Destination networks

Automatic connection selection

For automatic connection selection to work, your application must define a destination network, also known as a Service Network Access Point (SNAP) in Symbian terminology, in connection setup. These concepts are included from S60 3rd Edition, Feature Pack 2 onwards.

A destination network represents a network which provides a set of services. It provides applications and users a higher level abstraction of the connection than an Internet Access Point (IAP) and it decouples the connection from the radio bearer. Typically a destination network contains a number of IAPs and any one of them can be used to access the service.

From S60 3rd Edition, Feature Pack 2 onwards, it is recommended that destination networks be used instead of IAPs in connection set-up.

The following figure and the accompanying table illustrate the relationship between destination networks and IAPs.

Figure: Relationship between destination networks and IAPs

For more information about using destination networks, see Establishing a connection with destination networks.

Application-level roaming (ALR)

ALR allows applications to switch an active data connection from one IAP to another so that the application can control whether or not to roam and when the roaming happens. It works as follows:

1. The middleware keeps track of available IAPs and informs the application if a better IAP than the one the application is currently using becomes available.

2. The application can either switch to the new connection or ignore the event, in which case it keeps using the current connection.

3. If the new connection does not work for a particular application (because of local firewall configuration, for example), the application has a possibility to reject the connection later.

In order to receive mobility API-related notifications from the middleware, the client application must register for it. For application level roaming to happen, the application must use destination networks in the connection setup.

For more information about ALR, see Using application-level roaming.

Default connection

Default connection is a system-wide connection setting that is applied to data connections that start without connection preferences (destination network, IAP or a prompting flag). The goal of the default connection feature is to provide the benefit of automatic connection selection to applications that do not perform any connection management on their own and just open a connection by starting RConnection without parameters or by simply connecting to a socket. Any application that needs a connection to somewhere else than Internet should not rely on default connection, but instead define the connection preferences in the connection setup.

The possible values for default connection are:

• Destination network (for example, Internet)

• IAP

• Always ask (the user is shown a connection selection dialog in all connection setups that occur without connection preferences)

• Ask once (the user is shown a connection selection dialog in the first connection setup, and all successive connection setups automatically use that connection)