Hi Xuesong,

Traffic policy for subscribers is managed per PDU session at the UPF (and gNB).
GTP-u does provide encapsulation between the end points, but its control fields 
are meant for conveying control semantics between the GTP endpoints: they were 
not intended for IP transport/ traffic underlays. 5QI/QCI etc are in the GTP 
extension header which may not be ideal to lookup to classify each packet in 
the transport network.

The entity that classifies data packets (upstream at gNB and downstream at 
UPF-PSA) also inserts the DSCP for that GTP packet. The classification is based 
on subscriber aspects but may also on be based on its content (e.g., using DPI).

Best Regards,
John


From: dmm <[email protected]> On Behalf Of Gengxuesong (Geng Xuesong)
Sent: Wednesday, January 20, 2021 8:23 PM
To: Uma Chunduri <[email protected]>; Lizhenbin <[email protected]>
Cc: [email protected]; dmm <[email protected]>
Subject: Re: [DMM] [Apn] Regarding APN Usecase in Mobile Core

Hi Uma and all,

I have read the document and got a few questions:
In my understanding, in the UPF where traffic policy is enforced, the 
fine-granularity services are provided. Then what fields in the GTP-u 
encapsulation indicates the traffic's service requirements? When a GTP-u tunnel 
goes into a SRv6 policy, according to which fields in the GTP-u encapsulation 
the DSCP is generated? We know that there are parameters such as 5QI/QCI and 
QFI, whether they are associated with a GTP-u tunnel?

Best
Xuesong
From: Apn [mailto:[email protected]] On Behalf Of Uma Chunduri
Sent: Tuesday, January 19, 2021 3:17 AM
To: Lizhenbin <[email protected]<mailto:[email protected]>>
Cc: [email protected]<mailto:[email protected]>; dmm <[email protected]<mailto:[email protected]>>
Subject: Re: [Apn] [DMM] Regarding APN Usecase in Mobile Core

Hi Robin,

In-line..

Cheers!
--
Uma C.

On Mon, Jan 18, 2021 at 5:25 AM Lizhenbin 
<[email protected]<mailto:[email protected]>> wrote:
Hi APNers and DMMers,
I remember that in the mobile core scenarios the GTP-u tunnel can be set up 
according to the user and application requirements, but I do not understand the 
details.

[Uma]: Obviously, the best reference for GTP-U is TS 29.281. However, uou 
should look into 
https://datatracker.ietf.org/doc/draft-ietf-dmm-5g-uplane-analysis/<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fdraft-ietf-dmm-5g-uplane-analysis%2F&data=04%7C01%7Cjohn.kaippallimalil%40futurewei.com%7C77632db844b34a8e561108d8bdb38cb8%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637467926158632424%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=5nVGUJhkHBn7FWHUCFPC4lGhwr6lBqtIWNyY1o0dxsg%3D&reserved=0>
 where lot more details and other references related this topic was analyzed 
(primarily started after/during REL-15, when  any other use plane other than 
GTP-U is worthwhile is debated for 5G N9 interface).

I think when the packet tunneled by GTP-u traverses the APN-based transport 
network, it may be mapped to the corresponding tunnel according to the user and 
application requirements to implement the uniform service. If you are familiar 
with the principle of GTP-u in the mobile core, please help provide some 
details.


Best Regards,
Zhenbin (Robin)


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