Which Diameter interface connects I-CSCF/S-CSCF and HSS?

Interview
1

Q. Which Diameter interface connects I-CSCF/S-CSCF and HSS?

a) Gx
b) Cx
c) Rx
d) Sd

Check 🔎

:arrow_right: Correct answer: Letter b.

The Cx interface connects the I-CSCF/S-CSCF with the HSS in the IMS architecture using Diameter. It carries messages such as UAR, LIR, MAR, and SAR to manage user registration, authentication, and S-CSCF assignment, supporting key IMS functions like subscriber location and call routing.

Q. Which Diameter interface connects I-CSCF/S-CSCF and HSS?

a) :x: Gx
→ Incorrect. Gx connects the PCRF and P-GW for policy control, not CSCF and HSS.

b) :white_check_mark: Cx
→ Correct. Cx interface carries Diameter messages between CSCFs and HSS, such as UAR, LIR, MAR, and SAR.

c) :x: Rx
→ Incorrect. Rx is used between P-CSCF and PCRF to exchange session information.

d) :x: Sd
→ Incorrect. Sd is between PCRF and AF (Application Function).