To increase its performance, the Microsoft TCP/IP transport can offload one or more of the following tasks to a NIC that has the appropriate task-offload capabilities:

• Checksum tasks.

  The TCP/IP transport can offload the calculation and/or validation of IP and/or TCP checksums.

• Internet Protocol Security tasks

  The TCP/IP transport can offload the calculation and validation of encrypted checksums for authentication headers (AH) and/or encapsulating security payloads (ESP). The TCP/IP transport can also offload the encryption and decryption of ESP payloads. In addition, the transport can offload the encryption and decryption of UDP-encapsulated ESP data packets.

• Segmentation of large TCP packets

  The TCP/IP transport supports Large Send Offload (LSO). With LSO, the TCP/IP transport can offload the segmentation of large TCP packets.

The TCP/IP transport supports task offload only for IPv4 packets.

Offloading tasks from the TCP/IP transport to a NIC involves two major operations:

• Querying and enabling a NIC's task-offload capabilities. For more information, see Querying Task-Offload Capabilities and Enabling Task-Offload Capabilities.
• Passing per-packet information (extended out-of-band data) related to offloaded tasks. For more information, see Accessing Per-Packet Information, Offloading TCP/IP Checksum Tasks, Offloading IPsec Tasks, and Offloading the Segmentation of Large TCP Packets.