15-12-2012, 05:21 PM
Performance Analysis of Mobility Support in IPv4/IPv6 Mixed Wireless Networks
Performance Analysis.pdf (Size: 1.12 MB / Downloads: 26)
Abstract
The rapid growth of the Internet has led to the anticipated
depletion of addresses in the current version of the Internet
Protocol (IP), i.e., IPv4. This depletion has given rise to a newer
version of the IP, i.e., IP version 6 (IPv6). IPv6 provides sufficient
address space to meet the predicted increase of the Internet. Since
IPv4 has already widely been deployed, it is required that the existing
IPv4 and the newly added IPv6 can coexist and interoperate.
Due to the incompatibility of the IPv4 and IPv6 headers, various
mechanisms have been proposed to support the interoperability
between IPv4 and IPv6. However, they are mostly designed for
a static environment. Mobility support of mobile terminals in
a mixed IPv4/IPv6 environment remains largely unexplored. It
introduces additional overhead and delay to communications. In
this paper, we analyze various handoff scenarios for a dual-stack
mobile node with a predominant IPv6 home address roaming in
a mixed IPv4/IPv6 environment. We investigate how handoffs can
be supported and derive the handoff procedures for all scenarios.
In addition, we analyze the impact of mobility support on the
system performance in terms of handoff-signaling cost, handoff
delay, and handoff-failure probability using our designed analytical
models.
INTRODUCTION
THE RAPID growth of the Internet has led to the anticipated
depletion of addresses in the current version of the
Internet Protocol (IP) IPv4 [1]. This depletion has given rise
to a newer version of the Internet protocol, i.e., IP version
6 (IPv6) [2]. IPv6 provides sufficient address space and a
number of new features to meet the predicted increase of the
Internet. It has hierarchical addresses to reduce the size of
routing tables, improved security, and data-integrity features,
and an autoconfiguration facility that enables a host to directly
obtain an IP address via the network.
BACKGROUND ON INTERNET MOBILITY SUPPORT
Themobility solutions of IPv4 and IPv6 areMobile IPv4 [13]
and Mobile IPv6 [11], respectively.
Mobile IPv4
Mobile IPv4 is a solution for mobility on the existing global
Internet [13]. It was developed by IETF to provide continual
Internet connectivity to mobile users. Mobile IPv4 introduces
three new functional entities: 1) home agent (HA); 2) foreign
agent (FA); and 3) MN. Each MN has a permanent home
address (HoA) from its home network. When an MN moves
out of its home network, it obtains a temporary address: care-of
address (CoA). This address is used to identify the MN in the
visited local network. The mobility agent in the visited network,
i.e., FA, can provide a CoA to the MN that is shared by many
MNs or assign a unique colocated CoA to each MN. When the
MN moves from one foreign network to another, it registers its
new location, i.e., its new CoA, to the HA that is located in the
home network. The HA keeps a binding of the HoA and the
current CoA for each MN. Packets sent from a correspondent
node (CN) for an MN are sent to its permanent address, i.e., its
HoA first. The HA intercepts all the IP packets destined to the
MN and tunnels them to the CoA of the MN.
System Architecture
We consider a generic system architecture for the performance
analysis of mobility support in IPv4/IPv6 mixed wireless
networks. As shown in Fig. 2, various autonomous subnets are
connected to different Internet backbone networks. The subnets
that are connected to the IPv6 backbone are IPv6 networks,
such as Subnets 1 and 2 in the figure. The subnets that are
connected to the IPv4 backbone are IPv4 networks, such as
Subnets 4 and 5 in the figure. In addition, the subnets that
are connected to both backbone networks are IPv4/IPv6 dualstack
networks, such as Subnet 3 in the figure. Depending on
the type of network, each subnet has either an FA or an access
router (AR) handling the mobility of MNs. Moreover, there are
two types of CNs considered in our system architecture: 1) an
IPv4 CN connected to an IPv4 network and 2) an IPv6 CN
connected to an IPv6 network. The system architecture shown
in Fig. 2 is generic and can be applied to many practical mobile
environments.
Handoff Scenarios
We investigate different roaming scenarios of a dual-stack
MN with a predominant IPv6 HoA (DSMNv6) [16]. The MN
moves between different subnets, requiring the handoff support
from one subnet to another. We assume that the MN follows
the mobility solution of the subnet into which it is moving. For
example, if the MN is moving into an IPv4 or IPv6 network,
it will follow the handoff procedures defined in Mobile IPv4
[13] or Mobile IPv6 [11], respectively. In addition, if the MN is
moving into a dual-stack network, i.e., the network with dualstack
routers and hosts, it will follow Mobile IPv6 handoff
procedures as well, due to the distinct advantages provided by
Mobile IPv6. Under the considered system architecture, all the
possible handoff scenarios of a dual-stack MN are listed in
Table I.
Performance Metrics
The coexistence of IPv4 and IPv6 introduces extra operations
and overhead for mobility support. The extra overhead affects
the overall QoS performance of communications. The QoS
metrics chosen in this paper for the performance analysis of
mobility support are signaling cost, delay, and failure probability
of handoffs.
The signaling cost is defined as the total cost needed to
transmit and process the extra signaling messages that are
required during the handoff process. As discussed in [18], the
cost parameter has no unit but can be defined to be proportional
to the delay required to send or process a signaling message.
Other measurements for the cost parameters are possible. For
example, the network administration can assign specific cost
values to each operation based on the available bandwidth
of a link, computation resources at a node, and the expenses
required to operate a particular mobility agent.
Average Handoff Delay
Based on the length of each signaling message and the
assumption of 2- and 100-Mb/s link capacity of the wireless and
wired links, respectively [22], the transmission delay of each
signaling message can be calculated. In addition, it is reported
that the average service time at a router 1/μn is between 20
and 100 μs [23]. In this paper, we assume 1/μn = 100 μs.
Thus, the average service and queuing time at a node can be
calculated as Tsq = (1/ξ) = 1/(μn − λn), given any offered
traffic load λn. We also set the average one-hop propagation
delay over a wired link as 2.5 μs [24] and the average onehop
wireless propagation delay as 1 ms [25]. Table V lists all
the time values used for the performance evaluation on handoff
delay. Note that the message length used for the calculation is
the minimum length without considering options in the header.
CONCLUSION
In this paper, we have investigated the mobility support issue
when an MN moves in a mixed IPv4/IPv6 environment. As
more and more IPv6 networks are deployed, the mechanisms
addressing the issues of coexistence and interworking between
the current IPv4-based networks and the newly added IPv6-
based networks become imperative. In this paper, we have first
conducted comprehensive case studies on the mobility support
based on a generic system architecture and analyzed the handoff
procedures of all the possible roaming scenarios when an MN is
a dual-stackMNwith an IPv6 home address.