Techniques are disclosed to transmit packets by a network switch and according to a link protocol while reducing incidence of intra-packet transmission gaps unsupported by the link protocol. Whether a packet satisfies an underflow risk condition is determined by evaluating, for each of one or more cycles since receipt of one or more flits of the packet, a respective count of flits of the packet received by the network switch in the respective cycle. Only upon determining that the packet satisfies the underflow risk condition is selective underflow protection performed for the packet, including buffering an increased count of flits of the packet, prior to commencing transmission of the packet.