TABLE OF CONTENTS To Kunlun now I say,
Neither all your height
Nor all your snow is needed.
Could I but draw my sword overtopping heaven,
I'd cleave you in three:
One piece for Europe,
One for America,
One to keep in the East.
Now a world in peace, sharing together
The same warmth and cold throughout the globe.
Mao Zedong, Poems, 1935
A GSM network uses two separate networks: one for telephone calls (using the ISUP protocol, which is the foundation of the ISDN protocol, for call setup and release) and one for signaling, mainly for mobility-related messages (otherwise it would not be a mobile network) and for SMS. Each mobile operator has its own two private separate such networks that it builds with equipment and lines. To communicate with each other (in particular, to be able to offer roaming services), providers use international carriers (France Telecom, Belgacom, Teleglobe, Swisscom, British Telecom, and so on), which also provide them with an international telephone network (ISUP) and a signaling network for the exchange of signaling messages (using the SCCP protocol; see Chapter 2).
In a given mobile network, such as that shown in Figure 1.1, the gateway between the private networks and the international carrier is a piece of equipment called a gateway mobile switching center (GMSC), which is both a switch for telephone calls and a router for the SCCP signaling messages. The SMS service involves only the SCCP...
