How sessions between PGW and PCRF is maintained in LTE network?

Question

This regarding the sessions b/w the PGW and PCRF.

Lets say we have 2 default bearers(DEF1, ad DEF2) for UE1, and 2 dediicated bearers for each of these Default bearers. And for UE2 assume 2 def bearers, DEF3, and DEF4.

Now a CCR is sent for initial default bearer DEF1 creation for UE1. Lets say session(session1) is created for this. with CCRequest number=0.
For Ded bearer1 creation, will it use the same session Id ? and increment the CCRNumber ?
What about the UE2?

I am new to Diameter and earlier, these things were internal and didnot need diameter interface. So the questions are arising.

Answer 1

The session for a session let say UE 1 with PDN connection 1 will remain same through out, However CC-Request no will increment with each message.

CC-Request-Type will also be different. In case of initial attach CC-Request type will be 1(Initial), in case of updation CCR-Request no will increment by 1 and CC-Request will be 2(update).

Lets say you are now doing some modification to the existing session UE1 PDN1 then the CC-Request no will increment however CC-Request type will be Update(2). And finally when session will be terminated then in that case CC-Request Type will be 3(Terminate).

Also, its good that you are getting doubts..it means you are progressing :)

Comments

Great answer, deserves a wall recommendation :)

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Thank you for the appreciation salil

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Thanks a lot for the Very Quick response :) . I also hope .(that i am progressing :) )

Btw, i have some data from Create Session needs to be buffered in PGW, till i get response for the CCR.
.So CCRnumber can be stored for each default bearer. So i am thinking of storing the Sessionid, CCR number and default bearer id in the PGW along with the info to be buffered. So when i get the CCA back from PCRF, i can uniquely identify the buffered info in the PGW.

Btw, lets say we have Dedicated bearer1, is created for Default bearer, it will have same session id as the Default bearer1, but CCR number will be incremented to 2.

Hope i am not trying to push you too deep into my implementation details. Sorry about that.

Btw, in our implementation of PGW, we have a generic PGW handler, which spans a new PGW instance for each default bearer created

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"Btw, lets say we have Dedicated bearer1, is created for Default bearer, it will have same session id as the Default bearer1, but CCR number will be incremented to 2"

Yes your understanding is correct...and i guess this dedicated bearer is created from UE side

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Thankyou for clarifying :)