Ethernet Support Guide for HP-UX 11i v3

Example 17 Setting UDP multifragment CKO for ixgbe drivers
The ixgbe driver supports UDP IPv4 multifragment checksum offload. The configuration parameter
for setting multifragment checksum offload is HP_IXGBE_UDP_MF_CHECKSUM_OFFLOAD. The
nwmgr parameter is udpmf_cko. To enable or disable the feature, set the parameter to ON or
OFF. The receive and transmit CKO parameters must both be enabled.
Example 18 Setting TCP/UDP multifragment CKO for icxgbe drivers
The icxgbe driver supports TCP/UDP IPv4 multifragment checksum offload. You can set this feature
individually for receive and transmit. The icxgbe configuration file parameters are
HP_ICXGBE_CKO_IPV4_MF_RX and HP_ICXGBE_CKO_IPV4_MF_TX. The nwmgr parameters
for receive and transmit multifragment CKO are rxmf_cko and txmf_cko, respectively. You can
enable or disable the feature by setting parameters to ON or OFF. The corresponding receive and
transmit CKO parameters must also be enabled.
3.10 Displaying and setting the TCP segmentation offload (TSO)/Virtual
MTU parameter
Transmit TCP segmentation offload (TSO) is a mechanism by which the host stack offloads certain
portions of outbound TCP packet processing to the NIC, thereby reducing host CPU utilization.
This functionality can significantly reduce the load on the host for certain applications that primarily
transmit large amounts of data from the system. Examples include web serving and file transfer
applications. All HP drivers discussed in this document support TSO except btlan and gelan.
How TSO Works
The reduction in CPU utilization is achieved primarily by allowing the host to transmit large frames
(frames larger than the link's MTU) to the NIC. The NIC subsequently segments the frames into
smaller, MTU-sized frames, before transmitting them on the wire. Thus instead of processing many
small MTU-sized frames during transmit, the host sends fewer of the larger VMTU (Virtual MTU)
sized frames, thereby increasing the efficiency of the data transfer in the host. The VMTU is typically
much larger than the link MTU; for example, on a typical Ethernet card, the link MTU is 1500 bytes
while a VMTU could be as large as 32 Kbytes.
NOTE: TSO is settable for TCP/IP IPv4 only. Not all applications benefit from the TSO mechanism.
Only data intensive applications that transmit large data buffers using TCP over IPv4 are improved.
Other types of applications will not significantly benefit from the TSO mechanism. Performance
improvements vary depending upon the platform used.
34 Setting and displaying driver Ethernet parameters