Low Latency Ethernet 10G MAC Intel® FPGA IP User Guide

ID 683426
Date 3/01/2022
Public
Document Table of Contents

4.5.4. Frame Type Checking

The MAC RX checks the length/type field to determine the frame type:

  • Length/type < 0x600—The field represents the payload length of a basic Ethernet frame. The MAC RX continues to check the frame and payload lengths.
  • Length/type >= 0x600—The field represents the frame type.
    • Length/type = 0x8100—VLAN or stacked VLAN tagged frames (up to a total of two tags with value 0x8100). The MAC RX continues to check the frame and payload lengths.
    • Length/type = 0x8808—Control frames. The next two bytes are the Opcode field which indicates the type of control frame. For pause frames (Opcode = 0x0001) and PFC frames (Opcode = 0x0101), the MAC RX proceeds with pause frame processing. By default, the MAC RX drops all control frames. If configured otherwise (FWD_CONTROL bit in the rx_frame_control register = 1), the MAC RX forwards control frames to the client.
    • For other field values, the MAC RX forwards the receive frame to the client.
Table 16.  MAC Behavior for Different Frame Types
Category Packet Size Length/Type = Payload Length/Type > Payload Length/Type < Payload MAC Behavior
Frame Drop avalon_st_rx_error[]
Normal packet 64–1518 Yes No No No
No No Yes No
No Yes No No

avalon_st_rx_error[4] = 1

Undersized Packet < 64 Yes No No No

avalon_st_rx_error[2] = 1

No No Yes No
No Yes No No

avalon_st_rx_error[2] = 1

avalon_st_rx_error[4] = 1

Oversized 1518 < Packet < 1535 Yes No No No

avalon_st_rx_error[3] = 1

No No Yes No
No Yes No No

avalon_st_rx_error[3] = 1

avalon_st_rx_error[4] = 1

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