Q：网络切片是从RAN开始的吗？是不是走不同的APN？
来自知识星球
Q：⽹络切⽚是从RAN开始的吗？是不是⾛不同的APN？
Q：网络切片是从RAN开始的吗？是不是走不同的APN？
A：我的理解，APN还是要用的。跟切片没有直接联系，但因为切片是基于业务类型来切的（例如embb、物联网等），所以不同切片应
该是不同APN。是的，RAN也需要支持的。在23501里有，描述如下：
A Network Slice is defined within a PLMN and shall include:
- the Core Network Control Plane and User Plane Network Functions, as described in clause 4.2,
and, in the serving PLMN, at least one of the following:
- the NG Radio Access Network described in 3GPP TS 38.300 [27],
- the N3IWF functions to the non-3GPP Access Network described in clause 4.2.7.2.
另外，38300里提到了RAN需要对slice做哪些支持。包括：RAN awareness of slices、Selection of RAN part of the network slice、
Resource management between slices、Support of QoS、RAN selection of CN entity、Resource isolation between slices、Slice
Availability、Support for UE associating with multiple network slices simultaneously、Granularity of slice awareness、Validation of
the UE rights to access a network slice。
最基本的能够感知、识别不同的切片，并为不同的切片分配不同的qos等。
内容太多，不太好粘贴，建议看看38300里的16.3的原文。ran对切片的支持。
To enable differentiated handling of traffic for network slices with different SLA:
- NG-RAN is configured with a set of different configurations for different network slices;
目前来看，核心网切片是通过S-NSSAI （Subscribed S-NSSAI）来区分的。而S-NSSAI又是由SST+SD构成。SST就是切片类型，目
前规范只定义了3个SST的值。1：eMBB、2：URLLC、3：MIOT。如果同一种SST类型的不同切片，可以通过SD（Slice Differentiator
）来区分。
Enabling network slicing in 5G requires native support from the overall system architecture. Which contains access slices (both radio
access and fixed access), core network (CN) slices and the selection function that connects these slices into a complete network slice
comprised of both the access network and the CN.---来自GTI 5G Network Slicing White Paper。
追问：那这个参数会传到MME?
A：是的。如下图。
我看有些文档里还提到了ran切片的方案，不光ran切片，还提出了小区切片的概念，但好像没标准化。Cell Slice Id: It is used to identify
the cell slice within a NR cell。 Radio Slice Type (RST): It is a scalar used to represent a differentiating radio protocol behaviour for
UEs served through this cell slice. A pre-configured list of RSTs would be set up through the gNB EMS to support the requirements of
the different standardized SSTs (e.g. eMBB, URLLC, mIoT) or any other operator-specific targeted behaviour。 RAN Slice Id: It is
used to unambiguously identify a RAN Slice within a Subnetwork 。。。
上图的注解：As an illustrative example, Fig. 2 shows the deployment of 3 different RSIs. RSI#1 is configured with dedicated spectrum
resources (e.g. RF carrier #1), which are operated through a single dedicated cell covering a large area (e.g. NR Cell#1). This
dedicated cell is handled by a dedicated gNB#1 VNF deployed at PoP#1. This could be an appropriate realization for full isolation in
terms of spectrum and network functions between RSI#1 and the other RSIs. On the other hand, RSI#2 and RSI#3 are implemented
over the same spectrum resources (e.g. RF carrier#2) and sharing a common set of cells (NR Cell #2 and #3), which consequently
leads to sharing the same gNB functions realised in this case by means of gNB-CU#2 VNF deployed at PoP#2, gNB-DU#3 VNF at
PoP#3 and gNB-DU#4 VNF at PoP#1.