A C3 Network is a network consisting of either a C3 Command Unit and up to three C3 Slave Units or six C3i units. Basically a special tight-beam communications network, they are used to share targeting data between 'Mechs and Combat Vehicles. The original C3 Networks were introduced in 3050 by the Draconis Combine.
The C3 Networks that exist today are geared towards the smallest level of tactical command: This means that each 'Mech in a Lance (or a ComGuard Level I for C3i) can share targeting data. There have been efforts to expand this targeting coordination to the Company level by using a 'Mech with a pair of C3 Command Units, like the Draconis Combine's Tai-sho.
A C3 Network of C3 Command units and C3 Slave units cannot share targeting data with units using a C3i system.
 Alternate Meanings
The term C3 Network is also used to indicate the Command/Control/Communications function of a military unit.