<s>
The	O
Internet	B-Protocol
Stream	I-Protocol
Protocol	I-Protocol
(	O
ST	O
)	O
is	O
a	O
family	O
of	O
experimental	O
protocols	O
first	O
defined	O
in	O
Internet	O
Experiment	O
Note	O
IEN-119	O
in	O
1979	O
,	O
and	O
later	O
substantially	O
revised	O
in	O
RFC	O
1190	O
(	O
ST-II	O
)	O
and	O
RFC	O
1819	O
(	O
ST2+	O
)	O
.	O
</s>
<s>
The	O
protocol	O
uses	O
the	O
version	O
number	O
5	O
in	O
the	O
version	O
field	O
of	O
the	O
Internet	B-Protocol
Protocol	I-Protocol
header	O
,	O
but	O
was	O
never	O
known	O
as	O
IPv5	B-Protocol
.	O
</s>
<s>
The	O
successor	O
to	O
IPv4	B-Protocol
was	O
thus	O
named	O
IPv6	B-Protocol
to	O
eliminate	O
any	O
possible	O
confusion	O
about	O
the	O
actual	O
protocol	O
in	O
use	O
.	O
</s>
<s>
The	O
Internet	B-Protocol
Stream	I-Protocol
Protocol	I-Protocol
family	O
was	O
never	O
introduced	O
for	O
public	O
use	O
,	O
but	O
many	O
of	O
the	O
concepts	O
available	O
in	O
ST	O
are	O
similar	O
to	O
later	O
Asynchronous	O
Transfer	O
Mode	O
protocols	O
and	O
can	O
be	O
found	O
in	O
Multiprotocol	B-Protocol
Label	I-Protocol
Switching	I-Protocol
(	O
MPLS	B-Protocol
)	O
.	O
</s>
<s>
They	O
also	O
presaged	O
voice	B-Application
over	I-Application
IP	I-Application
.	O
</s>
<s>
ST	O
arose	O
as	O
the	O
transport	O
protocol	O
of	O
the	O
Network	B-Protocol
Voice	I-Protocol
Protocol	I-Protocol
,	O
a	O
pioneering	O
computer	O
network	O
protocol	O
for	O
transporting	O
human	O
speech	O
over	O
packetized	O
communications	O
networks	O
,	O
first	O
implemented	O
in	O
December	O
1973	O
by	O
Internet	O
researcher	O
Danny	O
Cohen	O
of	O
the	O
Information	O
Sciences	O
Institute	O
(	O
ISI	O
)	O
as	O
part	O
of	O
ARPA	O
's	O
Network	O
Secure	O
Communications	O
(	O
NSC	O
)	O
project	O
.	O
</s>
<s>
First	O
specified	O
in	O
1979	O
,	O
ST	O
was	O
envisioned	O
as	O
a	O
connection-oriented	O
complement	O
to	O
IPv4	B-Protocol
,	O
operating	O
on	O
the	O
same	O
level	O
,	O
but	O
using	O
a	O
different	O
header	O
format	O
from	O
that	O
used	O
for	O
IP	O
datagrams	B-Protocol
.	O
</s>
<s>
The	O
protocol	O
was	O
notable	O
for	O
introducing	O
the	O
concepts	O
of	O
packetized	B-Application
voice	I-Application
(	O
as	O
used	O
by	O
voice	B-Application
over	I-Application
IP	I-Application
)	O
,	O
a	O
talkspurt	O
(	O
a	O
continuous	O
segment	O
of	O
speech	O
between	O
silent	O
intervals	O
)	O
,	O
and	O
specified	O
delay	O
and	O
drop-rate	O
requirements	O
for	O
packet	O
services	O
.	O
</s>
<s>
It	O
was	O
implemented	O
in	O
the	O
Voice	B-Protocol
Funnel	I-Protocol
.	O
</s>
<s>
ST2	O
distinguishes	O
its	O
own	O
packets	O
with	O
an	O
Internet	B-Protocol
Protocol	I-Protocol
version	O
number	O
5	O
,	O
although	O
it	O
was	O
never	O
known	O
as	O
IPv5	B-Protocol
.	O
</s>
<s>
ST	O
uses	O
the	O
same	O
IP	O
address	O
structure	O
and	O
the	O
same	O
link	B-Protocol
layer	I-Protocol
protocol	B-Protocol
number	I-Protocol
(	O
ethertype	O
0x800	O
)	O
as	O
IP	O
.	O
</s>
<s>
In	O
datagram	B-Protocol
mode	O
,	O
ST	O
packets	O
could	O
be	O
encapsulated	O
with	O
IP	O
headers	O
using	O
protocol	B-Protocol
number	I-Protocol
5	O
.	O
</s>
