Low Latency 40-Gbps Ethernet IP Core User Guide

ID 683745
Date 3/08/2021
Document Table of Contents Inter-Packet Gap Generation and Insertion

If you set Average interpacket gap to 12 in the LL 40GbE parameter editor, the TX MAC maintains the minimum inter-packet gap (IPG) between transmitted frames required by the IEEE 802.3 Ethernet standard. The standard requires an average minimum IPG of 96 bit times (or 12 byte times). The deficit idle counter maintains the average IPG of 12 bytes.

If you set Average interpacket gap to 8, the TX MAC maintains a minimum average IPG of 8 bytes. This option is provided as an intermediate option to allow you to enforce an IPG that does not conform to the Ethernet standard, but which increases the throughput of your IP core.

If you set Average interpacket gap to Disable deficit idle counter, the IP core transmits Ethernet packets as soon as the data is available, without maintaining the 12-byte IPG. In this case the IP core maintains only a minimum 1-byte IPG. If you select this parameter value, you optimize the IP core throughput.