Sierra Wireless DART 200 CDPD Modem manual Broadcast, Multicast

DART 200 CDPD Modem User’s Guide 4 Broadcast and Multicast Operation

Broadcast

The Broadcast function is used on a geographic coverage basis. To support this function the MDIS is set up with a Broadcast Network Entity Identifier (NEI) that includes a list of the Mobile Data Base Stations (MDBSs) in the desired broadcast area in its definition. There can be multiple broadcast areas within the coverage area of a single MDIS. The message is sent (by the F-ES or an M-ES) to a Broadcast NEI at the MDIS that replicates the message, puts a special broadcast header on it, and sends it to the cells indicated by the broadcast list.

Any Data Access Radio Transmitter (DART) wishing to receive broadcast messages indicates its readiness by having specified the *B1 profile parameter and by being ready to receive UDP datagrams. The latter can be accomplished by having the UDP Server function active or, if in SLIP mode, by having a Winsock UDP application active, and by being ready to process any incoming broadcast datagrams.

For most applications broadcast is not appropriate, because broadcast messages are sent to all the CDPD modems in the covered geography. It is more useful to be able to specify that messages only go to all, or a subset of the IP Addresses associated with a specific customer; a capability offered by multicast.

Multicast

Multicast is set up similarly to broadcast, except that the MDIS is set up with a Multicast NEI and a list of the M-ESs that belong to that specific group rather than a list of cells, as is done by the broadcast function. The message to be multicast is sent (by the F-ES or an M-ES) to the Multicast NEI at the MDIS, that replicates the message and sends individual messages to the M-ESs indicated in its multicast group list.

An M-ES can be a member of any number of multicast groups, however it can only be active in one at any given time. An M-ES wishing to receive multicast messages indicates its readiness by registering a Multicast NEI and by being ready to receive UDP datagrams. The latter can be accomplished by having the UDP Server function active, or if in SLIP mode, by having a UDP application ready. In all of the preceding cases the MAS is assumed to be ready to process any incoming multicast datagrams.

Contact your service provider for information on the availability and use of multicast service in your area.

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