Selective underflow protection in a network switch

摘要

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.

主权项

1. A computer-implemented method to reduce incidence of intra-packet transmission gaps unsupported by a link protocol used by a network switch in transmitting packets, the computer-implemented method comprising:
determining whether each of a plurality of incoming packets satisfies the underflow risk condition, by evaluating, for each of one or more cycles since receipt of one or more flow control digits (flits) of the respective incoming packet, a count of flits of the respective incoming packet received by the network switch in the respective cycle; upon determining that a first of the plurality of incoming packets satisfies the underflow risk condition, providing selective underflow protection for the first incoming packet by buffering at least an increased count of flits of the first incoming packet, prior to commencing transmission of the first incoming packet and by operation of one or more computer processors; upon determining that a second of the plurality of incoming packets does not satisfy the underflow risk condition, refraining from selective underflow protection for the second incoming packet, by buffering no more than a reduced count, relative to the increased count, of flits of the second incoming packet, prior to commencing transmission of the second incoming packet; and transmitting the first and second incoming packets according to the link protocol, without any intra-packet transmission gaps unsupported by the link protocol, and without having to buffer more than the reduced count of flits for every one of the plurality of incoming packets.