr t irnt lvls slt thir MPRs to loo ontrol tri inormtion. Control mssgs r gnrt n propgt xlusivly within h lustr, unlss no is lot in th ovrlpping zon o svrl lustrs. For xmpl, in Fig. 1 no 2 is within th orr o lustr C1.A n my pt TC or HTC mssg rom no 3 lot in lustr C1.B. Howvr, no 2 rtins th inormtion without rtrnsmitting it to its lustr. Thus, xpt or th orr nos, knowlg o nos out th lustr is rstrit to th lustr itsl. Dt trnsr twn nos in th sm lustr is hiv irtly vi th inormtion in th routing tls. Howvr,whn trnsmitting t to stintions outsi th lol sop o lustr, th lustr hs r lwys us t gtwy mhnism y mmr

4 nos t lowr hirrhl lvls. A irnt strtgy might us, whn trnsmitting t twn orr nos in irnt lustrs t th sm lvl, th lustr h is not us s gtwy to rly th inormtion, n nry nos in irnt lustrs t th sm topology lvl n ommunit irtly without hving to ollow th strit lustring hirrhy. Thror, HOLSR ors two min vntgs () th tri ontrol mssgs rlting lol movmnt r rstrit to h lustr (thus, ruing th routing tl omputtion ovrh), n () n iint us o high-pity nos without ovrloing thm. Flooing Disruption Attks Inorrt MPR Sltion Inorrt Rlying Intity Spooing Link Spooing Slish Bhvior Slnrr Bhvior Hop Limit Attk On-hop Arss Duplition Two-hop Arss Duplition Inxistnt Links Phntom No Invli MPR st Figur 2. Txonomy o looing isruption ttks in HOLSR. A. Intity Spooing Th intity spooing ttk [7] is prorm y mliious no prtning to irnt no in th ntwork. Th gol o th ttk is to rport ls inormtion out nos on or two-hops wy in orr to mliiously t th MPR sltion pross. Figur 3() illustrts n xmpl whr no x spoos th intity o no n rosts hllo mssg vrtising vli link with no. Thn, no will riv Hllo mssgs rom no x initing tht no hs links with nos n. In this s, no slts inorrtly no s th only lmnt in its MPR st. In onsqun, no is unrhl through th MPR st n will nvr riv TC or HTC mssgs. Figur 3() prsnts n xmpl whr th ttkr ts th MPR sltion o no t istn two hops. Th mliious no x spoos th intity o no, i.., nos n will gnrt Hllo mssgs vrtising no s on-hop nighor. From th point o viw o no nos,, n hv no s onhop nighor. As rsult o th ttk, no n slt inorrtly nos or s MPR. In this s, nos n will not orwr ontrol tri inormtion to no us thy r not inlu in th MPR st. IV. Flooing Disruption Attks in HOLSR x spoos x spoos Th looing mhnism or ontrol tri inormtion in n HOLSR ntwork is s on th orrt sltion o th MPRs. Control tri mssgs (i.., TC n HTC mssgs) r orwr xlusivly y th MPRs. An ttkr sking to intrrupt th ontrol tri looing n ithr () mnipult th inormtion out th on n two-hop nighors o givn no to us th MPR sltion to il, or () mishv uring th gnrtion n orwring prosss. Thus, no will riv inomplt inormtion out othr nos in its lustr or in lowr lvl lustrs. Th ttk hs ross lyr impt i th t no is lustr h with n intr to n uppr lvl. In this s, nos in th uppr lvl will il to omput rout to nos in lowr lvls o th ntwork. For instn, onsir in Fig. 1 tht no E2 slts no H2 s its MPR, nonthlss H2 mishvs n os not rtrnsmit ny ontrol tri mssg. In onsqun, no F2 n nos in lustr C3.B will not wr o nos within lustr C1.E. Fig. 2 summrizs looing isruption ttks in n HOLSR ntwork n th mhnisms us to prorm thm. In th squl, w prsnt ths ttks mor in til. () No x spoos n rports n inorrt link twn nos n. On-hop rss uplition. () No x spoos n ts no s MPR sltion. Twohop rss uplition. Figur 3. Flooing isruption u to intity spooing ttks. x () No x spoos links to nos n. Figur 4. Flooing isruption u to link spooing ttks. g

5 B. Link Spooing Th link spooing ttk [7] is prorm y mliious no tht rports n inxistnt link to othr nos in th ntwork. Th ojtiv o th ttkr is to mnipult th inormtion out th nos on or two hops wy n slt s prt o th MPR st. On th mliious no hs n slt s n MPR, it nithr gnrts nor orwrs ontrol tri inormtion. Th looing isruption ttk u to link spooing is illustrt in Fig. 4(). In this xmpl, no x spoos links to nos n. No x sns Hllo mssgs n looks lik th st option to slt s n MPR or no. No rivs th Hllo mssgs rom no x n omputs inorrtly its MPR st y slting no x s th only lmnt to rh nos n. Thus, ll routing inormtion will not rh nos two hops wy rom no. A vrint o th ttk n prorm y rporting link to n inxistnt no. C. Invli MPR St In this ttk, mliious no isrupts th looing o topology ontrol inormtion y mishving uring th MPR sltion pross. Figur 5() illustrts th ttk. No x wnts to slt s th only MPR o no. Thn, it spoos link to no g n gnrts Hllo mssgs nnouning no g s on-hop nighor n its only MPR. From th prsptiv o no, nos n g n rh through no x. Thn, no x is th st nit to slt s n MPR or no. Thus, no x rivs n orwrs TC or HTC mssgs rom no. Howvr, thos mssgs nvr rh no us ny on-hop nighor o no x rtrnsmits th mssgs. This ttk xploits th sour pnnt rquirmnt in OLSR to orwr ontrol tri inormtion. In this s, or nos,, n, no x is not inlu in thir sltor tl n thy will nvr orwr ny mssg rom no x. x () No x nvr slts vli MPR st. g () No x moiis n orwrs inorrtly TC n HTC mssgs. Figur 5. Flooing isruption u to protool isoin. x D. Inorrt Rlying A mishving no n isrupt th intgrity o th ntwork y ithr inorrtly gnrting or rlying ontrol tri inormtion on hl o othr nos. Consir x in Figur 5() s mishving no. No x wnts to slt s th only MPR o no. Thn, it spoos link to no g n gnrts Hllo mssgs nnouning no g s on-hop nighor. From th prsptiv o no, nos n g n rh through no x. Thus, no x is slt y no s its only MPR n might prorm th ollowing inorrt hviors: Slish hvior. Th ttk is prorm y no tht mishvs n nithr gnrts nor orwrs TC or HTC mssgs. To inrs th tivnss o th ttk, th mliious no might stlish ls links to othr nos in th ntwork n or its on-hop nighors to slt it s thir MPR. Fig. 5() illustrts n xmpl whr no x hs n slt y no s n MPR ut it os not rly ontrol tri on hl o othr nos. In onsqun, no will not riv ontrol tri inormtion rom no. Noti tht in n HOLSR ntwork, th ttkr n hoos not to orwr ny prtiulr mssg, i.., TC, HTC, MID or HNA mssgs. Slnrr hvior. Th list o rsss rport in h TC mssg n prtil (.g., u to mssg siz limittions). Thus, mishving no n lwys gnrt TC mssgs without rporting ll nos in its sltor tl liming tht th siz o th mssgs is not nough to inlu ll nos in its sltor tl. As rsult, i no x gnrts TC mssgs without inluing no, no will not l to omput pth to no. Hop Limit ttk. A mliious no x n rstilly rs th hop limit (TTL vlu) whn orwring TC or HTC mssg,.g., stting th hop limit qul to zro. This will ru th sop o rtrnsmitting th mssg. Th ttk n prorm y mliious no tht hs not n slt s n MPR. For instn, in Figur 5(), ontrol mssg is orwr y no n riv y oth nos x n. Prviously no ws slt y no s its MPR. Howvr no x orwrs th mssg without ny ly or jittr suh tht its rtrnsmission rrivs or tht th vli mssg rom. Bor orwring, it rus th hop limit o th mssg. Th t no, no, will pross th mssg n mrk it s lry riv, ignoring utur vli opis rom. Thus, th mssg with vry low hop limit will not rh th whol ntwork. V. Countrmsurs In n HOLSR ntwork, th MPR sltion rus t minimum th ovrh gnrt y ontrol tri mssgs, i vry no slts its MPR st with th ollowing

6 onitions: (i) th MPR st is kpt t minimum, (ii) n MPR rtrnsmits ontrol tri mssgs i n only i th snr no is inlu in its sltor tl, n (iii) only prtil link stt inormtion is trnsmitt, i.., n MPR rports only links with its sltor nos. Nvrthlss, w n loosn up th prvious rstrition in orr to or highr lvl o surity whil mintining tro twn surity n prormn. In th ollowing sustions, w sri st o strtgis to ru th t o looing isruption ttks. Th strtgis tht w sri r s on th sltion o MPRs with itionl ovrg, gnrtion o TC mssgs with runnt link stt inormtion n non sour-pnnt orwring mhnism. A. MPRs with Aitionl Covrg Aitionl ovrg in th sltion o th MPRs is in in [4], s th ility o no to slt runnt MPRs. Th sltion o MPRs must s smll s possil to ru th ovrh gnrt y looing th ntwork with TC mssgs. Nvrthlss, itionl ovrg llows no to vrtis its prsn to mor nos in th ntwork. In this mnnr, xtr ovrg hlps to mintin th intgrity o th ntwork in spit o th prsn o mliious nos uring th xution o HOLSR. Th sltion o MPRs with xtr ovrg is in in th RFC3626 [4], w nm this pproh k-covr-mpr st. Howvr, th ovrh gnrt y th xssiv numr o TC n HTC mssgs rus th prormn o th ntwork. This prolm is rss with n improv k-roust-mpr sltion prsnt in [3], whih lns surity n tri ovrh. Figur 6 prsnts xmpls o th rsulting MPR sltion strtgis with or without itionl ovrg. 1) RFC3626 s MPR Covrg Prmtr: Th RFC3626 [4] ins th MPR Covrg prmtr to spiy y how mny on-hop nos ny two-hop nighors must ovr. I MPR Covrg is qul to on, thn th ovrh is kpt t minimum n th untion is quivlnt to th MPR sltion without itionl ovrg spii in [4], Stion I MPR Covrg is qul to k, no slts its MPR st suh s ny two-hop nighor is ovr y k on-hop nighors, whnvr possil. A poorly ovr no, is no in th two-hop nighorhoo tht nnot ovr y t lst k nos in th on-hop nighorhoo. Th MPR Covrg prmtr is lol to vry no in th ntwork. Nos with irnt vlus o MPR Covrg my oprt in sm ntwork. Th MPR sltion with itionl ovrg using th MPR Covrg prmtr is xplin in mor til in [3], [4]. Figur 6() shows k-covr-mpr sltion with vlu o k qul to two. () k-covr-mpr sltion k qul to two. h () k-roust-mpr sltion k qul to on. Figur 6. MPR sltion in n HOLSR lustr with itionl ovrg. 2) k-roust-mpr Sltion: A k-roust-mpr sltion [3] omputs n MPR st tht is ompos o, t most, k + 1 isjoint groups, i.., vry two-hop no is ovr, i possil, y k + 1 isjoint groups o on-hop nighors. Assum th ollowing nottion: (n, u): numr o hops twn nos n n u. N 1 (n) := {n 1 : (n, n 1 ) 1}. N 2 (n) := {n 2 : (n, n 2 ) 2}. N 2 (n) := N 2 (n) \ N 1 (n). h g M : M is n MPR st or no n i n only i M N 1 (n) suh tht or vry no n 2 N 2 (n), N 1 (n 2 ) M. Th k-roust-mpr sltion lgorithm works s ollows: 1) First, w otin sust M i suh tht M i is sust o N 1 (n) n ovrs ll th nos in N 2 (n). 2) W rpt th pross until it is not possil to in nw isjoint sust M i tht ovrs ll th nos in N 2 (n) or w hv oun mximum o k + 1 isjoint susts. 3) Th MPR st is orm y th union, i it is possil, o k isjoint susts M i. Th rsulting MPR st hs two min proprtis: () in k-roust-mpr st it is possil to isr mximum o k MPR sts, n th rmining st it is still vli MPR st, n () i w n only in k +1 isjoint MPR sts, suh tht k +1 is lss or qul thn vlu o k, w otin vli k -roust-mpr st. Figur 6() shows k- Roust-MPR sltion with vlu o k qul to on. For instn, no i n slt ithr {g} or {, j} s vli isjoint MPR sts, thn no i n omput 1-Roust- MPR st orm y {g,, j}. Thn, i no g mishvs, g j i j i l k l k

7 no i n isr it n th sust {,j} rmins s vli MPR st. B. Runnt Inormtion In ontrst to othr lssi link stt protools, suh s th OSPF [10], in n HOLSR ntwork only prtil link stt inormtion is ius. Prioilly, n MPR gnrts TC mssgs rporting only nos in its sltor tl to lult optiml routs to vry stintion. Howvr, th vrtis link st o no my inlu links to nighor nos whih r not in th MPR sltor st o th no. Th miniml st o links tht ny MPR must vrtis in its TC mssgs r th links to its MPR sltors. Nvrthlss, th vrtis link st my inlu links to th whol nighor st o th no. Th ius link-stt inormtion n tunn through th TC Runny prmtr in in th RFC3626 [4], Stion 15. Th prmtr TC Runny is lol to vry no n trmins th mount o inormtion tht shoul inlu in th TC mssgs. I th TC Runny prmtr is qul to zro, thn th vrtis link st o th MPR is limit to its MPR sltor st. I th TC Runny prmtr is qul to on, thn th MPR will vrtis its MPRs n its MPR sltor st. Finlly, i th prmtr is qul to two, thn th MPR will rport ll its on-hop nighors. For instn, in Fig. 6() no slts no {} s its only MPR. Howvr, suppos no mishvs n rports ls link to no n phntom no x, no n not slt isjoint MPR sts n will slt no s its only MPR st. I no os not gnrt or orwr ontrol tri, thn no will rmin isolt. Noti tht no is slt y no s its MPR, thn it rports in its TC mssgs no s its only sltor no. I no sts its TC Runny prmtr qul to thr, thn it will rport ll its on-hop nighors, inluing no. As rsult, th siz o th TC mssg will inrs ut this strtgy might us to prvnt looing isruption ttks. C. Non-Sour Dpnnt Mhnism In n HOLSR ntwork, n MPR rtrnsmit ontrol tri mssg (TC or HTC mssg) ollowing Sour Dpnnt (SD) strtgy, i.., n MPR orwrs ontrol tri mssg i n only i th snr o th mssg is inlu in its sltor tl. This mhnism llows to minimiz th numr o rtrnsmissions n ovrh gnrt y xssiv TC mssgs in th ntwork. In [9], Mkr t l. nlyz th ovrh gnrt y nonsour pnnt MPR (NSD-MPR) mhnism to support simplii multist IP routing in MANETs. Nonthlss, this pproh n us to nor surity in n HOLSR ntwork. In orr to voi n xssiv ovrh, th mhnism n usul to rtrnsmit xlusivly HTC mssgs oring th ollowing lgorithm or givn no n: I no n rivs n HTC mssg n no n s sltor tl is not mpty thn pross n orwr th mssg. Othrwis, just pross th mssg. I no n rivs TC mssg n no n s sltor tl is not mpty n th snr o th mssg is inlu in no n s sltor tl thn pross n orwr th mssg. Othrwis, just pross th mssg. For instn, in Fig. 6() onsir no s lustr h n n not slt isjoint MPR sts. Suppos, no mishvs n rports ls link to no n ls link to phntom no x. Thn, no is or to slt no s its only MPR. No gnrts TC mssgs n nnouns no s it sltor no ut it os not rtrnsmit HTC mssgs gnrt y no. In onsqun, ll nos rport y no in its HTC mssgs will not vrtis y othr nos in its lustr n in uppr lvls. Howvr, i no is slt y no s its MPR n it ollows non-sour pnnt strtgy to rtrnsmit HTC mssgs, no s mssgs will rtrnsmitt y no vn i no is not inlu in its sltor no. VI. Exprimnts W onut simultions to ssss th tivnss o our propos ountrmsurs ginst looing isruption ttks in HOLSR ntworks. W ount th numr o nos in HOLSR ntwork tht r l to uil omplt routing tls unr th prsn o on to our mliious nos. W otin s prormn rtio, th prntg o nos with omplt routing tls ovr th numr o mssgs gnrt uring th simultion. W onut our xprimnts using th NS-3 simultor [5], vrsion 3.9. W moii th originl OLSR o vlop y Ros n Crniro to implmnt th hirrhil pproh (i.., HOLSR) n th ountrmsurs sri in Stion V. Th mliious nos r slt mong th MPRs, thy o not ollu to prorm n ttk, no t tri is gnrt n ll th snrios r stti. W tst our propos ountrmsurs in HOLSR ntworks with thr lvls n two hunr nos in h s: 175 nos with on intr n trnsmission rng o 100 m, 20 nos with up to two intrs n trnsmission rng o 200 m, n iv nos with up to thr intrs n trnsmission rng o 500 m. Th nos with just on intr t th irst lvl, r pl ollowing n uniorm istriution. W ssum tht th ministrtor o th ntwork n i th st ritri to istriut th lustr hs. Figur 7 pits th vrg numr o nos with omplt routing tls n 95% onin intrvls. It shows how our

8 Aknowlgmnt Th uthors griously knowlg th innil support riv rom th ollowing orgniztions: Nturl Sins n Enginring Rsrh Counil o Cn (NSERC), Mthmtis o Inormtion Thnology n Complx Systms (MITACS), Institut Tlom, Spnish Ministry o Sin n Innovtion (grnts TSI C03-03 E- AEGIS n CONSOLIDER-INGENIO CSD ARES), Ntionl Counil o Sin n Thnology (CONACYT), n Ministry o Eution o Mxio (SEP, Progrm or Ami Improvmnt). Rrns () Prntg o nos with omplt routing tls. Prormn rtio NSD-MPR, k=1 k-roust-mpr, k=1 k-ovr-mpr, k= No. mishving nos (Slish) () Prormn rtio. Figur 7. Comprison o untions NSD-MPR, k-ovr-mpr, n k-roust-mpr unr th prsn o slish nos. strtgis or itionl prottion to mitigt th t o slish nos in ontrst with th sltion o MPRs without itionl ovrg. Noti tht th k-roust- MPR untion mitigts th t o mishving nos with ttr prormn thn th k-ovr-mpr n NSD-MPR pproh (. Figur 7()). Similr rsults r xpt or th othr two ss sri in Stion IV-D. VII. Conlusion In this ppr, w prsnt txonomy o looing isruption ttks tht t th topology mp quisition in HOLSR ntworks. Ths kin o ttks t ithr th MPR sltion pross or th looing o ontrol tri inormtion or intr-lustr or intr-lustr ommunition. Aitionlly, w prsnt st o strtgis to mitigt th t o this kin o ttks. Aoring to our xprimnts, it is possil to mitigt th t o looing isruption ttks y slting th MPR sts with itionl ovrg or gnrting ontrol tri with runnt inormtion. [1] P. Ar, J.C. Gurri, A. Pjrs, n O. Lázro. Prormn vlution o vio strming ovr ho ntworks using lt n hirrhil routing protools. Moil Ntworks n Applitions, 13(3-4): , [2] E. Blli. OLSR trs: A simpl lustring mhnism or OLSR. Chllngs in A Ho Ntworking, IFIP Intrntionl Frtion or Inormtion Prossing, 197: , [3] G. Crvr, M. Bru, J. Gri-Alro, n E. Krnkis. Mitigtion o topology ontrol ttks in OLSR ntworks. In 5th Intrntionl Conrn on Risks n Surity o Intrnt n Systms (CRISIS 2010), Jn-Mr Rort, itor, pgs 81 88, Montrl, Cn, Otor 10-13, [4] T. Clusn n P. Jqut. Optimiz link stt routing protool (OLSR), RFC3626. IETF Intrnt Drt, Otor [5] T. Hnrson t. l. Th NS-3 ntwork simultor. Sotwr pkg rtriv rom [6] A. Hjmi, K. Ouii, n M. Elkouti. An nhn lgorithm or MANET lustring s on multi hops n ntwork nsity. In Nw Thnologis o Distriut Systms (NOTERE), th Annul Intrntionl Conrn on, pgs IEEE, [7] U. Hrrg n T. Clusn. Surity Issus in th Optimiz Link Stt Routing Protool vrsion 2 (OLSRv2). Intrntionl Journl o Ntwork Surity & Its Applitions (IJNSA), Volum 2, Numro 2, [8] P. Jqut, P. Muhlthlr, T. Clusn, A. Louiti, A. Qyyum, n L. Vinnot. Optimiz link stt routing protool or ho ntworks. In IEEE Intrntionl Multi Topi Conrn, IEEE INMIC Thnology or th 21st Cntury. Proings, pgs Lhor Univrsity o Mngmnt Sins, Pkistn, Dmr [9] J. Mkr, I. Downr, J. Dn, n B. Amson. Evlution o istriut ovr st lgorithms in moil ho ntwork or simplii multist orwring. ACM SIGMOBILE Moil Computing n Communitions Rviw, 11(3):1 11, [10] J. Moy. Opn Shortst Pth First (OSPF) vrsion 2, RFC2328. IETF Intrnt Drt, April [11] D. Plm n M. Curo. Insi-out olsr slility nlysis. In Proings o th 8th Intrntionl Conrn on A-Ho, Moil n Wirlss Ntworks, ADHOC-NOW 09, pgs , Brlin, Hilrg, Springr-Vrlg. [12] F.J. Ros n P.M. Ruiz. Clustr-s OLSR xtnsions to ru ontrol ovrh in moil ho ntworks. In Proings o th 2007 intrntionl onrn on Wirlss ommunitions n moil omputing, pgs ACM, [13] L. Villsnor-Gonzlz, Y. G, n L. Lmont. HOLSR: A hirrhil protiv routing mhnism or moil ho ntworks. IEEE Communitions Mgzin, 43(7): , July [14] M. Voorhn, E. Vn Vl, n C. Bloni. MORHE: A trnsprnt multi-lvl routing shm or ho ntworks. In K. Al Agh, I. Gurin Lssous, n G. Pujoll, itors, Chllngs in A Ho Ntworking, volum 197 o IFIP Intrntionl Frtion or Inormtion Prossing, pgs Springr Boston, 2006.