5.3 Address management
23.2213GPPArchitectural requirementsRelease 17TS
A 3GPP network may be implemented as a number of logically separate IP networks which contain different parts of the overall system. Each of these elements is referred to as an "IP Addressing Domain". Within an "IP Addressing Domain" it is required that the nodes within the domain are part of a consistent non-overlapping IP-address space. It is also required that IP packets may be routed from any node in the domain to any other node in the domain using conventional IP routing. In a real implementation an IP Addressing Domain may be a physically separate IP network or an IP VPN.
IP Addressing Domains may be interconnected at various points. At these points of interconnect gateways, firewalls or NATs may be present. It is not guaranteed that IP packets from one IP Addressing Domain can be directly routed to any interconnected IP Addressing Domain. Rather inter-Domain traffic may be handled via firewalls or tunnels. This implies that different IP Addressing Domains can have different (and possibly overlapping) address spaces.
Figure 5-4 below shows an example of the IP Addressing Domains involved in PS-domain and IP-subsystem services.
Figure 5-4: IP Addressing Domains Involved In PS-Domain and IM Services
Though 3GPP networks can use different IP Addressing Domains as shown above, it is possible that several different IP Addressing Domains fall under a common co-operative management regime. In this case the different IP Addressing Domains may be implemented as a single administrative domain at the operator’s discretion, thus using a common IP-address space.
A UE accessing services in either an IM subsystem, the Internet, or an external Intranet, or a combination of these service domains within the same IP network, requires an IP address that is part of the target network’s IP Addressing Domain. For each of these IP networks, the IP address is linked to a specific PDP or EPS Bearer context, or set of PDP or EPS Bearer contexts sharing this IP address via a single APN.
When the UE establishes the PDP or EPS Bearer context to access an IP network, it may use an existing PDP or EPS Bearer context if it has an active context with a compatible IP addressing domain and quality of service profile.