<s>
XENPAK	B-Protocol
is	O
a	O
multisource	O
agreement	O
(	O
MSA	O
)	O
,	O
instigated	O
by	O
Agilent	O
Technologies	O
and	O
Agere	O
Systems	O
,	O
that	O
defines	O
a	O
fiber-optic	B-Architecture
or	O
wired	O
transceiver	O
module	O
which	O
conforms	O
to	O
the	O
10	O
Gigabit	O
Ethernet	O
(	O
10GbE	O
)	O
standard	O
of	O
the	O
Institute	O
of	O
Electrical	O
and	O
Electronics	O
Engineers	O
(	O
IEEE	O
)	O
802.3	O
working	O
group	O
.	O
</s>
<s>
XENPAK	B-Protocol
has	O
been	O
replaced	O
by	O
more	O
compact	O
devices	O
providing	O
the	O
same	O
functionality	O
.	O
</s>
<s>
The	O
XENPAK	B-Protocol
MSA	O
was	O
publicly	O
announced	O
on	O
March	O
12	O
,	O
2001	O
and	O
the	O
first	O
revision	O
of	O
the	O
document	O
was	O
publicly	O
released	O
on	O
May	O
7	O
,	O
2001	O
.	O
</s>
<s>
Although	O
the	O
XENPAK	B-Protocol
agreement	O
received	O
early	O
support	O
,	O
its	O
modules	O
were	O
thought	O
to	O
be	O
overly	O
large	O
for	O
high	O
density	O
applications	O
.	O
</s>
<s>
,	O
vendors	O
generally	O
changed	O
to	O
use	O
XFP	B-Protocol
modules	O
for	O
longer	O
distances	O
,	O
and	O
Enhanced	B-Protocol
small	I-Protocol
form-factor	I-Protocol
pluggable	I-Protocol
transceivers	I-Protocol
,	O
known	O
as	O
SFP+	B-Protocol
modules	O
,	O
for	O
higher	O
densities	O
.	O
</s>
<s>
The	O
newer	O
modules	O
have	O
a	O
purely	O
serial	B-Protocol
interface	I-Protocol
,	O
compared	O
to	O
the	O
four	O
"	O
lane	O
"	O
XAUI	B-Protocol
interface	O
used	O
in	O
XENPAK	B-Protocol
.	O
</s>
<s>
XENPAK	B-Protocol
modules	O
were	O
supplied	O
for	O
physical	O
layer	O
interfaces	O
supporting	O
multi-mode	B-Device
and	O
single	B-Device
mode	I-Device
fiber	I-Device
optic	O
cables	O
and	O
InfiniBand	B-Architecture
copper	O
cables	O
with	O
connectors	O
known	O
as	O
CX4	O
.	O
</s>
<s>
Newer	O
XENPAKs	B-Protocol
using	O
the	O
10GBase-LX4	O
standard	O
operated	O
using	O
multiple	O
wavelengths	O
on	O
legacy	O
multi-mode	B-Device
fibres	I-Device
at	O
distances	O
of	O
up	O
to	O
,	O
eliminating	O
the	O
need	O
to	O
reinstall	O
cable	O
in	O
a	O
building	O
when	O
upgrading	O
certain	O
1	O
Gbit/s	O
circuits	O
to	O
10	O
Gbit/s	O
.	O
</s>
<s>
The	O
XENPAK	B-Protocol
form	O
factor	O
was	O
initially	O
supported	O
by	O
numerous	O
network	O
equipment	O
manufacturers	O
and	O
module	O
makers	O
.	O
</s>
<s>
Soon	O
after	O
the	O
standard	O
was	O
introduced	O
in	O
2001	O
,	O
two	O
related	O
standards	O
emerged	O
:	O
XPAK	O
and	O
X2	B-Device
.	O
</s>
<s>
These	O
two	O
standards	O
have	O
the	O
same	O
electrical	O
interface	O
as	O
XENPAK	B-Protocol
(	O
known	O
as	O
XAUI	B-Protocol
)	O
but	O
different	O
mechanical	O
properties	O
.	O
</s>
<s>
The	O
X2	B-Device
group	O
was	O
announced	O
on	O
July	O
22	O
,	O
2002	O
,	O
and	O
published	O
their	O
specification	O
on	O
February	O
13	O
,	O
2003	O
.	O
</s>
<s>
Issue	O
3.0	O
of	O
the	O
XENPAK	B-Protocol
MSA	O
was	O
transferred	O
to	O
the	O
Small	O
Form	O
Factor	O
committee	O
as	O
document	O
INF-8474	O
on	O
September	O
18	O
,	O
2002	O
.	O
</s>
<s>
The	O
XENPAK	B-Protocol
MSA	O
website	O
existed	O
through	O
the	O
end	O
of	O
2008	O
.	O
</s>
<s>
As	O
of	O
2014	O
,	O
adapters	O
are	O
available	O
which	O
permit	O
use	O
of	O
any	O
modern	O
SFP+	B-Protocol
10Gb	O
optic	O
in	O
a	O
XENPAK	B-Protocol
interface	O
.	O
</s>
