pect that virtually every user terminal is a short message entity (SME) and has the capability of sending and receiving short messages. When a user terminal registers, the response message from the HLR to the serving MSC contains SMS service qualifi- cation information, but these are not extra messages because of SMS. The message loads are between a user terminal's serving MSC and the subscriber's SMS message center (SMSC). When mobile subscriber A sends a short message to mobile subscriber B, that mes- sage is sent from serving MSC A to the SMSC associated with subscriber A. The SMSC then contacts MSC B and the HLR for B to route the call to the serving MSC for sub- scriber B. All these information requests and the transmission of the message itself have acknowledgments, and all use ANSI-41 capacity. Thus a short message from A to B generates two messages between serving MSC A and the SMSC and two messages between the SMSC and serving MSC When subscriber A sends a message to an external SME (ESME), that messages is sent from serving MSC A through the SMSC to the outside world. There are two mes- sages between MSC A and the SMSC and two messages between the SMSC and the public Transmission Control Protocol/Internet Protocol (TCP/IP) network. When an ESME sends a short message to subscriber B, that message is sent to the SMSC for the ESME, which queries HLR B so that it can send the message to serving MSC B. There are two messages between the external SMSC and HLR B and two mes- sages between the external SMSC and serving MSC B. Superscript(2) The reason we call SMS a signaling wildcard is that it uses a high proportion of sig- naling to message size and also uses no voice or data channel resources on the cellular network. SMS messages are handled entirely on the signaling channel. If voice calls send 10 signals per minute of talk, then we might have 1000 bytes of ANSI-41 data for a million bytes of speech. High-speed data users are going to tip the proportion even further by sending tens of megabytes for each 100