What +is Bearer Mobility

Bearer Mobility is a feature that allows a device to change bearers without +interruption to the user's data sessions. An example of a bearer change is +if a device moves into the range of a Wi-Fi hot spot and the device moves +the GPRS connections over to Wi-Fi. Example data sessions include: streaming +videos; surfing the internet; and downloading emails. Example bearers include: +Wireless LAN (eg Wi-Fi); 3G (including HSUPA and HSDPA); Circuit Switched +Data (CSD); and GPRS.

Bearer Mobility operates in response to changes in the environment of the +device. A bearer is known as available when the device is in range +of the bearer and the device can potentially use the bearer.

NOTE: The bearer can be available but unusable because of the security +requirements of the bearer.

Symbian platform uses non-seamless Bearer Mobility. Non-seamless +indicates that clients of the Socket Server must reconnect all sockets after +the bearer has changed. The local IP address of the link changes if the bearer +changes.

Bearer Mobility APIs

Two Socket Server Bearer Mobility +APIs are available: RCommsMobilityApiExt and CActiveCommsMobilityApiExt. +A client of the Socket Server cannot change bearer if the client does not +use at least one Bearer Mobility API. A device can have clients that support +Bearer Mobility and clients that do not support Bearer Mobility. If clients +that support Bearer Mobility change bearer, the device does not disconnect +a client that does not support Bearer Mobility unless that client's bearer +is no longer available.

A client of the socket server can ask the +user to accept or deny the change of bearer. For example, the client can display +a dialog box to ask the user to accept or deny the change. The decision to +ask the user remains with the client.

A client of the socket server +can ask to use the default bearer. The default bearer is the highest priority +bearer that is available. The device manufacturer or network operator creates +the list of bearer priorities.

Bearer Mobility +Blacklists

The Bearer Mobility components in the Communications +Architecture implement a blacklist feature. The Socket Server implements +the blacklist feature on the server side. The blacklist feature affects the +notifications that a Socket Server client receives. The blacklist feature +stops notifications for bearer changes that have previously been rejected. +The device keeps a blacklist for each client.

For example:

A client receives a +notification for a bearer change
The client sends a response +to reject the bearer change
The device adds the +rejected bearer to the blacklist for that client
The device does not +notify the client of any further opportunities to change to that bearer

There can be variations in the operation of the blacklist. For example, +there can be a limit on the lifetime of the blacklist.

NOTE: The +blacklist scheme is dependent on the plug-ins and settings used for the Communications +Architecture for the particular device.