<s>
In	O
telecommunications	O
,	O
message	B-Protocol
switching	I-Protocol
involves	O
messages	O
routed	O
in	O
their	O
entirety	O
,	O
one	O
hop	O
at	O
a	O
time	O
.	O
</s>
<s>
It	O
evolved	O
from	O
circuit	B-Protocol
switching	I-Protocol
and	O
was	O
the	O
precursor	O
of	O
packet	B-Protocol
switching	I-Protocol
.	O
</s>
<s>
An	O
example	O
of	O
message	B-Protocol
switching	I-Protocol
is	O
email	B-Protocol
in	O
which	O
the	O
message	O
is	O
sent	O
through	O
different	O
intermediate	O
servers	O
to	O
reach	O
the	O
mail	O
server	O
for	O
storing	O
.	O
</s>
<s>
Unlike	O
packet	B-Protocol
switching	I-Protocol
,	O
the	O
message	O
is	O
not	O
divided	O
into	O
smaller	O
units	O
and	O
sent	O
independently	O
over	O
the	O
network	O
.	O
</s>
<s>
Western	O
Union	O
operated	O
a	O
message	B-Protocol
switching	I-Protocol
system	O
,	O
Plan	O
55-A	O
,	O
for	O
processing	O
telegrams	B-Application
in	O
the	O
1950s	O
.	O
</s>
<s>
Message	B-Protocol
switching	I-Protocol
was	O
built	O
by	O
Collins	O
Radio	O
Company	O
,	O
Newport	O
Beach	O
,	O
California	O
,	O
during	O
the	O
period	O
1959	O
–	O
1963	O
for	O
sale	O
to	O
large	O
airlines	O
,	O
banks	O
and	O
railroads	O
.	O
</s>
<s>
The	O
original	O
design	O
for	O
the	O
ARPANET	O
was	O
Wesley	O
Clark	O
's	O
April	O
1967	O
proposal	O
for	O
using	O
Interface	B-Protocol
Message	I-Protocol
Processors	I-Protocol
to	O
create	O
a	O
message	B-Protocol
switching	I-Protocol
network	O
.	O
</s>
<s>
Packet	B-Protocol
switching	I-Protocol
was	O
incorporated	O
into	O
the	O
design	O
by	O
Larry	O
Roberts	O
after	O
the	O
first	O
ACM	O
Symposium	O
on	O
Operating	O
Systems	O
Principles	O
in	O
October	O
1967	O
based	O
on	O
the	O
work	O
of	O
both	O
Donald	O
Davies	O
and	O
Paul	O
Baran	O
who	O
had	O
been	O
working	O
on	O
the	O
idea	O
of	O
packet	B-Protocol
switching	I-Protocol
independently	O
of	O
each	O
other	O
.	O
</s>
<s>
Message	B-Protocol
switching	I-Protocol
systems	O
are	O
nowadays	O
mostly	O
implemented	O
over	O
packet-switched	B-Protocol
or	O
circuit-switched	B-Protocol
data	O
networks	O
.	O
</s>
<s>
Because	O
of	O
this	O
it	O
is	O
also	O
known	O
as	O
a	O
'	O
store	B-Protocol
and	I-Protocol
forward	I-Protocol
 '	O
network	O
.	O
</s>
<s>
Email	B-Protocol
is	O
a	O
common	O
application	O
for	O
message	B-Protocol
switching	I-Protocol
.	O
</s>
<s>
A	O
delay	O
in	O
delivering	O
email	B-Protocol
is	O
allowed	O
real-time	O
data	O
transfer	O
between	O
two	O
computers	O
.	O
</s>
<s>
Hop-by-hop	O
Telex	O
forwarding	O
and	O
UUCP	B-Protocol
are	O
examples	O
of	O
message	B-Protocol
switching	I-Protocol
systems	O
.	O
</s>
<s>
router	B-Protocol
)	O
then	O
forwarded	O
later	O
one	O
hop	O
at	O
a	O
time	O
.	O
</s>
<s>
A	O
form	O
of	O
store-and-forward	B-Protocol
network	O
.	O
</s>
<s>
The	O
source	O
and	O
destination	O
terminal	O
need	O
not	O
be	O
compatible	O
,	O
since	O
conversions	O
are	O
done	O
by	O
the	O
message	B-Protocol
switching	I-Protocol
networks	O
.	O
</s>
<s>
Message	B-Protocol
switching	I-Protocol
multiplexes	O
data	O
from	O
different	O
sources	O
onto	O
a	O
common	O
facility	O
.	O
</s>
<s>
Since	O
message	B-Protocol
switching	I-Protocol
stores	O
each	O
message	O
at	O
intermediate	O
nodes	O
in	O
its	O
entirety	O
before	O
forwarding	O
,	O
messages	O
experience	O
an	O
end	O
to	O
end	O
delay	O
which	O
is	O
dependent	O
on	O
the	O
message	O
length	O
,	O
and	O
the	O
number	O
of	O
intermediate	O
nodes	O
.	O
</s>
<s>
Message	B-Protocol
switching	I-Protocol
is	O
thus	O
an	O
example	O
of	O
a	O
delay	O
system	O
or	O
a	O
queuing	O
system	O
.	O
</s>
<s>
Message	B-Protocol
switching	I-Protocol
is	O
still	O
used	O
for	O
telegraph	O
traffic	O
and	O
a	O
modified	O
form	O
of	O
it	O
,	O
known	O
as	O
packet	B-Protocol
switching	I-Protocol
,	O
is	O
used	O
extensively	O
for	O
data	O
communications	O
.	O
</s>
<s>
The	O
advantages	O
to	O
message	B-Protocol
switching	I-Protocol
are	O
:	O
</s>
