<s>
Realm-Specific	B-Protocol
IP	I-Protocol
was	O
an	O
experimental	O
IETF	O
framework	O
and	O
protocol	O
intended	O
as	O
an	O
alternative	O
to	O
network	B-Protocol
address	I-Protocol
translation	I-Protocol
(	O
NAT	O
)	O
in	O
which	O
the	O
end-to-end	O
integrity	O
of	O
packets	O
is	O
maintained	O
.	O
</s>
<s>
RSIP	B-Protocol
lets	O
a	O
host	O
borrow	O
one	O
or	O
more	O
IP	B-Protocol
addresses	I-Protocol
(	O
and	O
UDP/TCP	O
port	O
)	O
from	O
one	O
or	O
more	O
RSIP	B-Protocol
gateways	I-Protocol
,	O
by	O
leasing	O
(	O
usually	O
public	O
)	O
IP	B-Protocol
addresses	I-Protocol
and	O
ports	O
to	O
RSIP	B-Protocol
hosts	O
located	O
in	O
other	O
(	O
usually	O
private	O
)	O
addressing	O
realms	O
.	O
</s>
<s>
The	O
RSIP	B-Protocol
client	O
requests	O
registration	O
with	O
an	O
RSIP	B-Protocol
gateway	I-Protocol
.	O
</s>
<s>
The	O
gateway	O
in	O
turn	O
delivers	O
either	O
a	O
unique	O
IP	B-Protocol
address	I-Protocol
or	O
a	O
shared	O
IP	B-Protocol
address	I-Protocol
and	O
a	O
unique	O
set	O
of	O
TCP/UDP	O
ports	O
and	O
associates	O
the	O
RSIP	B-Protocol
host	O
address	O
to	O
this	O
address	O
.	O
</s>
<s>
The	O
RSIP	B-Protocol
host	O
uses	O
this	O
address	O
to	O
send	O
packets	O
to	O
destinations	O
in	O
the	O
other	O
realm	O
.	O
</s>
<s>
The	O
tunnelled	O
packets	O
between	O
RSIP	B-Protocol
host	O
and	O
gateway	O
contain	O
both	O
addresses	O
,	O
and	O
the	O
RSIP	B-Protocol
gateway	I-Protocol
strips	O
off	O
the	O
host	O
address	O
header	O
and	O
sends	O
the	O
packet	O
to	O
the	O
destination	O
.	O
</s>
<s>
RSIP	B-Protocol
can	O
also	O
be	O
used	O
to	O
relay	O
traffic	O
between	O
several	O
different	O
privately	O
addressed	O
networks	O
by	O
leasing	O
several	O
different	O
addresses	O
to	O
reach	O
different	O
destination	O
networks	O
.	O
</s>
<s>
RSIP	B-Protocol
should	O
be	O
useful	O
for	O
NAT	B-Protocol
traversal	I-Protocol
as	O
an	O
IETF	O
standard	O
alternative	O
to	O
Universal	B-Application
Plug	I-Application
and	I-Application
Play	I-Application
(	O
UPnP	B-Application
)	O
.	O
</s>
