Introduction to Technology
Gigabit Ethernet Overview
Chapter 1
19
NOTE Currently only two values are allowed for the tunable “vmtu”: 0 and 32160. Setting
“vmtu” to 0 (default) disables the TSO feature, and setting it to 32160 enables it.
Changes to the Output of Current Commands
If you are using NetTL or tcpdump to trace outbound packets may see differences from
current behavior. Tracing outbound packets in the host will display large packets (>
MTU size, as large as 64K) being transmitted on the link, while tracing the packets on
the wire or at the receiving end will display only packets that are lesser than or equal to
the link MTU size.
TSO Interaction with Other Software
TSO is supported on virtual LANs (VLANs). It is supported at all MTU values (that is,
TSO is supported over Jumbo frames) and speed settings on the link. Both Ethernet and
SNAP encapsulations are supported.
TSO is supported on link aggregations starting with the September 2004 version of the
HP Auto Port Aggregation [APA] product. For further details, please refer to the latest
release notes for the HP APA product. When used with HP APA product versions prior to
September 2004, the TSO functionality is automatically disabled on those link
aggregations.
