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I work for an international well-known terminal manufacturer , be responsible for modem Chip development .
stay 5G In the early stage, he was responsible for the terminal data service layer 、 Core network related development work , Current lead 6G Research on technical standards of computational power network .


The content of the blog mainly focuses on ：
       5G/6G Explanation of the agreement
        Explanation of computational power network （ Cloud computing , Edge of computing , End calculation ）
        senior C Language explanation
       Rust Language explanation

5G PDU Session and session type

brief introduction

       stay 5G In the system , One of the key tasks of the network is to provide the terminal with access to the data network （DN） The connection of , namely 5G DNN, Be similar to 4G APN. data network （DNN） It can be Internet, It can also be IMS Or any other industry or factory specific DNN.

      5G NAS-SM （Session Management） Be responsible for establishing and managing the user plane connection between the terminal and the data network PDU conversation .3GPP The specification maintains the flexibility of session management design , To support different 5G Use cases . for example , Session management supports different PDU Session protocol type , How to deal with different options for session and business continuity , And flexible user plane architecture .

PDU Session parameters

One PDU The session has the parameters listed below . The terminal can request Create multiple at the same time PDU session. When UE Simultaneous need Internet The connection and IMS The service , It's very useful , As shown below .

• PDU Session Identifier（PDU Session identifier ）：PDU Session ID yes UE and 5G In the network PDU Session The logo of ;
• S-NSSAI (Slice identifier)：Slice ID To establish PDU Session A slice of the Internet ;
• DNN (Data Network Name)：DNN yes PDU The name of the data network to which the session is connected ：
• PDU Session Type： The type is defined by PDU The end user protocol carried by the session . Support IPv4、IPv6、IPv4/IPv6 Double stack 、 Ethernet and unstructured ;
• SSC Mode (Service and Session Continuity mode)： Reference resources 《 Three SSC(Session and Service Continuity) Model is introduced 》;
• User Plane Security Information： This indicates whether it is PDU Session Activate user plane encryption and integrity protection .

PDU Type of conversation

5G The system supports the following three PDU Session type , To cover different potential uses ：

• IP PDU Session
  • IPv4 PDU Session
  • IPv6 PDU Session
  • Dual-Stack IPv4v6
• Ethernet PDU Session
• Unstructured PDU Session

4G EPS Medium IP based PDU Session The type and 5GS Similar to , But in 5GS In Chinese, it means IPv6 There are some extra features .5GS Medium Unstructured PDU Session Type similar to 4G EPS Medium non-IP PDN type , and Ethernet PDU Session The type was originally 4G EPS There is no corresponding session type in , But it was later added .

• IP based PDU Session： stay IP aspect ,5G System support and 4G EPS The same group PDU Session type , namely IPv4、IPv6 and IPv4v6. However , especially IPv6, There are more functions , As compared EPS stay 5GS Chinese support IPv6 multi-homing. seeing the name of a thing one thinks of its function , these PDU Session types are provided for terminals IPv4、IPv6 Or at the same time IPv4 and IPv6 service .IP based PDU Session Type of PDU You can use any SSC Pattern 1、2 or 3. It also supports all QoS function ;

• Ethernet PDU Session： stay 5GS in Ethernet PDU Session It's a new one PDU Type of conversation , For transmission UE And DN Between Ethernet frame （Ethernet frames）. Use this PDU The session type is to provide UE To Layer2 Connection of Ethernet data network . such PDU Application scenario of conversation , For example, the terminal connects the remote office to the enterprise network , Or industrial equipment with terminals connected to the factory LAN . Another application can be a fixed wireless access service , Among them, residential gateway provides bridge for fixed wireless broadband customers Layer2 service .Ethernet PDU Session Type can be used SSC Pattern 1 or SSC Pattern 2, I won't support it SSC Pattern 3;

• Unstructured PDU Session： When established PDU Session The type is Unstructured PDU Session Type ,5GC No particular format is assumed for user data .5GC Basically PDU As unstructured bits , Therefore, the possibility of differential treatment for different flows is very limited .Unstructured PDU Session Sessions can be used to carry any protocol , It can also be IP And Ethernet data , But this type of PDU The session The main application is to support the Internet of things Protocol , for example LoWPAN、MQTT、CoAP etc. .
  
  because 5GC Can't parse and carry unstructured PDU Session Of PDU, Therefore, no protocol address or other protocol parameters are assigned to the terminal . Besides , Because there is no mechanism based on packet filtering to distinguish PDU Session Different business flows in , therefore UE The business flow of is carried in a single QoS Up stream , And the QoS The flow should be the default QoS class .Unstructured PDU Session Support SSC Pattern 1 and SSC Pattern 2, I won't support it SSC Pattern 3.