Red Hat ENTERPRISE LINUX 5 - VIRTUALIZATION GUIDE Manual page 198

Chapter 12. KVM Para-virtualized Drivers
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Performance setting
b.
This screen configures advanced TCP settings for the network driver. TCP timestamps and
TCP window scaling can be enabled or disabled. The default is, 1, for window scaling to be
enabled.
TCP window scaling is covered by
the receive window size to a size greater than the default maximum of 65,535 bytes up to a
new maximum of 1 gigabyte (1,073,741,824 bytes). TCP window scaling allows networks to
transfer at closer to theoretical network bandwidth limits. Larger receive windows may not be
supported by some networking hardware or operating systems.
TCP timestamps are also defined by
calculate Return Travel Time estimates by embedding timing information is embedded in
packets. TCP timestamps help the system to adapt to changing traffic levels and avoid
congestion issues on busy networks.
Value
0
1
2
3
184
2
IETF RFC 1323
. The RFC defines a method of increasing
3
IETF RFC 1323
. TCP timestamps are used to better
Action
Disable TCP timestamps and window scaling.
Enable TCP window scaling.
Enable TCP timestamps.
Enable TCP timestamps and window scaling.