scope:

There has been a trend towards virtualized or "cloud" based networks where a physical device or network hosts several virtual instances meeting the needs of different customers. Different service models exist, usually utilising the terminology "X - as a service (xASS)" e.g. PAAS "Platform as a service", IAAS "Infrastructure as a service".

A common aspect of the different cloud service models is that a certain set of resources is allocated (via operations and maintenance (O&M) system) based on a set of requirements from a customer. These requirements may detail the applications, libraries, data, memory, processing resources, storage and associated configuration settings.

One of the main concepts of H.248 is the use of the "virtual media gateway (VMG)". This allows multiple virtual MG instances per physical MG. Each VMG is treated as separate MG instance and thus has its own control association and set of resources, configurations etc. Thus, it has similarities to cloud virtualisation concepts.

H.248 is largely silent on provisioning resources for VMGs, apart from clause 11.1/[ITU-T H.248.1], which states that the mechanism for allocating terminations to VMGs is a management method outside the scope of H.248.1. Whilst the provisioning of Terminations is out of scope of H.248, it does have the "H.248 Profile" concept. Profiles specify what options associated with [ITU-T H.248.1] have been used. [ITU-T H.248.1] Appendix III provides an example profile template showing the information that can be derived from the profile ID. H.248 Profiles when used by a (V)MG indicates what H.248 elements can be used. Profiles have been defined by several standards development organisations (e.g. 3GPP, ETSI TISPAN, MSF) and several vendors to define the H.248 functionality of certain interfaces.

H.248 provides an abstraction model for a MGC to access and control physical resources on a MG without having to address these physical resources. The concepts of Contexts, Terminations, Streams and Descriptors are used. Whilst Terminations are typically statically provisioned, the underlying resources may be statically or dynamically allocated between the VMGs. The physical resources may relate to CPU, DSP, memory, storage or power use. So whilst the H.248 options defined by a H.248 Profile are related to these resources there is not a one to one mapping due to the abstraction layer. Some form of provisioning is required to assign the physical resources to a VMG instance.

H.248 allows a MG and MGC to negotiate the use of a certain profile (functionality set) via the use of the ServiceChangeProfile parameter (see clause 7.2.8.1.5/[ITU-T H.248.1]). An example profile is the Mn interface (profile name: threegbicsn) defined by [b-3GPP TS 29.232]. However this does not identify a particular resource profile. The MGC cannot deduce from the profile name how resources are provisioned on the (V)MG. The set of provisioned resources could be tied the media gateway identity (H.248 Mid) but this unnecessarily ties transport network configuration to MG hardware configuration. Many H.248 packages specify a default of "provisioned" for the elements defined by the package. It assumed that these are co-ordinated via other provisioning means (e.g. SNMP MIBs). As a H.248 MG can be provisioned with different sets of resources per H.248 Profile Name and/or Mid another form of correlation identity between the MGC and MG to coordinate what has been provisioned is required.

This identifier can be used by network operators as a pointer to set of provisioned configuration data. Upon reception of the identifier the MGC can uniquely identify the provisioned defaults and other configuration data and then request (V)MG resources accordingly.

This Recommendation defines functionality that allows an MG to indicate to an MGC what Media Gateway Instance is in use. It also allows an MGC to audit an MG to determine the MG Instance in use. This Recommendation utilises a ServiceChangeExtension parameter that allows the MG Instance to be reported during an initial ServiceChange command exchange. A H.248 package is defined to allow an MGC to audit packages to determine if the MG Instance functionality is supported. It also allows the auditing of a root Termination property to determine the MG instance.