Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 11/27/2024
Public
Document Table of Contents

5.1.6.5.4. Header and Payload Fields of Segmented Packets

After segmentation, the split packets use the same header as the parent TCP packet for header fields other than the ones described in the TSO: TCP and IP Header Fields table. The following figure shows how the same header is used for the header fields of segmented packets.

The application must create the header in buffer 1 of the first descriptor of the packet to be segmented and provide the header length in TDES2 of the first descriptor (FD = 1). When the FD bit is set, the DMA reads the header from the header buffer to which the TDES0 is pointing. Buffer 2 of the first descriptor can be used for the payload and TDES0 and TDES1 of subsequent descriptors. For subsequent descriptors (FD = 0), the address to which the TDES0 and TDES1 are pointing is treated as payload buffer address of the same packet.

Figure 75. Header and Payload Fields of Segmented Packets