Hye-Young Kim, †Young-Sik Jeong and ††Laurence T. YangSchool of Games, Hongik University, South Korea
†Dept. of Computer Engineering, Wongkwang University, South Korea†† Dept. of Computer Science, St. Francis Xavier University, Canada
Abstract
The main advantage of a wireless network is usermobility, which calls for efficient routing support atthe network layer. An architecture combines Hier-archical Mobile IPv6 and Network Mobility for anetwork mobile and mobile nodes move in tandemand make a hierarchy in the wireless network tomanagement of micro-mobility and seamless hand-off. But the capability of the architecture for intradomain route optimization is impaired. So we pro-pose a functionality in domain nodes to enable intradomain path optimization for ubiquitous network.It is shown that intra domain cost effect is bene-ficial in every hierarchical domain that span meshnetwork topology. We address the key function forour proposed scheme and simulate the usefulnessof our proposed method using mathematically an-alyze. We then testify that the proposal has bestperformance compared with Network Mobility pro-tocol.
1 Introduction
The demand for wireless access to the Internetis increasing rapidly. Ubiquitous networks are anemerging concept where mobility is considered forentire mobile networks. These mobile networkscan provide, to mobile nodes (MNs), connectiv-ity toward Internet via one or more mobile routers(MRs). The aggregated hierarchy of mobile net-works is called a nested mobile network, where amobile network may attach inside another mobilenetwork. Network Mobility (NEMO) Basic [1],which is an extension of Mobile IPv6 (MIPv6) [2],sets up a bidirectional tunnel between MR andMR’s Home Agent (MR-HA). This provides con-nectivity to the MR and consequently to each nodein its embedded network. A major drawback of
∗This work was supported by the Korea Research Foun-dation Grant funded by the Korean Government(MOEHRD)(KRF-D00011)
NEMO Basic is that all communications to andfrom the mobile network must go through the tun-nel between MR and its HA. This results in extraoverhead and high delays. Moreover, with nestedmobile networks, the problem increases with eachnested level. Outbound packets must go throughthe Home Agents (HAs) of all MRs of higher levelsbefore reaching their destination.
Multiple solutions presented provide route opti-mization support for NEMO Basic. A new routingheader called the Reverse Routing Header (RRH)[3] is proposed. The RRH allows the building of anested mobile network to avoid the nested tunneloverhead. RRH provides an optimized path for thesingle tunnel. RRH records the route out of thenested mobile networks and can be converted intoa routing header for packets destined to the mobilenetwork. Each MR on the egress path places itscare-of address (CoA) in the RRH. Receiving thisheader, the HA can construct the chain of MRs thefirst MR is attached to. The major inconvenience ofthis solution is the additional overhead, introducedby RRH on each packet, which increases with thenumber of levels of the nested mobile network.
[4] proposes that a mobile network prefix (MNP)is changed to adapt to the hierarchical address ofthe AR to which the mobile network is connected.This method enables packets to be routed to MNsin the mobile network using only the CoA of theMN (MN-CoA). Thus, this allows MNNs behind aMR to be managed in a hierarchical manner. Tomanage the mobility of the mobile network, this so-lution also proposes a hierarchical address manage-ment, which reduces the number and the volume ofhandoff signals by managing the location addressesof all MNs in a hierarchical manner.
The problem is that mobility has an adverse in-fluence on the effectiveness of routing. Support forpath optimization has been studied since the in-troduction of MIP. With the occurrence of morecomplex mobility architectures that include MRs,route optimization is becoming a challenging prob-
22nd International Conference on Advanced Information Networking and Applications - Workshops
lem. Even through Hierarchical MIP (HMIP) sup-ports intra domain route optimization, this capabil-ity is lost if mobile routers are present within thedomain and NEMO technology is applied. [5]
Therefor we propose a scheme that intra domainroute optimization is beneficial in every hierarchi-cal domain that spans mesh network topology. Therest of the paper is structures as follows. Sec-tion 2 describes our proposed architecture and pro-vides the detailed routing and binding update pro-cedures. A performance evaluation of the proposedarchitecture and Section 3 presents the mathemat-ical analysis, and a comparison of performance be-tween the existing NEMO and the proposed newmodel. While Section 4 constitutes a summary ofthe proposal.
2 Proposed System Protocol
2.1 System Architecture
We propose a new routing optimal scheme com-bined HMIPV6 with NEMO for more efficient loca-tion management. Figure 1 shows the nested mo-bile network structure for proposed routing methodto meet the requirements for mobile network mobil-ity management. It consists of an IP network with aMobility Anchor Point (MAP) and Mobile IP com-ponents such as MRs, MNs, HAs, CorrespondentNode (CN), and Access Routers (ARs). The CoAfor each MNN, which is created using the Hierar-chical Mobile Network Prefix (HMNP) assignmentin the proposed scheme, is divided into a node lo-cator and a node identifier. The node locator is a64-bit network prefix made from HMNP advertisedin RA, which indicates the location of the mobilenetwork in the nested mobile network. In the caseof handoff, it is changed. On the other hand, thenode identifier is a globally unique IPv6 64-bit in-terface ID [6] which remains unchanged even whenhandoff occurs.
To support route optimization in this scheme,the MAP maintains binding information for allMNNs in its domain in its binding cache. Table1 shows MAP’s binding cache that is composed ofHome of Address (HoA), CoA, parent of the MR,and HMNP fields based on Figure 1. The CoAfield contains LCoAs of MNNs which are dividedinto the node locator and the node identifier. Theparent of MR field contains the home address of aMR associated with the MNNs in the MR’s net-work. The HMNP field contains a HMNP whichrepresents the location of each sub-net of the MR.Assume that the location registrations of all the
MNs and MRs are already done appropriately inTable 1.
As an example, MAP holds the binding infor-mation of MR1, that is, MR1HoA in HoA field,MR1LCoA created using AR1-prefix in CoA fieldand HMNPs (HMNP1, HMNP2) in HMNP field.MMR also stores MN2HoA, MN2LCoA and theparent of the MR’s HoA (MR3HoA) of MN2 whenit receives a BU from MN2. When a mobile net-work moves locally within the MAP domain, eachMNN in the mobile network updates its MNNLCoA
using a HMNP in RA from the MR associated withthe MNN. However, the MNNs need not send thehandoff signals to MMR as the MR sends a BU onlyto MAP containing the HMNP information.
When MAP receives a BU from the MR, it up-dates the binding information for the MR and foreach MNN behind the MR in its binding cachewhere MNNs can be found using the HoA of the MRin upper-MR field. Thus, MAP reduces handoff sig-nals significantly as well as localizes them becauseMAP is closer to the mobile network compared tothe MR-HA.
2.2 Procedures of Routing andBinding Update
When the MR has multiple links, the MR requestsmultiple HMNPs of its access router, gets HMNPsfrom the access router and advertises each HMNPon a separate subnet. In this scheme, MAP is intro-duced to have the functionality of MAP in HMIPv6.
First, AR1 sends a RA to MR1, containingAR1-prefix and the MAP address. MR1 detectsits movement, creates its local CoA (MR1LCoA),
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Table 1: The Entry of MAP
HoA CoA parentMR HMNPMR1HoA MR1LCOA
(ARprefix +mr1)
AR1 HMNP1,HMNP2
MR1HoA MR1LCOA
(HMNP1 +mr1)
MR1HoA1 -
MR2HoA MR2LCOA
(HMNP1 +mr2)
MR1HoA1 HMNP3
MR3HoA MR3LCOA
(HMNP2 +mr3)
MR1HoA2 HMNP4
MR4HoA MR4LCOA
(HMNP4 +mr4)
MR3HoA HMNP5
MR2HoA MR2LCOA
(HMNP4 +mn2)
MR3HoA -
MR3HoA MR3LCOA
(HMNP4 +mr3)
MR3HoA -
sets the MAP address as its regional CoA (RCoA)and gets HMNP1 and HMNP2 from its accessrouter. Then, MR1 sends a BU to MAP, containingMR1LCoA, its upper router address (AR1 address),and HMNPs (HMNP1 and HMNP2). After this,MR1 sends a BU to MR1-HA to register the MAPaddress as its RCoA. MR1 then advertises a RAto its each sub-net, containing a HMNP, MAP ad-dress and MR1HoA. Then, MR2 moves to MR1’snetwork. MR2 creates MR2LCoA using HMNP1and sets the MAP address as its RCoA. MR2 getsHMNP3 from MR1 and sends a BU to MAP, con-taining MR2LCoA, MR1HoA, and the HMNP3.MR2 then sends a BU to MR2-HA to register theMAP address as its RCoA. Then, MR2 sends a RAto its sub-net, containing HMNP3, MAP addressand MR2HoA.
When MR3 moves to MR2’s mobile network, itrepeats the same procedure as the MR2 moves toMR1’s mobile network. Each MNN behind a MRmakes its LCoA (MNNLCoA) using a HMNP, setsMAP address as its RCoA and the MRHoA as theaddress of the MR connected to it. The MNN thensends a BU to MAP, containing MNNLCoA andthe MRHoA. Then, each MNN behind the MRsends BUs to its HA/CNs, containing MNNRCoA
(MAP address). Packets from the CN are opti-
mally routed to the MNN via MAP, using a rout-ing header option (RHO). MAP encapsulates thepackets with MNNLCoA after searching for it inits binding cache and sends the packets to theMNN. On the other hand, when packets containthe MNNLCoA as its source address, the CN ad-dress as its destination address and MNNHoA inits home address option (HAO), the packets haveno problem in egress filtering, and directly reachCN with route optimization.
Figure 2 shows an intra domain handoff whenMR4’s network moves locally within a MAP do-main. MR4 sends a RS to MR2. Then, MR2sends a RA to MR4, containing HMNP1, MAP ad-dress and MR2HoA. After receiving a RA fromMR2, MR4 detects its movement within the sameMAP domain in case of its HoA of the parent ofthe MR changes from MR3HoA to MR2HoA butits RCoA (MAP address) does not change. Then,MR4 creates its LCoA and performs ICMP pre-fix delegation operations from step 4 to step 7 toacquire a HMNP (HMNP2) from MR2, such asHPD. MR4 then sends a BU to MAP, contain-ing MR4HoA, MR4LCoA, its Hoa of the parent ofthe MR (MR2HoA) and HMNP2. MAP registersthe information to bind the MR4HoA, MR4LCoA,MR2HoA, and HMNP2. After this, MAP searchesthe binding entries for MNNs behind the MR4 us-ing MR4HoA in the parent of the MR field of itsbinding cache.
Thus, when MAP updates MR4’s binding infor-mation, MAP also updates all MNNLCoAs withinMR4’s network by changing the common infor-mation, that being the node locator, to HMNP2.Then, MR4 sends a RA to MNNs within its mobilenetwork, containing MR4HoA, HMNP2, and MAPaddress. Each MNN within MR4’s network createsits new LCoA (MNNLCoA) using HMNP2, andalso sets its RCoA as MAP address and MR4HoA asits upper MR. Each MNN behind the MR4 does notneed to send a BU to the MAP, because MNNLCoA
(which MAP manages) has already been updated.If the handoff of a mobile network is caused bythe movement of the parent mobile network withina nested mobile network, the MR (MR4 in Fig.2) repeats the above-mentioned handoff procedurefor MNNs within its mobile network, which is per-formed by its upper MR (MR3) for MNNs withinMR3’s network.
Thus, if a mobile network moves locally withinthe nested mobile network, MR in the mobile net-work and all nested MRs on lower levels connectedto the MR send BUs on behalf of MNNs within theirmobile networks. On the other hand, in case that
Figure 2: Proposed Procedures of Routing andBinding Update
MR4 moves to AR3 within MAP domain, MR4 per-forms the similar procedures with AR3 as it doesone with MR2 when it moves to MR2’s networkfrom MR3’s network.
3 Performance Analysis
This section presents analysis of our proposedscheme, we have evaluated NEMO Basic, RRH andour scheme, using the network simulator (ns-2), ina nested mobile network environment. We definedthat MR under AR is zero-level (i.e., ARMR).
Therefore, AR-MR-MR means one nested-level.Figure 3 shows the network model for simulationwhere there may be at least one MR per level ina nested mobile network. In order to simulate realtraffic, we set up the CN as a traffic source at aconstant bit rate (CBR) over a user datagram pro-tocol (UDP), producing fixed length packets of 1500bytes every 10 ms. Then the MNN acts as a sinknode receiving packets from CN. The setup linktopology consists of wired link and wireless link.The wired link is fixed and used at the connec-tion of CN to MMR, CN to HA, HA to MMR, andMMR to the AR. The wired link bandwidth is setto 100 Mbps. The wireless link bandwidth is set to11 Mbps with the wireless link latency set to 2 ms.The packet service rate was 100 packets/second cor-responding to data rates of 1.2 Mbps. The handoffinterval was set to 2 seconds.
Figure 4: Data Transmission Delay according toMR or MNN’s Depth
We evaluated each scheme assuming 5, 10, 100MNNs in the mobile network. The simulation as-sumes that delay between HA and HA is 100 ms,delays between CN and HA, CN and MMR and HAand MMR are the same, 50ms and delay betweenMMR and AR is 5ms. Furthermore, packet headersize, BU size and BACK size are also predefined:40 bytes, 112 bytes and 96 bytes respectively.
Figure 4 shows to the reduction of the numberof nested tunnels. Indeed, the proposed solutionrequires only a unique tunnel from MMR to MN re-gardless of the number of nested levels in the mobilenetwork. The packets, in NEMO Basic, must passthrough multiple tunnels from the MN to MNHA.The packet transmission delay saving time betweenour proposed scheme and RRH method is 56.33 msat level 0 and 56.92 ms at level 4. RRH methodis superior to NEMO Basic but is inferior to our
15491549
0
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0 1 2 3 4
Number of Nesting Levels
Loca
tion
Upd
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Figure 5: Location Management Costs
proposed scheme.Figure 5 shows the location update costs
for each scheme as the increases of the nesteddepth. When MNN moves within MMR domain,our scheme requires that MNN only sends a BU toMMR, compared to its HA/CNs in other schemes.The difference of the location update cost betweenNEMO Basic and our scheme is 90.43 ms at level 0and 882.05 at level 4. The difference between RRHand our scheme 91.49 ms at level 0 and 92.89 msat level 4. Our proposed scheme has more efficientlocation update costs than other schemes, because69user mobility is contained within a local domain(an attribute of micro-mobility [7]).
4 Conclusion
In this paper, we propose a scheme which combinesHMIPv6 and NEMO to route optimization and re-duce of the binding update signal of micro-mobilityfor ubiquitous.
The MAP node intercepts all packets destined toMAP address and behave as a regular MAP node.Externsions are required in order to synchronizebinding update cache in MAP. The inter domaintraffic takes the optimal path because tunnels areterminated at the very border of the network. In-tra domain optimization improves flow performancebecause data usually experience less delay on opti-mized routes.
The simulation of mean route length in an HMIPdomain with multiple layers demonstrated the ef-fectiveness of our proposed scheme for ubiquitousnetwork.
References
[1] V. Devarapalli, R. Wakikawa, A. Petrescu, andP. Thubert, ”NEMO basic support protocol,”Internet Draft: draft-ietf-nemo-basicsupport-03.txt, June 2004.
[2] D. Johnson, C. Perkins and J. Arkko, ”Mobil-ity Support in IPv6”, draft-ietf-mobileip-ipv6-22.txt, May 2003.
[3] P. Thubert and M. Molteni, ”IPv6 reverserouting header and its application to mo-bile networks,” Internet Draft: draft-thubert-nemoreverse-routing-header-05.txt, June 2004
[4] T. Suzuki, K. Igarashi, A. Miura, M. Yabusaki,”Care-of Prefix Routing for Moving Net-works”, IEICE TRANS. COMMUN., VOL.E88-B, NO.7 JULY 2005.
[5] Watfa, M.,Commuri, S.:The three dimensionalcoverage problem. Journal of Networks, JNW1(4), pp. 10-20. 2006
[6] Alberto Escudero Pascual ”Location Privacyin IPv6 - Tracking the binding updates”,IMIT. August 2001.
[7] G. Kirby, ”Location the User”, Communica-tion International, 1995
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