<s>
FICON	B-Architecture
(	O
Fibre	B-Architecture
Connection	I-Architecture
)	O
is	O
the	O
IBM	O
proprietary	O
name	O
for	O
the	O
ANSI	O
FC-SB-3	O
Single-Byte	O
Command	O
Code	O
Sets-3	O
Mapping	O
Protocol	O
for	O
Fibre	B-Architecture
Channel	I-Architecture
(	O
FC	O
)	O
protocol	O
.	O
</s>
<s>
It	O
is	O
a	O
FC	O
layer	O
4	O
protocol	O
used	O
to	O
map	O
both	O
IBM	O
's	O
antecedent	O
(	O
either	O
ESCON	B-Device
or	O
parallel	O
Bus	B-Device
and	I-Device
Tag	I-Device
)	O
channel-to-control-unit	O
cabling	O
infrastructure	O
and	O
protocol	O
onto	O
standard	O
FC	O
services	O
and	O
infrastructure	O
.	O
</s>
<s>
The	O
topology	O
is	O
fabric	B-Architecture
utilizing	O
FC	B-Architecture
switches	I-Architecture
or	I-Architecture
directors	I-Architecture
.	O
</s>
<s>
FICON	B-Architecture
was	O
introduced	O
in	O
1998	O
as	O
part	O
of	O
fifth	O
generation	O
of	O
IBM	O
System/390	O
mainframes	B-Architecture
.	O
</s>
<s>
After	O
2011	O
FICON	B-Architecture
replaced	O
ESCON	B-Device
in	O
new	O
IBM	O
mainframe	B-Architecture
deployments	O
because	O
of	O
FICON	B-Architecture
's	O
technical	O
superiority	O
(	O
especially	O
its	O
higher	O
performance	O
)	O
and	O
lower	O
cost	O
.	O
</s>
<s>
Each	O
FICON	B-Architecture
channel	B-Device
port	O
is	O
capable	O
of	O
multiple	O
concurrent	O
data	O
exchanges	O
(	O
a	O
maximum	O
of	O
32	O
)	O
in	O
full	O
duplex	O
mode	O
.	O
</s>
<s>
Information	O
for	O
active	O
exchanges	O
is	O
transferred	O
in	O
Fibre	B-Architecture
Channel	I-Architecture
sequences	O
mapped	O
as	O
FICON	B-Architecture
Information	O
Units	O
(	O
IUs	O
)	O
which	O
consist	O
of	O
one	O
to	O
four	O
Fibre	B-Architecture
Channel	I-Architecture
frames	O
,	O
only	O
the	O
first	O
of	O
which	O
carries	O
32	O
bytes	O
of	O
FICON	B-Architecture
(	O
FC-SB-3	O
)	O
mapping	O
protocol	O
.	O
</s>
<s>
Each	O
FICON	B-Architecture
exchange	O
may	O
transfer	O
one	O
or	O
many	O
such	O
IUs	O
.	O
</s>
<s>
FICON	B-Architecture
channels	O
use	O
five	O
classes	O
of	O
IUs	O
to	O
conduct	O
information	O
transfers	O
between	O
a	O
channel	B-Device
and	O
a	O
control	O
unit	O
.	O
</s>
<s>
Only	O
a	O
channel	B-Device
port	O
may	O
send	O
Command	O
or	O
Command	O
and	O
Data	O
IUs	O
,	O
while	O
only	O
a	O
control	O
unit	O
port	O
may	O
send	O
Status	O
IUs	O
.	O
</s>
<s>
As	O
with	O
prior	O
Z	O
channel	B-Device
protocols	O
,	O
there	O
is	O
a	O
concept	O
of	O
a	O
channel	B-Device
to	O
control	O
unit	O
"	O
connection	O
"	O
.	O
</s>
<s>
In	O
its	O
most	O
primitive	O
form	O
,	O
a	O
connection	O
is	O
associated	O
with	O
a	O
single	O
channel	B-Device
program	O
.	O
</s>
<s>
In	O
practice	O
,	O
a	O
single	O
channel	B-Device
program	O
may	O
result	O
in	O
the	O
establishment	O
of	O
several	O
sequential	O
connections	O
.	O
</s>
<s>
When	O
the	O
control	O
unit	O
is	O
ready	O
to	O
resume	O
such	O
an	O
interrupted	O
connection	O
,	O
it	O
signals	O
the	O
channel	B-Device
to	O
reconnect	O
and	O
resume	O
the	O
interrupted	O
channel	B-Device
program	O
.	O
</s>
<s>
By	O
closing	O
temporarily	O
dormant	O
connections	O
,	O
channel	B-Device
and	O
control	O
unit	O
facilities	O
may	O
be	O
better	O
utilized	O
to	O
serve	O
other	O
active	O
channel	B-Device
programs	O
and	O
certain	O
protocol	O
timeouts	O
that	O
might	O
otherwise	O
occur	O
may	O
be	O
avoided	O
.	O
</s>
<s>
FICON	B-Architecture
uses	O
two	O
Fibre	B-Architecture
Channel	I-Architecture
exchanges	O
for	O
a	O
channel	B-Device
control	O
unit	O
connection	O
one	O
for	O
each	O
direction	O
.	O
</s>
<s>
So	O
while	O
a	O
Fibre	B-Architecture
Channel	I-Architecture
exchange	O
is	O
capable	O
of	O
carrying	O
a	O
command	O
and	O
response	O
on	O
a	O
single	O
exchange	O
,	O
and	O
all	O
other	O
FC-4	O
protocols	O
work	O
that	O
way	O
,	O
the	O
response	O
to	O
a	O
FICON	B-Architecture
IU	O
is	O
always	O
on	O
a	O
different	O
exchange	O
from	O
the	O
IU	O
to	O
which	O
it	O
is	O
a	O
response	O
.	O
</s>
<s>
While	O
other	O
FC-4s	O
have	O
a	O
single	O
"	O
data	O
structure	O
type	O
"	O
code	O
that	O
characterizes	O
their	O
IUs	O
in	O
Fibre	B-Architecture
Channel	I-Architecture
frame	O
headers	O
,	O
FICON	B-Architecture
has	O
two	O
.	O
</s>
<s>
One	O
is	O
for	O
IUs	O
from	O
channel	B-Device
to	O
control	O
unit	O
;	O
the	O
other	O
for	O
control	O
unit	O
to	O
channel	B-Device
.	O
</s>
<s>
Except	O
for	O
some	O
initialization	O
dialogue	O
that	O
requires	O
stronger	O
synchronization	O
,	O
FICON	B-Architecture
uses	O
Fibre	B-Architecture
Channel	I-Architecture
class	O
of	O
service	O
3	O
(	O
Datagram	O
)	O
.	O
</s>
<s>
Thus	O
,	O
at	O
the	O
Fibre	B-Architecture
Channel	I-Architecture
physical	O
(	O
FC-2	O
and	O
below	O
)	O
level	O
,	O
the	O
communication	O
is	O
connectionless	O
,	O
frames	O
and	O
sequences	O
may	O
arrive	O
out	O
of	O
order	O
,	O
and	O
there	O
is	O
no	O
acknowledgement	O
of	O
arrival	O
.	O
</s>
<s>
This	O
is	O
in	O
addition	O
to	O
the	O
standard	O
Fibre	B-Architecture
Channel	I-Architecture
CRC	O
used	O
to	O
verify	O
the	O
integrity	O
of	O
each	O
individual	O
FC	O
frame	O
.	O
</s>
<s>
As	O
such	O
,	O
the	O
FICON	B-Architecture
CRC	O
has	O
the	O
capability	O
of	O
detecting	O
missing	O
or	O
out	O
of	O
sequence	O
frames/IUs	O
.	O
</s>
<s>
FICON	B-Architecture
may	O
employ	O
Fibre	B-Architecture
Channel	I-Architecture
fiber	O
optic	O
cables	O
with	O
either	O
short	O
wavelength	O
(	O
multi-mode	O
;	O
62.5	O
or	O
50	O
micrometer	O
core	O
)	O
or	O
long	O
wavelength	O
(	O
single	O
mode	O
;	O
9	O
micrometer	O
core	O
)	O
.	O
</s>
<s>
FICON	B-Architecture
cannot	O
use	O
Copper	O
Fibre	B-Architecture
Channel	I-Architecture
cables	O
.	O
</s>
<s>
FICON	B-Architecture
is	O
used	O
exclusively	O
with	O
computers	O
based	O
on	O
the	O
IBM	B-Device
z/Architecture	I-Device
(	O
current	O
descendant	O
of	O
System/360	B-Application
,	O
System/370	B-Device
,	O
etc	O
.	O
</s>
<s>
)	O
,	O
commonly	O
called	O
mainframes	B-Architecture
.	O
</s>
<s>
FICON	B-Architecture
and	O
its	O
predecessors	O
are	O
the	O
only	O
protocols	O
sufficient	O
to	O
communicate	O
with	O
traditional	O
mainframe	B-Architecture
peripheral	O
devices	O
,	O
especially	O
for	O
z/OS	B-Application
.	O
</s>
<s>
However	O
,	O
most	O
mainframe	B-Architecture
operating	O
systems	O
also	O
support	O
FCP	O
(	O
SCSI	B-Architecture
command	O
set	O
over	O
Fibre	B-Architecture
Channel	I-Architecture
)	O
.	O
</s>
<s>
FICON	B-Architecture
is	O
technically	O
quite	O
similar	O
to	O
more	O
popular	O
storage	O
protocols	O
,	O
such	O
as	O
FCP	O
.	O
</s>
<s>
Both	O
FICON	B-Architecture
and	O
FCP	O
share	O
levels	O
1	O
–	O
3	O
of	O
Fibre	B-Architecture
Channel	I-Architecture
specifications	O
.	O
</s>
<s>
Some	O
administrators	O
argue	O
that	O
FICON	B-Architecture
offers	O
somewhat	O
easier	O
troubleshooting	O
in	O
mainframe	B-Architecture
environments	O
,	O
but	O
the	O
inherent	O
technical	O
advantages	O
and	O
disadvantages	O
between	O
FICON	B-Architecture
and	O
FCP	O
are	O
much	O
alike	O
.	O
</s>
<s>
Some	O
mainframe-specific	O
setups	O
,	O
such	O
as	O
GDPS	O
,	O
require	O
FICON	B-Architecture
(	O
or	O
its	O
predecessor	O
ESCON	B-Device
)	O
.	O
</s>
<s>
Mainframe-attached	O
storage	O
,	O
such	O
as	O
IBM	O
's	O
System	O
Storage	O
DS8000	B-Device
,	O
often	O
supports	O
both	O
protocols	O
.	O
</s>
<s>
The	O
storage	O
is	O
divided	O
into	O
fixed	O
block	O
storage	O
volumes	O
(	O
accessed	O
with	O
FCP	O
)	O
and	O
mainframe-specific	O
CKD/ECKD	O
storage	O
volumes	O
(	O
accessed	O
with	O
FICON	B-Architecture
and/or	O
ESCON	B-Device
)	O
.	O
</s>
<s>
Disk	O
storage	O
products	O
that	O
can	O
be	O
attached	O
via	O
FICON	B-Architecture
include	O
:	O
</s>
<s>
Hardware	O
Security	O
Module	O
(	O
HSM	O
)	O
products	O
that	O
support	O
FICON	B-Architecture
include	O
:	O
</s>
<s>
Switches/directors	O
that	O
support	O
FICON	B-Architecture
include	O
:	O
</s>
<s>
Managed	O
File	O
Transfer	O
products	O
that	O
support	O
FICON	B-Architecture
include	O
:	O
</s>
<s>
Other	O
older	O
FICON	B-Architecture
switching	O
platforms	O
are	O
still	O
in	O
use	O
.	O
</s>
<s>
Approximately	O
80%	O
of	O
FICON	B-Architecture
directors	O
and	O
switches	O
installed	O
in	O
mainframe	B-Architecture
environments	O
were	O
Brocade	O
products	O
at	O
the	O
time	O
.	O
</s>
<s>
McDATA	O
was	O
well	O
established	O
in	O
the	O
mainframe	B-Architecture
directors	O
space	O
,	O
manufacturing	O
the	O
9032-3	O
and	O
9032-5	O
ESCON	B-Device
directors	I-Device
for	O
IBM	O
,	O
as	O
well	O
as	O
the	O
FICON	B-Architecture
Bridge	O
Card	O
.	O
</s>
<s>
Brocade	O
has	O
many	O
co-patents	O
with	O
IBM	O
for	O
FICON	B-Architecture
and	O
ESCON	B-Device
technology	O
.	O
</s>
<s>
Cisco	O
Systems	O
was	O
a	O
relative	O
newcomer	O
to	O
this	O
space	O
,	O
with	O
their	O
first	O
FICON	B-Architecture
director	O
coming	O
out	O
in	O
2003	O
.	O
</s>
<s>
Other	O
manufacturers	O
producing	O
FICON-compatible	O
equipment	O
include	O
Optica	O
Technologies	O
,	O
and	O
InfoPrint	O
Solutions	O
Company	O
,	O
which	O
offers	O
high-volume	O
printers	O
that	O
can	O
attach	O
via	O
FICON	B-Architecture
.	O
</s>
