1. A method comprising: (a) receiving at a first node in a network a first message from a second node in said network, wherein said first message is for establishing a route in said network from a source node in said network to a destination node in said network, and wherein said first message comprises (i) a route R from said source node to said second node, and (ii) a value of a load metric at one or more nodes in said route R; (b) determining the value W of said load metric at said first node; (c) receiving at said first node from a third node in said network, after the receipt of said first message, a second message that is for establishing the route in said network from said source node to said destination node; and (d) inferring, after the receipt of said second message, that said second node did not receive a third message transmitted by said first node, when: (i) said first message indicates a value Y for said load metric at said second node; (ii) said first message indicates a value X for said load metric summed over the nodes in said route R; (iii) said second message comprises a route S that starts from said source node and does not include said second node; (iv) said second message indicates a value L for said load metric summed over the nodes in said route S; and (v) L+W+Y<X.