Session and Service Continuity

The Session and Service Continuity (SSC) support in 5G system architecture enables to address the various continuity requirements of different applications and services for the User Equipment (UE). The 5G system supports different SSC modes. The SSC mode associated with a PDU session does not change during the lifespan of a PDU session. The following three modes are specified:

  • With SSC mode 1, the network preserves the connectivity service provided to the UE. For the case of PDU session of IPv4 or IPv6 or IPv4v6 type, the IP address is preserved.

  • With SSC mode 2, the network may release the connectivity service delivered to the UE and also may release the corresponding PDU session(s). For the case of IPv4 or IPv6 or IPv4v6 type, the release of the PDU session induces the release of IP address(s) that had been allocated to the UE.

  • With SSC mode 3, changes to the user plane can be visible to the UE, while the network ensures that the UE suffers no loss of connectivity. A connection through new PDU session anchor point is established before the previous connection is terminated in order to allow for better service continuity. For the case of IPv4 or IPv6 or IPv4v6 type, the IP address is not preserved in this mode when the PDU session anchor changes.