5G Dial-Up Connection Process

5G dial-up is classified into the following types based on the conditions for triggering 5G dial-up:

• Automatic dial-up (always online)

  After a router starts, it automatically attempts to establish a dial-up connection with the remote device. The dial-up process does not need to be triggered by data packets. If the connection fails, the router attempts to establish a dial-up connection with the remote device at a specified interval. This dial-up mode applies to scenarios where users are not charged based on the traffic volume or online duration. For example, in the yearly-package service, there is no limit on the traffic volume and online duration of users within the specified period.

• On-demand dial-up (traffic-triggered connection establishment)

  A router establishes a dial-up connection with the remote device only when data needs to be transmitted. When the link becomes idle, the router automatically disconnects the connection to save traffic. This dial-up mode applies to scenarios where users are charged based on the traffic volume or online duration. For example, a traffic-package service allows users to use a certain volume of traffic within a specified period.

Figure 13-3 5G dial-up connection process

In Figure 13-3, when traffic is triggered or the dial-up time arrives, the router uses circular dial control center (C-DCC) to trigger automatic dial-up on a cellular interface and controls the establishment of the connection between the 5G modem and the external public data network (PDN) gateway (PGW). The router connects to the PDN through the PGW, which allocates an IP address to the 5G modem of the router. The following describes the process of establishing a 5G dial-up connection:

1. A router triggers dial-up on a cellular interface through C-DCC. The cellular interface sends a connection setup request to the 5G modem.
2. The 5G modem sends a connection setup request to the PGW. The request contains authentication information including the access point name (APN), user name, and password of the router.
3. The PGW authenticates the router's identity. After the router is successfully authenticated, the PGW establishes a connection with the 5G modem and assigns an IP address to the 5G modem.
4. The 5G modem instructs the cellular interface to go Up physically.
5. The cellular interface negotiates with the 5G modem to obtain the IP address assigned by the PGW.
6. The cellular interface establishes a connection with the PGW for data service forwarding.