| Internet-Draft | CATS 5G Edge Enhance | October 2024 |
| Jiang | Expires 12 April 2025 | [Page] |
This draft illustrates a computing-aware use case that is based on the study conclusion of the 3GPP 5G enhanced Edge Computing (eEdge). This use case takes into acount both network and computing metrics upon selecting edge application server (EAS) and user plane function (UPF).¶
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3GPP 5G Edge Computing & its successive enhancements, i.e., eEdge, standardize reference architectures, connectivity models along with edge hosting envivorments (or EHE), etc., so as to enable operator and/or 3rd party services to be hosted close to an end device's (i.e., end user or UE) access point of attachment [TS.23.501][TS.23.548]. The eEdge service achieves an efficient service delivery through the reduced end-to-end latency and load on the transport network. Edge application servers, or EAS'es, are deployed in corresponding (edge) domain networks (DNs) that are connected via the N6 interface of a (PSA) UPF. A DN may be under the control of either the operator or 3rd parties.¶
A 5GC can select either a UPF according to provided traffic steering rules, or an EAS based on 'holistic better metrics', etc., and then forward traffic to enable the optimal access to the DN via a N6 interface. This may be based on the UE's local settings, the measured or collected EAS (or edge application server) runtime information, network policy or other related traffic rules. As shown in the Figure 1, either the C-PSA UPF or the L-PSA UPF could be optimally selected to foward the UE (uplink) traffic to an EAS with the better (or even the best) 'holistic' metrics.¶
C-PSA: Central PSA UPF L-PSA: Local PSA UPF
DL: Downlink direction UL: Uplink direction
ULCL/BP: Uplink Classifier/Branch Point
EAS: Edge App Server in Data Domain (DN)
.....................................
: [-- 5G Core --] :
: / | | :
: N1 N2 N4 :
: / | | <== DL
: / | +-------+ +-----+ :
+----+ +-----+ | UPF | | UPF | : /---------\
| UE |--| gNB |--|ULCL/BP|--|C-PSA+(N6)-/ DN or \
+----+ +-----+ +-------+ +-----+ : |DN:local-part|
: | : | |
: | UL==> | EAS |
: +-----+ : | (1 or More) |
: | UPF | : \ /
: |L-PSA|(N6)-------:----\---------/
: +-----+ :
.....................................
Recently, the 3GPP 5G Rel-19 [TR.23.700-49] studied how to effectively and optimally select (local) UPFs in 5G CN (Core Network) and EAS'es residing in DN (or edge hosting environment) with the consideration of the N6 (transport) delay between (local) PSA UPFs and EAS'es, and, possibly, the computing capabilities, e.g., compute power, memory, runtime load, storage, etc., of EAS'es.¶
The 5G enhanced Edge (or eEdge) explores to discover one suitable EAS to handle an edge application that can be served by multiple EAS'es deployed in different sites (i.e., DNs or local DNs). The suitability of an EAS is dependant on both of the following:¶
Evidently, the integration of both network & compute metrics conform to the scope of the CATS charter.¶
The 3GPP 5G eEdge document [TR.23.700-49] provides a couple of 5G specific scenarios to justify the requirement. For example, when some of the available transport links in DNs get congested, a UE moves aways from the original location (very common in mobile network), or excessive load builds up on EAS(es), then a previously 'better-optimized' EAS may become less preferable, and thus a new EAS and/or local-PSA UPF need to be selected based on the weighted optimization of nework and compute metrics. The 5G eEdge emphasizes particularly on considering the EAS load and the end-to-end delay off the N6 interface between a local PSA and a candidate EAS residing in a (local) DN.¶
In the Figure 2, the UPF-1 to UPF-m indicate 'm' local PSA UPFs, all of which could fulfill an applicaiton service (AppService) to the UE (on the left side of the figure). The AppService is provisioned in multiple EAS'es that reside in remote DN(s) or local DN(s), denoted as EAS-1 to EAS-n. The selection of UPF and EAS may depend on both the N6 delay and EAS load.¶
C-PSA: Central PSA UPF
UPF-x(L-PSA): the x-th Local PSA UPF, x=1...m
EAS-y: the y-th Edge App Server in DN, y=1...n
DL: Downlink direction UL: Uplink direction
.....................................
: [-- 5G Core --] :
: / | | :
: N1 N2 N4 :
: / | | :
: / | +-------+ +-----+ :
+----+ +-----+ | UPF | | UPF | : /---------\
| UE |--| gNB |--|ULCL/BP|--|C-PSA+(N6)-/ DN or \
+----+ +-----+ +-------+ +-----+ : |DN:local-part|
: | : | -------- |
: | : | [EAS-1] |
: +------------+ : | |
: |UPF-1(L-PSA)|(N6)-----| [EAS-2] |
: +------------+ : | . |
: ...... : | . |
: +------------+ : | . |
: |UPF-m(L-PSA)|(N6)-----| [EAS-n] |
: +------------+ : \ /
....................................: \---------/
This subsection shows how to implement the computing-aware 5G eEdge via mappings to CATS functional componenents, e.g., C-PS, C-NMA, C-SMA, etc.[CATS.Framework]¶
There is no security concern.¶
There is no IANA requirement.¶