$4\mathrm{.}05-3.$ Generalized forwarding: specifying a flow table entry $($c$).$ Consider the three$-$node network below, that uses flow$-$based generalized forwarding $($e$.$g$.,$ as in OpenFlow$)$ in the network's routers. In the question below, we'll want to create match$+$action entries in the flow table at router $r2,$ with three ports Jabelled $1,2,3($in black$).$ In the question, matches are constrained to be over only four fields: the IP source address, the IP destination address, the upper$-$layer protocol field of the IP datagram, and the destination port number of the transport$-$layer segment. The actions are either to drop or to forward $(i),$ that is$,$ to forward a matching packet on port $i.$ The default action $($unless stated otherwise$)$ is that if a packet doesn't match a rule, it will be dropped.