All connections are peer-to-peer. This is facilitated by an Allstarlink server sending a file to each computer hosting a node or nodes a list of all registered nodes ( read that as identifying number), an IP address, and a UDP port number (bindport=xxxx in iax.conf).
When a connection (link) takes place, the host computer uses the information in the app_rpt config files associated with each node (number) to process communications and control of the repeater, or what ever you are controlling. EchoLink, SIP, and iax are supported. IRLP is not.