The DRA distributor is a load balancer that front ends the diameter connections inbound to the DRA. It then forwards the connections to a selected Director VM. For client facing traffic (for example, PGW, AF), two distributor VMs configured as an HA pair are used. In addition, two distributor VMs are used to support server facing entities (for example, PCRF).
When a new connection arrives at the Distributor, it employs the Weighted Least Connections algorithm to select a Director VM for the new connection. The return traffic is sent from the Director VM directly to the originator of the connection (PGW, PCRF, and so on) bypassing the Distributor VM. This forwarding mechanism is known as Direct Routing. A pair of Distributors synchronizes the connection information to continue with the forwarding traffic if one of the Distributor VMs fails.