Sierra Wireless DART 200 CDPD Modem manual Broadcast and Multicast, Operation, Overview

4	Broadcast and Multicast
	Operation

Overview

Broadcast and multicast are Cellular Digital Packet Data (CDPD) functions that support sending the same data to a large group of IP Addresses with a single transmission to the CDPD network. This capability is implemented through Mobile Data Intermediate System (MDIS) software.

The facility was originally defined for Fixed End System (F-ES) (host) to Mobile End System (M-ES) (terminal) transmissions. However, some MDIS manufacturers have implemented multicast to also support M-ES to M-ES transmissions. Protocol restrictions prevent broadcast or multicast messages from being encrypted. Check with your carrier to determine if these capabilities are offered before planning to use it as part of your application.

Broadcast and multicast transmissions are point-to-multi-point and provide a one-way connectionless service. The protocol used is User Datagram Protocol (UDP) or another unacknowledged protocol that operates over IP, for example, ICMP PING. The operational considerations are:

1.Broadcast or multicast data packets will not be received by a DART 200 with an active telnet or Transmission Control Protocol (TCP) PAD session.

2.If a User Datagram Protocol (UDP) PAD session is active the broadcast and multicast messages will be interspersed with the application data packets and must be separated by the application.

3.In the case of Serial Line Internet Protocol (SLIP), the disposition of the broadcast and multicast messages is a function of the support provided by the software stack and end-user applications (one must be UDP) operating on the Mobile Application Subsystem (MAS). If a UDP session is not active, the messages will be lost.

PN1197-00 Revision 1.0