Examples described herein include configuration of a transmitting network device to identify a source queue-pair identifier in at least some of the packets that are transmitted to an endpoint destination. A network device that receives packets and experiences congestion can determine if a congestion causing packet includes a source queue-pair identifier. If the congestion causing packet includes a source queue-pair identifier, the network device can form and transmit a congestion notification message with a copy of the source queue-pair identifier to the transmitting network device. The transmitting network device can access a context for the congestion causing packet using the source queue-pair identifier without having to perform a lookup to identify the context.