Editing IP Multimedia Subsystem (section)

=== NGN interconnection <span class="anchor" id="SoIx"></span><span class="anchor" id="CoIx"></span><!-- these are redirected here for definitional treatment --> ===
There are two types of [[Next Generation Networking|next-generation networking]] interconnection:
* '''Service-oriented interconnection''' (SoIx): The physical and logical linking of NGN domains that allows carriers and service providers to offer services over NGN (i.e., IMS and PES) platforms with control, signalling (i.e., session based), which provides defined levels of interoperability. For instance, this is the case of "carrier grade" voice and/or multimedia services over IP interconnection. "Defined levels of interoperability" are dependent upon the service or the QoS or the Security, etc.
* '''Connectivity-oriented interconnection''' (CoIx): The physical and logical linking of carriers and service providers based on simple IP connectivity irrespective of the levels of interoperability. For example, an IP interconnection of this type is not aware of the specific end to end service and, as a consequence, service specific network performance, QoS and security requirements are not necessarily assured. This definition does not exclude that some services may provide a defined level of interoperability. However, only SoIx fully satisfies NGN interoperability requirements.

An NGN interconnection mode can be direct or indirect. Direct interconnection refers to the interconnection between two network domains without any intermediate network domain. Indirect interconnection at one layer refers to the interconnection between two network domains with one or more  intermediate network domain(s) acting as [[transit network]]s. The intermediate network domain(s) provide(s) transit functionality to the two other network domains. Different interconnection modes may be used for carrying [[service layer]] signalling and media traffic.