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MIPv6 Experimental Evaluation using Overlay Network
MIPv6 Experimental Evaluation using Overlay
Networks
Pablo Vidales
a
Carlos Jes´us Bernardos
b
Ignacio Soto
b
David Cottingham
c
Javier Baliosian
d
Jon Crowcroft
c
a
Strategic Research, Deutsche Telekom Laboratories
Ernst-Reuter-Platz 7, D - 10587 Berlin (Germany)
b
Universidad Carlos III de Madrid
Avda. Universidad 30, 28911 Legan´es (Spain)
c
Computer Laboratory, University of Cambridge
William Gates Building, 15 JJ Thomson Avenue, Cambridge CB3 0FD (UK)
d
Network Management Research Centre, Ericsson R&D Ireland
Ericsson Software Campus, Athlone, Co Westmeath, Ireland.
Abstract
The commercial deployment of Mobile IPv6 has been hastened by the concepts of Inte-
grated Wireless Networks and Overlay Networks, which are present in the notion of the
forthcoming generation of wireless communications. Individual wireless access networks
show limitations that can be overcome through the integration of different technologies
into a single unied platform (i.e., 4G systems). This paper summarises practical exper-
iments performed to evaluate the impact of inter-networking (i.e. vertical handovers) on
the Network and Transport layers. Based on our observations, we propose and evaluate a
number of inter-technology handover optimisation techniques, e.g., Router Advertisements
frequency values, Binding Update simulcasting, Router Advertisement caching, and Soft
Handovers. The paper concludes with the description of a policy-based mobility support
middleware (PROTON) that hides 4G networking complexities from mobile users, pro-
vides informed handover-related decisions, and enables the application of different vertical
handover methods and optimisations according to context.
Key words:
Mobile IPv6, 4G, Overlay Networks, Handover Optimisations.
Email addresses: Pablo.Vidales@telekom.de
(Pablo Vidales),
cjbc@it.uc3m.es
(Carlos Jes´us Bernardos), isoto@it.uc3m.es (Ignacio Soto),
David.Cottingham@cl.cam.ac.uk
(David Cottingham),
javier.baliosian@ericsson.com
(Javier Baliosian),
Jon.Crowcroft@cl.cam.ac.uk
(Jon Crowcroft).
Preprint submitted to Computer Networks
May 22, 2006 1
Introduction
The Internet Protocol (IP) was developed in the early 1980s with the aim of sup-
porting connectivity within research networks, as part of catenet [1]. However, in
the last decade IP has become the leading network-layer protocol. It is the basic
tool for a plethora of client/server and peer-to-peer networks; it predominates in
both wired and wireless worlds, and now the current scale of deployment is strain-
ing many aspects of its twenty ve-year old design. To overcome the limitations
inherent in the original IP design, IPv6 has been proposed as the new protocol that
will provide a rmer base for the continued growth of todays inter-networks.
The Internet has experienced an enormous growth in recent years and the num-
ber of users accessing services on-the-move has also grown exponentially. Every
mobile device is potentially capable of accessing IP services, Wi-Fi networks are
becoming ubiquitous; the growth in the hotspot market is being accompanied by
similar growth in other wireless technologies (e.g., Bluetooth, UltraWideband, and
satellite), posing the urgent need for a larger address space and an adequate support
for mobility.
Whereas the main thrust of IPv6 is to increase the addressing space, it also provides
important functions to enable mobility (e.g., scaling and ease-of-conguration),
mainly derived from the larger address space. IPv4 has difculties managing mo-
bile terminals for several reasons such as address conguration and location man-
agement.
To drive the evolution in the mobile world, Mobile IPv6 (MIPv6) [2] was proposed
as a protocol that exploits the added features in IPv6 to extend it and enable micro
and macro-mobility. With the introduction of IPv6, many of the disadvantages of
the previous version of the mobility support (i.e. Mobile IPv4 [3]) were eliminated.
However, neither Mobile IPv4 (MIPv4) nor Mobile IPv6 were intended to support
seamless roaming in heterogeneous environments.
The rapidly growing demand for anywhere, anytime high-speed access to IP-
based services is becoming one of the major challenges for mobile networks. As
the demand for mobility increases, mobile terminals need to roam freely across
heterogeneous networks, posing the challenge of network integration into an All-
IP ubiquitous access platform [4]. Mobile IPv6 stands as the de facto solution for
mobility management in next-generation systems. Highlights of networking evolu-
tion are shown in Figure 1; we consider IP and Mobile IP as primary players in the
unfolding of networking in past, present, and future communication systems.
Our work targets networking issues in future 4G communication systems. In par-
ticular, we are interested in the impact of vertical handovers and terminal mobility
on the performance of the TCP/IP stack. Our work aims to:
2 (1) Build a convenient environment to evaluate MIPv6, emulating the networking
environment of 4G systems,
(2) Measure the latency when the terminal is roaming between heterogeneous
networks,
(3) Characterise the vertical handover latency, identifying its main components,
(4) Identify the main performance problems during vertical handovers and their
impact on the TCP/IP stack,
(5) Explore different optimisation methods that decrease the overall latency, and
evaluate each of them using the University of Cambridge Computer Labora-
tory testbed,
(6) Demonstrate the efciency of different optimisations, and the need for a high-
level mobility support middleware to enable informed decisions and drive the
handover process.
In this paper we present a detailed evaluation of Mobile IPv6, due to its role as the
standard for mobility management in next-generation networks. A brief introduc-
tion to the basic concepts of Mobile IPv6, and the most important improvements
to this protocol are mentioned in Section 2. In Section 3, we describe the tightly-
integrated MIPv6-based testbed used during the experiments. Then we describe the
testing environment, explain test conditions and scenarios, in Section 4. The verti-
cal handover latency study is summarised in Section 5 and latency partition detailed
in Section 6. We explore different handover optimisations, with the results and eval-
uations presented in Section 7. A high-level policy-based middleware, PROTON, is
described in Section 8, as a plausible solution to handle context related complexities
and enable informed handover decisions. Related work is presented in Section 9,
while Section 10 concludes this paper.
2
MIPv6-based Management
In the last decade, some protocols for the dynamic assignment of IP addresses to
nodes joining a network segment (e.g., DHCP [5]) have been designed and de-
ployed, but these solutions provide portability and not transparent mobility. By
portability we mean the terminal mobility support that allows a host to change its
location, but which requires stopping and restarting its upper layer connections
(e.g., TCP). In contrast, transparent mobility allows a terminal to move between
different networks without dropping any connection. IPv6 [6] provides portability
because of its mechanisms for automatic address conguration, but not transparent
mobility. Mobile IPv4 [3] and Mobile IPv6 (MIPv6) [2] are the protocols dened
to provide support for reachability and transparent mobility in future networks.
The latency due to a handover using basic MIPv6 is proportional to the round-
trip time necessary for a Binding Update message (BU) to reach either the Mobile
Nodes Home Agent (HA) or a Correspondent Node. This is further analysed in
3 Section 6.
Latency on MIPv6-enabled links can be very high, especially for interactive ap-
plications that have real-time requirements. Therefore, the research community is
working on mechanisms that decrease this latency as much as possible, at least to
levels that support real-time applications in a seamless manner. Two of the most
signicant proposals are Fast Handovers for Mobile IPv6 (FMIPv6) [7] and Hier-
archical Mobile IPv6 (HMIPv6) [8].
FMIPv6 [7] aims to decrease the total latency to almost only the Layer 2 handover
time. This approach has been shown to perform well in intra-technology (i.e. hori-
zontal) handovers [9], [10].
The HMIPv6 approach is designed to reduce the degree of signalling required and
to improve handover speed for mobile connections by managing local mobility in
a more efcient way. Previous work [11], [12] has analysed which of these ap-
proaches (i.e. FMIPv6 and HMIPv6) performs better, the conclusion being that a
combined approach would be optimal. However, given the implementation com-
plexity that this would require, the FMIPv6 optimisation by itself is good enough
(this has been experimentally evaluated in [10]).
Future 4G systems, in which heterogeneity will be the rule instead of the exception,
present some challenging characteristics when performing vertical (also known as
inter-technology) handovers:
Bandwidth, delay, and packet losses can be very disparate among the differ-
ent candidate access netw