This technical document describes how to temporarily enable or disable LSO on IBM i Ethernet resources.
A hosted partition may experience communication problems when delivering frames to a Virtual Input/Output Server (VIOS) Shared Ethernet Adapter (SEA). The VIOS SEA may discard frames that it receives when large send offload is enabled. The following problems have been seen when large send offload is enabled on virtual ethernet resources:
1. Discarded IP Packets
2. Retransmitted TCP Segments
3. Performance Problems On TCP Connections
4. TCP Connections Terminated Prematurely
A support representative may request that large send offload be disabled to help with problem determination.
Resolving The Problem
Disabling large send offload on virtual ethernet resources that deliver frames to SEA's can at times stabilize TCP/IP connections. For more information about the specific steps required to disable large send offload on IBM i ethernet resources, please refer to the video below:
Please note that disabling Large Send Offload (LSO) is only a temporary measure. It will be re-enabled automatically during an IPL. This method of disabling LSO is only intended to provide support with an indication of whether an issue may be caused by LSO being enabled.
22 January 2021