
Solarflare
Server
Adapter
User
Guide
Solarflare
Adapters
on
Windows
Issue
20
©
Solarflare
Communications
2017
233
The
Solarflare
network
adapter
driver
enables
RSC
by
default.
RSC
is
set
by
changing
the
Receive
Segment
Coalescing
settings
in
the
Network
Adapter’s
Advanced
Properties
Page.
TCP
and
IP
checksum
offloads
must
be
enabled
for
RSC
to
work.
Large
Receive
Offload
(LRO)
Large
Receive
Offload
(LRO)
is
a
feature
whereby
the
adapter
coalesces
multiple
packets
received
on
a
TCP
connection
into
a
single
larger
packet
before
passing
this
onto
the
network
stack
for
receive
processing.
This
reduces
CPU
utilization
and
improves
peak
throughput
when
the
CPU
is
fully
utilized.
The
effectiveness
of
LRO
is
bounded
by
the
interrupt
moderation
delay,
and
is
limited
if
interrupt
moderation
is
disabled
(see
).
Enabling
LRO
does
not
itself
negatively
impact
latency.
LRO
is
a
Solarflare
proprietary
mechanism
similar
to
the
Windows
Receive
Segment
Coalescing
feature.
Windows
Server
2012
and
newer
use
RSC
instead
of
LRO,
and
do
not
support
LRO.
Older
Windows
versions
that
do
not
support
RSC
may
use
LRO
instead.
The
Solarflare
network
adapter
driver
disables
LRO
by
default.
NOTE:
LRO
should
NOT
be
enabled
when
using
the
host
to
forward
packets
from
one
interface
to
another.
For
example,
if
the
host
is
performing
IP
routing.
LRO
is
set
by
changing
the
Large
Receive
Offload
settings
in
the
Network
Adapter’s
Advanced
Properties
Page.
TCP
and
IP
checksum
offloads
must
be
enabled
for
LRO
to
work.
Receive
Side
Scaling
(RSS)
Receive
Side
Scaling
(RSS)
was
first
supported
as
part
of
the
scalable
networking
pack
for
Windows
Server
2003
and
has
been
improved
with
each
subsequent
operating
system
release.
RSS
is
enabled
by
default
and
will
be
used
on
network
adapters
that
support
it.
Solarflare
recommend
that
RSS
is
enabled
for
best
networking
performance.
For
further
information
about
using
RSS
on
Windows
platforms
see
the
Microsoft
white
paper
“Scalable
Networking:
Eliminating
the
Receive
Processing
Bottleneck—
Introducing
RSS”
This
is
available
from:
http://download.microsoft.com/download/5/D/6/5D6EAF2B
Specific
RSS
parameters
can
be
tuned
on
a
per
‐
adapter
basis.
For
details
see
the
Microsoft
white
paper
“Networking
Deployment
Guide:
Deploying
High
‐
Speed
Networking
Features”
available
from: