or ALLOVER cells. As the networks grow, a subcell leader might create her or his own cell, so ALPINE-2 might become the leader of the ALIMONY cell. Fault-tolerant cellular structures Modern communications theory has introduced methods to increase fault tolerance in cell organizations. Game theory and graph theory have been applied to the study of optimal covert network design. In the past, if cell members only knew the cell leader, and the leader was neutralized, the cell was cut off from the rest of the organization. But if a traditional cell had independent communications with the foreign support organization, headquarters might be able to arrange its reconnection. Another method is to have impersonal communications as "side links" between cells, such as a pair of dead drops, one for Team ALAN to leave "lost contact" messages to be retrieved by Team ALICE, and another dead drop for Team ALICE to leave messages for Team ALAN. These links, to be used only on , do not guarantee a contact. When a team finds a message in its emergency drop, it might do no more than send an alert message to headquarters. Headquarters might determine, through SIGINT or other sources, that the enemy had captured the leadership and the entire team, and order the other team not to attempt contact. If headquarters can have reasonable confidence that there is a communications failure or partial compromise, it might send a new contact to the survivors. When has electronic communications, such as the Internet, it has a much better chance of eluding surveillance and getting emergency instructions than by using a dead drop that can be under physical surveillance. Non-traditional models, exemplified by al-Qaeda If the al-Qaeda Training Manual is authentic, it demonstrates that Eastern cell structures may differ from the Western mode. Al-Qaeda's minimal core leadership group can be viewed as a ring or chain network, with each leader/node heading their own particular hierarchy. Such networks function by having their sub-networks provide information and other forms of support (the 'many-to-one' model), while the core group supplies 'truth' and decisions/directions (the 'one-to-many' model). Trust and personal relationships are an essential part of the Al-Qaida network (, even while it provides enhanced security). Cell members are trained as 'replaceable' units and 'vetting' of members occurs during the training period under the observation of the core group. Cells of this structure are an internal leadership core. Superficially,