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TCP segmentation offload assisted TCP Large Receive offload Disclosure Number: IPCOM000198317D
Publication Date: 2010-Aug-04
Document File: 2 page(s) / 33K

Publishing Venue

The Prior Art Database


Disclosed is an invention for an improved method for a TCP segmentation offload receiver to recognize how long to wait for the arrival of more packets belonging to a current connection.

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TCP segmentation offload assisted TCP Large Receive offload

A Large Receive Offload (LRO) approach to Transmission Control Protocol (TCP) addresses the problem of inadequate receiver Central Processing Unit (CPU) bandwidth to manage a stateless offload that prevents 10 GbE adapters from reaching line rate with 1500 MTU. The approach also reduces TCP processing overhead on the receiver.*

With this feature, the Ethernet adapter coalesces incoming packets belonging to the same TCP connection as much as possible and transfers a large packet to Internet Protocol (IP) and TCP. To recognize the length of time it should wait for more packets belonging to the same connection, and to exit the coalescing mode, it uses either a timer or the arrival of a packet belonging to a different connection.

The problem with this method is that when the sender executes TCP segmentation offload the receiver may not recognize the need to wait for more packet arrivals; the receiver could either not wait long enough or could wait too long for more packets to arrive. When the sending side executes TCP segmentation offload or TCP large send, the risk of this method is sub-optimal performance.

Ethernet adapters do not support TCP URGENT pointers and the URGENT (URG) flag in their TCP large send implementation. This allows developers to make use of this field for the purpose of passing the suggested size for large receive offload. The procedure is as follows:

When TCP executes large send, the s...