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blog: 5G LAN-type service
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+# 5G LAN-type service Introduction
+>[!NOTE]
+> Author: Yuan-Ting Chen
+> Date: 2025/01/22
+
+## 5G LAN-type Services
+
+5G LAN-type service provides services with similar functionalities to Local Area Networks (LANs) and VPN’s but improved with 5G capabilities such as high performance, **long distance access, mobility and security**.
+
+For instance, Automated Guided Vehicles (AGVs) moving inside a large factory may communicate and cooperate through 5G LAN technology with low latency. This could be hard to achieve through Wi-fi due to the possibility of handover issue.
+
+## 5G VN Group
+
+> [!Tip] 
+> Definitions
+> 5G LAN-virtual network (5G LAN-VN): a virtual network capable of supporting 5G LAN-type service.
+> 5G VN Group: A set of UEs using private communication for 5G LAN-type service.
+> 
+
+### 5G VN group management
+
+A 5G VN group is characterized by the following:
+
+- **5G VN group identities**: 
+    used to identify the 5G VN group.
+    - External Group ID
+    - Internal Group ID
+- **5G VN group membership**: 
+    used to uniquely identify 5G VN group members.
+    - GPSIs
+- **5G VN group data**
+    - PDU session type
+    - DNN
+    - S-NSSAI
+    - Application descriptor
+    - Information related with secondary authentication / authorization (e.g. to enable IP address assignment by the DN-AAA).
+
+The 5G VN groups and 5G VN members are managed (e.g. add/delete/modify) via a set of services exposed by NEF.
+
+### 5G VN group creation
+
+![VN group management procedure 1](./VN%20group%20management%20procedure%201.png)
+
+
+- A 5G VN group is identified by the AF using **External Group ID**.
+- The NEF provides the External Group ID to UDM.
+- The **UDM** maps the External Group ID to **Internal Group ID.** 
+For a newly created 5G VN Group, an Internal Group ID is determined by the UDM.
+
+After the 5G VN group is created, UE with corresponding DNN and S-NSSAI would get the UE policy associated with the 5G VN group in the registration procedure.
+
+![VN group management procedure 2](./VN%20group%20management%20procedure%202.png)
+
+
+- After Registration Accept in the General Registration Procedure, the AMF performs a **UE Policy Association Establishment** procedure.
+- In the UE Policy Association Establishment procedure, the AMF sends a Npcf_UEPolicyControl Create Request, which contains the Internal-Group-ID-list of the UE and UE Policy Container, to PCF.
+- The PCF then get the **5G VN group data** and **5G VN group membership** for each Internal-Group-ID received from the AMF using Nudr_DM_Query (Internal-Group-Id, Subscription Data, 5G VN Group Configuration).
+
+![VN group management procedure 3](./VN%20group%20management%20procedure%203.png)
+
+
+- The PCF triggers **UE Configuration Update Procedure** to **update UE policy** and sends the UE policy container including UE policy information to the UE.
+- PCF invokes **Namf_Communication_N1N2MessageTransfer** service operation provided by the AMF. The message includes SUPI, **UE Policy Container**.
+- the AMF transfers transparently the UE Policy container (UE policy information) received from the PCF to the UE using **DL NAS TRANSPORT message**.
+
+### 5G VN Group Communication
+
+There are three types of traffic forwarding methods allowed for 5G VN communication:
+
+- **Local switch**, where traffic is locally forwarded by a single UPF if this UPF is the common PSA UPF of different PDU Sessions for the same 5G VN group.
+
+![user plane architechture local switch](./user%20plane%20architechture%20local%20switch.png)
+
+
+- **N19-based**, where the UL/DL traffic for the 5G VN group communication is forwarded between PSA UPFs of different PDU sessions via N19. N19 is based on a shared User Plane tunnel connecting PSA UPFs of a single 5G VN group.
+
+    ![user plane architechture N19-based](./user%20plane%20architechture%20N19-based.png)
+
+- **N6-based**, where the UL/DL traffic for the 5G VN communication is forwarded to/from the DN;
+
+Traffic forwarding within the 5G VN group is realized by using a UPF internal interface ("5G VN internal") 
+
+## Reference
+- TS 22.261 "6.26 5G LAN-type service"
+- TS 23.501 "4.4.6 5G LAN-type Services"
+- TS 23.501 "5.29 Support for 5G LAN-type service"
+- TS 23.502 "4.15.6.2 NEF service operations information flow"
+- TS 23.502 "4.2.2.2.2 General Registration"
+- TS 23.502 "4.16.11 UE Policy Association Establishment"
+- TS 23.502 "4.2.4.3 UE Configuration Update procedure for transparent UE Policy delivery"
+
+## About me
+Hi, I’m Yuan-Ting Chen, a newcomer to 5G and free5GC. I'm currently conducting research on 5G LAN. Please feel free to let me know if there is any mistake in the article.
diff --git a/docs/blog/20250122/VN group management procedure 1.png b/docs/blog/20250122/VN group management procedure 1.png
diff --git a/docs/blog/20250122/VN group management procedure 2.png b/docs/blog/20250122/VN group management procedure 2.png
diff --git a/docs/blog/20250122/VN group management procedure 3.png b/docs/blog/20250122/VN group management procedure 3.png
diff --git a/docs/blog/20250122/user plane architechture N19-based.png b/docs/blog/20250122/user plane architechture N19-based.png
diff --git a/docs/blog/20250122/user plane architechture local switch.png b/docs/blog/20250122/user plane architechture local switch.png
diff --git a/docs/blog/index.md b/docs/blog/index.md
@@ -3,6 +3,7 @@
 # Blogs
 
 ## Official
+- [2025/01/22: 5G LAN-type service](./20250122/20250122.md)
 - [2024/12/30: 5G Network Slicing](./20241230/20241230.md)
 - [2024/12/24: Debug gtp5g kernel module using stacktrace and eBPF](./20241224/index.md)
 - [2024/12/04: Paging in 5G Network](./20241204/20241204.md)