- Email: [email protected]
Resource-efficient network mobility support in Proxy Mobile IPv6 domain
Int. J. Electron. Commun. (AEÜ) 66 (2012) 390–394
Contents lists available at SciVerse ScienceDirect
International Journal of Electronics and Communications (AEÜ) journal homepage: www.elsevier.de/aeue
Resource-efficient network mobility support in Proxy Mobile IPv6 domain Seil Jeon a , Namhi Kang b , Younghan Kim a,∗ a b
The School of Electronic Engineering, Soongsil University, Sangdo-Dong 511, Dongjak-Gu, Seoul 156-743, Republic of Korea The Department of Digital Media, Duksung Women’s University, Ssangmoon-Dong, Tobong-Gu, Seoul 132-714, Republic of Korea
a r t i c l e
i n f o
Article history: Received 18 November 2010 Accepted 23 September 2011 Keywords: Network mobility NEMO Resource-efficient Proxy Mobile IPv6 PMIPv6
a b s t r a c t The basic standard protocol for supporting network mobility (NEMO) (i.e., NEMO-BSP specified by IETF) introduces several performance problems, such as multiple tunneling overhead and packet delivery latency, because it exploits mobile IPv6 (MIPv6), which was proposed for host mobility. To improve the basic NEMO solution, two network-based NEMO approaches, rNEMO and N-PMIPv6, have been proposed. The rNEMO is able to reduce significant packet tunneling overhead. The N-PMIPv6, on the other hand, reduces location update cost, but it leads to packet tunneling overhead. Thus, they commonly waste network resources in both wired and especially wireless network. No efficient and practical solutions for minimizing both the location update overhead and packet tunneling overhead have been presented until now. This situation motivated us to propose a resource-efficient network mobility scheme (RENEMO), reducing resource utilization required for network mobility support. We show that the proposed RENEMO outperforms both rNEMO and N-PMIPv6 in terms of network resource. © 2011 Elsevier GmbH. All rights reserved.
1. Introduction Advances in wireless hand-held devices increase the demand for Internet access, even though they are moving in vehicles such as trains, buses, and airplanes. To meet with the demand, the network mobility basic support protocol (NEMO-BSP) has been developed by the Internet Engineering Task Force (IETF) [1]. The NEMO-BSP allows mobile network nodes (MNNs) within a moving vehicle to continue their sessions. However, NEMO-BSP, which employs the mobile IPv6 (MIPv6) [2] as the host mobility management protocol for a mobile router (MR), introduces additional tunneling overhead while packets traverse between the home agent (HA) of an MN and MR placed in a bandwidth-limited wireless environment. To improve the performance of the NEMO-BSP, two NEMO approaches using Proxy Mobile IPv6 (PMIPv6) [3], which provides networkbased local mobility by mobile access gateway (MAG) and local mobility anchor (LMA), have been proposed: relay-based NEMO (rNEMO) [4] and NEMO-enabled PMIPv6 (N-PMIPv6) [5]. In the rNEMO, an MR is operated as simple relay station (RST), which can be either an amplify-and-forward (AF) or a decode-and-forward (DF) relay station. Thus, the MR simply relays both signal and data packets without an additional tunnel header except the PMIPv6 tunnel header for delivering packets as shown in Fig. 1(a). But this scheme requires an individual handoff signaling to manage MNN’s location when the network moves. In the N-PMIPv6, the moving
MAG (mMAG) on behalf of the MR is presented as shown in Fig. 1(b). The N-PMIPv6 focuses on the handover performance with regard to the latency it takes when an MNN moves from the mobile network to outside. In the N-PMIPv6, only LMA manages the entry information for an MNN. So, packets to destined MNN arrive at the LMA, the LMA adds a double tunneled IP header (expressed as ‘T’ in Fig. 1(b)) into all received packets from a correspondent node (CN) and delivers them to a MAG. Thereafter, the MAG removes only the outer header; then the packet containing the single tunneled header is reached at the MNN. In some scenarios, where lots of MNNs are in the vehicle, the N-PMIPv6 leads to severe packet delivery cost. Consequently, the two approaches waste network resources. In addition, no optimal solution has been presented so far to satisfy with the minimized location update and packet tunneling overhead. In this paper, we therefore propose a resource-efficient NEMO scheme (RENEMO) which reduces the location update cost in rNEMO and the packet delivery cost in N-PMIPv6 by extending the proxy binding update list (PBUL) in MAG and the binding cache entry (BCE) in LMA. The remainder of this paper is organized as follows. Section 2 describes the RENEMO architecture. Then, we provide performance analysis and results compared with rNEMO and N-PMIPv6 in Section 3. Finally, we offer our conclusion in Section 4. 2. Proposed scheme
∗ Corresponding author. E-mail addresses: [email protected] (S. Jeon), [email protected] (N. Kang), [email protected] (Y. Kim). 1434-8411/$ – see front matter © 2011 Elsevier GmbH. All rights reserved. doi:10.1016/j.aeue.2011.09.006
Fig. 2(a) and (b) shows the signaling operation for the mMAG’s attachment (step 1) and the MNN’s attachment (step 2), respectively. Fig. 2(c) shows the network handover procedure when an
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the mMAG address when the MAGA delivers the packets to the MNN, as shown in Fig. 2. The PBA message is again delivered to the mMAG. The mMAG creates an RA message, including the received HNP prefix for the MNN. • Step 3: When an mMAG moves to an area of MAGB , the MAGA detects the mMAG’s handoff from the layer-2 signal and exchanges a binding update message (PBU/PBA) with the LMA for de-registration. After the MAGB detects mMAG’s approaching, it sends a PBU message to the LMA. The LMA then changes the tunnel endpoint, which is distinguished by the IP address of the MAG, for packet delivery to the MNNs within the mMAG from MAGA to MAGB . Cached MNN-IDs and MNN-HNPs belong to the mMAG are delivered to the MAGB through a PBA message. The mMAG receives these prefixes from the MAGB through an RA message and uses only the first prefix option for home emulation. In the case of mMAG’s handoff, ‘G’ flag is not used. When the LMA receives packets that are destined for the MNN, it looks up the corresponding MAG IP address in BCE. Then the LMA appends only a single PMIPv6 tunnel header into the packets and sends them to the MAG. When the MAG sends packets to the MNN via mMAG, no tunnel is used because the MAG acts as an LMA proxy from the perspective of the mMAG. Fig. 3(a) and (b) shows extended MAG PBUL and LMA BCE information in the RENEMO. Both entries have a ‘G’ flag field to distinguish the MNN from other attached nodes. And they also have an ‘mMAG’ address field to deliver the packets to the mMAG in the MAG and to manage the MNNs’ location in the LMA. In the case of node mobility operation where an MNN moves to outside PMIPv6 domain from mobile network, the mMAG is required to inform MNN’s detachment to the current MAG. Then, the PBU/PBA message between mMAG and LMA for de-registration is processed via MAG. When an MNN approaches to the MAG, it follows standard procedure defined in [3]. 3. Performance analysis and results
Fig. 1. Protocol operation of rNEMO and N-PMIPv6.
mMAG, including MNNs, moves from MAGA area to MAGB area (step 3). The following steps present the RENEMO scheme in detail. • Step 1: When an mMAG approaches a PMIPv6 domain, the MAGA detects the mMAG’s movement triggered by L2 signal or router solicitation (RS) message. The mMAG performs a security association with the AAA (authentication, authorization and accounting) server. The MAGA then sends the proxy binding update (PBU) message to the LMA. When the MAGA receives the proxy binding acknowledgment (PBA) message, including the home network prefix (HNP) for the mMAG, it transmits the HNP to the mMAG through a router advertisement (RA) message. The mMAG configures its address based on the received HNP. • Step 2: For a newly attached MNN, the mMAG contacts the AAA server to authenticate the MNN. Thereafter, the mMAG creates a PBU message containing the MNN’s ID, the mMAG’s IP address, and the ‘G’ flag and then sends it to MAGA . The ‘G’ flag is only used for MNN’s location update. The MAGA appends its address to the received PBU and sends it to the LMA. On receiving the PBA message, the LMA distinguishes whether this PBU is for ordinary MN or MNN by examining the ‘G’ flag, which is only used for MNN’s location update. The LMA allocates the HNP and delivers it to MAGA . On receiving the PBA message, including the HNP for the MNN, the MAGA creates PBUL, which is extended to manage
In this section, we evaluate the performance of the RENEMO compared with rNEMO and N-PMIPv6 in terms of location update (LU) cost (CLU ) and packet tunneling (PT) cost (CPT ). In the CLU cost, the location update cost for initial attachment is not considered. By summing up two terms, we obtain the total cost (CTOT ), which is defined by the product of message size and hop distance from a bandwidth perspective during time T. Under such definition, a router processing cost is not considered. T denotes the total time required to move by the MN. For the performance analysis, we have the assumptions as followed. The inter-session arrival time follows an exponential distribution with rate S and average session length, in packets, is E(S). The MAG subnet crossing rate follows a general distribution with mean rate C , as presented in [6]. To analyze the each cost, some notations in the literature [6] are used as follows. • LP and LT : length of packet P and tunnel header (1500 bytes and 40 bytes) • LRS , LRA , and LAAA : length of RS message, RA message, AAA message (70 bytes, 110 bytes, and 100 bytes) • LPBU and LPBA : length of PBU message and PBA message (112 bytes and 96 bytes) • LMNN–ID and LMNN–HNP : length of ID and home network prefix option for MNN (20 bytes and 32 bytes) • d˛–ˇ : hop distance between ˛ and ˇ • LU˛–ˇ : unit cost of PBU/PBA message between network entity ˛ and ˇ (=d˛−ˇ ·(LPBU + LPBA )) • RS˛−ˇ : unit cost of RS message between network entity ˛ and ˇ (=d˛–ˇ ·(LRS ))
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Fig. 2. Proposed resource-efficient NEMO (RENEMO) operation based on PMIPv6 domain.
• RA˛−ˇ : unit cost of RA message between network entity ˛ and ˇ (=d˛–ˇ ·(LRA )) In the rNEMO scheme, the MAG detects detachment and attachment of MN and then sends/receives a PBU/PBA message with the
LMA for de-registration and registration. And an MNN exchanges the RS/RA message with the MAG when the mobile network moves to another MAG. Let C be the cell crossing rate. Then the average number of cell crossings during T is equal to C ·T as defined in [6]. We employ the unit of transmission cost for a wired link and a wireless link, and , as defined in [8]. Therefore, the location update for rNEMO can be represented by rNEMO CLU = C · T · ı · ( · RSMNN–MAG + · RAMAG–MNN
+ · AAAMAG–AAA + 2 · · LUMAG–LMA ),
(1)
where ı is the number of MNN, which is considered for the individual MNN update. All the packets transmitted by the CN are delivered to the MNN via the MAG and relay station; however, packet tunneling occurs between the LMA and the MAG. By Little’s law [7], the number of packets delivered during T is approximated by S ·T·E(S), where S is the session arrival rate from the CN. The E(S) is the average session length in numbers of packets. Therefore, the PT cost for rNEMO is derived as follows: rNEMO CPT = S · T · E(S) · ( · dLMA–MAG · LT ).
Fig. 3. Extended information entry in proposed RENEMO.
(2)
In the N-PMIPv6 scheme, the mMAG performs a location update on behalf of the MNNs. Therefore, the LU cost for N-PMIPv6 is constant regardless of the number of MNNs within the mMAG. It can
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5 rNEMO (E(S) = 10) N-PMIPv6 (E(S) = 10) RENEMO (E(S) = 10) rNEMO (E(S) = 30) N-PMIPv6 (E(S) = 30) RENEMO (E(S) = 30)
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Fig. 4. Total cost.
Table 1 Parameters for numerical result.
be presented by N-PMIPv6 CLU = C · T · ( · RSmMAG–MAG + · RAMAG–mMAG
+ · AAAMAG–AAA + 2 · · LUMAG–LMA ).
(3)
Once an LMA receives the packets sent by a CN, it makes two tunneling IP header for outer/inner and attaches the tunnel header to the packets. When the MAG receives the tunneled packets, it removes only outer header and delivers the rest to the mMAG. Therefore, we can express the PT cost by N-PMIPv6 CPT = S · T · E(S) · ( · dLMA–MAG · 2LT + · dMAG–mMAG · LT ).
(4)
In the proposed RENEMO scheme, the mMAG also performs a location update on behalf of the MNN. But the N-MAG needs the information of all the MNNs within the mobile network. In order to do that, a PBA message should include all the MN-ID and HNP options as the number of MNNs within the mMAG. To add the length of the MNN-ID and MNN-HNP options as the number of MNNs, we separately add ı··dLMA−MAG (LMNN−ID + LMNN−HNP ) to the LU cost. The LU cost of the RENEMO is derived by RENEMO CLU = C · T · ( · RSmMAG–MAG + · RAMAG–mMAG
+ · AAAMAG–AAA + 2 · · LUMAG–LMA + ı · · dLMA–MAG ·(LMNN–ID + LMNN–HNP )).
(5)
In the RENEMO, the PT cost is the same as that for the rNEMO because no tunneling is employed except for the PMIPv6 tunnel header between the MAG and the LMA. Therefore, it is expressed by RENEMO CPT = S · T · E(S) · ( · dLMA–MAG · LT ).
(6)
To calculate the total cost of the three schemes, we employ some of the parameter values used in the literature [8], which are shown in Table 1. In Fig. 4(a), the total cost of N-PMIPv6 is much higher than other schemes because packet tunneling makes an impact on the total cost when the session arrival rate increases. Compared with the rNEMO and the RENEMO, the total cost of the rNEMO is greater than that of the RENEMO due to individual location update cost for
Parameter
Value
Parameter
Value
dMNN–mMAG dmMAG–MAG dMAG–AAA dMAG–LMA
1 1 1 4
ı// T (s) E(S) (packets) S
10/0.5/2 1000 10 0.15
the number of MNNs even though they have same packet tunneling cost. In Fig. 4(b), when the number of MNNs increases, the PBA message sizes in the RENEMO increases more but the packet tunneling cost for increased MNNs also increases at the same time. If E(S) is 10 packets per a MNN at least, the increased packet tunneling cost is much greater than the increased location update cost. When we consider that one session has dozens of packets, we can imagine the cost difference will be larger. Fig. 4(c) shows the total cost when MAG subnet crossing rate increases where E(S) is 10. From these results, we confirm that the proposed RENEMO outperforms the rNEMO and the N-PMIPv6 in terms of network resource usage.
4. Conclusion This paper proposed a resource-efficient network mobility (RENEMO) scheme, which performs effective handoff when the network moves and minimizes packet tunneling overhead compared to the rNEMO and the N-PMIPv6. Performance analysis and results revealed that the proposed RENEMO can reduce the network resources for location update and packet delivery process. It is conjectured that RENEMO is a suitable network mobility solution for moving vehicles in a PMIPv6 domain.
Acknowledgements This research was partially supported by the KCC (Korea Communications Commission), Korea, under the R&D program supervised by the KCA (Korea Communications Agency) (KCA2011-08913-05001) and by the MKE (The Ministry of Knowledge Economy), Korea, under the Convergence-ITRC(Convergence Information Technology Research Center) support program (NIPA-2011 C6150-1101-0004) supervised by the NIPA (National IT Industry Promotion Agency).
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References [1] Devarapalli V, Wakikawa R, Petrescu A, Thubert P. Network mobility (NEMO) basic support protocol. In: IETF RFC 3963. 2005 January. [2] Johnson D, Perkins C, Arkko J. Mobility support in IPv6. In: IETF RFC 3775. 2004 June. [3] Gundavelli S, Leung K, Devarapalli V, Chowdhury K, Patil B. Proxy mobile IPv6. In: IETF RFC 5213. 2008 August. [4] Pack S. Relay-based network mobility support in proxy mobile IPv6 networks. Proc IEEE CCNC 2008.
[5] Soto I, Bernardos C, Calderon M, Banchs A. NEMO-enabled localized mobility support for Internet access in automotive scenarios. IEEE Commun Mag 2009 May;47(5):152–9. [6] Pack S, Shen X, Mark J, Pan J. Adaptive route optimization in hierarchical mobile IPv6 networks. IEEE Trans Mobile Comput 2007 August;6(8): 903–14. [7] Kleinrock L. Queueing systems, vol. 1: theory. John Wiley & Sons; 1975. [8] Jeon S, Kang N, Kim Y, Yoon W. Enhanced PMIPv6 route optimization handover. IEICE Trans Commun 2008 November;E91-B(11).
Contents lists available at SciVerse ScienceDirect
International Journal of Electronics and Communications (AEÜ) journal homepage: www.elsevier.de/aeue
Resource-efficient network mobility support in Proxy Mobile IPv6 domain Seil Jeon a , Namhi Kang b , Younghan Kim a,∗ a b
The School of Electronic Engineering, Soongsil University, Sangdo-Dong 511, Dongjak-Gu, Seoul 156-743, Republic of Korea The Department of Digital Media, Duksung Women’s University, Ssangmoon-Dong, Tobong-Gu, Seoul 132-714, Republic of Korea
a r t i c l e
i n f o
Article history: Received 18 November 2010 Accepted 23 September 2011 Keywords: Network mobility NEMO Resource-efficient Proxy Mobile IPv6 PMIPv6
a b s t r a c t The basic standard protocol for supporting network mobility (NEMO) (i.e., NEMO-BSP specified by IETF) introduces several performance problems, such as multiple tunneling overhead and packet delivery latency, because it exploits mobile IPv6 (MIPv6), which was proposed for host mobility. To improve the basic NEMO solution, two network-based NEMO approaches, rNEMO and N-PMIPv6, have been proposed. The rNEMO is able to reduce significant packet tunneling overhead. The N-PMIPv6, on the other hand, reduces location update cost, but it leads to packet tunneling overhead. Thus, they commonly waste network resources in both wired and especially wireless network. No efficient and practical solutions for minimizing both the location update overhead and packet tunneling overhead have been presented until now. This situation motivated us to propose a resource-efficient network mobility scheme (RENEMO), reducing resource utilization required for network mobility support. We show that the proposed RENEMO outperforms both rNEMO and N-PMIPv6 in terms of network resource. © 2011 Elsevier GmbH. All rights reserved.
1. Introduction Advances in wireless hand-held devices increase the demand for Internet access, even though they are moving in vehicles such as trains, buses, and airplanes. To meet with the demand, the network mobility basic support protocol (NEMO-BSP) has been developed by the Internet Engineering Task Force (IETF) [1]. The NEMO-BSP allows mobile network nodes (MNNs) within a moving vehicle to continue their sessions. However, NEMO-BSP, which employs the mobile IPv6 (MIPv6) [2] as the host mobility management protocol for a mobile router (MR), introduces additional tunneling overhead while packets traverse between the home agent (HA) of an MN and MR placed in a bandwidth-limited wireless environment. To improve the performance of the NEMO-BSP, two NEMO approaches using Proxy Mobile IPv6 (PMIPv6) [3], which provides networkbased local mobility by mobile access gateway (MAG) and local mobility anchor (LMA), have been proposed: relay-based NEMO (rNEMO) [4] and NEMO-enabled PMIPv6 (N-PMIPv6) [5]. In the rNEMO, an MR is operated as simple relay station (RST), which can be either an amplify-and-forward (AF) or a decode-and-forward (DF) relay station. Thus, the MR simply relays both signal and data packets without an additional tunnel header except the PMIPv6 tunnel header for delivering packets as shown in Fig. 1(a). But this scheme requires an individual handoff signaling to manage MNN’s location when the network moves. In the N-PMIPv6, the moving
MAG (mMAG) on behalf of the MR is presented as shown in Fig. 1(b). The N-PMIPv6 focuses on the handover performance with regard to the latency it takes when an MNN moves from the mobile network to outside. In the N-PMIPv6, only LMA manages the entry information for an MNN. So, packets to destined MNN arrive at the LMA, the LMA adds a double tunneled IP header (expressed as ‘T’ in Fig. 1(b)) into all received packets from a correspondent node (CN) and delivers them to a MAG. Thereafter, the MAG removes only the outer header; then the packet containing the single tunneled header is reached at the MNN. In some scenarios, where lots of MNNs are in the vehicle, the N-PMIPv6 leads to severe packet delivery cost. Consequently, the two approaches waste network resources. In addition, no optimal solution has been presented so far to satisfy with the minimized location update and packet tunneling overhead. In this paper, we therefore propose a resource-efficient NEMO scheme (RENEMO) which reduces the location update cost in rNEMO and the packet delivery cost in N-PMIPv6 by extending the proxy binding update list (PBUL) in MAG and the binding cache entry (BCE) in LMA. The remainder of this paper is organized as follows. Section 2 describes the RENEMO architecture. Then, we provide performance analysis and results compared with rNEMO and N-PMIPv6 in Section 3. Finally, we offer our conclusion in Section 4. 2. Proposed scheme
∗ Corresponding author. E-mail addresses: [email protected] (S. Jeon), [email protected] (N. Kang), [email protected] (Y. Kim). 1434-8411/$ – see front matter © 2011 Elsevier GmbH. All rights reserved. doi:10.1016/j.aeue.2011.09.006
Fig. 2(a) and (b) shows the signaling operation for the mMAG’s attachment (step 1) and the MNN’s attachment (step 2), respectively. Fig. 2(c) shows the network handover procedure when an
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the mMAG address when the MAGA delivers the packets to the MNN, as shown in Fig. 2. The PBA message is again delivered to the mMAG. The mMAG creates an RA message, including the received HNP prefix for the MNN. • Step 3: When an mMAG moves to an area of MAGB , the MAGA detects the mMAG’s handoff from the layer-2 signal and exchanges a binding update message (PBU/PBA) with the LMA for de-registration. After the MAGB detects mMAG’s approaching, it sends a PBU message to the LMA. The LMA then changes the tunnel endpoint, which is distinguished by the IP address of the MAG, for packet delivery to the MNNs within the mMAG from MAGA to MAGB . Cached MNN-IDs and MNN-HNPs belong to the mMAG are delivered to the MAGB through a PBA message. The mMAG receives these prefixes from the MAGB through an RA message and uses only the first prefix option for home emulation. In the case of mMAG’s handoff, ‘G’ flag is not used. When the LMA receives packets that are destined for the MNN, it looks up the corresponding MAG IP address in BCE. Then the LMA appends only a single PMIPv6 tunnel header into the packets and sends them to the MAG. When the MAG sends packets to the MNN via mMAG, no tunnel is used because the MAG acts as an LMA proxy from the perspective of the mMAG. Fig. 3(a) and (b) shows extended MAG PBUL and LMA BCE information in the RENEMO. Both entries have a ‘G’ flag field to distinguish the MNN from other attached nodes. And they also have an ‘mMAG’ address field to deliver the packets to the mMAG in the MAG and to manage the MNNs’ location in the LMA. In the case of node mobility operation where an MNN moves to outside PMIPv6 domain from mobile network, the mMAG is required to inform MNN’s detachment to the current MAG. Then, the PBU/PBA message between mMAG and LMA for de-registration is processed via MAG. When an MNN approaches to the MAG, it follows standard procedure defined in [3]. 3. Performance analysis and results
Fig. 1. Protocol operation of rNEMO and N-PMIPv6.
mMAG, including MNNs, moves from MAGA area to MAGB area (step 3). The following steps present the RENEMO scheme in detail. • Step 1: When an mMAG approaches a PMIPv6 domain, the MAGA detects the mMAG’s movement triggered by L2 signal or router solicitation (RS) message. The mMAG performs a security association with the AAA (authentication, authorization and accounting) server. The MAGA then sends the proxy binding update (PBU) message to the LMA. When the MAGA receives the proxy binding acknowledgment (PBA) message, including the home network prefix (HNP) for the mMAG, it transmits the HNP to the mMAG through a router advertisement (RA) message. The mMAG configures its address based on the received HNP. • Step 2: For a newly attached MNN, the mMAG contacts the AAA server to authenticate the MNN. Thereafter, the mMAG creates a PBU message containing the MNN’s ID, the mMAG’s IP address, and the ‘G’ flag and then sends it to MAGA . The ‘G’ flag is only used for MNN’s location update. The MAGA appends its address to the received PBU and sends it to the LMA. On receiving the PBA message, the LMA distinguishes whether this PBU is for ordinary MN or MNN by examining the ‘G’ flag, which is only used for MNN’s location update. The LMA allocates the HNP and delivers it to MAGA . On receiving the PBA message, including the HNP for the MNN, the MAGA creates PBUL, which is extended to manage
In this section, we evaluate the performance of the RENEMO compared with rNEMO and N-PMIPv6 in terms of location update (LU) cost (CLU ) and packet tunneling (PT) cost (CPT ). In the CLU cost, the location update cost for initial attachment is not considered. By summing up two terms, we obtain the total cost (CTOT ), which is defined by the product of message size and hop distance from a bandwidth perspective during time T. Under such definition, a router processing cost is not considered. T denotes the total time required to move by the MN. For the performance analysis, we have the assumptions as followed. The inter-session arrival time follows an exponential distribution with rate S and average session length, in packets, is E(S). The MAG subnet crossing rate follows a general distribution with mean rate C , as presented in [6]. To analyze the each cost, some notations in the literature [6] are used as follows. • LP and LT : length of packet P and tunnel header (1500 bytes and 40 bytes) • LRS , LRA , and LAAA : length of RS message, RA message, AAA message (70 bytes, 110 bytes, and 100 bytes) • LPBU and LPBA : length of PBU message and PBA message (112 bytes and 96 bytes) • LMNN–ID and LMNN–HNP : length of ID and home network prefix option for MNN (20 bytes and 32 bytes) • d˛–ˇ : hop distance between ˛ and ˇ • LU˛–ˇ : unit cost of PBU/PBA message between network entity ˛ and ˇ (=d˛−ˇ ·(LPBU + LPBA )) • RS˛−ˇ : unit cost of RS message between network entity ˛ and ˇ (=d˛–ˇ ·(LRS ))
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Fig. 2. Proposed resource-efficient NEMO (RENEMO) operation based on PMIPv6 domain.
• RA˛−ˇ : unit cost of RA message between network entity ˛ and ˇ (=d˛–ˇ ·(LRA )) In the rNEMO scheme, the MAG detects detachment and attachment of MN and then sends/receives a PBU/PBA message with the
LMA for de-registration and registration. And an MNN exchanges the RS/RA message with the MAG when the mobile network moves to another MAG. Let C be the cell crossing rate. Then the average number of cell crossings during T is equal to C ·T as defined in [6]. We employ the unit of transmission cost for a wired link and a wireless link, and , as defined in [8]. Therefore, the location update for rNEMO can be represented by rNEMO CLU = C · T · ı · ( · RSMNN–MAG + · RAMAG–MNN
+ · AAAMAG–AAA + 2 · · LUMAG–LMA ),
(1)
where ı is the number of MNN, which is considered for the individual MNN update. All the packets transmitted by the CN are delivered to the MNN via the MAG and relay station; however, packet tunneling occurs between the LMA and the MAG. By Little’s law [7], the number of packets delivered during T is approximated by S ·T·E(S), where S is the session arrival rate from the CN. The E(S) is the average session length in numbers of packets. Therefore, the PT cost for rNEMO is derived as follows: rNEMO CPT = S · T · E(S) · ( · dLMA–MAG · LT ).
Fig. 3. Extended information entry in proposed RENEMO.
(2)
In the N-PMIPv6 scheme, the mMAG performs a location update on behalf of the MNNs. Therefore, the LU cost for N-PMIPv6 is constant regardless of the number of MNNs within the mMAG. It can
S. Jeon et al. / Int. J. Electron. Commun. (AEÜ) 66 (2012) 390–394 5
5 rNEMO (E(S) = 10) N-PMIPv6 (E(S) = 10) RENEMO (E(S) = 10) rNEMO (E(S) = 30) N-PMIPv6 (E(S) = 30) RENEMO (E(S) = 30)
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3
2
1
0
0
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0.4
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1
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10 rNEMO (E(S) = 10) N-PMIPv6 (E(S) = 10) RENEMO (E(S) = 10) rNEMO (E(S) = 30) N-PMIPv6 (E(S) = 30) RENEMO (E(S) = 30)
4
3
Total cost (hops x kbytes)
x 10
Total cost (hops x kbytes)
Total cost (hops x kbytes)
5
2
1
0
393
0
Session arrival rate (a) Total cost as a function of session arrival rate
5
10
15
5
rNEMO (# of MNN = 20) N-PMIPv6 (# of MNN = 20) RENEMO (# of MNN = 20) rNEMO (# of MNN = 40) N-PMIPv6 (# of MNN = 40) RENEMO (# of MNN = 40)
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x 10
The number of MNNs (b) Total cost as a function of the number of MNNs
0
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MAG subnet crossing rate (c) Total cost as a function of MAG subnet crossing rate
Fig. 4. Total cost.
Table 1 Parameters for numerical result.
be presented by N-PMIPv6 CLU = C · T · ( · RSmMAG–MAG + · RAMAG–mMAG
+ · AAAMAG–AAA + 2 · · LUMAG–LMA ).
(3)
Once an LMA receives the packets sent by a CN, it makes two tunneling IP header for outer/inner and attaches the tunnel header to the packets. When the MAG receives the tunneled packets, it removes only outer header and delivers the rest to the mMAG. Therefore, we can express the PT cost by N-PMIPv6 CPT = S · T · E(S) · ( · dLMA–MAG · 2LT + · dMAG–mMAG · LT ).
(4)
In the proposed RENEMO scheme, the mMAG also performs a location update on behalf of the MNN. But the N-MAG needs the information of all the MNNs within the mobile network. In order to do that, a PBA message should include all the MN-ID and HNP options as the number of MNNs within the mMAG. To add the length of the MNN-ID and MNN-HNP options as the number of MNNs, we separately add ı··dLMA−MAG (LMNN−ID + LMNN−HNP ) to the LU cost. The LU cost of the RENEMO is derived by RENEMO CLU = C · T · ( · RSmMAG–MAG + · RAMAG–mMAG
+ · AAAMAG–AAA + 2 · · LUMAG–LMA + ı · · dLMA–MAG ·(LMNN–ID + LMNN–HNP )).
(5)
In the RENEMO, the PT cost is the same as that for the rNEMO because no tunneling is employed except for the PMIPv6 tunnel header between the MAG and the LMA. Therefore, it is expressed by RENEMO CPT = S · T · E(S) · ( · dLMA–MAG · LT ).
(6)
To calculate the total cost of the three schemes, we employ some of the parameter values used in the literature [8], which are shown in Table 1. In Fig. 4(a), the total cost of N-PMIPv6 is much higher than other schemes because packet tunneling makes an impact on the total cost when the session arrival rate increases. Compared with the rNEMO and the RENEMO, the total cost of the rNEMO is greater than that of the RENEMO due to individual location update cost for
Parameter
Value
Parameter
Value
dMNN–mMAG dmMAG–MAG dMAG–AAA dMAG–LMA
1 1 1 4
ı// T (s) E(S) (packets) S
10/0.5/2 1000 10 0.15
the number of MNNs even though they have same packet tunneling cost. In Fig. 4(b), when the number of MNNs increases, the PBA message sizes in the RENEMO increases more but the packet tunneling cost for increased MNNs also increases at the same time. If E(S) is 10 packets per a MNN at least, the increased packet tunneling cost is much greater than the increased location update cost. When we consider that one session has dozens of packets, we can imagine the cost difference will be larger. Fig. 4(c) shows the total cost when MAG subnet crossing rate increases where E(S) is 10. From these results, we confirm that the proposed RENEMO outperforms the rNEMO and the N-PMIPv6 in terms of network resource usage.
4. Conclusion This paper proposed a resource-efficient network mobility (RENEMO) scheme, which performs effective handoff when the network moves and minimizes packet tunneling overhead compared to the rNEMO and the N-PMIPv6. Performance analysis and results revealed that the proposed RENEMO can reduce the network resources for location update and packet delivery process. It is conjectured that RENEMO is a suitable network mobility solution for moving vehicles in a PMIPv6 domain.
Acknowledgements This research was partially supported by the KCC (Korea Communications Commission), Korea, under the R&D program supervised by the KCA (Korea Communications Agency) (KCA2011-08913-05001) and by the MKE (The Ministry of Knowledge Economy), Korea, under the Convergence-ITRC(Convergence Information Technology Research Center) support program (NIPA-2011 C6150-1101-0004) supervised by the NIPA (National IT Industry Promotion Agency).
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