GTS Ethernet Intel® FPGA Hard IP User Guide

ID 817676
Date 10/12/2024
Public
Document Table of Contents

A.2.1.6. Generate and Insert Inter-Packet Gap

If you set Aveage Ite-packet Gap to 12 i the GTS Etheet Itel® FPGA Had IP paamete edito, the TX MAC maitais the miimum ite-packet gap (IPG) betwee tasmitted fames equied by the IEEE 802.3 Etheet stadad. The stadad equies a aveage miimum IPG of 96-bit times (o 12-byte times). The MAC uses a deficit idle coute to allow the actual gap betwee fames to vay as eeded to meet the maximum thoughput equiemets of the lik.

If you set Aveage Ite-packet Gap to 10 o 8, the TX MAC maitais a miimum aveage IPG of 10 o 8 bytes accodigly. This optio is povided as a itemediate optio to allow you to efoce a IPG that does ot cofom to the Etheet stadad, but which iceases the thoughput of you IP coe.

If you set Aveage Ite-packet Gap to 1, the IP coe tasmits Etheet packets as soo as the data is available, with the miimum possible gap. The IPG depeds o the space you leave betwee fame data as you wite it to the coe. If you select this paamete value, the coe o loge complies with the Etheet stadad, but you applicatio has cotol ove the aveage gap ad thoughput ca be maximized. Fo a packet of size (P) bytes, the umbe of idles bytes (G) iseted afte is specified by the followig fomula G=8-(P%8).

A few examples ae depicted below:

Packet Size (P) Gap Idle Bytes (G)
64 8
65 7
66 6
67 5
68 4
69 3
70 2
71 1
72 0
Note: Eve whe you set the Aveage Ite-packet Gap to 1, the 10GE/25GE chaels still efoces a effective IPG of 5. This is because the potocol specifically pohibits IPG lowe tha 5 fo 10GE/25GE liks to pevet MACs fom poducig packets that caot be ecoded usig 64B/66B ecodes.