There are a number of ways that the {productname} Server can communicate with clients. Which one you use depends on the type of client, and your network architecture.
The {productname} daemon (rhnsd) runs on traditional client systems and periodically connects with {productname} to check for new updates and notifications.
It does not apply to Salt clients.
Push via SSH and Push via Salt SSH are used in environments where clients cannot reach the {productname} Server directly. In this environment, clients are located in a firewall-protected zone called a DMZ. No system within the DMZ is authorized to open a connection to the internal network, including the {productname} Server.
OSAD is an alternative contact method between {productname} and traditional clients. OSAD allows traditional clients to execute scheduled actions immediately. It does not apply to Salt clients.