CCRequest message in the Gx interface

Question

Could you help me figure out CCRequest basic message contents sent from the PGW to PCRF. I am in a process of replacing our Gx interface from the static calls to the Diameter interface.

I am interested in any discussion about this interface.

I am also trying to understand , how the APN info is passed from the PGW(PCEF) to PGW. I think the Called-Party-AVP is used. It is bit contradicting info in the net than the one given in spec, (which says it is used to indicate Emergency APN)

Comments

A default bearer is for IMS signalling or GENERAL traffic is convyed by bearer-usage avp

Answer 1

You can refer to 29.212 3gpp spec for Gx interface.

In the initial CCR message pgw conveys the information it received from sgw towards pcrf like IMSI, msisdn, APN, bearer control mode, default bearer QoS, IP address of ue(pgw provides it, one of its functionality)

Try reading it and post if you come across any specific doubts.
The AVP used to convey APN into is Called-Station-Id

As per my understanding there is no such AVP to define if call is emergency or not. In case of emergency call an APN based policy should be defined.
Let's say the call comes to pcrf and in CCR initial the called-station-id is emergency.T-Mobile.mcc310.mnc310.GPRS then allow some particular service related to emergency.

I hope that it helped

Regards,
Peeyush Sharma

Comments

Thanks for the reply.

PCRF is supposed to receive the APN information in the CCRequest message. But I am not not very sure whether the "Called-Station-ID" AVP is used to convey that info to PCRF (from PGW).
As per Sec 4.5.1 of 25.212, it says "the PDN information, if available, within the Called-Station-Id AVP,". But then this AVP is of octetstring type . So what will the info in this AVP look like. Lets say Default bearer for IMS, so Called-station-id AVP is "IMS".

It would have been nice to compare some pacp logs.

thanks,
pdk

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A bearer is used for IMS_SIGNALLING or GENERAL traffic is conveyed by Bearer-Usage AVP
In called station Id AVP information related to APN name is conveyed as received from APN IE on S5/S8 or Gn/Gp from SGW/SGSN

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Thanks a lot Peeyush. That clasrifies a lot. But meanshile I was bit stuck with the way we handle our AVPS. CalledstationId is of type octetstring type, unlike the UTFString type like eg, imsi. So i donot have a reference template to convert this string to OctetString AVP. Just some internal implementation complexities.
Thanks a lot for quick response and appreciate your knowledge on the Network side

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Its very simple actually. It will be convey in the same way as it is received from SGW. I might not be right however UTFString is where every character is read in ASCII values and octet string is just one byte string

Let me know if you have more query regarding it. I will try to get back with the information which you need. :)

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Thanks Peeyush, As of now i am proceeding furher . Hoping that my soln works. But will update soon on this. Btw, i have another query, which i will post as a separate question, which is basically about the sessions b/w PGW and PCRF for the diameter connections. Please kindly reply to that, as you have quite good knowledge on the network side.