Fig. 31 illustrates the SI Distributed Architecture.
Fig. 31. SI Distributed Architecture.
By a local area network, we will mean any integration of computers and communication devices using the same transport protocol and technological (network-specific) addressing system that may differ from those applied to an outer network. SI proxy (border) server acts as a border and bridge between a local and outer network. National and regional servers are elements of an outer network like the Internet.
Every SI server provides all the functionality specified for an SI server regardless of its topological level and location.
Additionally, every server in the SI Distributed Architecture has its own address that is also the name of a public contact group joining users living in the same area. For the user convenience, such a server name must be the same as usual name of a country, a city or region, a local area or network segment for a national, regional and proxy servers respectively.
The functionality of any SI proxy server includes:
- In case the user, service or resource indicates his, her or its readiness, SI proxy server not only records the SI address indicated in association with corresponding technological address but also propagates this information to an upper regional (national) SI server with messages about public name and technological address of the proxy server.
- In case of a call request with indication of outer server name received, SI proxy server does not search the called address in its internal database but delivers the request to the indicated SI server or to an upper SI server. (For example, in case a proxy server does not know a call transmission path for a public contact group specified).
- SI proxy server delivers quality-of-service parameters requested by the user to an upper server.
- SI proxy server switches data transmission for a communication session.
The functionality of any SI regional server includes:
- In case the user (service or resource) indicates his, her or its readiness directly or via a proxy server, SI regional server records the SI address indicated with a corresponding technological address of the user or the proxy server.
- In case of a call request with indication of outer name received, SI regional server does not search the called address in its internal database but delivers the request to the indicated SI server or to another SI server or rejects a request. (For example, in case a regional server does not know a call transmission path for a public contact group specified).
- In case an SI address of the called user (service, resource) found in internal database, SI regional server generates a message about communication session start and sends it to technological addresses of servers and terminals contributing in communication session with messages about corresponding servers and terminals technological addresses.
- SI regional server delivers to corresponding SI servers and directly provides quality-of-service parameters requested by the user.
- If needed, SI regional server switches data transmission for a communication session initiated with help of this server.
Fig. 32 illustrates possible data transmission schemes for a communication session between the user and another user or an information resource in case of the distributed SI architecture.
Fig. 32. Possible data transmission schemes for the distributed SI architecture. Double lines indicate traffic paths for a data transmission during communication sessions.
The actual choice of a data transmission scheme depends on the user’s option, the transport provider’s option, the requested quality of service, the business model of collaboration between various SI service providers, etc. It is also possible to use two or more data transmission schemes simultaneously for the same communication session to provide a higher level of transport reliability and quality, for example. |
