<s>
It	O
represents	O
landmarks	O
in	O
two	O
key	O
areas	O
of	O
Internet	O
development	O
:	O
games	O
and	O
multicasting	O
,	O
and	O
notable	O
advancement	O
in	O
creating	O
rendered	O
virtual	B-General_Concept
environments	I-General_Concept
.	O
</s>
<s>
Flight	O
is	O
a	O
flight	B-Application
simulator	I-Application
,	O
dog	O
is	O
an	O
air	O
combat	O
game	O
in	O
which	O
multiple	O
people	O
use	O
the	O
flight	O
interface	O
to	O
control	O
their	O
aircraft	O
,	O
and	O
shadow	O
is	O
an	O
observation	O
program	O
that	O
allows	O
a	O
user	O
to	O
see	O
what	O
a	O
user	O
of	O
either	O
dog	O
or	O
flight	O
sees	O
.	O
</s>
<s>
With	O
-o	O
,	O
the	O
path	O
taken	O
by	O
the	O
plane	O
would	O
be	O
saved	O
to	O
a	O
file	O
instead	O
of	O
being	O
broadcast	B-Operating_System
to	O
the	O
network	O
.	O
</s>
<s>
This	O
would	O
replace	O
the	O
standard	O
instrument	O
panel	O
with	O
a	O
head-up	B-Application
display	I-Application
(	O
HUD	B-Application
)	O
.	O
</s>
<s>
This	O
was	O
added	O
because	O
Williams	O
Air	O
Force	O
Base	O
were	O
interested	O
in	O
using	O
flight	O
for	O
F-16	O
training	O
,	O
debriefing	O
and	O
"	O
human-interaction	O
studies	O
"	O
,	O
but	O
wanted	O
it	O
to	O
have	O
a	O
HUD	B-Application
similar	O
to	O
the	O
HUD	B-Application
on	O
a	O
real	O
F-16	O
.	O
</s>
<s>
F-15	O
(	O
In	O
the	O
GT/GTX/VGX	O
version	O
,	O
this	O
was	O
described	O
as	O
looking	O
like	O
an	O
F-14	B-Device
model	O
with	O
the	O
wings	O
swept	O
back	O
.	O
</s>
<s>
It	O
was	O
inspired	O
by	O
the	O
Blue	B-Application
Angels	I-Application
airshows	O
at	O
Moffett	O
Field	O
,	O
across	O
the	O
street	O
from	O
SGI	O
's	O
original	O
headquarters	O
.	O
</s>
<s>
This	O
allowed	O
about	O
7	O
frames	O
per	O
second	O
and	O
500	O
polygons	O
per	O
second	O
on	O
a	O
machine	O
with	O
a	O
Motorola	B-Device
68000	I-Device
CPU	O
capable	O
of	O
approximately	O
1	O
MIPS	O
.	O
</s>
<s>
By	O
SIGGRAPH	O
1984	O
,	O
XNS	B-Protocol
multicast	O
support	O
was	O
added	O
,	O
allowing	O
play	O
over	O
an	O
Ethernet	O
network	O
.	O
</s>
<s>
Probably	O
in	O
early	O
1985	B-Application
,	O
dog	O
was	O
created	O
,	O
and	O
dog	O
and	O
flight	O
were	O
shipped	O
as	O
demonstration	O
software	O
included	O
with	O
SGI	O
workstations	O
.	O
</s>
<s>
In	O
1986	O
,	O
UDP	B-Protocol
broadcast	B-Operating_System
protocol	O
capability	O
was	O
added	O
(	O
using	O
port	O
5130	O
)	O
.	O
</s>
<s>
Information	O
was	O
transmitted	O
via	O
broadcast	B-Operating_System
packets	I-Operating_System
and	O
at	O
frame	O
rate	O
,	O
meaning	O
that	O
the	O
program	O
made	O
intensive	O
use	O
of	O
network	O
resources	O
and	O
even	O
a	O
small	O
number	O
of	O
players	O
was	O
capable	O
of	O
saturating	O
an	O
Ethernet	O
.	O
</s>
<s>
So	O
while	O
it	O
was	O
probably	O
the	O
first	O
game	O
to	O
use	O
the	O
Internet	O
Protocol	O
Suite	O
,	O
the	O
game	O
could	O
not	O
pass	O
through	O
a	O
router	B-Protocol
,	O
and	O
thus	O
could	O
not	O
be	O
played	O
across	O
the	O
Internet	O
itself	O
.	O
</s>
<s>
In	O
the	O
Irix	B-Operating_System
6.5	O
documentation	O
,	O
it	O
was	O
noted	O
that	O
the	O
Boeing	O
727	O
and	O
F-14	B-Device
were	O
not	O
available	O
to	O
choose	O
as	O
planes	O
in	O
the	O
normal	O
version	O
of	O
the	O
software	O
,	O
but	O
were	O
present	O
in	O
the	O
GT/GTX/VGX	O
version	O
.	O
</s>
<s>
Several	O
programmers	O
used	O
this	O
code	O
as	O
an	O
example	O
,	O
to	O
teach	O
themselves	O
UDP	B-Protocol
and	O
how	O
to	O
use	O
it	O
in	O
their	O
own	O
code	O
.	O
</s>
<s>
For	O
the	O
IRIX	B-Operating_System
3.3	O
version	O
,	O
circa	O
1989	O
,	O
IP	B-Protocol
multicast	I-Protocol
capability	O
was	O
added	O
,	O
and	O
the	O
game	O
became	O
playable	O
between	O
any	O
compatible	O
hosts	O
on	O
the	O
Internet	O
,	O
assuming	O
that	O
they	O
had	O
multicast	O
access	O
(	O
which	O
was	O
quite	O
uncommon	O
)	O
.	O
</s>
<s>
The	O
multicast	O
address	O
was	O
224.0.1.2	O
(	O
SGI-DOG.MCAST.NET	O
)	O
,	O
making	O
this	O
only	O
the	O
third	O
multicast	O
application	O
to	O
receive	O
an	O
address	O
assignment	O
,	O
with	O
only	O
the	O
Versatile	O
Message	O
Transaction	O
Protocol	O
(	O
VMTP	O
)	O
protocol	O
(	O
224.0.1.0	O
)	O
and	O
the	O
Network	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
(	O
224.0.1.1	O
)	O
having	O
arrived	O
first	O
.	O
</s>
<s>
A	O
version	O
replacing	O
the	O
UDP	B-Protocol
broadcast	B-Operating_System
with	O
point-to-point	O
communication	O
between	O
two	O
hosts	O
was	O
created	O
at	O
the	O
Lund	O
Institute	O
of	O
Technology	O
in	O
Sweden	O
.	O
</s>
<s>
It	O
may	O
also	O
have	O
been	O
intended	O
to	O
reduce	O
network	O
congestion	O
compared	O
to	O
the	O
broadcast	B-Operating_System
version	O
,	O
and	O
probably	O
pre-dated	O
the	O
addition	O
of	O
multicast	O
to	O
the	O
official	O
version	O
.	O
</s>
<s>
Prior	O
to	O
1988	O
,	O
the	O
US	O
Army	O
's	O
Ballistic	O
Research	O
Laboratory	O
(	O
BRL	O
)	O
had	O
a	O
copy	O
of	O
the	O
XNS	B-Protocol
version	O
of	O
the	O
software	O
,	O
but	O
XNS	B-Protocol
did	O
not	O
work	O
on	O
their	O
network	O
.	O
</s>
<s>
In	O
a	O
1992	O
thread	O
on	O
the	O
rec.aviation.simulators	O
Usenet	O
group	O
,	O
a	O
list	O
of	O
available	O
flight	B-Application
simulators	I-Application
included	O
a	O
port	O
of	O
dog/flight	O
to	O
pixrect	O
-	O
a	O
"	O
low-level	O
raster	O
operations	O
library	O
for	O
writing	O
device-independent	O
applications	O
for	O
Sun	O
products.	O
"	O
</s>
<s>
Another	O
Sun	O
port	O
-	O
specifically	O
compiled	O
for	O
Sun	O
's	O
SPARCstation	B-Device
hardware	O
-	O
was	O
also	O
mentioned	O
.	O
</s>
<s>
In	O
a	O
1990	O
post	O
to	O
comp.sys.sgi	O
,	O
a	O
Sun	O
port	O
was	O
mentioned	O
which	O
"	O
runs	O
reasonably	O
well	O
on	O
a	O
colour	O
GX	O
Sparcstation	B-Device
although	O
it	O
does	O
n't	O
fill	O
the	O
polygons	O
so	O
a	O
lot	O
of	O
the	O
realism	O
is	O
lost	O
"	O
.	O
</s>
<s>
In	O
a	O
1993	O
Usenet	O
posting	O
,	O
one	O
user	O
mentioned	O
having	O
seen	O
a	O
version	O
of	O
flight	O
with	O
X-wing	B-Application
and	O
TIE	B-Application
fighter	I-Application
models	O
in	O
the	O
autumn	O
1987	O
issue	O
of	O
SGI	O
's	O
house	O
magazine	O
"	O
IRIS	O
Universe	O
"	O
.	O
</s>
<s>
X-wing	B-Application
,	O
with	O
lasers	O
as	O
weapons	O
.	O
</s>
<s>
TIE	B-Application
fighter	I-Application
,	O
also	O
with	O
laser	O
weapons	O
,	O
and	O
with	O
Snoopy	B-Application
as	O
the	O
pilot	O
.	O
</s>
<s>
Sopwith	O
Camel	O
,	O
again	O
with	O
Snoopy	B-Application
as	O
its	O
pilot	O
.	O
</s>
<s>
Fokker	O
Tri-Plane	O
,	O
again	O
with	O
Snoopy	B-Application
as	O
the	O
pilot	O
.	O
</s>
<s>
Asked	O
about	O
this	O
version	O
,	O
flight	O
lead	O
developer	O
Rob	O
Mace	O
said	O
that	O
it	O
had	O
come	O
"	O
from	O
a	O
university	O
"	O
,	O
and	O
that	O
due	O
to	O
the	O
copyrighted	O
status	O
of	O
Snoopy	B-Application
and	O
the	O
sci-fi	O
vehicles	O
,	O
SGI	O
could	O
not	O
legally	O
supply	O
copies	O
of	O
it	O
.	O
</s>
<s>
The	O
manual	O
page	O
for	O
the	O
IRIX	B-Operating_System
6.5	O
(	O
circa	O
1998	O
)	O
version	O
of	O
the	O
program	O
lists	O
the	O
following	O
:	O
</s>
<s>
Network	O
communications	O
David	O
"	O
Ciemo	O
"	O
Ciemiewicz	O
(	O
Ciemiewicz	O
worked	O
on	O
the	O
UDP	B-Protocol
broadcast	B-Operating_System
code	O
)	O
and	O
Andrew	O
Cherenson	O
(	O
IP	B-Protocol
multicast	I-Protocol
)	O
.	O
</s>
<s>
Listed	O
as	O
responsible	O
for	O
IRIX	B-Operating_System
6.5	O
version	O
.	O
</s>
<s>
Credited	O
with	O
the	O
geometry	O
for	O
the	O
F-14	B-Device
.	O
</s>
<s>
In	O
a	O
Usenet	O
post	O
referring	O
to	O
this	O
version	O
,	O
David	O
Jevans	O
of	O
the	O
University	O
of	O
Calgary	O
mentioned	O
that	O
several	O
other	O
versions	O
of	O
flight	O
now	O
existed	O
,	O
including	O
a	O
version	O
running	O
on	O
the	O
IRIS	O
Power	O
Series	O
with	O
Gouraud	B-Algorithm
shaded	I-Algorithm
planes	O
.	O
</s>
<s>
A	O
group	O
of	O
researchers	O
interfaced	O
the	O
flight	B-Application
simulator	I-Application
with	O
the	O
US	O
military	O
's	O
SIMNET	B-General_Concept
.	O
</s>
<s>
The	O
software	O
written	O
to	O
perform	O
this	O
operation	O
uses	O
UDP/IP	B-Protocol
to	O
capture	O
the	O
SG	O
broadcast	B-Operating_System
packets	I-Operating_System
and	O
saves	O
them	O
to	O
a	O
disk	O
file	O
.	O
</s>
<s>
Information	O
contained	O
in	O
the	O
SG	O
PDU	O
was	O
reformatted	O
or	O
translated	O
into	O
SIMNET	B-General_Concept
type	O
packets	O
,	O
and	O
then	O
retransmitted	O
over	O
the	O
ETHERNET	O
to	O
the	O
SIMNET	B-General_Concept
M1	O
tank	O
modules.	O
"	O
</s>
<s>
A	O
researcher	O
at	O
the	O
US	O
Air	O
Force	O
Institute	O
of	O
Technology	O
attempted	O
to	O
reduce	O
the	O
cost	O
of	O
flight	B-Application
simulators	I-Application
used	O
in	O
pilot	O
training	O
by	O
using	O
a	O
head-mounted	O
display	O
with	O
a	O
simulator	O
that	O
could	O
run	O
on	O
PC	O
hardware	O
.	O
</s>
<s>
As	O
part	O
of	O
this	O
,	O
an	O
attempt	O
was	O
made	O
to	O
port	O
dog/flight	O
to	O
a	O
PC	O
platform	O
based	O
on	O
a	O
20MHz	O
80386	O
processor	O
with	O
80387	O
coprocessor	O
,	O
and	O
a	O
Real	O
World	O
Graphics	O
Ltd	O
.	O
PC	O
Reality	O
board	O
containing	O
two	O
Intel	B-General_Concept
i860	I-General_Concept
RISC	O
processors	O
.	O
</s>
<s>
The	O
flight	B-Application
simulator	I-Application
program	O
needed	O
to	O
maintain	O
cross-platform	O
portability	O
,	O
so	O
rewriting	O
it	O
in	O
assembler	O
instead	O
of	O
C	O
was	O
not	O
allowed	O
.	O
</s>
<s>
The	O
PC	O
's	O
performance	O
was	O
also	O
compared	O
to	O
that	O
of	O
the	O
Silicon	O
Graphics	O
IRIS	O
4D/85GT	O
with	O
an	O
unmodified	O
version	O
of	O
the	O
flight	B-Application
simulator	I-Application
.	O
</s>
<s>
One	O
problem	O
was	O
that	O
ESIX	O
's	O
UDP/IP	B-Protocol
support	O
did	O
not	O
support	O
programming	O
below	O
the	O
OSI	O
transport	O
layer	O
,	O
unlike	O
SGI	O
's	O
.	O
</s>
<s>
Code	O
from	O
the	O
SGI	O
flight	B-Application
simulator	I-Application
was	O
incorporated	O
into	O
a	O
project	O
to	O
develop	O
a	O
low-cost	O
flight	B-Application
simulator	I-Application
using	O
object-oriented	B-Language
programming	I-Language
techniques	O
and	O
the	O
C++	B-Language
language	I-Language
.	O
</s>
<s>
The	O
researchers	O
noted	O
that	O
the	O
flight	B-Application
simulator	I-Application
was	O
non-deterministic	O
,	O
since	O
it	O
"	O
runs	O
on	O
a	O
multi-tasking	O
Unix	O
system	O
,	O
not	O
on	O
a	O
dedicated	O
real-time	O
system	O
.	O
</s>
<s>
Thus	O
,	O
it	O
is	O
not	O
possible	O
to	O
give	O
a	O
guaranteed	O
real-time	O
response	O
because	O
the	O
flight	B-Application
simulator	I-Application
can	O
be	O
interrupted	O
by	O
other	O
processes	O
or	O
I/O	O
traffic.	O
"	O
</s>
<s>
This	O
meant	O
that	O
simply	O
repeating	O
the	O
same	O
set	O
of	O
inputs	O
across	O
multiple	O
runs	O
of	O
the	O
flight	B-Application
simulator	I-Application
would	O
not	O
be	O
guaranteed	O
to	O
give	O
the	O
same	O
results	O
.	O
</s>
