treme, a corporate mainframe can generate thousands of messages and send one to every employee in the corporate database. In either case, the message is prepared in submit format and submitted to the serving SMSC. If the originating SME is on the cellular network, the short message travels across the cellular network, through an STP, and to the SMSC. If the originating SME is an ESME, then it reaches the SMSC through the Internet, via modem, or on some other landline data connection. There is a special category of ESMEs that are not wireless but are on the wireless net- work: ESMEs that belong to the wireless service provider. The voice message entity (VME) that holds voice messages for cellular subscribers is one example. The VME can send a subscriber an SMS message informing the subscriber that voice mail is waiting. SMSCs do not offer broadcast services, so if a user wants to send a message to multi- ple recipients, one message must be prepared and sent for each recipient. The SMSC receives messages from the originating SME and ensures their delivery or proper disposition. If the destination SME is on the cellular network, it communi- cates through the STP to the destination home location register (HLR), asking for the location of the destination SME. If the destination SME is registered on the network, the HLR sends its location and status to the SMSC, and the message is sent. If the des- tination SME is not available, then the SMSC leaves a message at the HLR asking it to notify the SMSC when the destination SME registers. If the destination SME is available, the SMSC sends the message to the serving MSC of the SME. If the destination SME is not available, the SMSC holds onto the message and waits to hear from the HLR. If the expiration time is reached before the recipient is available, the SMSC handles the failure to deliver according to a protocol pro- grammed in by the originating SME. The message simply may be abandoned, the SMSC may inform the originating SME that the message did not go through, or the 