Introduction to MobilityDo van Thanh

Forelesning på NTNU19. September 2001

2

What is mobility?

Immobile

Moving, in motion

Migrating, changing location

Changingroles

Mobile

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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.

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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)

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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

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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

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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)

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Mobility Functions

4. Registration/Deregistration

• User registration– Default registration– Local registration– Remote registration– Registration through profiles

• User Deregistration– Local deregistration– Remote deregistration– Forced deregistration

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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_

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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

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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?"

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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

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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

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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

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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

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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

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Conclusion

Registration/Deregistration

AuthenticationAccess Control

Identification

User Profile Mgmt

Delivery of services

Initiation of services

Mobility-basedapplication support

Discovery ofService/facility

Generic Mobility Layer