In addition to the MultiNet Driver, the other major software component is the MultiNet Service. This service is implemented at the user level and implements the buffering and switching logic. It interacts with other MultiNet nodes, and passes signaling messages to the MultiNet Driver to either start or stop a switching and buffering action. The MultiNet Service is responsible for signaling the switching time to the MPD. This signal indicates the time to switch the card, and activate another network. We have implemented the strategies described in Section 5.3 to determine the Activity Period of a network.
The MultiNet Service on the switching node broadcasts a message just before the MPD switches the card to another network. This message is received by the MultiNet Service running on other MultiNet nodes, and indicates the state of the sending card. The MultiNet Service on the receiving nodes indicates this state to its MultiNet Driver, which then starts to buffer packets.
The MultiNet Service uses I/O Control Codes (ioctls) to interact with the MultiNet Driver. Query and set ioctls are implemented for exposing the features and managing the behavior of the driver. We note that although the switching signal logic can be implemented in the MPD using the NDIS timer, for ease of programming we implement it at the user-level.