Most weapons and funding from western and Arab countries goes through central command, but some states and private donors also hand over aid directly.
Aid to Syrian rebels flows through a complex maze
Rebels say there is also a complex, shadowy system of weapons movement, with diverse, sometimes parallel, supply routes.
The command centre works with the FSA and the Supreme Military Council - the FSA high command headed by General Selim Idriss and allied with the Syrian National Coalition, the opposition political alliance backed by Arab states and the West.
The United States and European nations, including France and Britain, provide military advice and non-lethal supplies to rebels through the command centre, rebels said. Arabian Gulf states, predominantly Saudi Arabia, reportedly provide the firepower.
Most of this is transferred to front-line FSA brigades via the Deraa Military Council, headed by Ahmed Nehmeh, a Jordan-based Syrian rebel officer. It is an FSA organisation and part of the Supreme Military Council's chain of command.
However some weapons from the command centre are given directly to front-line FSA brigades, bypassing Mr Nehmeh and the supreme council's chain of command.
FSA units in Deraa say the Gulf states that provide weapons through the command centre also supply weapons directly to brigades - bypassing both the command centre and the supreme council.
In addition, private donors in the Gulf pump money in directly to front-line rebel units, often donations worth hundreds of thousands of dollars, which are entirely outside the command centre's control, outside of the supreme council supply chain and not linked to any state authority in the Gulf.
Islamist rebel units that are not part of the FSA are also key players in Deraa, and opposition figures said these factions were also supplied directly with weapons from Gulf states and cash from private donors.
Some of the direct funding and munitions supplies ends up in the hands of Jabhat Al Nusra, a group with links to Al Qaeda, rebels in Deraa said. Al Nusra, while small in terms of numbers in Deraa, is well equipped, and cooperates with the FSA and other Islamist rebel factions in carrying out attacks against regime forces, rebels said.
Another key source of weapons are those seized by rebel brigades from regime bases they overrun, with factions sharing out the spoils. Rebel groups sometimes sell these weapons to each other, or trade weapons they may not want or be able to use, such as artillery pieces, for those they more urgently need, such as small arms ammunition.