<s>
In	O
computer	B-Architecture
networking	I-Architecture
,	O
the	O
Transport	B-Application
Layer	I-Application
Interface	I-Application
(	O
TLI	O
)	O
was	O
the	O
networking	O
API	B-Application
provided	O
by	O
AT&T	B-Operating_System
UNIX	I-Operating_System
System	B-Operating_System
V	I-Operating_System
Release	I-Operating_System
3	I-Operating_System
(	O
SVR3	B-Operating_System
)	O
in	O
1987	O
and	O
continued	O
into	O
Release	O
4	O
(	O
SVR4	O
)	O
.	O
</s>
<s>
TLI	O
was	O
the	O
System	B-Operating_System
V	I-Operating_System
counterpart	O
to	O
the	O
BSD	B-Protocol
sockets	I-Protocol
programming	B-Application
interface	I-Application
,	O
which	O
was	O
also	O
provided	O
in	O
UNIX	B-Operating_System
System	I-Operating_System
V	I-Operating_System
Release	O
4	O
(	O
SVR4	O
)	O
.	O
</s>
<s>
TLI	O
was	O
later	O
standardized	O
as	O
XTI	O
,	O
the	O
X/Open	B-Application
Transport	I-Application
Interface	I-Application
.	O
</s>
<s>
It	O
was	O
originally	O
expected	O
that	O
the	O
OSI	O
protocols	O
would	O
supersede	O
TCP/IP	O
,	O
thus	O
TLI	O
is	O
designed	O
from	O
an	O
OSI	O
model-oriented	O
viewpoint	O
,	O
corresponding	O
to	O
the	O
OSI	O
transport	B-Architecture
layer	I-Architecture
.	O
</s>
<s>
Otherwise	O
,	O
TLI	O
looks	O
similar	O
,	O
API-wise	O
,	O
to	O
sockets	B-Protocol
.	O
</s>
<s>
and	O
,	O
up	O
to	O
UNIX	O
98	O
,	O
may	O
have	O
been	O
preferred	O
over	O
the	O
POSIX	B-Protocol
Sockets	I-Protocol
5API	O
with	O
respect	O
to	O
existing	O
standards	O
.	O
</s>
<s>
However	O
,	O
it	O
was	O
clear	O
at	O
least	O
since	O
the	O
early	O
1990s	O
that	O
the	O
Berkeley	B-Protocol
Socket	I-Protocol
interface	I-Protocol
would	O
ultimately	O
prevail	O
.	O
</s>
<s>
TLI	O
and	O
XTI	O
are	O
still	O
supported	O
in	O
SVR4-derived	O
operating	B-General_Concept
systems	I-General_Concept
and	O
operating	B-General_Concept
systems	I-General_Concept
conforming	O
to	O
branded	O
UNIX	O
(	O
UNIX	O
95	O
,	O
UNIX	O
98	O
and	O
UNIX	O
03	O
Single	O
UNIX	O
Specifications	O
)	O
such	O
as	O
Solaris	B-Application
and	O
AIX	B-Application
(	O
as	O
well	O
as	O
the	O
classic	B-Application
Mac	I-Application
OS	I-Application
,	O
in	O
the	O
form	O
of	O
Open	B-Protocol
Transport	I-Protocol
)	O
.	O
</s>
<s>
Under	O
UNIX	O
95	O
(	O
XPG4	O
)	O
and	O
UNIX	O
98	O
(	O
XPG5.2	O
)	O
,	O
XTI	O
was	O
the	O
preferred	O
and	O
recommended	O
supported	O
API	B-Application
for	O
new	O
transport	B-Architecture
protocols	I-Architecture
.	O
</s>
<s>
As	O
a	O
result	O
of	O
deliberations	O
by	O
the	O
Austin	O
Group	O
with	O
the	O
goal	O
of	O
bringing	O
flavors	O
of	O
UNIX	O
that	O
do	O
not	O
provide	O
STREAMS	B-Operating_System
,	O
such	O
as	O
BSD	B-Operating_System
and	O
Linux	B-Application
,	O
under	O
the	O
Single	O
UNIX	O
Specification	O
,	O
the	O
UNIX	O
03	O
Single	O
UNIX	O
Specification	O
both	O
declares	O
STREAMS	B-Operating_System
as	O
optional	O
,	O
and	O
declares	O
POSIX	B-Protocol
Sockets	I-Protocol
as	O
the	O
preferred	O
API	B-Application
for	O
new	O
transport	B-Architecture
protocols	I-Architecture
.	O
</s>
