IPv6 Autoconfiguration in Large Scale Mobile Ad-Hoc Networks

Transcription

1 IPv6 Autocofiguratio i Large Scale Mobile Ad-Hoc Networks Kilia Weiger, Martia Zitterbart Istitute of Telematics Uiversity of Karlsruhe, 768 Karlsruhe, Germay Ph: {65/600}, {weiger,zit}@tm.uka.de ABSTRACT Mobile ad-hoc etworks are ifrastructure-free, highly dyamic wireless etworks, where cetral admiistratio or cofiguratio by the user is impractical. The Iteret Protocol IPv6 defies mechaisms to autocofigure iterfaces of odes i wired etworks i a distributed maer. I this paper, the applicability of IPv6 Stateless Address Autocofiguratio ad IPv6 Neighbor Discovery Protocol to large scale mobile ad-hoc etworks is ivestigated. A hierarchical approach based o so-called leader odes is proposed together with a leader electio algorithm. Address autocofiguratio with IPv6 i very dyamic ad-hoc etworks requires special support as, for example, outlied withi this paper. Extesios to the IPv6 Neighbor Discovery Protocol are proposed to eable a efficiet ad scalable usage i ad-hoc etworks. INTRODUCTION I mobile ad-hoc etworks, odes spotaeously form a etwork, where each ode ca reach ot oly odes i its direct trasmissio rage, but also distat odes, accessible through a chai of itermediate odes. Figure illustrates a sceario, where ode seds a packet over multiple hops towards its jourey to the destiatio. Because of ode mobility, the available paths to a destiatio chage over time with a cosiderably higher frequecy tha i ifrastructure etworks. Furthermore, the etwork may partitio ad merge agai later, depedet o the mobility patters ad trasmissio rages of the mobile odes. Cosequetly, ehaced requiremets exist for routig protocols operatig i such a eviromet. This has bee addressed by various research efforts o mobile ad-hoc routig (e.g., Moarch Project at CMU [], Wireless Adaptive Mobility Laboratory at UCLA []). Much less attetio has bee give to autocofiguratio mechaisms, such as address autocofiguratio. I geeral, the purpose of address autocofiguratio is the assigmet of a address to a iterface, which is uique ad routable i the etwork. I ad hoc etworks, this mechaism eed to cope with the high dyamics withi such etworkig eviromets. This work was supported by the Germa Federal Miistry of Educatio ad Research (BMBF). It was part of the IPoAir project belogig to the research focus hypernet. HyperNET stads for Uiversal Utilizatio of Commuicatios Networks for Future Geeratios of Mobile Commuicatios Systems. I this paper, we ivestigate the applicability of IPv6 autocofiguratio mechaisms to ad hoc etworkig. It is assumed, that the mobile odes will be idetified through IPv6 addresses. Trasmissio Rage Figure : Multi-hop ad-hoc Routig The approach preseted i this paper is based o the followig requiremets: The mechaism eeds to cope with the etwork dyamics preset i mobile ad-hoc etworks. Therefore, a distributed approach is used. The mechaism shall scale to large ad-hoc etworks with, e.g., thousads of odes with multiple iterfaces. Amog others, address space limitatios ad sigalig traffic load must be cosidered carefully. Because there exist may routig protocols for ad hoc etworks, each optimized for special etwork scearios, the mechaism shall be idepedet of the routig protocol. However, optimizatios are possible if both are cooperatig. If two idepedetly cofigured ad hoc etworks merge, the uiqueess of the addresses shall be guarateed afterwards, i.e. etwork partitioig ad mergig shall be supported. Because IPv6 is i discussio for mobile commuicatio systems beyod the rd geeratio, we adopt the IPv6 Stateless Address Autocofiguratio (SAA) [] ad the correspodig Neighbor Discovery Protocol (NDP) [] [5] to ad-hoc etworks with the goal of scalability i 5

2 mid. We choose a hierarchical approach, where some odes are resposible for parts of the address cofiguratio of other odes. The paper is structured as follows: Related research efforts are discussed i sectio. A brief overview of IPv6 Stateless Address Autocofiguratio is give i sectio. Sectio describes how to adapt the process to ad-hoc etworks ad presets a electio algorithm for the leader odes. Sectio 5 discusses the iteractio with routig protocols. Ad, fially, sectio 6 cocludes the paper. RELATED WORK Withi the IETF workig group for Mobile Ad-Hoc Networks (MANET) several routig protocols were proposed. These protocols ca be roughly classified ito proactive ad reactive protocols [6] [7] [8]. Most proactive protocols evolved from distace-vector or lik-state routig protocols. By periodically exchagig cotrol messages with eighborig odes, each ode maitais a up-to-date versio of the etwork topology. I cotrast, reactive protocols, e.g. the Dyamic Source Routig protocol (DSR) [9], discover the route to the destiatio o demad. Depedig o etwork dyamics, size, topology ad traffic patters, each protocol has its advatages ad drawbacks. Hybrid protocols try to combie both approaches, mostly by buildig a hierarchy. Address autocofiguratio i large ad-hoc etworks is still a uresolved issue. Cetral admiistratio, e.g., based o DHCP, or maual cofiguratio by the user is impossible i large mobile ad-hoc etworks. The IETF ZEROCONF workig group deals with autocofiguratio issues, but with a focus o wired etworks. A simple solutio for address autocofiguratio i ad-hoc etworks by usig IPv lik-local addresses was proposed by Perkis [0]. Addresses are radomly chose from the etwork 69.5/6. Duplicate addresses are detected by usig protocol messages of the route discovery phase of a reactive routig protocol like DSR [9]. Duplicate Address Detectio (DAD) is performed oly oce by each ode. Subsequetly, the uiqueess of addresses is ot guarateed i partitioed etworks that merge later o. Each ode performig the DAD uses the route discovery mechaism of the routig protocol. This mechaism, i tur, is based o floodig the etire etwork to fid the destiatio. This is ot suitable for large scale ad-hoc etworks, especially if the DAD is repeated to support etwork mergig. Furthermore, the address space is limited to 07 durig ad 6555 after the DAD. The probability of a address coflict icreases with the umber of iterfaces that wish to operate i the etwork. It should be cosidered that mobile odes may have multiple iterfaces to differet ad hoc etworks. Durig DAD, a tetative IPv address is used as source address, which is selected radomly out of the rage -07. Although these addresses should ever be used for more tha a few secods, problems may arise i large ad hoc etworks, especially if a lot of odes power o at the same time. I summary, the approach preseted i [0] oly works with specific proactive routig protocols, has address space limitatios ad does ot cope with dyamic etwork partitioig ad mergig. Park et. al. [] propose to use site-local IPv6 addresses ad Neighbor Discovery for DAD. The use of IPv6 addresses reduces the problem of the limited address space, but leaves a lot of issues uresolved. I [], subet IDs are selected radomly by each ode ad are ot used to divide the etwork ito subetworks. This results i a flat address scheme. Usually the subet IDs are assiged by routers o the lik usig Router Advertisemets (RA). I summary, this approach requires all odes to flood the etire ad-hoc etwork with forwarded NDP messages ad does ot cosider etwork mergig as well. Aother approach [] [], called the Dyamic Registratio ad Cofiguratio Protocol (DRCP), tries to exted DHCP to a stateless autocofiguratio protocol for wired ad wireless etworks. Therefore, each ode represets a DRCP cliet ad server ad ows a IPv address pool. The Dyamic Address Allocatio Protocol (DAAP) is resposible for the distributio of the address pools. Therefore, each ode requestig a pool obtais half of the pool of a eighborig ode. This may lead to a lot of uassiged addresses i the already scarce IPv private etwork address space ad, subsequetly, to scalability problems. Network mergig is ot cosidered as well. IPV6 STATELESS ADDRESS AUTOCONFIGURA- TION The IPv6 SAA [] is based o NDP [] which is specified for liks that support a ative form of multicast or broadcast. Some other liks are covered by extesio documets, but there is o extesio for ad hoc etworks yet. The IPv6 SAA basically cosists of three phases:. Costructio of a lik-local address for the use o the local lik. Duplicate Address Detectio. Costructio of a site-local address for the use o the site The use of a global address is ot part of the SAA. Therefore, Stateful Address Autocofiguratio (DHCPv6) [] may be used. The process begis with the costructio of a liklocal address that is based o the iterface idetifier ad a well-kow lik-local prefix. It is first cosidered as a tetative address. IEEE defies a 6-bit Exteded Uiversal Idetifier (EUI-6), which is used for this purpose. It is calculated, e.g., from the MAC-address of a IEEE 80.x iterface. Although the EUI-6 umber is desiged to be globally uique, this caot be guarateed, because of maufacturers usig uregistered 80.xaddresses, support for chagig the MAC-address by the user or obscure etwork devices, which choose a MACaddress radomly. The DAD process is eeded to detect ad hadle duplicate addresses. Therefore, the ode issues a Neighbor Solicitatio (NS) message (see Figure )

3 with the well-kow uspecified address as source IP address. This address must ever be assiged to a ode ad idicates the absece of a address [5]. Versio Prio. Payload Legth Type: 5 Code: 0 Reserved Flow Label Next Header Source Address: uspecified address Destiatio Address: solicited ode multicast address Target Address: tetative address Checksum Hop Limit: 55 Figure : The Neighbor Solicitatio (NS) message The solicited-ode multicast address is used as destiatio IP address, which is based o a well-kow prefix ad the last bits of the tetative address. The tetative address is used as solicitatio target address ad a hop limit of 55 is used to limit the message o the local lik. NDP messages with a hop limit of less tha 55 are discarded. This prevets hackers from itroducig NDP messages to the local lik from outside. If the address is already i use by aother ode, this ode respods with a Neighbor Advertisemet (NA) message carryig the all-odes multicast address as destiatio IP address. A address coflict is recogized, if the seder receives a NA message i reply to the NS message or if a NS message with the same solicitatio target address is received, idicatig that aother ode with the same tetative address curretly performs the DAD. If Router Advertisemets cotaiig a subet ID are received, hosts costruct a site-local address usig the lik-local address, a well-kow site-local prefix ad the aouced subet ID. IPV6 STATELESS ADDRESS AUTOCONFIGURA- TION IN AD-HOC NETWORKS. Hierarchical Approach Nodes i mobile ad-hoc etworks are itegrated hosts ad routers. As a cosequece, all odes execute all router fuctioalities. The pre-requisite to apply IPv6 SAA i eviromets other tha a sigle broadcast lik is the presece of routers, which issue Router Advertisemets (RA). Durig the DAD, floodig is eeded, because all routig or multipoit relayig algorithms assume uique ode idetifiers. The floodig leads to the scalability problems already metioed. I order to limit the floodig to a bouded area, broadcast liks "emulated". Each ode defies its broadcast lik, from ow o called scope, as the group of odes, that are less or IPv6 Header NS message equal tha r s hops away. A hierarchy is established by special odes, the so-called leader odes, that cofigure a group of odes by issuig Router Advertisemets (RA). The routig protocol used i the ad-hoc etwork does ot ecessarily eed to follow this hierarchical structure. However, it may be advatageous if it does (see sectio 5). Furthermore, it is preferable that odes move i logical groups. Otherwise, the cost of maitaiig the hierarchical structure may icrease cosiderably.. Lik-Local Address ad Duplicate Address Detectio A mobile ode joiig the ad-hoc etwork first geerates a tetative lik-local address. Subsequetly, DAD eeds to be performed. I order to do so, the mobile ode issues a modified NS message cotaiig the tetative lik-local address ad a hop limit of r s. The latter limits the messages to the scope of the ode. Cosequetly, the scope forms a abstractio of a broadcast lik i wired LANs ad hides the multi-hop structure from the SAA process. Furthermore, odes use the all-odes multicast address istead of the solicited-ode multicast address. Packets set to the all-odes multicast address are received ad processed by all odes. A multicast tree caot be established, because the uiqueess of the IP addresses caot be assumed. Whe a NDP message is received, the odes decremet the hop limit field ad forward the message. Forwardig oly takes place, if the hop limit is greater tha zero. The detectio of a address coflict used i fixed etworks caot be directly applied to ad-hoc etworks, because each mobile ode receives echos of recetly set NS ad NA messages multiple times, depedig o the umber of adjacet odes receivig ad forwardig this message. This umber, however, is ot kow to the mobile host ad chages over time. Additioally, a message set by a ode caot be distiguished from a message origiated from aother ode, that performs DAD ad that has the same tetative address. This meas, that a address coflict caot be detected. The messages are completely idetical: The source address is the uspecified address, the destiatio address is the solicited-ode multicast address ad the target address is the tetative address. Therefore, we propose to defie a ew optio for Neighbor Discovery messages, called the Mobile Ad- Hoc Networks (MANET) optio, which cotais a Radom Source ID (RS-ID) field (see Figure ). It s value is radomly chose by a mobile ode for each NDP message set ad eables the distictio of messages set by differet odes. Nodes cache the RS-ID of each message received for a certai period of time ad oly forward NDP messages with RS-IDs that are ot i the cache. If a scope is desely populated, a broadcast storm resultig from all the forwarded messages ca lead to heavy cotetio ad collisios. This problem is alleviated by, e.g., a couterbased scheme as proposed i [6]. I this case, a message is forwarded oly, if the ode does ot receive the same message forwarded by adjacet odes more tha a predefied umber of times. If the DAD succeeds, the address ca be cosidered as

4 valid for a certai period of time. With the mechaism outlied above, lik-local addresses are guarateed to be uique withi the scope of each ode. But they are ot yet guarateed to be uique withi the etire ad-hoc etwork. If the DAD fails, maual cofiguratio is eeded or aother tetative address may be chose radomly. I summary, the followig approaches are applied to overcome shortcomigs of NDP with respect to ad-hoc etworks. MANET optio At first, NS messages are limited to a sigle hop. I order to exted NDP for multi-hop use, a hop limit of r s istead of 55 is used ad the solicitedode address as destiatio IP address is replaced by the all-odes multicast address i NS ad NA messages. Furthermore, NDP messages with a hop limit less tha r s ad bigger tha 0 are forwarded withi the scope usig a couter-based scheme to prevet broadcast storms. Because the messages are limited to the scope, the mechaism works eve i large scale ad-hoc etworks. The detectio of duplicate addresses caot be applied i a multi-hop eviromet as described i the specificatio. Therefore, the RS-ID is itroduced to distiguish NS ad NA messages set by odes durig the DAD. Versio Prio. Payload Legth Type: 5 Code: 0 Reserved Flow Label Next Header Source Address: uspecified address Destiatio Address: all odes multicast address Target Address: tetative address Checksum Hop Limit: r Type: 6 Legth: Radom Source ID Prerelay Hop L. Node Status # Nodes i Scope Isolated Node Flag Figure : The modified Neighbor Solicitatio message with the MANET optio. Leader electio algorithm I order to establish the hierarchical structure ad guaratee etwork wide uique addresses, leader odes eed to be elected. The electio algorithm should follow some requiremets to fuctio i a proper ad efficiet maer: The umber of leader odes i the etire ad-hoc etwork should be small compared to the overall umber of odes. This assures a efficiet operatio i s IPv6 Header NS message terms of sigalig traffic overhead ad a ecoomic hadlig of the limited umber of available subet IDs. Leader odes should ot chage too frequet i order to keep the etwork topology stable ad to keep the sigalig overhead as small as possible. Uique ode idetifiers caot be assumed, although it is assumed that duplicate idetifiers are seldom. The first requiremet is accommodated by choosig the ode with the highest umber of eighbors as the leader ode. I order to determie this umber, the electio algorithm ca beefit from NS messages set durig the DAD procedure. I order to keep chages of leader odes ifrequet, the followig states are itroduced for a ode: Leader state (S), Cadidate state (C), or Host state (H). The leader ode is i leader state. Oe or more odes, that are ot i leader state, but have the highest umber of eighbors i the scope, qualify themselves as potetial leader odes ad, thus, are i cadidate state. All other odes are i host state. The umber of eighbors is determied by coutig the etries i the Neighbor Cache. Therefore, solicitatio target addresses of exchaged NS messages eed to be saved i the Neighbor Cache for a limited time. These etries are marked with a special flag. Nodes lear the umber of eighbors from other odes i the scope by exchagig the modified Neighbor Solicitatio cotaiig a Number of Nodes i Scope field durig DAD. I order to maitai the hierarchy despite of ode mobility, the leader electio eeds to be performed periodically by exchagig NS messages withi the scope. Simultaeously, uique addresses ca be guarateed, eve i the case of etwork partitioig ad mergig. The period for the DAD is t dad, which is assumed to be equal for all odes i the etwork. A Node Status field (see Figure ) idicates, whether this message was set by a actual leader ode. Furthermore, the electio algorithm ca be subdivided ito three tasks:. Receivig ad processig NDP messages: The umber of eighbors is determied based o the umber of received NS messages. If a NS message is received from a leader ode, the umber of eighbors of the seder is stored i l. Subsequetly, each ode kows the umber of eighbors of the curret leader ode. Otherwise, the umber is compared to the umber of the curret cadidate c. If > c, the seder of the NS message is a ew cadidate ad c is replaced by. Otherwise, c is left uchaged ad the seder is i host state. The leader ode is ot affected by this procedure.

5 . Chagig the leader: If the DAD timer expires, the umber of eighbors of the correspodig ode is compared to the umber of eighbors of the leader ode ad the cadidate ode. If the ode is i leader state ad < c d, the ode withdraws its leader state. Otherwise, if is equal to c, the ode is a cadidate ode. If > l + d, the cadidate odes have sigificat more eighbors tha the actual leader ode. The oe with the highest RS-ID becomes the ew leader ode. To prevet oscillatios of leader odes, a hysteresis represeted by d is used to lead the replacemet of a leader ode. If the leader ode powers off or leaves the etwork, l is zero i the ext roud ad the ode i cadidate state becomes the ew leader ode.. Sedig a NS message: If the DAD timer expires, a NS messages is issued cotaiig the actual umber of eighbors ad the state of the ode represeted by the Node Status field. Fially, c ad l are iitialized to zero ad a ew period t dad starts. The electio process outlied above is illustrated i the flow diagram show i figure. The optimal choice of the system parameters d ad t dad depeds o the ode movemet ad the scope size. They are subject to further.. Formig a Site-Local Address The iterface that is i leader state, subscribes to the all-routers multicast group, chooses a subet ID radomly ad geerates a site-local address based o the lik-local address ad the subet ID. The leader ode seds a Router Advertisemet (RA) messages withi its scope cotaiig the subet ID ad its lik-local address as source address. Oly the lik-local address may be used for this purpose to avoid cofusio about the seder of the RA messages. All odes withi the scope of the leader ode receive the subet ID ad geerate their site-local address. Because the lik-local address is oly guarateed to be uique withi the scope of each ode ad the site-local address is costructed from the lik-local address ad the subet ID, the subet ID eeds to be uique withi the etire ad-hoc etwork. To esure this, a DAD has to be performed betwee the leader odes withi the etire ad-hoc etwork. The NS message would use the all-routers multicast address as destiatio address ad the site-local address as solicited target address. Because more tha 55 hops shall be supported, a hop limit of 55 is defied as ulimited forwardig i this cotext. Furthermore, the RS-IDs of these messages eed to be cached for a much loger time tha for the DAD withi the scope, because the time a message eeds to travel the etire ad hoc etwork is much higher. Floodig of the etire etwork caot be avoided here, but it is limited. Oly leader odes eed to flood the etwork ad their umber is small compared to the overall umber of odes i the etwork. Because the uiqueess ew NS received with eighbors ad Node Status S o S = L? o > = = c l Iit DAD Timer o wait < c c d withdraw L state i L state? DAD Timer expired o > l + d ad C? o c= 0 l = 0 = sed NS msg Figure : The leader electio algorithm chage to L state of the subet IDs shall eve be guarateed i the case that two idepedet etworks merge, the DAD betwee the leader odes eeds to be repeated. The easiest way would be to do that periodically. A better way is to somehow detect the situatio of mergig etworks. This could be doe with the aid of the Neighbor Cache: If the marked etries i the Neighbor Cache suddely icrease dramatically ad if it was ot empty before, it is cocluded that two etworks merged. Subsequetly, this ode triggers a DAD process betwee all leader odes. Neighborig odes detectig the same situatio recogize this ad do ot trigger the DAD agai. Additioally, a timer ca esure, that the DAD is ot repeated too ofte i the case the etwork partitios ad merges frequetly. Furthermore, a leader ode itroducig a ew subet ID eeds to perform a DAD of its subet ID. If the DAD fails, oe leader ode eeds to choose a ew subet ID. Subsequetly, the odes geerate ew site-local addresses ad a process called graceful site reumberig takes place. Therefore, each ode is allowed to keep usig the old address for ogoig coectios for a special period of time, the so-called preferred lifetime. After exceedig the valid lifetime, the ode is forbidde to use the old address at all. Because the DAD is doe withi the scope of each

6 ode, which is obviously differet from the scope of the leader ode, duplicate site-local addresses may occur. Oe of such scearios is illustrated i figure 5, where the leader ode B is i betwee ode A ad C. Despite Node A ad B are boud to the same leader ode, they are outside the scope of each other ad, therefore, they caot detect that they ow the same lik-local address. Additioally, they build the same site-local address, because they use the same subet ID. A solutio is, that the leader ode forwards each NS ad NA message that it receives with the hop limit set to r s. Cosequetly, the message set by ode A reaches ode C ad vice versa. This way, the scope of each ode is exteded by the scope of the leader ode ad the coflict is resolved. The uiqueess of the site-local addresses of all odes i the etire adhoc etwork is esured. Because these message should ot be couted for the leader electio, a Prerelay Hop Limit field i the modified NS message is defied, which cotais the value of the hop limit field i the IPv6 header before maipulatio by the relayig ode. This esures the recogitio of messages relayed by the leader ode ad the distace to the leader ode. scope Leader Nodes Figure 6: A multi-homed ode multi homed ode optio cotais the Isolated Node Flag, which tells other odes i the scope about a isolated ode. Subsequetly, the odes o the edge of the subet relay RA ad NDP messages to ad from the isolated ode by maipulatig the hop limit field i the same way the leader ode does for the RA messages. Nodes receivig the RAs from the leader ode with a hop limit of 0 lear that they are edge odes. Node A Head Node B Node C Figure 5: Two odes withi the same leader ode scope, but outside the scope of each other If a leader ode is replaced by a cadidate ode, the ew leader ode adopts the former subet ID. Thus, o reumberig of the site is eeded. If a ode moves from oe scope of a leader ode to aother, the graceful reumberig is used oly for this ode. This situatio is detected by the absece of RAs with the former subet ID ad the presece of RAs with a ew subet ID. The ode receives the ew subet ID ad geerates a ew site-local address. A ode may be withi the scope of more tha oe leader ode. I this case, the ode is multi-homed ad eeds to geerate may site-local addresses. A sceario with two leader odes is illustrated i figure 6. There may be some odes receivig NS messages from eighborig odes, but o RAs from leader odes. These so-called isolated odes are ot withi the scope of ay leader odes ad, subsequetly, do ot have a site-local address. The easiest way to solve this would be, to elect all isolated odes to leader odes. A better solutio is, to exted the subetwork to these odes. The MANET 5 INTERACTION WITH ROUTING PROTOCOLS I this sectio, possible iteractio of routig protocols with the autocofiguratio mechaisms described above are outlied. We specifically refer to the hierarchical routig protocol LANMARK [7], which is a mixture of ladmark routig [8] ad a scoped lik-state routig protocol, like, e.g., the Fisheye State Routig (FSR) protocol [9]. Ladmarks are special odes, whose presece is aouced withi the etire etwork. They might be compared to leader odes used i our approach. Nodes use a proactive lik-state protocol withi a limited area, the so-called scope. Each ode defies its scope as the area, which comprises all odes with a distace less or equal to r s hops. This defiitio is directly utilized i our approach. Routes to destiatio odes outside the scope are marked as ukow. Subsequetly, packets to these destiatios are set toward the correspodig ladmark. The closer the packet gets to the ladmark ad, therewith, to the destiatio ode, the more accurate is the routig iformatio. If the LANMARK routig protocol is used, the leader odes should correspod to the ladmark odes. This is desirable, because oe electio mechaism ca be used for buildig the hierarchy of both, the address autocofiguratio ad the routig protocol. Furthermore, routig should beefit from the hierarchical address structure by usig the subet ID of the site-local address for aggregatio. I LANMARK, the correspodig ladmark is idetified by a subet ID of the destiatio ode. Furthermore, the DAD of subet IDs could be combied with the eed of some hierarchical routig protocols to aouce the presece of hierarchical compoets, e.g., ladmark odes. However, this would violate the requiremet of beig idepedet from the routig protocol. Further optimizatios are possible, if the NS messages

7 exchaged durig DAD are used to build, e.g., a scoped distace-vector routig table. Additioal routig cotrol iformatio could be ecapsulated i NDP as a optio. The hierarchical address structure established by our system may be applied to o-hierarchical routig protocols as well, by cosiderig the site-local addresses as a flat address space. Nevertheless, they are ot able to beefit from aggregatio possibilities offered. 6 CONCLUSION The basic goal of this paper was the applicability of the IPv6 Stateless Address Autocofiguratio ad the Neighbor Discovery Protocol to mobile ad-hoc etworks. Several drawbacks have bee discovered, that prevet these protocol mechaisms from beig applied i mobile adhoc etworks. Some extesios to the Neighbor Discovery Protocol have bee proposed that try to overcome these shortcomigs. I order to make autocofiguratio scalable to large scale mobile ad-hoc etworks, a hierarchical approach is applied. For buildig ad maitaiig the hierarchical structure, we proposed a simple leader electio mechaism. Our system ca cope with the dyamic ature of mobile ad-hoc etworks ad with etwork partitioig ad mergig. It is idepedet of the routig protocol, although optimizatios are possible i cojuctio with special routig protocols. REFERENCES [] The Moarch Project, Caregie Mello Uiversity, [] The Wireless Adaptive Mobility (WAM) Laboratory, Uiversity of Califoria Los Ageles, [] S. Thomso ad T. Narte, IPv6 Stateless Address Autocofiguratio, Dec. 998, RFC 6. [] T. Narte, E. Nordmark, ad W. Simpso, Neighbor Discovery for IP Versio 6 (IPv6), Dec. 998, RFC 6. [5] T. Narte Neighbor Discovery ad Stateless Autocofiguratio i IPv6, IEEE Iteret Computig, Volume, Issue, July-Aug. 999 Pages 5-6 [6] Charles E. Perkis, Ad Hoc Networkig, 000, Addiso-Wesley. [7] J. Broch, D.A. Maltz, D.B. Johso, Y.-C. Hu, J. Jetcheva, A Performace Compariso of Multi- Hop Wireless Ad Hoc Network Routig Protocols, I Proceedigs of ACM/IEEE MOBICOM 98, Dallas, TX, Oct. 998, Pages [9] Yih-Chu Hu, Jorjeta G. Jetcheva, David B. Johso, David A. Maltz, The Dyamic Source Routig Protocol for Mobile Ad Hoc Networks, Mar. 00, Iteret Draft: draft-ietf-maet-dsr-05.txt. [0] Charles E. Perkis, Elizabeth M. Royer, ad Samir R. Das, IP Address Autocofiguratio for Ad Hoc Networks, 000, Iteret Draft: draft-ietfmaet-autocof-00.txt, expired. [] Jug-Soo Park, Yog-Ji Kim, ad Sug-Woo Park, Stateless Address Autocofiguratio i Mobile Ad Hoc Networks Usig Site-Local Address, 00, Iteret Draft: draft-park-zerocof-maetipv6-00.txt. [] A. J. McAuley, K. Maousakis Self-Cofigurig Networks, MILCOM 000. st Cetury Military Commuicatios Coferece Proceedigs, Volume, 000 Pages 5-9 [] A. Misra, S. Das, A. McAuley, S.K. Das Autocofiguratio, registratio, ad mobility maagemet for pervasive computig, IEEE Persoal Commuicatios, Volume 8, Issue, Aug. 00 Pages - [] J. Boud, M. Carey, C. Perkis, ad R. Droms, Dyamic Host Cofiguratio Protocol for IPv6 (DHCPv6), 00, Iteret Draft: draft-ietf-dhcdhcpv6-9.txt. [5] R. Hide ad S. Deerig, IPv6 Address Architecture, July 998, RFC 7. [6] Sze-Yao Ni, Yu-Chee Tseg, Yuh-Shya Che, ad Ja-Pig Sheu, The Broadcast Storm Problem i a Mobile Ad Hoc Network, 999, Proceedigs of Mobicom 999. [7] Mario Gerla, Xiaoya Hog, Li Ma, ad Guagyu Pei, Ladmark Routig Protocol (LANMARK) for Large Scale Ad Hoc Networks, May 00, Iteret Draft: draft-ietf-maet-lamark-0.txt. [8] P. F. Tsuchiya, The Ladmark Hierarchy: a ew hierarchy for routig i very large etworks, 998, Computer Commuicatio Review, vol.8, o., pp. 5-. [9] Mario Gerla, Guagyu Pei, Xiaoya Hog, ad Tsu-Wei Che, Fisheye State Routig Protocol (FSR) for Ad Hoc Networks, Nov. 000, Iteret Draft: draft-ietf-maet-fsr-0.txt, expired. [8] S.R. Das, C.E. Perkis, E.M. Royer, Performace Compariso of Two O-demad Routig Protocols for Ad Hoc Networks, I Proceedigs of IEEE IN- FOCOM 000, Tel Aviv, Israel, Mar. 000, Pages -