6.2 IP connectivity
6.2.1 ASN/MN-CSE Pre-configuration
The ASN/MN-CSE or ADN-AE is preconfigured with the fully qualified domain name (FQDN) of the serving CSE (SCS) or the IP address of the serving CSE (SCS). If the FQDN is known, DNS resolution is used to obtain the IP address.
6.2.2 ASN/MN-CSE or ADN-AE Initiated Connectivity Establishment Procedure
Figure 6.2.2-1: ASN/MN-CSE or ADN-AE initiated connectivity establishment
Step-0: Trigger
Subsequent procedures are triggered either when the ASN/MN-CSE or ADN-AE powers on or resulting from Device Triggering
Step-1: Bearer Setup Procedure
Establish a 3GPP bearer(s) if not already available by using the procedures available in the underlying 3GPP network.
Step-2: DHCP Query & Response
The ASN/MN-CSE or ADN-AE sends a query to a DHCP server to find a particular DNS server IP address. The DHCP server responds with the IP address of a corresponding DNS server. Additionally, it is also possible to include one or a list of domain names, i.e. FQDNs of target CSEs (SCS).
Step-3: DNS Query & Response
The ASN/MN-CSE or ADN-AE performs a DNS query to retrieve the CSE(s) (SCS) IP addresses from which one is selected. If the response does not contain the IP addresses, an additional DNS query is needed to resolve a Fully Qualified Domain Name (FQDN) of the serving CSE (SCS) to an IP address.
Step-4: Connection Establishment
After reception of domain name and IP address of an CSE (SCS), the ASN/MN-CSE or ADN-AE can initiate communication towards the CSE (SCS) via the IP connection. The CSE (SCS) at this time shall be informed which Trigger Recipient ID of the ASN/MN-CSE or ADN-AE or the AE-PoA of the ADN-AE to use for establishing communication.
Step-5: CSE- PoA Update
Once the M2M Service Connection (Mcc or Mca) is established to the CSE (SCS), the CSE-PoA of the ASN-CSE/MN-CSE or the AE-PoA of the ADN-AE shall be updated with the new established IP address.
6.2.3 CSE (SCS) initiated connectivity establishment procedure
See clause 7.1 for NIDD based connection establishment and clause 7.5 for 3GPP Based Device Triggering.