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Shall we apply paging technologies to proxy mobile IPv6?

J.-H. Lee, T.-M. Chung, S. Pack, and S. Gundavelli

in Proceedings of the 3rd international workshop on Mobility in the evolving internet architecture, Seattle, WA, USA, 2008, pp. 37-42

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Outline • Introduction• Preliminaries– Proxy Mobile IPv6– Paging Mechanism

• Paging Extension for PMIPv6• Performance Evaluation• Conclusions and Future Work

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Introduction • The Host-Based Mobility protocol depends on the

mobility stack installed in a mobile host (MH).– which typically operates in a limited capacity

• maintaining binding information has a strong influence on the limited resource.

• Proxy Mobile IPv6 (PMIPv6) supports network-based mobility for the MH.– the MH does not need to install the mobility stack into its

protocol stack.• handoff across different networks without its own mobility signaling cost

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Introduction (cont.)

• Drawbacks of PMIPv6– all mobility signaling is controlled through the mobility entities– data traffic of MH must be managed by the mobility entities– This network-based mobility architecture

• not only lacks the network resource, • but also limits the scalability in support of very large numbers of MHs

• we propose a paging extension scheme – to minimize the signaling overhead and optimize mobility

management cost in PMIPv6.

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Outline • Introduction• Preliminaries– Proxy Mobile IPv6– Paging Mechanism

• Paging Extension for PMIPv6• Performance Evaluation• Conclusions and Future Work

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Proxy Mobile IPv6 (PMIPv6)• Mobile IPv6 requires client functionality in the IPv6 stack

of a mobile node.– Host-based

• Network-based mobility is another approach to solving the IP mobility challenge.

• Per-MN-Prefix model – an addressing model where there is a unique network prefix or

prefixes assigned for each node.

S. Gundavelli, K. Leung, V. Devarapalli, K. Chowdhury, and B. Patil, "Proxy Mobile IPv6," IETF, RFC 5213, 2008.

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• Local Mobility Anchor (LMA)– has the functional capabilities of a MIPv6 home agent as with

the additional capabilities– the topological anchor point for the MN’s “home network”

prefix(es) in a PMIPv6 domain• Mobile Access Gateway (MAG)– a function on an access router– tracks the MN’s movements– manages the mobility signaling on behalf of an MN

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homedomain

wide area network

correspondent node

MAG2MAG1

AP1 AP2

Initiation

LMA

home domain(e.g., 1400:0112::0/40)

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L2 access authenticationwith MN-ID

2Proxy Binding Update:

with MN-ID and the address of MAG1

(e.g., proxy-CoA1)

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Proxy Binding Ack.: with a home prefix

for the MN(e.g., 1400:0112::1/64)

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1) Unicast Router Advertisement2) Configure “home address”

(e.g., 1400:0112::1::30)

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homedomain

wide area network

correspondent node

MAG2MAG1

AP1 AP2

LMA

home domain(e.g., 1400:0112::0/40)

CommunicationCommunicate with the MN using the MN’s “home address” (1400:0112::1::30::MN_MAC)

Downlink : LMA tunnels packets that

destined to the MN’s “home address”

to Proxy-CoA1Uplink:

MAG1 tunnels packets from the MN to the LMA

data

packets

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homedomain

wide area network

correspondent node

MAG2MAG1

AP1 AP2

Handover within the Home Domain

LMA

home domain(e.g., 1400:0112::0/40)

1

L2 access authentication

2Proxy Binding Update:

with MN-ID and the address of MAG2

(e.g., proxy-CoA2)

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Proxy Binding Ack.: with the same home prefix

for the MN(i.e., 1400:0112::1/64)

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1) Unicast Router Advertisement2) use the same “home address”

(e.g., 1400:0112::1::30)

data

packets

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homedomain

wide area network

correspondent node

MAG2MAG1

AP1 AP2

LMA

home domain(e.g., 1400:0112::0/40)

Communication-2Communicate with the MN using the MN’s “home address” (1400:0112::1::30::MN_MAC)

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• Network traffic bottleneck at the LMA while it tries to support a large number of MHs– all registration messages generated by MAGs, – data traffic generated by MHs, and – data traffic destined for MHs

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Paging Mechanism• operates on a set of neighboring networks which

constitutes a paging area.– active mode

• the mobility entity, i.e., home agent or LMA recognizes the exact location of the MH

– idle mode • the MH hands off across different networks in a paging area without the

registration procedure resulting in need for paging

• achieve a reduction in signaling loads occurred by MHs in the idle mode

• a battery consumption at the MH is reduced significantly

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paging mechanisms for Mobile IPv4 in [3]

• Home Agent paging – the paging initiator is the home agent– simple required only at the home agent and mobile host– flexible different update and paging algorithms may be

implemented in the home agent and mobile hosts.– reduced efficiency home agents may be located some distance

from the mobile hosts– poor scalability– decreasing reliability the failure of a home agent or paging

process in a home agent would render all the mobile hosts it serves unreachable

– deployment the paging information could be considered confidential and may not be available

[3] R. Ramjee et al. IP Paging Service for Mobile Hosts. In Proc. of ACM SIGMOBILE, pages 332–345, July 2001.

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• Foreign Agent paging – the previous foreign agent is the paging initiator– simple requiring changes to foreign agents and mobile hosts.– scalability the processing load of paging is distributed among

the different foreign agents– efficient and deployable the confidentiality issues of Home

Agent paging are avoided– somewhat flexible different update and paging algorithms can

be implemented in the mobile hosts and foreign agents– will not work with the mobile host co-located CoA option of

Mobile IP– reliability the failure of the previous foreign agent could result

in the mobile host being unreachable indefinitely

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• Domain paging – paging initiator selected dynamically– load balancing for performance– fail-over for reliability– reliability a completely distributed approach, retaining the

scalability and efficiency– confidentiality issues of Home Agent paging are avoided– truly localized no updates to the home agent due to paging– works both with the co-located care-of option of Mobile IP as

well as the network-based foreign agent option.– additional functionality in the routers– not as simple to implement nor as easy to deploy

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paging performance study [6]

• the paging size is the most important unit for acquiring the effect of IP paging.

• IP paging shows its ability only when the number of cells per network is small.

• However, we argue that this interpretation of paging in IP-based mobility protocols has to be examined under various performance parameters, not only by the cell size.

[6] J. Kempf and P. Mutaf. IP Paging Considered Unnecessary: Mobile IPv6 and IP Paging for Dormant Mode Location Update in Macrocellular and Hotspot Networks. In Proc. of IEEE WCNC, pages 1032–1036, March 2003.

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Outline • Introduction• Preliminaries• Paging Extension for PMIPv6• Performance Evaluation• Conclusions and Future Work

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Design considerations• Support for unmodified mobile hosts– the previous paging mechanisms proposed for HBM protocols

require paging response messages sent from the MH• Reduction in mobility signaling cost– signaling converging to the LMA

• increases the network unavailability probability• decreases the scalability in support of very large numbers of MHs

• Avoidance of paging processing at a single point– the paging processing would be distributed among the MAGs

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Paging Architecture• the MAGs in the same paging

area are involved in the same multicast group

• time-based state– a lifetime of a currently active

binding for an MH turns into the idle mode when the lifetime is expired

– the serving MAG informs other MAGs located in the same paging area

• The paging area information is only updated in the LMA when the MH hands off to a new paging area

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Paging Message Sequence

Idle Indication?Idle Indication?

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Outline • Introduction• Preliminaries• Paging Extension for PMIPv6• Performance Evaluation• Conclusions and Future Work

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Network Model• each paging area is consisted of the

same number of cells • an MAG is located in each cell– a cell is considered as a subnet

• The number of cells in the L-level paging area is calculated as follows

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Mobility Model• Fluid-flow model– suitable for MHs having a high mobility and static velocity

• The direction of an MH is distributed uniformly in the range of (0, 2π)

• The cell and paging area crossing rate:

– ν the average velocity of the MH– ρ the MH’s density– Lc the cell perimeter– Lp the paging area perimeter

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Cost Analysis• the location update for the basic PMIPv6

MH-MAG

MAG-LMA

tunnel Move out of cell

location update refreshing

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• the location update for the PMIPv6 with paging extension

tunnel

active mode MH 移出cell

location update refreshing

incoming/outgoing session for idle mode MH

Signaling between MAGs

MH-MAG

MAG-LMA

paging when session incoming

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Numerical Results• it is typically assumed that

the distance between the MAG and the LMA (tγ) is larger than the distance between the MAGs (tβ)

• pα includes CPU processing time, queuing delay, etc

[11] X. Zhang, J. Castellanos, and A. Campbell. P-MIP: Paging Extensions for Mobile IP. ACM Mobile Networks and Applications, 7(2):127–141, March 2002

Size of a cell = 6500 m2 32~130 MHs per cell

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• slow moving MHs stay in the same cell (subnet) for longer periods than the fast moving MHs.

• the size of paging areas is carefully designed and deployed in networks. • such a problem can be absorbed by applying the dynamic paging

algorithm [10]– the paging area is dynamically allocated based on several performance units

[10] Xie, H., Tabbane, S. and Goodman, D.J. Dynamic Location Area Management and Performance Analysis. In Proc. of IEEE VTC, pages 536–539, May 1993.

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• the fast moving MHs frequently hand off across the cell boundary

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• small percentage of MHs operating in the active mode

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• if there are all MHs operating in the active mode, the paging extension scheme cannot improve the network performance

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Outline • Introduction• Preliminaries• Paging Extension for PMIPv6• Performance Evaluation• Conclusions and Future Work

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Conclusions • PMIPv6 follows a centralized mobility management architecture

– poses heavy burden on the LMA and – causes network traffic bottleneck at the LMA.

• The proposed paging scheme has a decentralized paging architecture that distributes the paging state among the MAGs – the processing load of paging MHs is decentralized.

• We have modeled the location update cost – using layered hexagonal network model and the fluid flow model.

• numerical results confirm that the proposed paging extension scheme provides significant reduction in the location update cost

• In future, we would like to explore dynamic paging algorithms to further reduce the signaling load.