Network Reference - SBD
Short Burst Data or SBD is a simple and efficient bi-directional transport capability used to transfer messages with sizes ranging from zero (a mailbox check) to 1960 bytes for Mobile Originated (MO-SBD) and zero to 1890 bytes for Mobile Terminated (MT-SBD). SBD takes advantage of signals within the existing air interface, without using the dedicated traffic channels. As a result, small amounts of data can be transferred more efficiently than those associated with circuit-switched data calls.
For MO-SBD, messages are transmitted across the Iridium satellite network utilizing inter-satellite links to reach the gateway. From there messages are disseminated to end-users via e-mail (SMTP). For MT-SBD, messages are sent to the Iridium gateway via e-mail from an end-user host computer. From there messages are delivered to an ISU immediately following a MO-SBD or "mailbox check" by an ISU. Global network transmit latency for delivery of messages ranges from ~5 seconds for short messages to ~20 seconds for maximum length messages. This latency is the elapsed time before the Iridium SBD system sends the SBD message to its e-mail destination. Additional latency introduced by the Internet/NIPRNet or the customer's host system is not in Iridium's control. There are addition delivery MO-SBD and MT-SBD methods via the DoD gateway.