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Mobility Protocols and Handover Optimization
Speaker: Ashutosh Dutta, Ph.D.
Founding Co-Chair – IEEE 5G Initiative
Director Industry Outreach
New Jersey
Email: [email protected]
Phone: 908-642-8593
April 16 2018, Denver Section, ComSoc Chapter
Copyright 2015 © IEEE. All rights reserved. 2
Talk Outline
Motivation for Optimization
Mobility protocols for multimedia
Systems analysis of mobility events
Modeling Mobility Handoff
Mobility Optimization Techniques
Sample Use Cases
Best Current Practices for Handoff Optimization
Copyright 2015 © IEEE. All rights reserved. 3
What are Characteristics of Next Generation Networks?
Heterogeneous networks, many access networks
–Access-independent converged IP network
Order-of-magnitude increases in bandwidth
–MIMO, smart antennas
–Increase in video and other high bandwidth traffic
New terminals
New services and service enabling platforms
Large range of cell sizes, coverage areas
–PAN, LAN, WAN
–Pico-cellular, micro-cellular, cellular
Densification of Cells
Changes in traffic and traffic patterns
–Rise in video on demand? Requires good high-bandwidth multicast
Copyright 2015 © IEEE. All rights reserved. 4
Evolution of wireless access technologies
2020
20 Gbp/s DL SpeedF-OFDM, SCMA
Copyright 2015 © IEEE. All rights reserved. 6
Mobile Wireless Internet: A Scenario
802.11a/b/g
Bluetooth
IPv6
Network
UMTS/CDMA
Network
InternetDomain1
Domain2
UMTS/
CDMA
PSTN gateway
Hotspot
CHRoaming
User Ad Hoc
Network
PAN
LAN
WAN
WAN
LAN
PSTN
802.11 a/b/g
Copyright 2015 © IEEE. All rights reserved. 7
Handover Taxonomy
Inter-subnet
Intra-subnet
Intra-tech &
Inter-domain
Intra-tech & Intra-domain
Inter-tech &
Inter-domain
Inter-tech &
Intra-domain
Intra-tech &
Intra-domain
802.11 (provider X) to CDMA (provider X)
802.11 (provider X) to CDMA (provider Y)
802.11b (provider X) to 802.11n (provider X)
802.11b (provider X) to 802.11n (provider Y)
Inter-tech & Intra-domain
802.11 (provider X) to CDMA (provider X)Some scenario could be homogeneous as well, e.g., intra-tech &
intra-domain
Copyright 2015 © IEEE. All rights reserved. 8
Use Case: Using Multiple Radios
Ne
tw
or
k
Ty
pe
S
SI
D/
C
ell
ID
B
S
SI
D
Op
er
at
or
Se
cu
rit
y
N
W
C
ha
nn
el
Q
o
S
Ph
ysi
cal
La
yer
Dat
a
Rat
e
GS
M
13
98
9
N/
A
AT
&T
NA NA 1
9
0
0
N
/
A
N/A 9.6
kbps
80
2.1
6d
N
A
N
A
T-
Mo
bile
PK
M
EAP-
PEA
P
1
1
Y
e
s
OF
DM
40
Mbp
s
Wakeup WLANDownload over WLANShutdown GPS
Café
Airport
Zone 1 Zone 2 Zone 3
Zone 4 Zone 5 Zone 6
Zone 7 Zone 9
Wi-Fi
Wi-MAX
WLAN Link Going Down.
Switch to WiMAXDownload over WiMAXShutdown WLANWakeup GPS Zone 8
Wi-Fi
Connect to WLAN
Battery level lowShutdown WiMAXDownload over GSM/GPRS
Wakeup WLAN
Wi-MAX
Shutdown GPSStart Download over WLAN
Network
Type
SSID/
Cell ID
BSSID Operator Security NW Channel QoS Physical
Layer
Data Rate
GSM 13989 N/A AT&T NA NA 1900 N/A N/A 9.6 kbps
Network
Type
SSID/
Cell ID
BSSID Operator Security NW Channel QoS Physical
Layer
Data Rate
GSM 13989 N/A AT&T NA NA 1900 N/A N/A 9.6 kbps
802.11b Café 00:00:… Café .11i EAP-
PEAP
6 .11e OFDM 11 Mbps
Network
Type
SSID/
Cell ID
BSSID Operator Security EAP
Type
Channel QoS Physical
Layer
Data Rate
GSM 13989 N/A AT&T NA NA 1900 N/A N/A 9.6 Kbps
802.11b Airport 00:00:… Airport .11i EAP-
PEAP
6 .11e OFDM 11 Mbps
Radio State
GSM
WLAN
WiMAX
GPS
Radio State
GSM
WLAN
WiMAX
GPS
Radio State
GSM
WLAN
WiMAX
GPS
Radio State
GSM
WLAN
WiMAX
GPS
Radio State
GSM
WLAN
WiMAX
GPS
Radio State
GSM
WLAN
WiMAX
GPS
Radio State
GSM
WLAN
WiMAX
GPS
802.21 and MP Enabled Seamless Mobility Deployment Scenario
Courtesy: Vivek Gupta, IEEE 802.21 chair
Copyright 2015 © IEEE. All rights reserved. 9
Non-optimized handoff results
Handoff between heterogeneous access
(802.11 – CDMA)
Handoff between homogeneous access
(802.11 – 802.11)
c. SIP-based non-optimized
handoff between 802.11 networks
802.11 802.11Handoff
Delay 4 s
Handoff Delay
~ 18 s
802.11 CDMA
Handoff Delay
16 s
802.11 CDMA
a. MIP-based Non-optimized handoff
b. SIP-based Non-optimized handoff
Copyright 2015 © IEEE. All rights reserved. 10
Multiple Interface Case (802.11b – CDMA1XRTT) – MIP as mobility protocol
802.11 802.11CDMAHandoff19 s
Effect of handoff delay during non-optimized mobility management (experimental results)
Single Interface Case (802.11b – 802.11b) – SIP as mobility
802.11 802.11Handoff
4 s
Handoff
17 s802.11 CDMA 802.11
Multiple Interface Case (802.11b – CDMA1XRTT) – SIP as mobility protocol
Copyright 2015 © IEEE. All rights reserved. 11
Motivation for OptimizationHandoff contributes to– Change in network connection path between communicating nodes– Discrete Sate Event change at different layers– Rebinding of common set of properties (e.g., association, endpoint address,
locator)– Associated delay and packet loss due to these discrete events and rebinding
Limit jitter, delay and packet loss for real-time applications during different types of handoff
– 150 ms end-to-end delay and 3% packet loss for interactive traffic such as VoIP– ITU-T G.114
Essential to reduce handoff delay across layers during re-association and mitigate the effect of handoff delay (i.e., packet loss)– Currently it takes between 4s – 17 s– Packet loss depends upon the CODEC, packet generation rate (G711, G729)
The challenge is even greater when moving between– Heterogeneous domains – Heterogeneous access technologies (e.g., CDMA, 802.11)– Simultaneous mobility
Copyright 2015 © IEEE. All rights reserved. 12
Cellular mobility typically involves handoff across homogeneous access technology – Optimization techniques are carefully engineered to
improve the handoff performanceIP-based mobility involves movement across access technologies, administrative domains, at multiple layers and involve interaction between multiple protocols– Mechanisms and design principles for optimized
handover are poorly understood– Currently there are ad hoc solutions for IP mobility
optimization, not engineering practice – No formal methodology to systematically discover or
evaluate mobility optimizations – No methodology for systematic evaluation or
prediction of "run-time" cost/benefit tradeoffs
12
Optimization for IP-based Mobility
Copyright 2015 © IEEE. All rights reserved. 18
LTE 4G Deployment Scenario
HSS
AAA
PGW (PCEF)MME
ePDG
PCRF
eNodeB eNodeB
SGW
SGSN S10
S11 S11S4
S3
S8Gx
RxS6aSGi
S2b
SWx
X2
S1-U
App Servers
S6b
DNS
ENUM
Non-LTE Access (WiFi)
• Monitoring traffic
at control and user
planes
• Monitoring tunnels and
pair performance
• Correlating traffic to mobile device
• Handover and roaming
• Registration/Admission Control on AAA server
• IP multimedia services
Data Center/IMS
Mobile Core/EPC
Access & Backhaul
UE
Monitoring PointSGW HSGW
MME
I-CSCF
Internet
Gm
S1-MME
3G Access (UTRAN)
RNC
P-CSCF
Cx
S-CSCF
Cx
Mw
LTE Access
Mw
S2a
Mw
Trusted non-LTE Access (EV-DO)
S103
S6d
SGi
Iu-psS12
GGSN
Gn
Gm
• D2D Communications
• Efficient Small Data Transmission
• Wireless Backhaul / Access Integration
• Flexible Networks
• Flexible Mobility
• Context Aware Networking
• Information Centric Networking
• Moving Networks19
Key Characteristics of 5G
• Massive MIMO
• RAN Transmission –Centimeter and Millimeter Waves
• New Waveforms
• Shared Spectrum Access
• Advanced Inter-Node Coordination
• Simultaneous Transmission Reception
• Multi-RAT Integration & Management
20
Types of 5G Applications
Enhanced Mobile Broadband
- Mobile Broadband, UHD / Hologram, High-mobility, Virtual PresenceCritical Communications
- Interactive Game / Sports, Industrial Control, Drone / Robot / Vehicle, EmergencyMassive Machine Type Communications
- Subway / Stadium Service, eHealth, Wearables, Inventory ControlNetwork Operation
- Network Slicing, Routing, Migration and Interworking, Energy SavingEnhancement of Vehicle-to-Everything
- Autonomous Driving, safety and non-safety features
Massive Sensing
1b/s over 10 years
off an AAA battery
Speed: >10 Gb/s Tb/s
Massive Content
Massive Control
Response: 1 msCourtesy: Gerhard Fettweis
Copyright 2015 © IEEE. All rights reserved. 23
Mobility TaxonomyIP Mobility
PersonalTerminal Service
Application
Layer
Network
Layer
Session
• Systems
Optimization
MIPv4 CIPHAWAIIIDMP MIP-LR MIPV6ProxyMIPv6
SIPMM
MIP-LR(M)
Proxy
Transport
Layer
MSOCKS,
Migrate
mSCTP
Shim
Layer
HIP
Issues
• Host controlled
vs.
Mobile Controlled
• Mobility pattern
Copyright 2015 © IEEE. All rights reserved. 26
ForeignSubnet
ForeignSubnet
Hierarchical Mobile IP
IP-based Network
CH
HomeSubnet
HA
<CH.IP, MH.IP>
<MH.IP, CH.IP>
MH
RFA
CH to MH
CH sends packet to MH home address as usual
HA in home subnet intercepts packet, tunnels it to GFA
GFA un-encapsulates packet, tunnels it to RFA
RFA un-encapsulates packet, sends to MH
home
network
GFA coverage area
GFA
RFA
Copyright 2015 © IEEE. All rights reserved. 29
Backbone
Administrative
Domain A
L2 PoA
Corresponding
Host
128.59.10.7
IPch
207.3.232.10
207.3.240.10
128.59.11.8
N2
N1N1
N2
N1- Network 1 (802.11)
N2- Network 2 ( CDMA/GPRS)
Configuration
Agent
L3 PoA
207.3.232.10
Mobile
Host
Authentication
Agent
Authorization
AgentRegistration
Agent
Registration
Agent
Administrative
Domain B
Configuration
Agent
Authorization
Agent
Signaling
Proxy
Authentication
Agent
Signaling
Proxy
L3 PoA
L2 PoA
L2 PoA
L2 PoA
L2 PoA
L2 PoA
L3 PoA
Mobility Illustration in IP-based 4G network
128.59.9.6
900 ms
900 ms
802.11 802.11
802.11802.11Handoff
Delay 4 s
4 seconds
Handoff Delay
~ 18 s
802.11 CDMA
18 seconds
Copyright 2015 © IEEE. All rights reserved. 30
Mobility/
Function
Access
Type
Network
Discovery
Resource
Discovery
Triggering
Technique
Detection
Technique
Configuration Key exchange/
Authentication
Encryption Binding
Update
Media
Rerouting
GSM TDMA BCCH FCCH Channel
Strength
SCH TMSI SRES/A3 DES MSC
Contld.
Anchor
WCDMA CDMA PILOT SYNC
Channel
Channel
Strength
Frequenc
y
TMSI SRES/A3 AES Network
Control
Anchor
IS-95 CDMA PILOT SYNC
channel
Channel
Strength
RTC TMSI Diffie-
Hellman
AKA
Kasumi MSC
Contld.
Anchor
MSC
CDMA
1X-
EVDO
EVDO PILOT
Channel
SYNC
Channel
Channel
Strength
RTC TMSI Diffie-
Hellman/
CAVE
AES MSC PDSN/MSC
802.11 CSMA/
CA
Beacon
11R
11R
802.21
SNR at
Mobile
Scanning.
Channel
Number,
SSID
SSID,
Channel
number
Layer 2
authenticate
802.1X
EAP
WEP/WPA
802.11i
Associate IAPP
Cell IP Any Gateway
beacon
Mobile
msmt.
AP
beacon
ID
GW
Beacon
MAC
Address
AP address
IPSec IPSec Route
Update
Intermediate
y
Router
MIPv4 Any ICMP
Router
adv.
FA adv.
ICMP
Router
Adv.
FA adv.
L2
triggering
FA adv FA-CoA
Co-CoA
IKE/PANA
AAA
IPSec MIP
Registrati
on
FA
RFA
HA
MIPv6 Any Stateless
Proactive
CARD
802.21
11R
Router
Adv.
Router
Prefix
CoA IKE/PANA
AAA
IPSEC MIP
update
MIP RO
CH
MAP
HA
SIPM Any Stateless
ICMP
Router
802.21
11R
L3
Router
Adv.
Router
Prefix,
ICMP
CoA
AOR
Re-Register
INVITE
exchange/AA
A
IPSEC/
SRTP/
S/MIME
Re-
INVITE
B2BUA
CH
RTPtrans
Functional Matrix of Mobility Event
Copyright 2015 © IEEE. All rights reserved. 31
Mobility
Event
Network
discovery &
selection
Network
attachment
Configuration Security
association
Binding
update
Media
reroute
Channel
discovery
L2
association
Router
solicitation
Domain
advertisement
Identifier
acquisition
Duplicate
Address
Detection
Address
ResolutionAuthentication
Key
derivation
Identifier
update
Identifier
mapping
Binding
cache
Tunneling
Buffering
Forwarding
Bi-casting/
Multicasting
Server
discovery
Identifier
Verification
Subnet
discovery
P1 P2 P3 P4 P5 P6
P11
P13
P12
P21
P22
P23
P31
P32
P33P41
P42P51
P52
P53
P54
P61 P62
P63
P64
System decomposition of handover process
Copyright 2015 © IEEE. All rights reserved. 32
Handover: Distributed operation across multiple layers
Time
L2
PoA
L3
PoA
Discovery Detection Configuration
Security
Association
p11
p12
p21
p31
p32 p42
p41Server
(Proxy,
/HA)
p22
Binding
Update
Media
Rerouting
p51p31
p32
p41 p42
p42p63
p62
p13p23
p31
p33
MN
p11 p12 p21 p22p31 p41
p61p32 p42
p13 p23p33
p51
p51
p52
p52
CN
p42p52
p61
p54
p53 p54
p61
p61p62
p64p51
Copyright 2015 © IEEE. All rights reserved. 33
Inter-domain Handoff Delay Analysis (example)
Operation
L2
Delay
L 2 Scanning
Association
L2 security
L3
Delay
Address
Acquisition
Duplicate
Address
Detection
ARP
Update
Local
Authentication
AAA
Profile
Binding
Update
Media
RedirectionApplication
Layer
Delay
-Reduce the handoff delay
-Reduce the packet Loss
Copyright 2015 © IEEE. All rights reserved. 35
Why need a mobility model ?Optimization techniques for a mobility event can be designed based on precedence relations amongst events and concurrent, conflicts or resource sharing type operations
Need a framework and model
– to analyze and schedule handoff processes for systems optimization
– to conduct trade-off analysis between systems resources and performance metrics
Specific expected results
– Determine the extent of parallelism possible among the handoff operations based on dependency and
– Determine systems performance (e.g., handoff delays) based on the execution of primitive handoff operations under constraints of limits on parallelism and constraints on the use of shared resources
– A mechanism to verify and predict the systems performance of a specific optimization technique
– A mechanism that can help design the optimal path of sequence of execution of events
35
Copyright 2015 © IEEE. All rights reserved. 36
Specifics of IP-mobility model Mobility event exhibits concurrent, sequential, conflicts or resource sharing behavior
Handoff-related processes can be modeled as Discrete Event Dynamic Systems (DEDS) that span across multiple layers
Proposed approach to build a mobility model
– Determine data dependency among mobility events
– Determine the consumption of shared resources the handoff operations
– Apply Deterministic Timed Transition Petri Net (DTTPN) to build various un-optimized mobility models and their associated optimization techniques
– Evaluate and predict the performance of the handoff system that demonstrates parallelism, optimistic or predictive operations
36
Copyright 2015 © IEEE. All rights reserved. 37
The system model can be used to investigate parallelism and opportunities for optimization during a handoff operation. Using the model, one can predict or verify the systems performance of an un-optimized handover and of any specific handoff optimization technique.
The model can predict the performance of any mobility protocol in any specific deployment scenario, such as intra-domain, inter-domain, or heterogeneous handoff.
The model can also be used to analyze the trade-off between performance metrics and resources when a mobility event includes parallel, optimistic, or speculative operations.
Key Benefits of Mobility Model
Copyright 2015 © IEEE. All rights reserved. 40
Petri net dependency of mobility eventsHandoff Process Precedence
RelationshipData it depends on
P11 – Channel Discovery P00 Signal-to-Noise Ratio value
P12 – Subnet discovery P21,P22 Layer 2 beacon ID
L3 router advertisement
P13 – Server discovery P12 Subnet address
Default router address
P21- Layer 2 association P11 Channel number
MAC address
Authentication key
P22- Router solicitation P21, P12 Layer 2 binding
P23- Domain advertisement P13 Server configuration
Router advertisement
P31 – Identifier acquisition P23,P12 Default gateway
Subnet address
Server address
P32 – Duplicate address
Detection
P31 ARP
Router advertisement
P33 – Address resolution P32, P31 New identifier
P41 – Authentication P13 Address of authenticator
P42 – Key Derivation P41 PMK (Pairwise Master Key)
P51 – Identifier update P31,P52 L3 Address
Uniqueness of L3 address
P52 – Identifier verification P31 Completion of COTI
P53 – Identifier mapping P51 Updated MN address
at CN and HA
P54 – Binding cache P53 New Care-of-address mapping
P61 – Tunneling P51 Tunnel end-point address
Identifier address
P62 – Forwarding P51, P53 New address of the mobile
P63 – Buffering P62, P51 New identifier acquisition
P64 – Multicasting/Bicasting P51 New identifier acquisition
Copyright 2015 © IEEE. All rights reserved. 41
Handoff Transitions and Sub-transitions
Transition v Handoff Operation Sub transitions Sub-operations
t0 Disconnect trigger t00 Layer 2 un-reachability test
t01 Layer 3 unreachability
t1 Network
discovery
t11 Discover layer 2 channel
t12 Discover layer 3 subnet
t13 Discover server
t2 Network
attachment
t21 Layer 2 association
t22 Router solicitation
t23 Domain advertisement
t3
configuration
t31 Identifier acquisition
t32 Duplicate address detection
t33 Address resolution
t4 Authentication t41 Layer 2 open authentication
t42 Layer 2 EAP
t5 Security association t51 Master key derivation
t52 Session Key derivation
t6 Binding update t61 Identifier update
t62 Identifier verification
t63 Identifier mapping
t64 Binding cache
t7 Hierarchical binding
update
t71 Fast binding update
t72 Local caching
t8 Media redirection t81 Tunneling
t82 Forwarding
t83 Buffering
t9 Local data redirection t91 Local id mapping
t92 Multicasting/bicasting
Copyright 2015 © IEEE. All rights reserved. 43
t1p1p0
t2 p2 t3
Disconnect
Trigger
ScanningL3 subnet
discoveryServer
discovery
2 1 2
32
Resources
discovered
p6
p3 p4 p5
(Resource: Battery power) (Resource: CPU cycles )(Resource: Bandwidth)
Handoff discovery process
Copyright 2015 © IEEE. All rights reserved. 44
t1p1p0 t2 p2 t3
p4p3 p5
3
1
Identifier
Acquisition
Duplicate
Address
Detection
Address
Resolution
12
2
Mobile
Configured
Mobile
Authenticated
(Resource: Battery Power) (Resource: CPU cycles)(Resource: Bandwidth)
p6
Handoff configuration process
Copyright 2015 © IEEE. All rights reserved. 45
Sub-process - 1(Identifier Acquisition)
Client is in
process of
getting IP address
Initial Client
Sends
Discover
Message
Server
Offers
Address
Client
Requests
Address
Server
Acknowledges
P1
P3
P4t1
t2 t3 t4
(Resource battery) (Resource Bandwidth) (Resource Processing power)
p5p4 p6
P2
Client is
checking the
address
Client
Waits for the
address
Copyright 2015 © IEEE. All rights reserved. 46
Sub-process - 2Duplicate Address Detection
Initial Client
Sends
ARP/Neighbor
Discovery
Client
confirms
the address
P1P2 P3
t1t2 t3
Client
Listen for
ARP response
(Resource PM) (Resource PB) (Resource PP)
3 3
Copyright 2015 © IEEE. All rights reserved. 47
Sub-process 3-IP Address Resolution (MAC-IP Address mapping)
Idle Send
ARP Broadcast
P1t1
(Resource PM) (Resource PB) (Resource PP)
33
2 2
Maps
IP address
And MAC
P 2
Network
Processing
ARP
Copyright 2015 © IEEE. All rights reserved. 48
t1p1p0 t2 p2
t3
Layer 2
associationRouter
SolicitationDomain
advertisement
2
Mobile
connected
p6
p3 p4 p5
Channel
available
(Resource: Battery Power) (Resource: CPU Cycles)(Resource: Bandwidth)
Handoff attachment process
Copyright 2015 © IEEE. All rights reserved. 49
t1p1p0
t2
WEP
Key
Open
AuthEAP
p3p2
p4
2
2
Mobile
Authenticated
p5
3
22
(Resource: Battery power) (Resource: CPU cycles)(Resource: Bandwidth)
Handoff authentication process
Copyright 2015 © IEEE. All rights reserved. 50
32 33
11 21 22 12 23
1341 42
31
52 51 53
54
64
61
62
63
00
Dependence graph for sequential operations
Copyright 2015 © IEEE. All rights reserved. 51
P00
t01
t11
t41
p11
p41
t13
p13
t42
p42
t21
p21
t22
p22
t12
p12
t23
p23 P52
t52 t51 P51
t53 p53
t64p64
t62
p62
t63
p63
t54 p54
p61
t31 t32 t33
p31 p32 p33
t00
Dependence graph for parallel operations
Copyright 2015 © IEEE. All rights reserved. 52
Mobility
Event
Network
discovery &
selection
Network
attachment
Configuration Security
association
Binding
update
Media
reroute
Channel
discovery
L2
association
Router
solicitation
Domain
advertisement
Identifier
acquisition
Duplicate
Address
Detection
Address
ResolutionAuthentication
Key
derivation
Identifier
update
Identifier
mapping
Binding
cache
Tunneling
Buffering
Forwarding
Bi-casting/
Multicasting
Server
discovery
Identifier
Verification
Subnet
discovery
P1 P2 P3 P4 P5 P6
P11
P13
P12
P21
P22
P23
P31
P32
P33P41
P42P51
P52
P53
P54
P61 P62
P63
P64
System decomposition of handover process
Copyright 2015 © IEEE. All rights reserved. 55
802.11 Networks
A handoff occurs when a mobile station moves
beyond the radio range of one AP and enters
another BSS.
Copyright 2015 © IEEE. All rights reserved. 57
Layer 2 discovery process (802.11)
State1 Unauthenticated
Unassociated
State 2Authenticated
Unassociated
State 3Authenticated
Associated
Successful
Authentication
Successful
Authentication or
Re-association
Disassociation
Notification
De-authentication
Notification
De-authentication
NotificationClass 1
Frames
Class 1 & 2
Frames
Class 1, 2 &3
Frames
Class 1 Frames – Control Frames
Class 2 Frames – Management Frames
Class 3 Frames – Data Frames
State1 Unauthenticated
Unassociated
State 2Authenticated
Unassociated
State 3Authenticated
Associated
Successful
Authentication
Successful
Authentication or
Re-association
Disassociation
Notification
De-authentication
Notification
De-authentication
NotificationClass 1
Frames
Class 1 & 2
Frames
Class 1, 2 &3
Frames
Class 1 Frames – Control Frames
Class 2 Frames – Management Frames
Class 3 Frames – Data Frames
Discovery
Scanning
Authentication Association
Beaconing
MN
L2
PoA
MN L2
PoAMN L2
PoA
Discovery
Scanning
Authentication Association
Beaconing
MN
L2
PoA
MN L2
PoAMN L2
PoA
Copyright 2015 © IEEE. All rights reserved. 58
Layer 2 Handoff Delay (802.11)
Discovery Phase
– Active scanning
MN probes AP
– Passive scanning
AP sends beacons periodically
Authentication Phase
– Open authentication
– Shared authentication
– 802.11i – 4 way handshake
Association Phase
Copyright 2015 © IEEE. All rights reserved. 59
Layer 2 handoff sequence
Old AP
Target APsMobile
Node
Existing
association
Probe request
Probe response
Probe request
Probe response
Authentication request
Authentication response
Re-association request
Re-association response
IAPP: Send security block
IAPP: Ack security block
IAPP: Move request
IAPP: Move response
New
association
EAPOL key
EAPOL key
EAPOL key
Scanning
Delay
Authentication
Delay
4-way
handshake
delay
Association
delay
Optional
Copyright 2015 © IEEE. All rights reserved. 60
Key principles for discovery optimizationLimiting the number of signaling exchanges between the mobile and the centralized server needed to discover the network resources.
In the case of passive scanning, an increase in the rate of beacon advertisement reduces the time to discover the new point of attachment at the cost of additional network bandwidth and processing at the end hosts.
Caching of neighboring network resource parameters before the mobile moves to the new network.
Use of a media-independent application layer discovery protocol to discover network resources to support handover in heterogeneous access networks without depending upon any access-specific technology.
Copyright 2015 © IEEE. All rights reserved. 61
Layer 2 Discovery Optimization
General techniques: Reduce the scanning time Caching of ESSID Use of second interface 802.11 specific discovery Proactive Discovery (no
scanning)
Proposed Solutions: Shin et al introduces selective
scanning and caching strategy Montavont et al propose
periodic scanning Velayos et al propose reduction
of beacon interval and performs search in parallel with data transmission
Brik et al propose to use a second interface to scan while communicating with the first interface
802.11u, 802.11k Forte and Schulzrinne Application Layer proactive
discovery (e.g., Dutta et al)
Copyright 2015 © IEEE. All rights reserved. 62
Expreriment Result – Handoff
time
Handoff Time
0
100
200
300
400
500
600
1 2 3 4 5 6 7 8 9 10
Experiments
mse
cOriginal HandoffSelective ScanningCaching
Copyright 2015 © IEEE. All rights reserved. 64
Components that affect L3 configuration and optimization techniques for layer 3 configuration
Layer 3 address acquisition
– Proactive caching
Duplicate Address Detection
– Optimistic DAD, Proactive DAD, Passive DAD,
– Router Assisted DAD
NUD (Neighbor Unreachability Detection)
– Aggressive Router Selection
Configuration
Identifier
AcquisitionDuplicate
Address
Verification
Identifier
Mapping
Layer 2
Layer 3
Mobile
NodeServer Network
Mobile
Node L3 POA Network
MNServer
L3
PoA
Configuration
Identifier
AcquisitionDuplicate
Address
Verification
Identifier
Mapping
Layer 2
Layer 3
Mobile
NodeServer Network
Mobile
Node L3 POA Network
MNServer
L3
PoA
Copyright 2015 © IEEE. All rights reserved. 65
Key principles for Layer 3 Configuration
Reduction of the number of signaling messages exchanged between the mobile node and the DHCP server during stateful IP address acquisition.
Minimizing the time taken to verify the uniqueness of the IP address of the mobile.
Performing the address uniqueness checking ahead of layer 3 handoff.
Prefetching and caching of the new IP address reduces the time taken for IP address acquisition after the handoff.
Performing the address resolution by mapping between the IP address of the target router and the MAC address before the mobile has moved to the new network.
Copyright 2015 © IEEE. All rights reserved. 69
How security related protocols affect performance
Security protocols have an impact on the performances of the network
– End-to-end latency
– Throughput
– Handoff delay
Main components that affect the performance
– Authentication/authorization, Key Derivation, Encryption
Security related delays may affect all the layers
Layer 2 (e.g., 802.11i, WEP)
Layer 3 (IPSEC/IKE)
Upper Layers (e.g., TLS, SRTP)
Security
Association
Key
Distribution Authentication Encryption
Layer 2
Layer 3
Layer 4
ServerMobile Network
MN
MN Server
L3
POA
Security
Association
Key
Distribution Authentication Encryption
Layer 2
Layer 3
Layer 4
ServerMobile Network
MN
MN Server
L3
POA
Copyright 2015 © IEEE. All rights reserved. 70
Key principles for Authentication optimization
Minimization of the time needed to authenticate and authorize the mobile after each handoff during the re-authentication procedure.
Reduction of the number of signaling messages that need to be exchanged between the mobile node and the authenticator to generate a shared secret key.
Use of an appropriate key generation algorithm that reduces the processing load on the end hosts.
Placement of the authenticator and authentication server closer to the mobile.
Reduction in installation time of the pre-shared keys (PSKs) on the authenticator in the case of proactive authentication.
Proactive caching of the security context at the neighboring access points prior to handoff, either by proactive authentication or by context transfer.
Copyright 2015 © IEEE. All rights reserved. 71
Optimizing authentication Related Work
IEEE Standards– IEEE 802.11i provides pre-authentication at link-layer in the
distribution system (DS)– IEEE 802.11r improves 11i by introducing a new key
hierarchy but it does not work between DSs either.
Context transfer solutions (Bargh et al, Georgiades et al, Duong et al)– Security problems such as “domino effect”– Assume certain trust relationships which might not be
possible in certain scenarios.– Oriented towards the same technology
Re-authentication
Pre-installation based on movement pattern (Mishra et al, Pack et al )– AAA assisted key installation– Works within the same administrative domain
MIPv6 and AAA assisted (Ruckforth et al)– Limited to MIPv6 and within the same domain
Cooperative Roaming (Forte et al)– Works within a domain
Copyright 2015 © IEEE. All rights reserved. 72
Authentication Optimization
Authentication mechanism requires 802.1x message exchange with the authenticator in the target network
Number of round trip signaling and key derivation process need to be minimized
Low latency re-authentication
Authentication can be done proactively
Context can be transferred
Layer 3 authentication bootstraps layer 2 authentication process
Copyright 2015 © IEEE. All rights reserved. 73
Network-Layer Assisted Pre-Authentication Technique
Assists link-layer optimization mechanism to work accross subnets and domains
It is independent of link-layer technology (e.g., 802.11, CDMA)
It does not suffer from context transfer security problems and only assumes basic trust relationship
It supports handover across inter-technology, inter-subnet and inter-domain.
Copyright 2015 © IEEE. All rights reserved. 74
Experimental Testbed
Home AAA
Domain
IEEE 802.11i
Pre-authentication
nAR/PAA
AAAv
AAAh
pAR165.254.55.116/24
165.254.55.115/24
155.54.204.82
10.1.30.1/24
10.1.30.3/2410.1.30.2/24
10.1.10.2/24
10.1.10.1/2410.1.20.2/2410.1.20.1/24
MN
PSK PSK
AP0AP1AP2
Radius/Diameter
PANA pre-auth
Association
&
4-way handshake
Network A Network B
PANA Pre-authentication
Roaming AAA
Domain*
* Roaming AAA Domain in roaming case.
For non-roaming case, it acts as MN’s home AAA
domain.
Non-Roaming: [email protected]
Roaming: [email protected]
Copyright 2015 © IEEE. All rights reserved. 77
Optimizing Binding Update
Techniques– Reduce the latency due to
longer binding update when the communicating host is far away
– Limit the binding update within a domain
Proposed Solutions– IDMP– Regional registration-
based Mobile IP– HMIPv6– Anchor-based Application
Layer B2BUA
– Proactive Binding Update
Binding
Update
Tunneling Mapping Caching
Mobile Network Anchor Mobile CN
Anchor
PointCN
Binding
Update
Tunneling Mapping Caching
Mobile Network AnchorMobile Network Anchor Mobile CN
Anchor
PointCN
Copyright 2015 © IEEE. All rights reserved. 78
Key principles for Layer 3 Binding UpdateLimiting the traversal of the binding update closer to the mobile after every handoff.
Use of two levels of binding update by using an anchor agent between the home agent and the mobile node.
Applying the binding update proactively in the previous network before the mobile has moved to the new network.
Simulcasting the data to help reduce the data loss due to a longer binding update delay. This can probably be achieved by using a localized multicast approach.
Copyright 2015 © IEEE. All rights reserved. 79
Media redirection and optimized binding update for SIP-based mobility
Capture the transient packets in-flight and redirects to the mobile–SIP Registrar and NAT-like functionality
RTPtrans (RTP translator an application layer Translator)
Mobility Proxy (Linux iptables)
–Outbound SIP proxy server
Local SIP proxy captures outbound packets
Limit the signaling due to Intra-domain Mobility–B2B SIP UA
Emulates Third Party Call control
–Multicast Agent
–Small group multicast
–Duration limited locally scoped Multicast
Copyright 2015 © IEEE. All rights reserved. 80
SIP-based Fast-Handoff
MN
Internet
Visited Domain
MN
MN
Public SIP Proxy
Public SIP Proxy
Public SIP Proxy
IP0
IP1
IP2
Visited
Proxy
Home SIP
Proxy
RTP
Media
(Existing SIP
Session)
OKACK
CNHome
Domain
Subnet
S0
Subnet
S1
Subnet
S2
RTP
Media after
Re-Invite
Register
1
2
3
4
5
Translator
Translator
Translator
Copyright 2015 © IEEE. All rights reserved. 81
Hierarchical Mobility Management IDMP+MIP
Home Network
1
2
1
3
2
MA
SA
MN
• All packets from the global Internet tunneled (re-directed) to the
GCoA and are intercepted by the MA.
• MA tunnels each packet to the MN’s current LCoA.
CN
SASA
HADomain
Copyright 2015 © IEEE. All rights reserved. 82
Experimental Results on Mobility Optimization(Systems Evaluation)
Copyright 2015 © IEEE. All rights reserved. 83
Experimental Validation of Mobility OptimizationCase Studies
Following are the experimental case studies where we have beenable to optimize the handoff delay and reduce the packet loss bydeploying several Optimization Techniques
Case I - Optimizing data path between CH and MH Case II - Optimizing Binding Update Case III - Optimizing Layer 3Case IV - Optimizing Security AssociationCase V - Make-before-Break Technique Case VI - Maintaining Security Association Case VII - Media Independent Pre-authentication proactive handover and bufferingCase VIII – Optimized IMS HandoffCase IX - Multicast Mobility
Copyright 2015 © IEEE. All rights reserved. 84
Media-independent Pre-Authentication
MPA is:
–a mobile-assisted higher-layer authentication, authorization and handover scheme that is performed a-priori to establishing L2 connectivity to a network where mobile may move in near future
MPA provides a secure and seamless mobility optimization that works for
–Inter-subnet handoff
–Inter-domain handoff
–Inter-technology handoff
Use of multiple interfaces
MPA works with any mobility management protocol
Copyright 2015 © IEEE. All rights reserved. 85
Functional Components of Proactive Handoff
1) Pre-authentication/authorization
– Used for establishing a security association (SA) between the mobile and a network to which the mobile may move
2) Pre-configuration
– Used for obtaining parameters (e.g., an IP address) from the network to which the mobile may move
– The SA created in (1) are used to perform secured configuration procedure
3) Secured Proactive Handover (PH)
– Used for sending/receiving IP packets from the current network using the pre-configured parameters of the new network
Copyright 2015 © IEEE. All rights reserved. 86
Media-independent Pre-Authentication (MPA)
MPA is a mobile-assisted higher-layer authentication, authorization and handover scheme that is performed a-priori to establishing L2 connectivity to a network where mobile may move in near future
MPA provides a secure and seamless mobility optimization that works for Inter-subnet handoff, Inter-domain handoff and Inter-technology handoff
MPA works with any mobility management protocol
TimeConventional
Method
AP DiscoveryAP
Switching
MPA
Pre-authentication
IP address
configuration
& IP handover
Time
Client
Authentic
ation
Packet Loss Period
Copyright 2015 © IEEE. All rights reserved. 87
Media Independent Pre-authentication -
Seamless Handoff (a deployment scenario)
AA CA
MN-CA keyAR
Network 3
AR
AA CA
MN-CA key
Network 2
INTERNET
Information
Server
Mobile
Current
Network 1AR
AP1 Coverage Area AP 2 & 3 Coverage Area
AR
Network 4
CN
AP3AP2AP1 CTN
TN
CTN – Candidate Target Networks
TN – Target Network
Copyright 2015 © IEEE. All rights reserved. 88
Home
Network HA
MPA Overview
CN: Correspondent Node
MN: Mobile Node
AA: Authentication Agent
CA: Configuration Agent
AR: Access Router
AA CA
A(X)
2. DATA [CN<->A(Y)]
over proactive handover
tunnel [AR<->A(X)]
AR
L2 handoff
procedure
Domain X Domain Y
CN
Data in new
domain
1. DATA[CN<->A(X)]
MN-CA key
Pre
configuration
pre-authentication
MN-AR key
3. DATA[CN<->A(Y)]
Data in old
domain
MN
A(Y)
BU
Proactive handover
tunneling end
procedure
Tunneled Data
MN
Copyright 2015 © IEEE. All rights reserved. 89
Proactive Handoff Experimental Results (Case III)
Mobility Type MIPv6
Handoff
Parameters
Buffering
Disabled
+ RO
Disabled
Buffering
Enabled
+ RO
Disabled
Buffering
Disabled
+ RO
Enabled
Buffering
Enabled
+ RO
Enabled
Buffering
Disabled
Buffering
Enabled
L2 handoff
(ms)
4.00 4.33 4.00 4.00 4.00 5.00
Avg. packet
loss
1.33 0 0.66 0 1.50 0
Avg. inter-
packet interval
(ms)
16.00 16.00 16.00 16.00 16.00 16.00
Avg. inter-
packet arrival
time during
handover (ms)
n/a 45.33 n/a 66.60 n/a 29.00
Avg. packet
jitter (ms)
n/a 29.33 n/a 50.60 n/a 13.00
Buffering
period (ms)
n/a 50.00 n/a 50.00 n/a 20.00
Avg. Buffered
Packets
n/a 2.00 n/a 3.00 n/a 3.00
SIP Mobility
Copyright 2015 © IEEE. All rights reserved. 90
Performance (MPA-Non-MPA) – Single I/F
MPA– No packet loss during pre-
authentication, pre-configuration and pro-active handoff before L2 handoff
– Only 0 packet loss, 4 ms delay during handoff mostly transient data Includes delay due to layer 2,
update to delete the tunnel on the router
We also reduced the layer 2 delay in hostap
Driver L2 delay depends upon driver
and chipset
non-MPA– About 200 packets loss, ~ 4 s
during handover Includes standard delay due to
layer 2, IP address acquisition, Re-Invite, Authentication/Authorization
– Could be more if we have firewalls also set up
MPA Approach
Non-MPA Approach
handoff
802.11 802.11
4 s
Copyright 2015 © IEEE. All rights reserved. 91
Handoff Delay
~ 18 s
802.11 CDMA
Handoff Delay
16 s
802.11 CDMA
a. MIP-based Non-optimized handoff
b. SIP-based Non-optimized handoff
c. MPA and 802.21 assisted optimized
handoff
802.11 CDMA
Optimized handoff delay with MPA (Multiple I/F)
Copyright 2015 © IEEE. All rights reserved. 92
Optimization in IMS Testbed
P-CSCFP-CSCF S-CSCF
AS
HSS
I-CSCF
PDSN HA
VN1-re2VN2-re3
802.11b 802.11b
Visited Network 1
Visited Network 2
DHCPDHCP
RAN Emulator
Mobile Node
K6Router
192.168.6.0/24192.168.8.0/24
6.2
6.1
8.2HN-HA
HN-AS-SCSCFHN-HSS-ICSCF
VN1-PCSCF
VN1-DHCP
VN2-PCSCF
VN2-DHCP
VN2-PDSN
VN1-PDSN
VN1-RE-12
PDSN
RAN Emulator
VN2-RE-21
8.1
Mobile Node
Domain: kddi.testbed
VN1-re1
802.11b
Home Network
IPTV Server
HN-IPTVServer
RAN Emulator
VN1-RE-11
6.3
PDIF
VN2-PDIF
VN2-re4
802.11b
::5::10::15::25::5::10::15
3ffe:2::/64
3ffe:1::/643ffe:5::/64
::1
::1
::1
::10::5
3ffe:5::30
(Mobile IP case) mh2
3ffe:5::35
(Mobile IP case)
::20::15::25
PDIF
VN1-PDIF
VN1-re5
802.11b
<PPP address on PDSN>
mh1 3ffe:11::MAC/64
mh2 3ffe:11::MAC/64
<PPP address on PDSN>
mh1 3ffe:22::MAC/64
<Address on PDIF>
mh1 3ffe:33::MAC/64
<Address on PDIF>
mh1 3ffe:44::MAC/64
PCRF
VN2-PCRF
::30
VN1-PCRF
::30
PCRF
To visited domain
mh3
3ffe:5::40
(Mobile IP case)
Mobile NodeMobile Node3ffe:5::30
(Mobile IP case)
Current demonstration
• P-CSCF fast handover– Non-Optimized
– Reactive
– Proactive
• Optimized Roaming– Dual anchoring
– Home address anonymity
Copyright 2015 © IEEE. All rights reserved. 93
0
1458
1502
0
1501
1408
0
2399
5980
89
200
195
0 3000 6000 9000 12000
Proactive
Reactive
Non-Optimized
Time in ms
Typ
es o
f H
an
do
ff
Link (PPP) Termination
Layer 2 (802.11) Delay
Link (PPP) Activation
MIP-Solicitation
MIP-Binding Update
DHCP Trigger
DHCP Inform
SIP Registration
SIP(AKA) Security
Media Redirection
Handoff components optimized
Copyright 2015 © IEEE. All rights reserved. 97
Scheduling of handoff operations
97
Association
Network
discovery
P11
t11
PA2
4-way
Handshake
(SA)
t1
t4 t5
P2 P3
Connected
Dis
connected
Pre-
authentication
Current Network Target Network
PA1
PC
PB1
PD
t12
t13
AP
Key
installation
P12
P1
Resources CPUPC
Resource s BatteryPB
4-way handshakecompletet3
t4 t5
P2
P3
t2
Scanning
Authentication
NetworkDiscovered
4-wayHandshakeOperation
P1
ResourcesNetwork capacity
MobileAuthenticated
Connected
Association
P0
P01
P02
2 2
t1
PA
PC CPU
BatteryPB
t3
t4
t5
P2
t2
Scanning
Authentication
NetworkDiscovered
4-wayHandshake
P1
ResourcesNetwork Capacity
MobileAuthenticated
Connected
P0
P01
P02
2
t1
P03
P3Association
4
PA
C. Proactive operations
B. Parallel operations – Level of concurrency =2
D. Parallel operations – Level of concurrency = 3
A. Sequential operations
Battery
power
scanning Authentication 4-way
Handshake
t2 t3 t4 t5
P2 P3 P4
Association
Connected
Mobile
Disconnected
Network
capacity
CPU
cycles
P1
PA
PB
PC
P0
t1Disconnection
Network
Discovered
Mobile
authenticated
1 token
Copyright 2015 © IEEE. All rights reserved. 98
Deadlock analysis for simultaneous mobility using MATLAB models
98
Deadlock Scenario (non-optimized) Deadlock verification (deadlock exists)
Deadlock avoidance with retransmission Deadlock verification (No deadlock)
Copyright 2015 © IEEE. All rights reserved. 99
Summary of Experimental results for optimization techniquesHandoff components Optimization techniques
Discovery Application layer proactive discovery
Authentication Network layer assisted layer 2 pre-authentication
Layer 3 security association Anchor assisted security association
Proactive security context transfer
Layer 3 configuration Router assisted duplicate address detection
Proactive IP address configuration
Route optimization Maintain direct path
Interceptor assisted packet modifier
Intercepting proxy assisted route optimization
Binding cache-based route optimization
Binding update Hierarchical binding update
Proactive binding update
Proactive proxy-based join for multicast traffic
Simultaneous mobility
Media rerouting Data redirection using forwarding agent
Mobility proxy assisted time-bound data redirection
Time bound localized multicasting
Media buffering Dynamic buffer control protocol
Cross layer triggers Media independent handover primitives
Copyright 2015 © IEEE. All rights reserved. 100
100
Scheduling
types
Relevant
optimization
principles
Example experimental mobility systems Potential
Target
Mobility
System
SIP-based
Fast
handoff
Mobile
VPN
Media
Independent
Pre-authentication
Simultaneous
Mobility
Optimized
handoff
In IMS
Muti-layer
Mobility
Multicast
fast
handoff
Sequential Direct path between
CH and MHX
Limit binding update
between CH and MHX X
Maintain Security
association
between end-points
X √
Anchor-based
ForwardingX X √
Post-handoff triggers X
Predictive Pre-handoff triggers X X
Proactive network
discoveryX
Proactive
authentication X
Proactive identifier
configurationX √
Proactive
binding updateX X
Dynamic Buffering X
Proactive context
transferX
Parallel Discovery of Layer 2
and
Layer 3 PoA
X √
Binding update
during configurationX
Target mobility system design
Copyright 2015 © IEEE. All rights reserved. 101
Key Takeaway• Identification of fundamental properties that are rebound during a
mobility event. Analysis of these properties provides a systematic framework for describing mobility management and the operations that are intrinsic to handover.
• A model of the handover process that allows one to predict performance both for an unoptimized handover and for specific optimization methodologies under conditions of resource constraints. This model also allows one to study behavioral properties of the handoff system such as data dependency and deadlocks.
• A series of optimization methodologies, experimental evaluations of them, and optimization techniques that can be applied to the link, network, and application layers and preserve the user experience by optimizing a handover.
• Application of the model to represent optimizations, and comparison of the results with experimental data.
Copyright 2015 © IEEE. All rights reserved. 102
Since the current mobility protocols and associated optimization techniques are ad hoc in nature, it is useful to have a systematic analysis of the mobility event when designing appropriate optimization techniques.
Since mobility involves various layers of the protocol stack, it is important to discover the type of mobility that a mobile will be subject to, such as layer 2, layer 3, or application layer mobility.
– The type of mobility is determined by the mobile node’s mobility pattern, such as cell handoff, subnet handoff, or domain handoff, the type of application supported on the mobile node, and the type of access network.
Since layer 2 handoff optimization techniques are access-dependent, it is important to consider the access characteristics of each network, such as the channel access algorithm (e.g., CSMA/CA, OFDM, or TDMA). For example, a CDMA network will have different access characteristics from an 802.11 network. The amount of resources used (e.g., channel bandwidth) will vary with the type of access network.
Mobility Optimizaion Best Current Practice
Copyright 2015 © IEEE. All rights reserved. 103
Each mobility event (e.g., handoff) can be considered to consist of a set of primitive functions, such as discovery, configuration, authentication, security association, registration, binding update, and media delivery. Optimizations of these primitive functions can take place independently of each other but often benefit from cross-layer triggers.
A mobility event can be considered as a discrete-event dynamic system, where each of the abstract functions can be considered as a specific discrete event. Optimizing each of the discrete events can contribute to the overall optimization of the system.
The scheduling of the primitive functions that are part of these handoff events plays an important role in the overall systems behavior, including systems performance and resource usage.
The scheduling of the handoff primitives needs to take account of the data dependency among the abstract operations. The data dependency will determine the extent of parallelism that is possible during the handoff operations.
Best Current Practice – contd.
Copyright 2015 © IEEE. All rights reserved. 104
Deadlocks need to be avoided during any mobility operation. Deadlocks are typically caused by a lack of data from previous primitive operations or a lack of resources needed for an operation.
Thus, the scheduling of the primitive events should ensure that there are enough resources available for parallel or speculative operations of any kind and that data is available.
It is important to consider the type of transport (e.g., RTP or TCP) supported by an application running on the mobile when it is subjected to handoff, as each of these applications has different performance requirements in terms of packet loss, delay, and jitter.
Since there are several mobility protocols available and each of these protocols is suitable for a specific type of application (e.g, RTP- or TCP-based transport) and a specific type of handoff (e.g., layer 2, layer 3, or interdomain handoff), a policy-based mobility management scheme can be appropriate in many cases.
Best Current Practice – contd.
Copyright 2015 © IEEE. All rights reserved. 105
Since the primitive handoff operations in each layer take place independently of the operations in other layers, cross-layer triggers from lower layers can help to expedite the handoff operations in the upper layers. Thus, any optimization framework needs to apply some of the available cross-layer optimization techniques. IEEE 802.21 has defined a Media Independent Handover Function that provides cross-layer triggers to expedite a handover.
It is always useful to have a handoff model that can predict the systems performance based on the schedule and the available systems resources. When the systems parameters and resource availability are varied, the performance of the system will also vary. Service providers can use such a handoff model to determine what types of protocol and optimization techniques are needed in a specific scenario.
The scheduling of handoff primitives is largely determined by the systems resources and the data dependency among the events. Since the scheduling of handoff primitives affects the systems performance, it can be changed to meet performance requirements at the cost of added systems resources.
Best Current Practice – contd.
Copyright 2015 © IEEE. All rights reserved. 106
The scheduling of handoff operations can also affect the trade-off between the resources expended (e.g., battery, CPU, and bandwidth) and systems performance (e.g., delay and packet loss). Thus, the types of optimization that should be used are largely determined by the extent of the trade-off that can be allowed against resources.
In the case of multi-interface mobility, a make-before-break mechanism helps to reduce the delay and packet loss at the cost of additional resources,1 since both of the interfaces remain active during handoff. The extent of overlap of the operations is determined by the amount of resources that can be expended during handoff.
Proactive operations appear to be more attractive for providing the desired handoff performance (e.g., delay and packet loss) compared with sequential and parallel operations. However, there is a trade-off between the amount of resources and the performance when there are multiple target networks, since the mobile needs to complete proactive handoff-related operations with multiple target networks to increase the probability of a successful handover.
Best Current Practice – contd.
Copyright 2015 © IEEE. All rights reserved. 107
The mobility model could be enhanced to study the behavioral properties and systems performance of any type of mobility protocol, such as transport layer protocols and mobility in other types of networks such as ad hoc networks.
The model could be enhanced so that one could use it in an automated fashion to generate a specific schedule for the handoff operations given a set of resource constraints and performance objectives, and a dependency graph. Automatic generation of schedules for handoff operations to provide the desired quality of service with the available resources will help one to use the right set of protocols.
Using a systematic analysis of the mobility functions, one can design a customized mobility protocol suitable for one’s own set of requirements.
This model could be enhanced to predict performance based on the resource parameters of all of the network elements that are involved in the mobility event.
The formalization of key techniques, the models of systems dependencies, and the ability to calculate or predict optimization metrics provide a foundation for the automated discovery and implementation of mobility optimization.
Future work for Research
Copyright 2015 © IEEE. All rights reserved. 108
"Mobility Protocols and Handover Optimization: Design, Evaluation and Application" written by Ashutosh Dutta and Henning Schulzrinne and published by Wiley-IEEE Press in 2014. (ISBN 978-0-470-74058-3, Hardcover, 476 pages.)
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