Arrangement for improving availability of services in a communication system

DETAILED DESCRIPTION OF EMBODIMENTS Definition of User Mobility Let us now consider an example consisting of a telecom system.
sub.
N domain, a Terminal.
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m domain and a User.
sub.
a domain.
The User.
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a domain consists of the User.
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a object and an arbitrary computational object called CO1.
Note that the object CO1 may or may not reside physically in the terminal.
sub.
m.
In the case where the user is also a terminal or hardware device, CO1 may reside on the user itself and not on the Terminal.
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m domain.
To offer user mobility means to allow the whole user domain including COi, to move and change terminal and still be able to interact with an object CO2 residing in the telecom system.
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N domain.
By interactions it is meant both operations and stream flows.
This is depicted in FIG.
1.
Use of Agents Let us now introduce the agents necessary to enable interactions between domains.
To represent the User.
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a an agent called PD_UA.
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a (ProviderDomain_User_Agent.
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a) is introduced in the telecom system.
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N domain.
This agent assumes security functions such as identification, authentication, encryption, etc.
and is also responsible for the functions supporting the mobility of the user.
Another agent called TDm_UA.
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a (TerminalDomain_User_Agent.
sub.
a) is introduced in the Terminal.
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m domain to represent the User.
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a and to assume the security functions of the Terminal.
sub.
m.
If the User.
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a is also using another terminal, namely Terminal.
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n then a TDn_UA.
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a is also defined for him on the Terminal.
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n domain.
We assume further that every terminal must have an owner and it is reasonable to define this owner as the default user of the terminal.
A legal and operative terminal will always have a default user.
This default user is permanently registered at the terminal.
Definition of a default user for a terminal allows us to implement access control procedures which may restrict the usage of the terminal.
Of course, the default user can also be registered at another terminal but the former registration is always valid and we have a multiple terminal registration case