82598EB Datasheet, PDF (241/596 Pages) Intel Corporation – Intel® 82598EB 10 Gigabit Ethernet Controller Datasheet

Intel^® 82598EB 10 GbE Controller - Receive Functionality
3.5.2.12 Receive Checksum Offloading
The 82598 supports the offloading of four receive checksum calculations:
• Fragment Checksum
• IPv4 Header Checksum
• TCP Checksum
• UDP Checksum
For supported packet/frame types, the entire checksum calculation can be off-loaded to the 82598. The
82598 calculates the IPv4 checksum and indicates a pass/fail indication to software via the IPv4
Checksum Error bit (RDESC.IPE) in the Error field of the receive descriptor. Similarly, the 82598
calculates the TCP checksum and indicates a pass/fail condition to software via the TCP Checksum Error
bit (RDESC.TCPE). These error bits are valid when the respective status bits indicate the checksum was
calculated for the packet (RDESC.IPCS and RDESC.L4CS respectively). Similarly, if RFCTL.Ipv6_DIS and
RFCTL.IP6Xsum_DIS are cleared to zero the 82598 calculates the TCP or UDP checksum for IPv6
packets. It then indicates a pass/fail condition in the TCP/UDP Checksum Error bit (RDESC.TCPE).
Supported Frame Types:
• Ethernet II
• Ethernet SNAP
Table 3-59. Supported Receive Checksum Capabilities
Packet Type
Hardware IP Checksum
Calculation
IP header’s protocol field contains a protocol #
Yes
other than TCP or UDP.
IPv4 + TCP/UDP packets
Yes
IPv6 + TCP/UDP packets
No (n/a)
IPv4 Packet has IP options (IP header is longer
Yes
than 20 bytes)
IPv6 packet with next header options:
Hop-by-Hop options
Destinations options
Routing (with LEN 0)
Routing (with LEN >0)
Fragment
Home option
No (n/a)
No (n/a)
No (n/a)
No (n/a)
No (n/a)
No (n/a)
Packet has TCP or UDP options
Yes
IPv4 tunnels:
IPv4 packet in an IPv4 tunnel
IPv6 packet in an IPv4 tunnel
No
Yes (IPv4)
Hardware TCP/UDP Checksum
Calculation
No
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
Yes
No
No
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