User's Guide

User’s Guide CDPD Operation
2110059 Rev 1.0 Proprietary and Confidential Page 45
5.7.2.5. Escaping Data State
Escaping a UDP server session is handled exactly the same way as a client session. See
Section 5.7.2.2 above for details.
5.7.2.6. Closing a UDP Server Session
Closing a server session is handled exactly the same way as a client session. See Section 5.7.2.3
above for details.
Provided the modem is set to auto-register and H1 is not used to close the session, the modem is
ready for the next UDP server session without further configuration. Auto-answer will remain
enabled and the modem registered on the network.
To disable auto-answer, you must set register S0=0. This will prevent the modem from starting
any further server sessions.
5.7.2.7. UDP Broadcast and Multicast
These services are not yet supported by the SB300 Series modems but are planned for future
firmware upgrades.
Broadcast and multicast are 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. 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 UDP
connectionless service. The operational considerations are:
• Protocol restrictions prevent broadcast or multicast messages from being encrypted.
• Broadcast or multicast data packets will not be received by a SB300 Series modem with an
active TCP PAD session.
• If a 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.
• In the case of 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.
Broadcast
The Broadcast function is used on a geographic coverage basis. To support this function the
MDIS is set up with a Broadcast 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. A message is transmitted 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.
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 terminals that belong to that specific group rather than a list of cells, as used by the
broadcast function. The message to be multicast is sent to the Multicast NEI at the MDIS, which
replicates the message and sends individual messages to the terminals indicated in its multicast
group list.
A terminal can be a member of any number of multicast groups, however it can only be active in
one at any given time. A terminal wishing to receive multicast messages indicates its readiness by