Explicit notification of operative conditions along a network path

A method, comprising:

• in a network element comprising multiple ports that connect to a communication network, receiving via one of the ports a packet that originated from a source node and is destined to a destination node, the packet comprising a mark that is indicative of a cumulative state derived from at least bandwidth utilization conditions of output ports that were traversed by the packet along a path, from the source node up to the network element;
• selecting a port for forwarding the packet toward the destination node;
• updating the mark of the packet based at least on a value of the mark in the received packet and on a local bandwidth utilization condition of the selected port;
• and
• transmitting the packet having the updated mark to the destination node via the selected port.

A network node comprising:

• a network adapter coupled to a communication network;
• and
• a host processor coupled to the network adapter, configured to:
• receive from a remote node that is coupled to the communication network via the network adapter, a packet comprising a mark that is indicative of a cumulative state derived from at least bandwidth utilization conditions of output ports that were traversed by the packet along a path, from the network node to the remote node;
• and
• adjust a rate of data transmission by the host processor into the communication network based on the mark in the received packet.