#Checksum definition how to
#Checksum definition driver

Jumbo frames is a NIC and network feature that allows an application to send frames that are much larger than the default 1500 bytes. High performance or low latency applications may need to evaluate the impact of disabling or reducing Interrupt Moderation. Generally, packet processing is more efficient with Interrupt Moderation enabled. There is a balance to be struck between reducing interrupts and excessively delaying packet delivery. The different rates represent shorter or longer timers and appropriate buffer size adjustments to reduce latency (low interrupt moderation) or reduce interrupts (high interrupt moderation). Most NICs support the concepts of a low, medium, and high rate for IM. Many NICs support more than just on/off for Interrupt Moderation. When the buffer is full, or the timer expires, whichever comes first, the NIC interrupts the operating system. When a NIC receives a packet, it starts a timer.

IM buffers multiple received packets before interrupting the operating system. Checksum offloading is also required for other stateless offloads to work including receive side scaling (RSS), receive segment coalescing (RSC), and large send offload (LSO). This most basic of all offload technologies always improve your network performance. For example, the following cmdlet enables the TCP (IPv4) and UDP (IPv4) checksum calculations: Enable-NetAdapterChecksumOffload –Name * -TcpIPv4 -UdpIPv4Īddress Checksum Offloads should ALWAYS be enabled no matter what workload or circumstance. The Checksum Offloads can be managed using the Enable-NetAdapterChecksumOffload and Disable-NetAdapterChecksumOffload cmdlets. We recommend always enabling all of these offloads. In the Advanced Properties there are several distinct properties:īy default, these are all always enabled. To disable all checksum offload calculations, the user must also disable LSO.

#Checksum definition driver

On the send path, the checksum offload calculates and inserts the checksums into the IP, TCP, or UDP header as appropriate.ĭisabling checksum offloads on the send path does not disable checksum calculation and insertion for packets sent to the miniport driver using the Large Send Offload (LSO) feature. If the computed checksum fails, the packet gets discarded. If the NIC asserts the checksums are invalid or not checked, the IP/TCP/UDP stack internally calculates the checksums again. If the NIC asserts that the checksums are valid, the OS accepts the packet unchallenged. On the receive path, the checksum offload calculates the checksums in the IP, TCP, and UDP headers (as appropriate) and indicates to the OS whether the checksums passed, failed, or not checked. Address Checksum OffloadĪddress checksum offloads are a NIC feature that offloads the calculation of address checksums (IP, TCP, UDP) to the NIC hardware for both send and receive.

#Checksum definition how to

The feature descriptions below will cover how to tell if your NIC supports the feature. SH and HO features are available if the installed NIC supports it.