What is the difference between Gx and Gz?

Question

Hi,
What is the difference between Gx and Gz interface.
As we know the interface between P-GW and OFCS is Gz interface and P-GW to PCRF is Gx.
Why both the interfaces are considered as Offline Charging

Answer 1

Chinmoy, as far as I know, interface is between PECF and PCRF is known as Gx and it is used to policy and charging rules exchanges between these two nodes. This interface as such is not used for charging purpose.

CDRs generated by PGW are sent to OFCS by using the Gz interface.

Answer 2

Gx and Gy are different Diameter "Applications". Their PDUs different. Though they use the same Diameter commands (CCR/CCA, RAR/RAA), similarity ends there.
Gx is used for policy control. PCEF sends request for Policies and PCRF responds with Policies.

Gy is used for billing and related authorization etc. PCEF or some other function sends the subscriber information and Onile Charging System responds with authorization (for the usage of resources) and any additional information like how long the service can be consumed, when to report back etc.

So, apart from the fact that they are Diameter extensions (and thus connection setup, request forwarding, session management etc are done in the same way), they don't have much in common. Of course, they have many AVPs in common.

Comments

Hi Rathnakumar,
Thanks for the information.Could you please edit your answer,my question is regarding Gz and Gx interface, the above explanation gives the difference about Gy and Gx interface.

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Sorry that I spoke about Gy instead of Gz, but the answer is the same. Except that Gz is used for Offline Charging (Gy is used for Online Charging). Gz uses different commands (ACR/ACA) and is session less. But the key point is, these are different protocols (or applications) serving different purposes.

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Thanks Chinmoy and others for these discussions..
Btw, just to add to this discussions, it would be helpful, if somebody explains me how to correlate the initial Gx (CCA) , basically the charging information, with the Gy/Gz AVPS..Sorry for jumping into this thread, but i felt this is related to this q. @Chinmoy, if this not ok, i can start a new thread (if this is diverting your query)

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Hi Rathnakumar,
Could you please suggest which 3GPP spec is used for Gz Interface

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32.299 - this is the starting point. It further refers to "domain specific" documents.