AN-MSCSP-05-Mobility management advanced

Integrated Communication Systems GroupIlmenau University of Technology

Mobility Management – Advanced

Summer Semester 2011

Integrated Communication Systems Group

Advanced Networking (MSCSP) & Wireless Internet (II,IN) 2

Outline

• Motivation

• Mobility Management Approaches in the TCP/IP Reference Model

• Link Layer Mobility Management

• Network-based Mobility Management

• Conclusions

• References



Motivation

• The Internet and mobile communication networks areexperiencing an enormous growth

• Future networks will interconnect various heterogeneous networksby means of a common IP core, also referred to as All-IP

• Goals: always-on connectivity, higher bandwidth, reduced delay,lower cost, etc.

• Challenge: support mobility between cells connected through anIP core while satisfying real-time requirements



Mobility Management Approaches in the TCP/IP Reference Model



Which Layer Handles Mobility?

Application layer

Application layerPresentation layer

Session layer

Transport layer Transport layer

Network layer Internet layer

Data link layer

Network Interface Hardware

Physical layer

ISO/OSI TCP/IP

Link layer mobility

Network layer mobility

Transport layer mobility

Session layer mobility

Application layer mobility

Required to build radio links



Which Layer Handles Mobility?

• Link layer mobility management is responsible for theestablishment of a radio link between the MN and the new AccessPoint (AP)

• No more procedures are required if the old as well as the new APbelongs to the same subnet

• If the new AP belongs to a new subnet, we need mobility supporteither– in the network layer, i.e. the Internet layer of the TCP/IP reference

model,– in the transport layer or– in the application layer



Mobility Management in Different Layers, Why?

• Link layer mobility– Required when changing the point of attachment– Responsible for establishment of a wireless link

• Network layer mobility– Transparency to higher layer protocols, e.g. TCP and UDP– Applications on mobiles can further communicate with existing

applications without any modifications– Change of network architecture is allowed

• Transport layer mobility– End-to-end mobility management while keeping the Internet

infrastructure unchanged– End hosts take care of mobility, i.e. TCP and UDP are updated to

support mobility



Mobility Management in Different Layers, Why?

• Session layer mobility– Migration of sessions between devices

• Application layer mobility– No changes to current networks– Extending IP telephony infrastructure to fulfill mobility requirements– Usage of SIP protocol and support for mobility by change of the

mapping between a name of a user (e.g. mail address) and the IPaddress

• Hybrid layer mobility– Optimization of the performance of a certain layer mobility

management approach using information from other layers or theIntegration of solutions from several layers

– Synchronization between layers is essential



Link Layer Mobility Management



Link Layer Handoff

• Responsible for the establishment of a radio link between the MNand the AP

• The handoff comprises 4 phases– Recognizing the loss of the wireless connection– Search for and detection of a new adequate AP– Re-/Authentication with the new discovered AP– Re-/Association with the new discovered AP



Recognizing the Loss of the Wireless Connection

• Connection loss is detected based on– Weakness of the received signal or– Failed frame transmissions

• Weakness of the received signal– Most frequently used approach– A layer 2 handoff is prompted, if the received signal strength goes

below a certain threshold

• Failed frame transmissions– Slower than received-signal-strength-based approach– The MN first assumes a collision as reason for failed frame

transmissions; if not, radio signal fading is assumed; if not, an out ofrange is declared



Search and Detection of A New Adequate AP

• Passive scanning

AP operating in frequency B

AP operating in frequency A

Beacon Beacon100 msec

t

t

t

Change to frequency A

BeaconBeacon

Change to frequency B

Change to frequency C



Search and Detection of A New Adequate AP

• Active scanning

Probe request

Probe delay MinChannelTime

No activities on this channel

Probe response

t

t

t

Change to frequency A

Change to frequency B

AP operating in frequency B

AP operating in frequency C

MaxChannelTime

Probe request

Probe delay MinChannelTime



Re-/Authentication With the New Discovered AP

• The MN authenticates itself to the new AP

• Two authentication methods are defined for the IEEE 802.11standard– Open system: null-authentication (default method)– Shared key authentication: none null-authentication

• Exchange of authentication request & authentication responsemessages

• More messages can be exchanged between the authenticationrequest & response; details depend on the authenticationalgorithm



Re-/Association With the New Discovered AP

• Exchange of association request & association responsemessages

• After this phase, the wireless link is established



Link Layer Handoff

• Large variation for the samehardware with same configurationmainly due to stochastic behaviorof radio interface

• Scanning is the main factor in thelatency, it accounts for– about 90 % of the overall handoff

delay and– 80 % of the messages

exchanged (depends on mobilityand radio conditions)

MN APs

New AP



Research Issues

• Speeding up the layer 2 handoff requires accelerating thescanning phase– Periodic scanning

• Scanning the medium while the MN is still connected to the old AP• When the signal strength of the current AP is decreasing, the MN

switches to another frequency for a short time and scans for otheravailable APs

– Selective scanning• Use of a channel mask to reduce the channels that must be scanned

– Information about neighbors• Utilizing information about neighbor APs to reduce the number of

channels that must be scanned



Network-based Mobility Management



Terminal vs. network-based mobility management

• Terminal-based mobility management approaches– Mobility support in the network and MNs– MNs participate in mobility procedures

– Status• Wide range of solutions has been developed• Employed in current networks

– Disadvantages• MNs have to be updated, which is mostly not preferable by users

– Example• Mobile IP (MIP)



Terminal vs. network-based mobility management

• Network-based mobility management– Mobility support in the network only (terminals with legacy IP stack can

be mobile)– No interaction between the network and MNs

– Status• Under development

– Disadvantages• Many features are hard to realize, e.g. route optimization• Focus is on support of global mobility; achieving fast and smooth handoffs

is not the focus yet

– Example• Proxy Mobile IP version 6 (Proxy MIPv6)



Proxy MIPv6

Mobile AccessGateway

(MAG)

MAG

MAG

MAG

Corresponding Node (CN)Internet

Localized Mobility Anchor (LMA)

MN does not have to understand mobility; from the MN´s point of view, it is located in its home network and

the whole domain represents a single point of attachment

Support of mobility is required in the MAGs; each MAG emulates the home network of each MN

served by it

Unicast RA with the Home Network Prefix

(HNP) of the MN

RA



Proxy MIPv6 – Handoff

MAG

MAG

MAG

MAG

CNInternet

LMA

The MAG detects a detach event

De-Registration Proxy Binding Update(DeReg PBU)

Proxy Binding Acknowledgement (PBAck)

Start a timer to delete the mobility binding of the MN



Proxy MIPv6 – Handoff

MAG

MAG

MAG

Internet

The MAG detects an attach event&

acquires the MN-ID and profile, from AAA server for example

PBU

LMA

MAG

Accepts the binding, allocates MN-HNP and sets

up a tunnel to the MAG

PBAck

A unicast RA with the MN-HNP the MN assumes that it is located in its home network and thus there is no need for a

re-configuration of its IP address

RA

CN



Proxy MIPv6 – Data Communication

MAG

MAG

MAG

CNInternet

LMA

MAG



Proxy MIPv6 – Pros & Cons

• Pros– Transparency to MNs (MNs with no mobility support can be mobile)– Protocol is robust against control messages dropping (no control

messages are sent on wireless links)– Reduced signaling cost– Terminating the tunnel in the MAG instead of MNs reduces the data

traffic volume sent over the wireless link

• Cons– Triangular routing increased end-to-end delay– Overhead due to the encapsulation– Handoff latency due to contacting the LMA each time the MN moves

from one point of attachment to another communication disruption– Route optimization is not possible



Conclusions

• Mobility management in future networks is IP-based

• Mobility can be implemented in different layers of the TCP/IPreference model; each layer has positive and negative impacts

• Network layer mobility approaches are the most deployedsolutions– Terminal-based approaches interact with MNs to support mobility– Network-based approaches do not involve MNs in mobility support– Both approaches are categorized into macro and micro mobility

management approaches• Macro mobility approaches aim at supporting global mobility• Micro mobility approaches aim at accelerating the mobility management

through processing of mobility locally



References

• E. Weiss, A. Otyakmaz, E. López, B. Xu, “Design and Evaluation of a new Handoff Protocol inIEEE 802.11 Networks”, Proceedings of the 11th European Wireless conference 2005, Nicosia,Cyprus 2005.

• IEEE Computer Society, “Part 11: Wireless LAN Medium Access Control (MAC) and PhysicalLayer (PHY) Specifications”, Standard IEEE 802.11, ISBN: 0-7381-5656-6 SS95708, June2007.

• C. Perkins, “IP Mobility Support for IPv4”, RFC 3344, August 2002.

• D. Johnson, C. Perkins, J. Arkko, “Mobility Support in IPv6”, RFC 3775, June 2004.

• H. Soliman, C. Castelluccia, K. El-Malki, L. Bellier, “Hierarchical Mobile IPv6 mobilitymanagement (HMIPv6)”, RFC 4140, August 2005.

• A. G. Valko, “Cellular IP - A New Approach to Internet Host Mobility”, in the proceeding of ACMComputer Communication Review, January 1999.

• S. Gundavelli, K. Leung, V. Devarapalli, K. Chowdhury, B. Patil, “Proxy Mobile IPv6”, RFC5213, August 2008.


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fon: +49 (0)3677 69 2819 (2788)fax: +49 (0)3677 69 1226e-mail: [email protected]

[email protected]

www.tu-ilmenau.de/ics


Univ.-Prof. Dr.-Ing. Andreas Mitschele-ThielDr. rer. nat. habil. Oliver Waldhorst

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AN-MSCSP-05-Mobility management advanced