Sierra Wireless DART 200 CDPD Modem - Manual (Page 51)

PN1197-00 Revision 1.0
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.