Section: 12.3.9.3.2 Based on procedures
Content: Message prioritization may be performed based on the relative priority of the procedure for which the message is being sent. Procedures are grouped into various categories and each of these categories is assigned a priority. Additionally, within a given category of procedures, messages may be further prioritized based on session parameters such as: APN, QCI, ARP and/or LAPI (as described in clause 12.3.9.3.3). Subsequently, messages with a high priority shall be given lower preference to throttle and messages with low priority shall be given higher preference to throttle. The grouping of the procedures is not performed based on an individual GTP-C entity but whilst considering all the procedures in general. A GTP-C entity should consider the procedures applicable to it and apply prioritized message throttling based on the category of the procedure, as described below. The categories are listed in decreasing order of priority with category 1 having the highest priority. For each category a non-exhaustive list of messages is provided. Any existing or newly defined message in future should be considered based on the category (as specified below) of the procedure for which the message is sent. 1. UE session mobility within and across 3GPP or non-3GPP access: Procedures involving active or idle mode UE mobility, such that GTP-C signalling is involved, shall be classified under this category. Some examples are X2/S1 based handover with/without an SGW change, TAU/RAU with a change of MME/SGSN with/without an SGW change, 3GPP access to trusted non-3GPP access handover, etc. Throttling of these messages, during the procedures related to UE session mobility, would result in the failure of the corresponding procedures. This could result potentially in the loss of the PDN connection and/or the interruption of the services. Hence, the messages, as identified below, when sent during the procedures belonging to this category, shall be considered with the highest priority and hence, shall be given the lowest preference to throttle. - Create Session Request, - Create Session Request with "handover" indication bit set, - Modify Bearer Request, - Modify Bearer Request with "handover" indication bit set, - Modify Access Bearer Request. 2. Release of PDN connection or bearer resources: Procedures resulting in the deactivation of an existing PDN connection, the deactivation of bearer(s) or of data forwarding tunnel of an UE leads to freeing up of the resources at the overloaded node and hence, can potentially ease the overload situation, since the freed up resources can be used for serving the remaining of the UEs. Thus, the messages belonging to this category resulting in the deactivation of PDN connection or bearer(s) or data forwarding tunnel(s), as identified below, shall be treated with the next lower level of priority and hence shall be given the corresponding preference whilst throttling: - Delete Session Request, - Delete Bearer Request, - Delete Bearer Command, - Delete Indirect Data Forwarding Tunnel Request. 3. Miscellaneous session management procedures: This category shall consist of the session management procedures, except PDN connection creation and bearer creation/modification procedures. Some examples are location reporting, when it is not combined with other mobility procedures, Service request and S1 release procedure. These procedures do not severely impact the on-going service of the UE. Hence, the messages, as identified below, when sent during the procedures identified under this category, shall be treated with the next lower level of priority and hence, shall be given the corresponding preference whilst throttling: - Release Access Bearer Request, - Modify Bearer Request, - Change Notification, - Suspend Notification, - Resume Notification. 4. Request for new PDN Connection or bearer resources: Procedures requesting the creation of PDN connection, creation or modification of bearer(s) or creation of data forwarding tunnel shall be classified in this category. Throttling of the messages belonging to this category would result in denial of new services while continuing with the existing services. However, this is the natural outcome of an overload condition, i.e. the overloaded node, due to lack of resources, is not able to provision new services while the trying to maintain the existing services and hence, the messages, as identified below, when sent during the procedures belonging to this category, shall be considered with the lowest level of priority and hence shall be given highest preference to throttle: - Create Session Request during PDN connection request, - Create Bearer Request, - Update Bearer Request, - Bearer Resource Command, - Modify Bearer Command, - Create Indirect Data Forwarding Tunnel Request.