HSS can do authentication then why we go for AAA server ?
There are many reason but one of the key reason is that HSS is a LTE/UMTS node where as AAA is not its a common Auth/Acct server which not only serves telecom users but also broadband etc so there is practical implementation impact if we dont have AAA.
Why Diameter server(AAA) is needed for authentication - authorizaion messages AAR , AAA, ACR, ACA messages in order to authenticate if authentication/security is done at MME/eNB/HSS while attach.? Could you please explain in detail?
Is it the wish of HSS or MME or UE ?
CDMA2000 uses Radius for all AAA.
3GPP uses GTP' for accounting in both UMTS and LTE but (afaik) uses Diameter for accounting in IMS.
What is the rationale behind this?