Short Message Service: What, How, and Where?

Short Message Service: What, How, and Where? This little page from about the year 2000 explains the basic process of SMS on a GSM network. The most interesting thing is that SMS is not a packet-based service (so you can't use a packet-sniffer to intercept the messages), it does however have an SMC (short message center) where all the messages are routed before delivery. So interception of SMS would require cooperaton of the wireless provider and a damn good text-recognition system which can deal with inherent irregularities of 180 character-limit of pure text. SMS uses a signalling channel rather than a dedicated channel to transmit the messages, which makes it possible to be sent/received simultaneously with other services (voice/data) on the same phone. Return receipts can track message sending. I still have to find out if there is a system out there to track SMS propagation for law enforcement purposes, however, this information suggests that it wouldn't be as easy as email for example.