LTE: What does the difference between CLR and DSR command over S6a interface ?

Answer 1

CLR is sent from the HSS to the MME, for various purposes such as "Offloading the UE onto another MME/SGSN", "Init Attach for Emergency services when normal services cannot be offered to the UE"/

Whereas DSR is invoked by the HSS only when "the Subscriber is attached and some data is deleted at HSS".Now HSS informs MME with this message that some part of subscription data is deleted at HSS

Answer 2

CLR command is used when a location of a UE gets changed due to mobility. This message is triggered by HSS to MME. Whereas DSR command is being used to inform MME when UE's subscription deleted.