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Introduction to MobilityDo van Thanh
Forelesning på NTNU19. September 2001
2
What is mobility?
Immobile
Moving, in motion
Migrating, changing location
Changingroles
Mobile
3
What is mobility?
In the Merriam-Webster's Collegiate Dictionary:Main Entry: 1mo·bile
Pronunciation: 'mO-b&l, -"bIl also -"bElFunction: adjectiveEtymology: Middle English mobyll, from Middle French mobile, from Latin mobilis, from movEre to moveDate: 15th century1 : capable of moving or being moved : MOVABLE <a mobile missile launcher>2 a : changeable in appearance, mood, or purpose <mobile face> b : ADAPTABLE, VERSATILE3 : moving habitually or occasionally from one region or climate to another <the study of migratory birds> MIGRATORY4 a : characterized by the mixing of social groups b : having the opportunity for or undergoing a shift in status within the hierarchical social levels of a society <socially mobile workers>5 : marked by the use of vehicles for transportation <mobile warfare>6 : of or relating to a mobile- mo·bil·i·ty /mO-'bi-l&-tE/ noun
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Mobility Types
Terminal Mobility
Personal Mobility
Role Mobility
Session Mobility
Visiting Domain
Visiting Services•Communication
•Computing
Visiting Facilities•Printers
•Fax•Projector
Application/Service Portability/Mobility
Con
tinu
ous
Dis
cret
Por
tabi
lity
Component Mobility
HomeServices/Applications
Communication•Voice telephony
•Multimedia •conference
•Mail•Synchronous
•Asynchronous
Computing•Word Processor
•Spreadsheet•Information
•Database•Games
•E-commerce
Home Domain Data
Profile
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Mobility Types
• Terminal mobility allows the terminal to change location while maintaining all services.
• Component mobility allows components e.g. earphone, microphone, etc. of a terminal to change location while maintaining all services. The components form a PAN (Personal Area Network)
• Personal mobility allows the user to access all services independently of terminals and networks.
• Role mobility allows the user to change roles and get access to distinct preferences, rights and limitations.
6
Mobility Types
• Session mobility ensures that active sessions are not disrupted while users change terminals.
• Application/service portability or mobility allows software entities (codes, objects, processes) to be relocated from one machine to another or even moved between machines while processing.Ex: Applets (code) – Mobile Agents (object)
7
Mobility Types
• Continuous Mobility enables continuous availability of services while the user moves.– Ex: Cellular systems
• Discrete Mobility enables the availability of services within certain areas and for certain access points, e.g. Home an Office, but not while moving from one area to another– Ex: DECT, Wireless LAN
• Portability is an example of discrete terminal mobility, where it is allowed to move a terminal from one plug to another.
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What is mobility?
• Mobility is confined to any particular networks.– Mobile does not mean necessarily wireless since
wireline networks can also offer mobility– Wireless does not mean mobile since devices like
parkometer, soft drink automate may communicate wireless and remain immobile.
• Mobility is not a service because mobility as such has no value for a user if not supplemented with other services.Mobility enhances the availability of other services.
• Mobility is a capability that can be added to any network system
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How can mobility be introduced?
Communication System
Network Layer
Mobility Layer
Application/Service Layer Example: IP-based networks do not originally support mobility.By introducing Mobile IP than discrete terminal mobility is supported
10
The Mobility functions1. Identification• When moving the mobile
entity needs to change Network Access Point
• Every mobile entity (person, terminal) must have it’s own identity– For terminal mobility: Every
terminal must have an identity distinct from the Network Access point's one ( Network Address)
– For Personal mobility: Every person must have an identity distinct from the terminal' one
Access Points
Network
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The Mobility functions1. Identification
• Every entity has only one identity, but may have several identifiers
• An identifier is assigned uniquely to one mobile entity
• An identifier may be permanent or temporarily allocated according to time, location, context, etc.
• A human user may have several identifiers, one public such as email or personal such as login name
Example: In GSMEach terminal has a IMEI (International Mobile Equipment Identity)Each mobile subscriber has two identifiers:
IMSI (International Mobile Subscriber Identity)TMSI (Temporary Mobile Subscriber Identity)
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The Mobility Functions
2. Authentication• It is not sufficient that the mobile entity identifies
itself, but the system must be capable to verify that the mobile entity is the one it claimed to be
• A generic security function that is more necessary and more difficult to realize with mobility
Principal Entity Authentication
claim
verify
Claimant Verifier
claim
verify
Trusted Third Party Trusted Third Party
claim
verify
delegation
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The Mobility Functions2. Authentication
• Authentication methods relies on:– Something known, e.g password, pin code, etc.– Something possessed, e.g magnetic card, smart card,
etc.– Some immutable characteristics, e.g. biometric
identifiers– Accepting that a 3rd entity has established
authentication– Context e.g. Location of principal
• Authentication method must fit the principal's characteristics:– Passive characteristics, e.g. Fingerprint, retinal, etc.– Information storage capability– Information exchange and processing capability– Unique fixed location
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Mobility Functions
2. Authentication• Authentication of the human user must in addition fit the used
terminal when a user is allowed to use different terminals• Authentication of the communication system by the mobile entity
is also necessary – ( Not in GSM but in UMTS)
MS VLR HLR
IMSI or TMSI
IMSI, VLR
a set of (RAND;SRES;Kc)
RAND
SRES
stored Ki
Authentication in GSM
SRES = A3(Ki, RAND)Kc= A8(Ki, RAND)
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Mobility Functions
3. Access Control (or Authorisation)
• Even though a mobile entity is authenticated it is not necessarily authorised to access services.
• Access control' s goal is to counter the threat of unauthorized access.
• The access rights of the mobile entity is limited by:– Roaming restriction– Time restriction– Credit limit
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Mobility Functions3. Access ControlIn a system supporting both terminal and
personal mobility, a user is subject to three types of access control:– Access control for the use of the terminal (protection
of 3rd party)– Access control concerning the access to the
communication system– Access control concerning the use of the service
requested
User
Terminal telecom system Services
17
Mobility Functions
4. Registration/Deregistration
• When a terminal moves and uses different access points
• Or when a user is using different terminals
The system must know about it. A registration is necessary.
• Registration is the procedure that associates a mobile entity with a location directly or indirectly.
Access Points
Network
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Mobility Functions
4. Registration/Deregistration
User
Terminal
Network Access Point
User Profile
Terminal Capability
has
has
registered_at
registered_at
1+
Physical Characteristicshas
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Mobility Functions4. Registration/Deregistration• Initiated by communication system
– On-the-fly or Lazy– Predetermination:
• Periodic• Based on changes
• Initiated by mobile entity• Example of GSM: combination of both On-the-fly & Predetermination
Registration
GNAP
NAP NAPNAP
Registration
MTA
NAP NAPNAP
Òon the flyÓ method
a) b)
20
Mobility Functions
4. Registration/Deregistration
• User registration– Default registration– Local registration– Remote registration– Registration through profiles
• User Deregistration– Local deregistration– Remote deregistration– Forced deregistration
21
Mobility Functions5. User Profile Management
• Every user has specific preferences concerning services and their presentation, look and feel, etc.
• The setup data is saved in the user profile
• The profile can be extended to comprise a address book, a list of favorite links, etc.
User_Profile
Routing_Info Charging_Info Security_InfoService_Restriction
User_Application_Profile
Routing_Info Charging_Info Security_InfoAppl_
Spec_InfoRestrictionAppl_ Appl_ Appl_ Appl_
22
Mobility Functions5. User Profile Management
• Requirements on the user profile:– The user should be able to modify his profile from any
terminal anywhere and anytime– The applications must be configured according to the profile– Must be saved in a secured manner
• When the user is using different terminals and different access points, the usage of the profile must be in concordance with the terminal capabilities and the access point physical characteristics.
User
Terminal
Network Access Point
is represented by
is represented by
is represented by
User Profile
Terminal Capability
Physical Characteristics
has
has
has
23
Mobility Functions
5. User Profile Management
• With the demand for more customisation of applications combined with the plurality of terminals and devices, the User Profile will play a crucial role in the future
• However, not much has been done yet.
• The challenge is: "Who is doing the User Profile Management?"
24
Mobility Functions
6. Initiation of services/applications
• Distinction between service and application: An application when being executed will offer a service to a user through a session.• Ex: The application "MS Word" when running will offer a word
processing service to the user.
• The user must have the possibility to initiate or start the same services independently of the access point and the terminal.
• Application initiated by the user is called outgoing application (”pull”)
Two cases according to the location of the applications:
• Application located in the mobile terminal: no problem Ex: Laptop or PDA with all applications
25
Mobility Functions
6. Initiation of services/applications• Application located at the Home domain:Alt 1. Establish a connection with Home domain
– Use for confidential or large applications which are not convenient to move e.g. Information, database, etc.
– Long connection– Firewall problem since terminal has a
foreign address– Ex: Telnet - rlogin
Home Domain
Visiting DomainTerminal
Application
Client
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Mobility Functions
6. Initiation of services/applications• Application located at the Home domain:Alt 2. Static Replication of application logic
– The same application logic is replicated at all domains
– The user just use the replicate atvisiting domain
– Ex: GSM – the basic call logic is replicated and installed at all domains
Home Domain
Visiting DomainTerminal
ApplicationClient
Application
27
Mobility Functions
6. Initiation of services/applications• Application located at the Home domain:Alt 3. Dynamic replication of application logic
– The replication is done only on requestfrom the user
– The mobile agent may be used to copy, pack and bring an application to the visiting domain
– The Mobile agent technology is not yet mature and suffers from insufficient security and standardisation
Home Domain
Visiting DomainTerminal
ApplicationClient
Application
Move
28
Mobility Functions7. Delivery of services• The services are initiated by someone else e.g. Another
user, the system, etc.• Also called incoming services (”Push”).• The system must
– find the terminalthat the user is using
– establish connectionto the respective visiting domain
– Deliver output to the terminal according tothe terminal capabilities
• Ex: Mobile IP
Home Domain
Visiting DomainTerminal
Application
Client
Application X
Terminal Y
Client
initiates
29
Mobility Functions8. Service/facility discovery and usage.
• When visiting a domain the user may want to use facilities like printers, faxes, projectors, etc. or services like local informations, weather,etc.
• Nowadays it is not simple since complex tasks must be done, e.g. Discover the Services/Facilitiesavailable, install drivers, etc.
• One solution could be using mobile agent technology
Home Domain
Visiting DomainTerminal
ApplicationClient
Application
agent
agent
move
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Mobility Functions9. Support of mobility-based applications• Mobility-based applications are born with mobility.
They are meaningless without mobility.• Examples are taxi dispatch, fleet management,
public safety, etc.• Such application needs location information that
the mobility layer has.• Provides a mobility interface to mobility-based
applications– Ex: GetAddress (in TerminalID, out Address, Out Status)GetTerminal (in UserID, out TerminalID, Out Status)
• For UMTS, OSA (Open Service Architecture) /Parlay has specified such a mobility interface
31
Conclusion
Registration/Deregistration
AuthenticationAccess Control
Identification
User Profile Mgmt
Delivery of services
Initiation of services
Mobility-basedapplication support
Discovery ofService/facility
Generic Mobility Layer