MACsec Intel® FPGA IP User Guide

ID 736108
Date 10/21/2022

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6.1.7. Minimum Packet Size

The minimum packet size sent/received through Ethernet is always 64 bytes according to Ethernet specification. In the event where the packet originates from a host and is sent to the MACsec IP through PCIe (for example, SmartNIC use case), the packet size can be less than 64B. Packets less than 16B are not expected since the L2 frame size should be greater than 16 bytes. The MACsec IP does not operate correctly if the packet size is less than 16B, when protectFrames is configured to 0 where the packet is bypassed in the MACsec IP.

When the buffer in Multi Interface Buffering Mux is full and the last cycle contains a start of packet in the last segment, the Multi Interface Buffering Mux masks out the new packet to avoid truncating the packet and causing the packet size to be less than 16B.