Macro Mobility Management

Transcription

Mobility Management
Prof. Dr.-Ing. habil. Andreas Mitschele-Thiel
Dipl.-Ing. Ali Diab
Integrated HW/SW Systems Group
Ilmenau University of Technology
Integrierte Hard- und Softwaresysteme
Outline
•
Introduction
•
Mobility Management Approaches in the TCP/IP Reference Model
•
Link Layer Mobility Management
•
Network Layer Mobility Management
•
Conclusions
•
Questions Catalog
Mobility Management
2
Introduction
Mobility Management
3
Motivation
•
The Internet and mobile communication
experiencing an enormous growth
•
Future networks will interconnect various heterogeneous networks
by 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 an
IP core while satisfying real-time requirements
Mobility Management
networks
are
4
Problem Statement
TCP
UDP
153 . 12 . 0 . 0
Internet
165 . 115 . 0 . 0
153 . 12 . 24 . 118
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Problem Statement
TCP
Dropping
UDP
Slow start mechanism
Internet
165 . 115 . 0 . 0
153 . 12 . 0 . 0
165 . 115 . 215 . 9
Communication disruption should be minimized or even eliminated
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6
Mobility Management Requirements
•
Fast and smooth handoffs (lossless handoffs are the ideal case)
•
Fixed identifier for the Mobile Node (MN)
•
Inter-working properly with IP
•
Minimized signaling cost
•
No impairments of ongoing applications
•
No additional security vulnerabilities
•
Scalability, robustness and deployability
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7
Mobility Management Approaches in
the TCP/IP Reference Model
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Which Layer Handles Mobility?
Application layer
Application layer mobility
Presentation layer
Application layer
Session layer
Session layer mobility
Transport layer
Transport
layer
Transport
layer
mobility
Network layer
Internet
layer
Network
layer
mobility
Data link layer
Link layer mobility
Network Interface Hardware
Physical layer
ISO/OSI
Mobility Management
Required to build radio links
TCP/IP
9
Which Layer Handles Mobility?
•
Link layer mobility management is responsible for the
establishment of a radio link between the MN and the new Access
Point (AP)
•
No more procedures are required if the old as well as the new AP
belongs to the same subnet
•
If the new AP belongs to a new subnet, we need mobility support
either
– in the network layer, i.e. the Internet layer of the TCP/IP reference
model,
– in the transport layer or
– in the application layer
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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
infrastructure unchanged
while
keeping
the
Internet
– End hosts take care of mobility, i.e. TCP and UDP are updated to
support mobility
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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 IP
address
•
Hybrid layer mobility
– Optimization of the performance of a certain layer mobility
management approach using information from other layers or the
Integration of solutions from several layers
– Synchronization between layers is essential
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Link Layer Mobility Management
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Link Layer Handoff
•
Responsible for the establishment of a radio link between the MN
and 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
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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 of
range is declared
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Search and Detection of A New Adequate AP
•
Passive scanning
Change to
frequency B
Change to
frequency A
AP operating in
frequency A
AP operating in
frequency B
Mobility Management
Beacon
Beacon
100 msec
Change to
frequency C
t
t
Beacon
Beacon
t
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Search and Detection of A New Adequate AP
•
Active scanning
No activities on this channel
Change to
frequency A
Probe delay
AP operating in
frequency B
Probe
request
MinChannelTime
Change to
frequency B
Probe delay
Probe
request
t
MinChannelTime
MaxChannelTime
Probe
response
t
t
AP operating in
frequency C
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Re-/Authentication With the New Discovered AP
•
The MN authenticates itself to the new AP
•
Two authentication methods are defined for the IEEE 802.11
standard
– Open system: null-authentication (default method)
– Shared key authentication: none null-authentication
•
Exchange of authentication request & authentication response
messages
•
More messages can be exchanged between the authentication
request & response; details depend on the authentication
algorithm
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Re-/Association With the New Discovered AP
•
Exchange of
messages
•
After this phase, the wireless link is established
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association
request
&
association
response
19
Link Layer Handoff
MN
APs
Probe requ
es
•
•
ts
Large variation for the same
hardware with same configuration
mainly due to stochastic behavior
of radio interface
Scanning is the main factor in the
latency, it accounts for
– about 90 % of the overall handoff
delay and
– 80
%
of
the
messages
exchanged (depends on mobility
and radio conditions)
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spons
e
r
e
b
o
Pr
es
Authentica
tion reques
t
r es po
n
o
i
t
a
tic
Authen
Association
New AP
nse
request
respo
n
o
i
t
a
i
Assoc
nse
20
Research Issues
•
Speeding up the layer 2 handoff requires accelerating the
scanning 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 other
available 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
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Network Layer Mobility Management
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Overview
•
End-to-end mobility management
•
Implemented in
– Network layer of the ISO/OSI reference model or
– Internet layer of the TCP/IP protocol suite
•
Termed as layer 3 mobility management as well
•
Benefits
– Transparency to higher layer protocols, e.g. TCP and UDP
– Applications on MNs can further communicate with existing
applications without any modifications
•
However
– The infrastructure has to be adapted
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Network Layer Mobility Management Approaches
•
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
– Classification
• Terminal-based macro mobility management solutions
• Terminal-based micro mobility management solutions
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Network Layer Mobility Management Approaches
•
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
– Classification
• Network-based macro mobility management solutions
• Network-based micro mobility management solutions
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Terminal-Based Mobility Management
•
Macro mobility management approaches
– Aim at global mobility support
– Base protocols: Mobile IPv4 (RFC 3344) & Mobile IPv6 (RFC3775)
•
Micro mobility management approaches
– Performance improvements through localizing the mobility processing
inside administrative domains
– Introducing of new intermediate nodes to the network
– Hierarchical network topology is typically required
– Categorized in
• Proxy Agent Approaches (PAA) and
• Localized Enhanced Routing Schemes (LERS)
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Macro Mobility Management – Mobile IPv6 (MIPv6)
CN
Internet
Corresponding Node (CN)
Home Agent (HA)
No support for mobility
(standard IPv6 router)
AR
AR
Access Router (AR)
AR
Periodic broadcast
of Router
Advertisements (RA)
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Mobility support; use of two IP
addresses (Home Address
(HoA) & Care of Address (CoA))
27
MIPv6 - Handoff
CN
Internet
CN
HA
AR
Binding Updates (BUs)
AR
AR
AR
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MIPv6 - Handoff
CN
Internet
CN
HA
Binding Acknowledgements (BAs)
AR
AR
AR
AR
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MIPv6 – Data Communication
CN
Internet
CN
HA
AR
Uplink data packets are
dealt with as standard IP
packets
AR
AR
AR
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MIPv6 - Pros & Cons
•
Pros
– Enabling end-to-end mobility
– Transparency to upper layer protocols
– Works properly with IP
•
Cons
– Overhead due to encapsulation
– High handoff latencies due to contacting the HA and the CN each
time the MN changes the point of attachment Æ Communication
disruption
– Considerable signaling load due to frequent BUs especially when
MNs move at high speeds
– Sub-optimal routing and increased end-to-end delay due to triangular
routing where CN is not MIPv6 enabled (binding updates) or due to
lack of security
Mobility Management
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Micro Mobility Management
HA is not aware of each
change in the point of
attachment
HA
Internet
Movements inside the
domain are controlled by
the intermediate node,
also called intra-domain
mobility
Intermediate node
Administrative
domain
Administrative
domain
Movements between different
domains are typically handled
by MIP, also called interdomain mobility
Mobility Management
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Proxy Agent Approaches (PAA)
•
Extend the principle of MIP to provide micro mobility
•
Introduce new intermediate nodes to the network to process the
mobility inside an administrative domain locally
•
Data packets destined to the MN are forwarded to the
intermediate node, which tunnels them towards the MN’s current
point of attachment
•
Examples
– Hierarchical MIPv6 (HMIPv6),
Seamless MIP (S-MIP), etc.
Mobility Management
Anchor
Foreign
Agent
(AFA),
33
HMIPv6
HA is not aware of the MN’s
mobility as long as the
RCoA has not been
changed
Internet
HA
CN
RCoA
MAP
Mobility Anchor Point (MAP)
AR1
AR2
AR3
AR4
AR5
AR6
LCoA
MN registers a Regional CoA (RCoA),
i.e. a CoA in the MAP’s subnet, in its HA
as the MN’s CoA; the location of the MN
inside the domain is defined by the local
CoA (LCoA), which is a CoA in the
current AR subnet
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HMIPv6 – Handoff
Internet
HA
CN
RCoA
MAP
MAP
BA
AR1
AR3
AR2
LCoA
AR4
AR5
AR6
Local BU
RA
The MN configures a new LCoA
Mobility Management
35
HMIPv6 – Data Communication
Internet
HA
MAP
MAP
AR1
Mobility Management
AR2
CN
AR3
AR4
AR5
AR6
36
HMIPv6 – Pros & Cons
•
Pros
– Localizing of mobility management inside administrative domains
– Improving the performance: reduced handoff latency compared to
MIPv6, reduced packet loss, etc.
– Reducing the signaling load traveling towards the HA
•
Cons
– Restrictions on the network topology
– Single point of failure (all traffic passes through the MAP)
– Increased signaling and packet forwarding overhead inside the
domain
– Security issues: how to authenticate arriving MNs?
Mobility Management
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Localized Enhanced Routing Schemes (LERS)
•
Similar principle as PAA approaches
•
Typically introduce a new dynamic layer 3 routing protocol inside
the domain (per-hop routing)
•
Data packets destined for the MN are forwarded to the
intermediate node controlling the domain, which forwards them
hop per hop towards the MN
•
All nodes in the domain should be mobility-aware
•
Examples
– Cellular IP, HAWAII
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Cellular IP
CN
Internet
HA
Gateway
The gateway controls the
domain
IP-based routing of data
packets inside the domain is
replaced by a special CIP
routing and location
management
BS2
BS1
BS3
Beacon messages flooded
periodically Æ all BSs know how to
route packets towards the gateway
BS4
BS5
The MN registers the address
of the gateway as its CoA;
inside the domain, the MN
uses its HoA
Mobility Management
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Cellular IP – Hard Handoff
CN
Internet
HA
Gateway
Update its routing cache and starts
forwarding data packets towards
the new location of the MN
BS3
BS4
Beacon
Mobility Management
BS2
BS1
BS5
Route-update
40
Cellular IP – Semi-Soft Handoff
CN
Internet
HA
Gateway
Update its routing cache and
starts forwarding data packets
towards the MN via the old and
new BS
BS2
BS1
BS3
BS4
BS5
Semi-soft packet
The MN detects a handoff in the near future
Æ it switches for a short time to the radio of
the new BS
Mobility Management
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Cellular IP – Semi-Soft Handoff
CN
Internet
HA
Gateway
Update its routing cache and
stops forwarding to the old BS
BS2
BS1
BS3
BS4
BS5
Route-update
After the layer 2 handoff, the MN sends a
route-update packet to stop the bicast
Mobility Management
42
Cellular IP – Data Communication
CN
Internet
HA
Routed using IP towards their
destination
Gateway
Uplink packets are forwarded hop
by hop towards the gateway; they
are used to refresh the routing
caches
BS3
Mobility Management
BS2
BS1
BS4
BS5
43
Cellular IP – Pros & Cons
•
Pros
– Localizing of mobility management inside administrative domains
– Improving the performance: reduced handoff latency, less lost packets,
etc.
– Reducing the signaling traveling towards the HA
– Mobile to mobile communication in the domain is routed via the gateway
•
Cons
–
–
–
–
Restrictions on the network topology
Single point of failure (all traffic travels through the gateway)
Signaling and packet forwarding overhead inside the domain
A new layer 3 dynamic routing protocol is implemented, which highly
reduces the throughput of TCP
– Every node in the domain have to be mobility-aware
– Security issues: authentication of arriving MNs, authentication of routeupdate messages, etc.
Mobility Management
44
Network-Based Mobility Management
•
Macro mobility management approaches
– Aim at global network-based mobility support
– Base protocols: Proxy MIPv6 (RFC 5213)
– Developed by the IETF-NETLMM working group
•
Micro mobility management approaches
– Use similar principles as terminal-based micro mobility management
approaches
– Performance improvements through localizing the mobility processing
inside administrative domains
– Introduction of new intermediate nodes to the network and deploying
a hierarchical topology
– Example: Terminal Independent MIP (TIMIP)
Mobility Management
45
Macro Mobility Management – Proxy MIPv6
Internet
Corresponding Node (CN)
Localized Mobility
Anchor
(LMA)
Support of mobility is required in
the MAGs; each MAG emulates
the home network of each MN
served by it
MAG
Mobile Access
Gateway
(MAG)
MAG
MAG
RA
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
Unicast RA with the
Home Network Prefix
(HNP) of the MN
Mobility Management
46
Proxy MIPv6 – Handoff
Start a timer to delete the
mobility binding of the MN
Internet
CN
LMA
Proxy Binding
Acknowledgement (PBAck)
De-Registration Proxy Binding Update
(DeReg PBU)
MAG
MAG
MAG
The MAG detects a detach event
MAG
Mobility Management
47
Proxy MIPv6 – Handoff
Accepts the binding,
allocates MN-HNP and sets
up a tunnel to the MAG
Internet
CN
LMA
PBAck
The MAG detects an attach event
&
acquires the MN-ID and profile,
from AAA server for example
PBU
MAG
RA
MAG
MAG
MAG
A unicast RA with the MN-HNP Æ 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
Mobility Management
48
Proxy MIPv6 – Data Communication
Internet
CN
LMA
MAG
MAG
MAG
MAG
Mobility Management
49
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 Æ 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 Æ communication disruption
– Route optimization is not possible
Mobility Management
50
Research Issues
•
Fast and smooth handoffs without restricting the network or
introducing new nodes
•
Privacy through location-independent addressing
•
IP-based mobility between different access topologies, also called
vertical handoffs
•
Support of route
management
•
Security & scalability
Mobility Management
optimization
for
network-based
mobility
51
Conclusions
•
Mobility management in future networks is IP-based
•
Mobility can be implemented in different layers of the TCP/IP
reference model; each layer has positive and negative impacts
•
Network layer mobility approaches are the most deployed
solutions
– 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
Mobility Management
52
Control Questions
•
Where do we need mobility support in case the MN has moved to an AP belonging
to a different subnet? Why do we need such mobility support?
•
What are the advantages obtained when supporting mobility in the network layer?
•
Propose a solution to accelerate the layer 2 handoff procedure.
•
What are the differences between terminal-based and network-based mobility
management approaches?
•
Compare between MIPv6 and HMIPv6?
•
What are the differences between PAA and LERS approaches?
•
What is the main idea behind network-based mobility management? How can such
mobility support be realized?
•
Propose some mechanisms to improve Proxy MIPv6?
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53
References
•
E. Weiss, A. Otyakmaz, E. López, B. Xu, “Design and Evaluation of a new Handoff Protocol in
IEEE 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 Physical
Layer (PHY) Specifications”, Standard IEEE 802.11, ISBN: 0-7381-5656-6 SS95708, June
2007.
•
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 mobility
management (HMIPv6)”, RFC 4140, August 2005.
•
A. G. Valko, “Cellular IP - A New Approach to Internet Host Mobility”, in the proceeding of ACM
Computer Communication Review, January 1999.
•
S. Gundavelli, K. Leung, V. Devarapalli, K. Chowdhury, B. Patil, “Proxy Mobile IPv6”, RFC
5213, August 2008.
Mobility Management
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Macro Mobility Management

Transcription

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