The proxy will download settings and configuration settings from the STS 's via port 443. The proxy will then load the configuration to itself using port 8553 locally.
As for the high availability configuration it is designed more like a cluster because some scenarios may require more proxies that STS's for example.
When a new proxy registers with CAM system it's FQDN will be registered in the CAM DB. Internally all STS nodes need to be able to resolve all proxy nodes and vice versa; whether this is achieved via DNS or hosts files is completely up to you.
Externally only the proxy hostname configured in the the CAM Admin UI should be contactable and will resolve to the load balancer which in turn will route to the proxy's
Each Proxy will select an STS for each new user session on a round-robin basis and then maintain that session until its conclusion.
The Proxy will assign a cookie called CAMCLONE_ID which determines which STS which is to be used for that session
The first session will get a value of 0, then next 1, etc. until the number of STS’ has been reached, then the next session will be assigned a value of 0
Ultimately it does not matter which STS the proxy first connects to as long as it is successful so it can get the remainder of its configuration.