<s>
The	O
iSCSI	B-Protocol
Extensions	I-Protocol
for	I-Protocol
RDMA	I-Protocol
(	O
iSER	O
)	O
is	O
a	O
computer	O
network	O
protocol	O
that	O
extends	O
the	O
Internet	O
Small	B-Architecture
Computer	I-Architecture
System	I-Architecture
Interface	I-Architecture
(	O
iSCSI	B-Protocol
)	O
protocol	O
to	O
use	O
Remote	B-General_Concept
Direct	I-General_Concept
Memory	I-General_Concept
Access	I-General_Concept
(	O
RDMA	B-General_Concept
)	O
.	O
</s>
<s>
RDMA	B-General_Concept
is	O
provided	O
by	O
either	O
the	O
Transmission	B-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
TCP	O
)	O
with	O
RDMA	B-General_Concept
services	O
(	O
iWARP	B-Device
)	O
that	O
uses	O
existing	O
Ethernet	O
setup	O
and	O
therefore	O
no	O
need	O
of	O
huge	O
hardware	O
investment	O
,	O
RoCE	O
(	O
RDMA	B-Operating_System
over	I-Operating_System
Converged	I-Operating_System
Ethernet	I-Operating_System
)	O
that	O
does	O
not	O
need	O
the	O
TCP	O
layer	O
and	O
therefore	O
provides	O
lower	O
latency	O
,	O
or	O
InfiniBand	B-Architecture
.	O
</s>
<s>
It	O
permits	O
data	O
to	O
be	O
transferred	O
directly	O
into	O
and	O
out	O
of	O
SCSI	B-Architecture
computer	O
memory	O
buffers	O
(	O
which	O
connects	O
computers	O
to	O
storage	O
devices	O
)	O
without	O
intermediate	O
data	O
copies	O
and	O
without	O
much	O
CPU	B-Device
intervention	O
.	O
</s>
<s>
An	O
RDMA	B-General_Concept
consortium	O
was	O
announced	O
on	O
May	O
31	O
,	O
2002	O
,	O
with	O
a	O
goal	O
of	O
product	O
implementations	O
by	O
2003	O
.	O
</s>
<s>
The	O
OpenIB	B-General_Concept
Alliance	I-General_Concept
was	O
renamed	O
in	O
2007	O
to	O
be	O
the	O
OpenFabrics	B-General_Concept
Alliance	I-General_Concept
,	O
and	O
then	O
released	O
an	O
open	B-Application
source	I-Application
software	I-Application
package	O
.	O
</s>
<s>
The	O
motivation	O
for	O
iSER	O
is	O
to	O
use	O
RDMA	B-General_Concept
to	O
avoid	O
unnecessary	O
data	O
copying	O
on	O
the	O
target	O
and	O
initiator	O
.	O
</s>
<s>
SCSI	B-Architecture
read/write	O
commands	O
.	O
</s>
<s>
exception	O
of	O
iSCSI	B-Protocol
unsolicited	O
data	O
)	O
by	O
issuing	O
RDMA	B-General_Concept
write/read	O
operations	O
,	O
respectively	O
.	O
</s>
<s>
When	O
the	O
iSCSI	B-Protocol
layer	O
issues	O
an	O
iSCSI	B-Protocol
command	O
PDU	O
,	O
it	O
calls	O
the	O
Send_Control	O
primitive	O
,	O
</s>
<s>
The	O
target	O
calls	O
the	O
Put_Data	O
or	O
Get_Data	O
primitives	O
(	O
which	O
are	O
part	O
of	O
the	O
DI	O
)	O
to	O
perform	O
an	O
RDMA	B-General_Concept
write/read	O
operation	O
respectively	O
.	O
</s>
<s>
will	O
use	O
the	O
STags	O
later	O
for	O
RDMA	B-General_Concept
read/write	O
operations	O
.	O
</s>
