Tickrates for Photon Server and Client

Hello.

From what I could understand, a Photon Client always sends its data with a rate defined by PhotonNetwork.SendRate and PhotonNetwork.SerializationRate.

But how does Photon Server handle received packets? Does the server receive and send them synchronously at a certain tickrate or asynchronously? What exactly happens with the packets in the server (enqueued, then dequeued)?

Does a Client receive packets synchronously at a certain tickrate or asynchronously?

Thank you.