Section: 12.2.4.2 Justifications for APN load control support
Content: Following are the justifications to support the APN level load control in the network when the pre-condition specified in 12.2.3.1 is applicable: 1) To achieve load balancing at the APN level granularity: The PGW may be configured to handle more than one APN in the network. In such a case, the PGW may be additionally configured to allocate different resources for each of the configured APNs, e.g. the PGW may be configured to handle "X" number of sessions for the "consumer" APN and to handle "Y" number of session for the "corporate" APN. The ratio of this limit, i.e. "X" and "Y", to the PGW's capacity may not be the same across all the PGWs in the network. In this case, the load information with node level granularity is not sufficient and could result in a network where one PGW has more sessions for the "consumer" APN while another PGW has more sessions for the "corporate" APN. Thus, an evenly load balanced network at APN level load granularity cannot be realized. 2) To ensure effective overload control in the network: If the distribution of sessions at APN level is uneven, then there is a higher risk of overload of some PGWs, as compared to other PGWs, e.g. the PGW handling more sessions for "consumer" APN may have to handle more messages, (e.g. generated due to mobility events resulting from a change of ULI, RAT type, Serving GW, etc.) as compared to the PGW handling more sessions for the "stationary-machine" APN. Hence, the PGW handling "consumer" APN sessions may be at higher risk of overload, as compared to the other PGWs in the network, and hence, this situation may result in poor overload control of the network. 3) To ensure an efficient node selection algorithm: Based on the node level load information, the source node, (e.g. the MME) may end-up selecting the PGW for a new session for the given APN. However, the selected PGW may reject the new session request, if it is running at 100% load capacity for the given APN, or the new session request may be throttled by the source node based on the overload information of the APN for the given PGW. Thus the new session request may be denied, (i.e. rejected by the selected PGW or throttled by the source node based on PGW's APN level overload information) while the other PGW may have the capacity to handle the same. Thus, the lack of APN level load information may result in inefficient node selection algorithm by the source node.