Section: 12.3.10.2.3 Self-protection by the overloaded GTP-C entity
Content: A source GTP-C entity enforcing the overload control cannot ensure that the overloaded peer will not receive more messages than what it can handle during the overload condition, e.g. the "loss" algorithm does not guarantee that the future traffic reaches perfectly that requested by the overloaded GTP-C entity. Hence, the overloaded target GTP-C entity shall protect itself from the risk of meltdown even in a network where all the sending GTP-C entities support the overload control mechanism. As a part of this self-protection, the overloaded target GTP-C entity may reject the messages which it cannot handle during an overloaded state. A GTP-C entity which decides to not process an incoming request message due to overload should still send a reject response message, if possible, indicating the temporary unavailability of the resources; otherwise the request message may be dropped. NOTE: Without a response message, the source GTP-C entity cannot determine whether the request did not reach the target GTP-C entity due to a network error or whether the target GTP-C entity was in overload and not able to process the request and send a response message. This will cause the source GTP-C entity to retransmit the request message and hence will increase further the overload at the target node. The GTP-C entity may apply message prioritization as described in clause 12.3.9.3 when selecting the incoming request messages to be throttled. While rejecting the message due to overload, the GTP-C entity shall set the cause to "GTP-C Entity Congestion" or "APN congestion" (for node level or APN level overload respectively) and may include the Overload Control Information in the rejection response as specified in clauses 12.3.5.1.1 and 12.3.11.