<s>
TCP	B-Protocol
Westwood	O
(	O
TCPW	O
)	O
is	O
a	O
sender-side-only	O
modification	O
to	O
TCP	B-Protocol
New	O
Reno	O
that	O
is	O
intended	O
to	O
better	O
handle	O
large	O
bandwidth-delay	O
product	O
paths	O
(	O
large	O
pipes	O
)	O
,	O
with	O
potential	O
packet	O
loss	O
due	O
to	O
transmission	O
or	O
other	O
errors	O
(	O
leaky	O
pipes	O
)	O
,	O
and	O
with	O
dynamic	O
load	O
(	O
dynamic	O
pipes	O
)	O
.	O
</s>
<s>
TCP	B-Protocol
Westwood	O
relies	O
on	O
mining	O
the	O
ACK	O
stream	O
for	O
information	O
to	O
help	O
it	O
better	O
set	O
the	O
congestion	O
control	O
parameters	O
:	O
Slow	O
Start	O
Threshold	O
(	O
ssthresh	O
)	O
,	O
and	O
Congestion	B-Protocol
Window	I-Protocol
(	O
cwin	O
)	O
.	O
</s>
<s>
In	O
TCP	B-Protocol
Westwood	O
,	O
an	O
"	O
Eligible	O
Rate	O
"	O
is	O
estimated	O
and	O
used	O
by	O
the	O
sender	O
to	O
update	O
ssthresh	O
and	O
cwin	O
upon	O
loss	O
indication	O
,	O
or	O
during	O
its	O
"	O
Agile	O
Probing	O
"	O
phase	O
,	O
a	O
proposed	O
modification	O
to	O
the	O
well-known	O
slow	O
start	O
phase	O
.	O
</s>
<s>
The	O
resultant	O
performance	O
gains	O
in	O
efficiency	O
,	O
without	O
undue	O
sacrifice	O
of	O
fairness	O
,	O
friendliness	O
,	O
and	O
stability	O
have	O
been	O
reported	O
in	O
numerous	O
papers	O
that	O
can	O
be	O
found	O
on	O
The	O
TCP	B-Protocol
WESTWOOD	O
Home	O
Page	O
.	O
</s>
<s>
"	O
opportunistic	O
friendliness	O
"	O
,	O
TCP	B-Protocol
Westwood	O
is	O
shown	O
to	O
have	O
good	O
,	O
and	O
controllable	O
,	O
friendliness	O
.	O
</s>
<s>
The	O
main	O
idea	O
of	O
Westwood	O
TCP	B-Protocol
,	O
which	O
is	O
an	O
end-to-end	O
bandwidth	O
estimation	O
for	O
setting	O
control	O
windows	O
after	O
congestion	O
,	O
was	O
proposed	O
by	O
Saverio	O
Mascolo	O
.	O
</s>
<s>
He	O
came	O
out	O
with	O
the	O
idea	O
after	O
reading	O
the	O
chapter	O
on	O
TCP	B-Protocol
congestion	O
control	O
in	O
the	O
book	O
Data	O
Networks	O
by	O
Larry	O
Peterson	O
.	O
</s>
<s>
The	O
first	O
implementation	O
of	O
TCP	B-Protocol
Westwood	O
in	O
ns2	O
was	O
done	O
at	O
University	O
of	O
California	O
,	O
Los	O
Angeles	O
(	O
UCLA	O
)	O
in	O
1999	O
.	O
</s>
<s>
TCP	B-Protocol
Westwood+	O
is	O
an	O
evolution	O
of	O
TCP	B-Protocol
Westwood	O
.	O
</s>
<s>
TCP	B-Protocol
Westwood+	O
is	O
a	O
sender-side	O
only	O
modification	O
of	O
the	O
TCP	B-Protocol
Reno	O
protocol	B-Protocol
stack	I-Protocol
that	O
optimizes	O
the	O
performance	O
of	O
TCP	B-Protocol
congestion	O
control	O
over	O
both	O
wireline	O
and	O
wireless	B-General_Concept
networks	I-General_Concept
.	O
</s>
<s>
TCP	B-Protocol
Westwood+	O
is	O
based	O
on	O
end-to-end	O
bandwidth	O
estimation	O
to	O
set	O
congestion	B-Protocol
window	I-Protocol
and	O
slow	O
start	O
threshold	O
after	O
a	O
congestion	O
episode	O
,	O
that	O
is	O
,	O
after	O
three	O
duplicate	O
acknowledgments	O
or	O
a	O
timeout	O
.	O
</s>
<s>
The	O
bandwidth	O
is	O
estimated	O
by	O
properly	O
low-pass	B-Algorithm
filtering	I-Algorithm
the	O
rate	O
of	O
returning	O
acknowledgment	O
packets	O
.	O
</s>
<s>
The	O
rationale	O
of	O
this	O
strategy	O
is	O
simple	O
:	O
in	O
contrast	O
with	O
TCP	B-Protocol
Reno	O
,	O
which	O
blindly	O
halves	O
the	O
congestion	B-Protocol
window	I-Protocol
after	O
three	O
duplicate	O
ACKs	O
,	O
TCP	B-Protocol
Westwood+	O
adaptively	O
sets	O
a	O
slow	O
start	O
threshold	O
and	O
a	O
congestion	B-Protocol
window	I-Protocol
which	O
takes	O
into	O
account	O
the	O
bandwidth	O
used	O
at	O
the	O
time	O
congestion	O
is	O
experienced	O
.	O
</s>
<s>
TCP	B-Protocol
Westwood+	O
significantly	O
increases	O
throughput	O
over	O
wireless	O
links	O
and	O
fairness	O
compared	O
to	O
TCP	B-Protocol
Reno/New	O
Reno	O
in	O
wired	O
networks	O
.	O
</s>
<s>
When	O
Saverio	O
Mascolo	O
returned	O
to	O
Italy	O
and	O
"	O
his	O
evolution	O
of	O
Westwood	O
TCP	B-Protocol
"	O
was	O
named	O
Westwood+	O
.	O
</s>
<s>
This	O
phenomenon	O
was	O
explained	O
in	O
terms	O
of	O
aliasing	B-Error_Name
effects	O
.	O
</s>
<s>
The	O
new	O
version	O
Westwood+	O
was	O
implemented	O
for	O
the	O
first	O
time	O
in	O
the	O
kernel	O
of	O
Linux	B-Application
2.2	O
by	O
Roberto	O
Ferorelli	O
and	O
in	O
the	O
kernel	O
of	O
Linux	B-Application
2.4	O
and	O
2.6	O
by	O
Angelo	O
Dell'Aera	O
,	O
both	O
working	O
at	O
Politecnico	O
di	O
Bari	O
as	O
undergraduate	O
students	O
in	O
2003	O
and	O
2004	O
.	O
</s>
