an-mscsp-05-mobility management advanced · – transparency to higher layer protocols, e.g. tcp...
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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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 3
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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 4
Mobility Management Approaches in the TCP/IP Reference Model
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 5
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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 6
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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 7
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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 8
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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 9
Link Layer Mobility Management
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 10
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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 11
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
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Advanced Networking (MSCSP) & Wireless Internet (II,IN) 12
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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 13
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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 14
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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 15
Re-/Association With the New Discovered AP
• Exchange of association request & association responsemessages
• After this phase, the wireless link is established
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 16
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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 17
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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 18
Network-based Mobility Management
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Advanced Networking (MSCSP) & Wireless Internet (II,IN) 19
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)
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 20
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)
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Advanced Networking (MSCSP) & Wireless Internet (II,IN) 21
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
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Advanced Networking (MSCSP) & Wireless Internet (II,IN) 22
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
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Advanced Networking (MSCSP) & Wireless Internet (II,IN) 23
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
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 24
Proxy MIPv6 – Data Communication
MAG
MAG
MAG
CNInternet
LMA
MAG
Integrated Communication Systems Group
Advanced Networking (MSCSP) & Wireless Internet (II,IN) 25
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
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Advanced Networking (MSCSP) & Wireless Internet (II,IN) 26
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
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Advanced Networking (MSCSP) & Wireless Internet (II,IN) 27
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.
Integrated Communication Systems GroupIlmenau University of Technology
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www.tu-ilmenau.de/ics
Integrated Communication Systems GroupIlmenau University of Technology
Univ.-Prof. Dr.-Ing. Andreas Mitschele-ThielDr. rer. nat. habil. Oliver Waldhorst
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