The frame decoder performs frame classification to determine the applied protocols.
The frames are not modified by the frame decoder operation. The information is stored in a separate frame decoder status word forwarded together with the frame in the subsequent frame processing.
The following protocols are identified for the different layers:
- Layer 2 ISL encapsulation.
- Layer 2 VLAN tagging with up to 3 levels of VLAN tags, using a programmable TPID in addition to standard 0x8100 and 0x88A8.
- Layer 2 MPLS encapsulation with up to 7 MPLS labels. Any encapsulated packet under the MPLS label(s) is assumed to be IPv4 or IPv6.
- Layer 2 Ethernet frame is either of Ether II, IEEE 802.3 LLC, IEEE 802.3 with 802.2 SNAP header, PPPoE Discovery, PPPoE Session or Raw Novell type.
- Layer 3 packet is either of IPv4, IPv6 or other type.
- Layer 4 packet is either of TCP, UDP, ICMP, SCTP or other type.
- Only for PCIe Gen3 and PCIe Gen2 accelerators: Tunnel type is either GTPv0U, GTPv1v2-C, GTPv1-U_signaling, GTPv1-U_GPDU, IPinIP or other type. GTPv1-U_GPDU and IPinIP can hold tunneled IP packets.
- Tunnel type is either GTPv0U, GTPv1-C, GTPv2-C, GTPv1-U, GRE_v0, GRE_v1 (including NVGRE), IPinIP, EtherIP or other type. GTPv1-U, GRE, IPinIP and EtherIP can hold tunneled IP packets.
- Tunneled IP packets are identified for the following layers: Layer 2 is either VLAN, MPLS, EtherII or other type. Layer 3 is either IPv4, IPv6 or other type. Layer 4 is either TCP, UDP, ICMP, SCTP or other type.
Detailed description of frame classification is shown in Frame Classification.
Error indications indicated by the MAC are described in Error Indications.
Miscellaneous information about the frame is also provided:
- Ethernet frame broadcast address, when the destination MAC address is all 1s or, for an ISL-encapsulated frame, when the encapsulated frame is a broadcast frame.
- Ethernet frame multicast address, when the least significant bit of the most significant address octet of the destination MAC address is set to 1 or, for an ISL-encapsulated frame, when the encapsulated frame is a multicast frame.
Size information in extended packet descriptor 9
Information about the size of the frame is provided in extended packet descriptor 9:
- Jumbo frame, based on frame size and various configuration details
- IPv4/IPv6 header length
- Layer 4 header length (TCP, UDP, ICMP, SCTP)