Bandwidth restriction at PGW

Question

I am looking for some inputs regarding the way to restrict the BW at PGW to be within the authorized one.

I read some articles, the P-GW will use the Subscribed APN-AMBR value to limit the IP data traffic to a maximum rate.

Now my query is how the PGW derives this info? (Is it uses the windowing to check the num of packets in certain period or is it at a particular time?)

Answer 1

UE-APN AMBR parameter informs to network elements regarding maximum throughput for an APN . It is measured in terms of number of bits per second. Since downlink packets flow through PGW and policy enforcement entity sits with PGW, it's responsibility of PCEF to maintain subscribed APN AMBR.

Comments

Thanks Harshita

Yes, i was referring to PGW ( which includes core PGW and PCEF).. I am looking for inputs on how it is implemented PGW (i.e PCEF)

- I am also looking for another info.
I read somewhere the PCEF sends the CCRequest to OCS saying lets say 1MB is available, which in turn sends the CCREvent to PCRF . PCRF needs to change the QOS and send in RAR message. How the Quota is mapped to Qos at PCRF ?
How this is mapped to particular bearer ?

Answer 2

Hi Priya,

As per my understanding CCR-I is sent to PCRF first not to the OCS and only after getting response from PCRF, PGW will decide if CCR-I to OCS should be sent or not. Also, PGW can always sed requested quota and hence it can never tell that 1 Mb quota is remaining or available. OCS is the decision making body for that part.

Regards,
Peeyush Sharma

Comments

Hi Peeyush,

Thanks a lot for the info and reply.
Yes i.e true. My understanding on this area is limited. I am not into much aware of spec in this area.
Just to put what i understood from the google, in steps, so you can correct or provide comments on this.

1.CCR-I is sent from the PCEF to PGW and PCRF sends Query subscriber Profile to OCS and receives the response, "Retrieve subscriber profile". PCRF sends the CCA with some Qos.
2.PCEF sends the CCR-I to get quota from OCS. OCS sends CCA with quota lets say 1MB.
3.When the allocated 1MB is used by the PCEF, it sends CCR Update (Used Quota, =1MB).
4.Which in turn sends the CCA with the New Quota (lets say another 1MB).. Now OCS also sends the CCR Event to PCRF ..which sends the RAR to PCEF with Qos .
5.RAA is sent from PCEF to PCRF.

Now my Q is on step
3) how the PCEF checks the allocated quota is exceeded ?
4) How PCRF derives the Qos based on the CCR Event ?

thanks,
Priya

Answer 3

Priya,

Can you please tell me the use-case. In that way it will be easy for me to drive the call flow and interaction between different nodes. When you are saying that PCRF and OCS communicates are you referring to Sy interface?

Also, PCRF will contact SPR when it receives CCR-I usually.

I'll try to go through Sy interface messages and parameters today as it has been a while since I have gone through it.

In meantime try to explain the use-case so that we can look at the big picture and cover maximum scenarios out of this :)

Regards,
Peeyush Sharma

Comments

Hi Peeyush,
I am trying to comeout with the simple message sequence(This is for purely internal implementation), for interactions between PCRF, PCEF and OCS. I think PCEF to OCS is via Gy interface and PCRf and OCS is via Sy interface.
Thanks,
Priya

Answer 4

Will try to get back with the proper flows by tomorrow.

Comments

Thanks a lot