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Network Configuration—BasicsHardware OffloadingYou can offload some processor-intensive tasks to your network interface cards, ifyour network interface can support it. Offloading increases the network performanceby releasing more CPU resources for applications and performs some network tasksin the network interface hardware-level.This includes offloading TCP/IP checksum calculations, TCP segmentation, VLANtagging, and TCP Large Receive offloading.You can use ifconfig –m to find out which options are supported by yournetwork interface.For example, on a bge interface, it would look like following:# ifconfig -m bge0 | grep capcapabilities=9bIn the above example, the bge supports RXCSUM and TXCSUM, that are checksumoffloading for RX and TX traffic respectively. To enable RXCSUM on this interfaceyou may use the following command:# ifconfig bge0 rxcsumOr to disable RXCSUM you may use the following command:# ifconfig bge0 –rxcsumThe same applies to TXCSUM. You can also enable or disable both RXCSUM andTXCSUM, together, using the hwcsum flag. For example, the following commandenables both RXCSUM and TXCSUM on the bge0 interface:# ifconfig bge0 hwcsumTCP Segmentation Offloading (TSO) and Large Receive Offloading (LRO) are alsotwo Intel-specific hardware offloading features that allow some layer4 segmentationto be offloaded to the network interface hardware. Currently only the em(4) driversupports these features. In order to enable TSO and LRO on an interface, you mayuse the following commands respectively:# ifconfig em0 tso# ifconfig em0 lro[ 114 ]