<s>
In	O
computer	B-Architecture
networking	I-Architecture
,	O
the	O
User	B-Protocol
Datagram	I-Protocol
Protocol	I-Protocol
(	O
UDP	O
)	O
is	O
one	O
of	O
the	O
core	O
communication	O
protocols	O
of	O
the	O
Internet	B-Protocol
protocol	I-Protocol
suite	I-Protocol
used	O
to	O
send	O
messages	O
(	O
transported	O
as	O
datagrams	B-Protocol
in	O
packets	B-Protocol
)	O
to	O
other	O
hosts	O
on	O
an	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	O
)	O
network	O
.	O
</s>
<s>
Within	O
an	O
IP	B-Protocol
network	I-Protocol
,	O
UDP	O
does	O
not	O
require	O
prior	O
communication	O
to	O
set	O
up	O
communication	O
channels	O
or	O
data	O
paths	O
.	O
</s>
<s>
UDP	O
uses	O
a	O
simple	O
connectionless	B-Protocol
communication	I-Protocol
model	O
with	O
a	O
minimum	O
of	O
protocol	O
mechanisms	O
.	O
</s>
<s>
UDP	O
provides	O
checksums	B-Algorithm
for	O
data	O
integrity	O
,	O
and	O
port	B-Protocol
numbers	I-Protocol
for	O
addressing	O
different	O
functions	O
at	O
the	O
source	O
and	O
destination	O
of	O
the	O
datagram	B-Protocol
.	O
</s>
<s>
It	O
has	O
no	O
handshaking	B-Protocol
dialogues	O
,	O
and	O
thus	O
exposes	O
the	O
user	O
's	O
program	O
to	O
any	O
unreliability	B-Protocol
of	O
the	O
underlying	O
network	O
;	O
there	O
is	O
no	O
guarantee	O
of	O
delivery	O
,	O
ordering	O
,	O
or	O
duplicate	O
protection	O
.	O
</s>
<s>
If	O
error-correction	O
facilities	O
are	O
needed	O
at	O
the	O
network	O
interface	O
level	O
,	O
an	O
application	O
may	O
instead	O
use	O
Transmission	B-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
TCP	B-Protocol
)	O
or	O
Stream	B-Protocol
Control	I-Protocol
Transmission	I-Protocol
Protocol	I-Protocol
(	O
SCTP	B-Protocol
)	O
which	O
are	O
designed	O
for	O
this	O
purpose	O
.	O
</s>
<s>
UDP	O
is	O
suitable	O
for	O
purposes	O
where	O
error	O
checking	O
and	O
correction	O
are	O
either	O
not	O
necessary	O
or	O
are	O
performed	O
in	O
the	O
application	O
;	O
UDP	O
avoids	O
the	O
overhead	O
of	O
such	O
processing	O
in	O
the	O
protocol	B-Protocol
stack	I-Protocol
.	O
</s>
<s>
Time-sensitive	O
applications	O
often	O
use	O
UDP	O
because	O
dropping	O
packets	B-Protocol
is	O
preferable	O
to	O
waiting	O
for	O
packets	B-Protocol
delayed	O
due	O
to	O
retransmission	B-Protocol
,	O
which	O
may	O
not	O
be	O
an	O
option	O
in	O
a	O
real-time	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
UDP	O
is	O
a	O
simple	O
message-oriented	O
transport	B-Architecture
layer	I-Architecture
protocol	O
that	O
is	O
documented	O
in	O
.	O
</s>
<s>
Although	O
UDP	O
provides	O
integrity	O
verification	O
(	O
via	O
checksum	B-Algorithm
)	O
of	O
the	O
header	O
and	O
payload	O
,	O
it	O
provides	O
no	O
guarantees	O
to	O
the	O
upper	B-Protocol
layer	I-Protocol
protocol	I-Protocol
for	O
message	O
delivery	O
and	O
the	O
UDP	O
layer	O
retains	O
no	O
state	O
of	O
UDP	O
messages	O
once	O
sent	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
UDP	O
sometimes	O
is	O
referred	O
to	O
as	O
Unreliable	B-Protocol
Datagram	I-Protocol
Protocol	I-Protocol
.	O
</s>
<s>
It	O
is	O
transaction-oriented	O
,	O
suitable	O
for	O
simple	O
query-response	O
protocols	O
such	O
as	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
or	O
the	O
Network	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
.	O
</s>
<s>
It	O
provides	O
datagrams	B-Protocol
,	O
suitable	O
for	O
modeling	O
other	O
protocols	O
such	O
as	O
IP	B-Protocol
tunneling	I-Protocol
or	O
remote	B-Operating_System
procedure	I-Operating_System
call	I-Operating_System
and	O
the	O
Network	B-Protocol
File	I-Protocol
System	I-Protocol
.	O
</s>
<s>
It	O
is	O
simple	O
,	O
suitable	O
for	O
bootstrapping	B-Application
or	O
other	O
purposes	O
without	O
a	O
full	O
protocol	B-Protocol
stack	I-Protocol
,	O
such	O
as	O
the	O
DHCP	B-Protocol
and	O
Trivial	B-Device
File	I-Device
Transfer	I-Device
Protocol	I-Device
.	O
</s>
<s>
The	O
lack	O
of	O
retransmission	B-Protocol
delays	O
makes	O
it	O
suitable	O
for	O
real-time	B-General_Concept
applications	I-General_Concept
such	O
as	O
Voice	B-Application
over	I-Application
IP	I-Application
,	O
online	B-Application
games	I-Application
,	O
and	O
many	O
protocols	O
using	O
Real	B-Protocol
Time	I-Protocol
Streaming	I-Protocol
Protocol	I-Protocol
.	O
</s>
<s>
Because	O
it	O
supports	O
multicast	O
,	O
it	O
is	O
suitable	O
for	O
broadcast	O
information	O
such	O
as	O
in	O
many	O
kinds	O
of	O
service	B-Protocol
discovery	I-Protocol
and	O
shared	O
information	O
such	O
as	O
Precision	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
and	O
Routing	B-Protocol
Information	I-Protocol
Protocol	I-Protocol
.	O
</s>
<s>
Applications	O
can	O
use	O
datagram	B-Protocol
sockets	I-Protocol
to	O
establish	O
host-to-host	O
communications	O
.	O
</s>
<s>
An	O
application	O
binds	O
a	O
socket	O
to	O
its	O
endpoint	O
of	O
data	O
transmission	O
,	O
which	O
is	O
a	O
combination	O
of	O
an	O
IP	B-Protocol
address	I-Protocol
and	O
a	O
port	B-Protocol
.	O
</s>
<s>
In	O
this	O
way	O
,	O
UDP	O
provides	O
application	O
multiplexing	B-Architecture
.	O
</s>
<s>
A	O
port	B-Protocol
is	O
a	O
software	O
structure	O
that	O
is	O
identified	O
by	O
the	O
port	B-Protocol
number	I-Protocol
,	O
a	O
16-bit	O
integer	O
value	O
,	O
allowing	O
for	O
port	B-Protocol
numbers	I-Protocol
between	O
0	O
and	O
65535	O
.	O
</s>
<s>
Port	B-Protocol
0	O
is	O
reserved	O
but	O
is	O
a	O
permissible	O
source	O
port	B-Protocol
value	O
if	O
the	O
sending	O
process	O
does	O
not	O
expect	O
messages	O
in	O
response	O
.	O
</s>
<s>
The	O
Internet	O
Assigned	O
Numbers	O
Authority	O
(	O
IANA	O
)	O
has	O
divided	O
port	B-Protocol
numbers	I-Protocol
into	O
three	O
ranges	O
.	O
</s>
<s>
Port	B-Protocol
numbers	I-Protocol
0	O
through	O
1023	O
are	O
used	O
for	O
common	O
,	O
well-known	O
services	O
.	O
</s>
<s>
On	O
Unix-like	O
operating	B-General_Concept
systems	I-General_Concept
,	O
using	O
one	O
of	O
these	O
ports	O
requires	O
superuser	B-Application
operating	O
permission	O
.	O
</s>
<s>
Port	B-Protocol
numbers	I-Protocol
1024	O
through	O
49151	O
are	O
the	O
registered	B-Protocol
ports	I-Protocol
used	O
for	O
IANA-registered	O
services	O
.	O
</s>
<s>
Ports	O
49152	O
through	O
65535	O
are	O
dynamic	B-Protocol
ports	I-Protocol
that	O
are	O
not	O
officially	O
designated	O
for	O
any	O
specific	O
service	O
,	O
and	O
may	O
be	O
used	O
for	O
any	O
purpose	O
.	O
</s>
<s>
These	O
may	O
also	O
be	O
used	O
as	O
ephemeral	B-Protocol
ports	I-Protocol
,	O
which	O
software	O
running	O
on	O
the	O
host	O
may	O
use	O
to	O
dynamically	O
create	O
communications	O
endpoints	O
as	O
needed	O
.	O
</s>
<s>
A	O
UDP	O
datagram	B-Protocol
consists	O
of	O
a	O
datagram	B-Protocol
header	O
followed	O
by	O
a	O
data	O
section	O
(	O
the	O
payload	O
data	O
for	O
the	O
application	O
)	O
.	O
</s>
<s>
The	O
UDP	O
datagram	B-Protocol
header	O
consists	O
of	O
4	O
fields	O
,	O
each	O
of	O
which	O
is	O
2	O
bytes	B-Application
(	O
16	O
bits	O
)	O
:	O
</s>
<s>
The	O
use	O
of	O
the	O
checksum	B-Algorithm
and	O
source	O
port	B-Protocol
fields	O
is	O
optional	O
in	O
IPv4	B-Protocol
(	O
pink	O
background	O
in	O
table	O
)	O
.	O
</s>
<s>
In	O
IPv6	B-Protocol
only	O
the	O
source	O
port	B-Protocol
field	O
is	O
optional	O
.	O
</s>
<s>
This	O
field	O
identifies	O
the	O
sender	O
's	O
port	B-Protocol
,	O
when	O
used	O
,	O
and	O
should	O
be	O
assumed	O
to	O
be	O
the	O
port	B-Protocol
to	O
reply	O
to	O
if	O
needed	O
.	O
</s>
<s>
If	O
the	O
source	O
host	O
is	O
the	O
client	O
,	O
the	O
port	B-Protocol
number	I-Protocol
is	O
likely	O
to	O
be	O
an	O
ephemeral	B-Protocol
port	I-Protocol
.	O
</s>
<s>
If	O
the	O
source	O
host	O
is	O
the	O
server	O
,	O
the	O
port	B-Protocol
number	I-Protocol
is	O
likely	O
to	O
be	O
a	O
well-known	O
port	B-Protocol
number	I-Protocol
from	O
0	O
to	O
1023	O
.	O
</s>
<s>
This	O
field	O
identifies	O
the	O
receiver	O
's	O
port	B-Protocol
and	O
is	O
required	O
.	O
</s>
<s>
Similar	O
to	O
source	O
port	B-Protocol
number	I-Protocol
,	O
if	O
the	O
client	O
is	O
the	O
destination	O
host	O
then	O
the	O
port	B-Protocol
number	I-Protocol
will	O
likely	O
be	O
an	O
ephemeral	B-Protocol
port	I-Protocol
number	I-Protocol
and	O
if	O
the	O
destination	O
host	O
is	O
the	O
server	O
then	O
the	O
port	B-Protocol
number	I-Protocol
will	O
likely	O
be	O
a	O
well-known	O
port	B-Protocol
number	I-Protocol
.	O
</s>
<s>
This	O
field	O
specifies	O
the	O
length	O
in	O
bytes	B-Application
of	O
the	O
UDP	O
header	O
and	O
UDP	O
data	O
.	O
</s>
<s>
The	O
minimum	O
length	O
is	O
8	O
bytes	B-Application
,	O
the	O
length	O
of	O
the	O
header	O
.	O
</s>
<s>
The	O
field	O
size	O
sets	O
a	O
theoretical	O
limit	O
of	O
65,535	O
bytes	B-Application
(	O
8-byte	O
header	O
+	O
65,527	O
bytes	B-Application
of	O
data	O
)	O
for	O
a	O
UDP	O
datagram	B-Protocol
.	O
</s>
<s>
However	O
the	O
actual	O
limit	O
for	O
the	O
data	O
length	O
,	O
which	O
is	O
imposed	O
by	O
the	O
underlying	O
IPv4	B-Protocol
protocol	O
,	O
is	O
65,507	O
bytes	B-Application
(	O
65,535	O
bytes	B-Application
−	O
8-byte	O
UDP	O
header	O
−	O
20-byte	O
IP	O
header	O
)	O
.	O
</s>
<s>
Using	O
IPv6	B-Protocol
jumbograms	B-Protocol
it	O
is	O
possible	O
to	O
have	O
UDP	O
datagrams	B-Protocol
of	O
size	O
greater	O
than	O
65,535	O
bytes	B-Application
.	O
</s>
<s>
The	O
checksum	B-Algorithm
field	O
may	O
be	O
used	O
for	O
error-checking	O
of	O
the	O
header	O
and	O
data	O
.	O
</s>
<s>
This	O
field	O
is	O
optional	O
in	O
IPv4	B-Protocol
,	O
and	O
mandatory	O
in	O
most	O
cases	O
in	O
IPv6	B-Protocol
.	O
</s>
<s>
The	O
method	O
used	O
to	O
compute	O
the	O
checksum	B-Algorithm
is	O
defined	O
in	O
,	O
and	O
efficient	O
calculation	O
is	O
discussed	O
in	O
:	O
</s>
<s>
Finally	O
,	O
the	O
sum	O
is	O
then	O
one	O
's	O
complemented	O
to	O
yield	O
the	O
value	O
of	O
the	O
UDP	O
checksum	B-Algorithm
field	O
.	O
</s>
<s>
If	O
the	O
checksum	B-Algorithm
calculation	O
results	O
in	O
the	O
value	O
zero	O
(	O
all	O
16	O
bits	O
0	O
)	O
it	O
should	O
be	O
sent	O
as	O
the	O
one	O
's	O
complement	O
(	O
all	O
1s	O
)	O
as	O
a	O
zero-value	O
checksum	B-Algorithm
indicates	O
no	O
checksum	B-Algorithm
has	O
been	O
calculated	O
.	O
</s>
<s>
The	O
differences	O
between	O
IPv4	B-Protocol
and	O
IPv6	B-Protocol
are	O
in	O
the	O
pseudo	O
header	O
used	O
to	O
compute	O
the	O
checksum	B-Algorithm
,	O
and	O
that	O
the	O
checksum	B-Algorithm
is	O
not	O
optional	O
in	O
IPv6	B-Protocol
.	O
</s>
<s>
Under	O
specific	O
conditions	O
,	O
a	O
UDP	O
application	O
using	O
IPv6	B-Protocol
is	O
allowed	O
to	O
use	O
a	O
zero	O
UDP	O
zero-checksum	O
mode	O
with	O
a	O
tunnel	O
protocol	O
.	O
</s>
<s>
When	O
UDP	O
runs	O
over	O
IPv4	B-Protocol
,	O
the	O
checksum	B-Algorithm
is	O
computed	O
using	O
a	O
"	O
pseudo	O
header	O
"	O
that	O
contains	O
some	O
of	O
the	O
same	O
information	O
from	O
the	O
real	O
IPv4	B-Protocol
header	O
.	O
</s>
<s>
The	O
pseudo	O
header	O
is	O
not	O
the	O
real	O
IPv4	B-Protocol
header	O
used	O
to	O
send	O
an	O
IP	O
packet	B-Protocol
,	O
it	O
is	O
used	O
only	O
for	O
the	O
checksum	B-Algorithm
calculation	O
.	O
</s>
<s>
The	O
source	O
and	O
destination	O
addresses	O
are	O
those	O
in	O
the	O
IPv4	B-Protocol
header	O
.	O
</s>
<s>
The	O
protocol	O
is	O
that	O
for	O
UDP	O
(	O
see	O
List	B-Protocol
of	I-Protocol
IP	I-Protocol
protocol	I-Protocol
numbers	I-Protocol
)	O
:	O
17	O
(	O
0x11	O
)	O
.	O
</s>
<s>
UDP	O
checksum	B-Algorithm
computation	O
is	O
optional	O
for	O
IPv4	B-Protocol
.	O
</s>
<s>
If	O
a	O
checksum	B-Algorithm
is	O
not	O
used	O
it	O
should	O
be	O
set	O
to	O
the	O
value	O
zero	O
.	O
</s>
<s>
As	O
IPv6	B-Protocol
has	O
larger	O
addresses	O
and	O
a	O
different	O
header	O
lay-out	O
,	O
the	O
method	O
used	O
to	O
compute	O
the	O
checksum	B-Algorithm
is	O
changed	O
accordingly	O
:	O
</s>
<s>
When	O
computing	O
the	O
checksum	B-Algorithm
,	O
again	O
a	O
pseudo	O
header	O
is	O
used	O
that	O
mimics	O
the	O
real	O
IPv6	B-Protocol
header	O
:	O
</s>
<s>
The	O
source	O
address	O
is	O
the	O
one	O
in	O
the	O
IPv6	B-Protocol
header	O
.	O
</s>
<s>
The	O
destination	O
address	O
is	O
the	O
final	O
destination	O
;	O
if	O
the	O
IPv6	B-Protocol
packet	B-Protocol
does	O
not	O
contain	O
a	O
Routing	O
header	O
,	O
that	O
will	O
be	O
the	O
destination	O
address	O
in	O
the	O
IPv6	B-Protocol
header	O
;	O
otherwise	O
,	O
at	O
the	O
originating	O
node	O
,	O
it	O
will	O
be	O
the	O
address	O
in	O
the	O
last	O
element	O
of	O
the	O
Routing	O
header	O
,	O
and	O
,	O
at	O
the	O
receiving	O
node	O
,	O
it	O
will	O
be	O
the	O
destination	O
address	O
in	O
the	O
IPv6	B-Protocol
header	O
.	O
</s>
<s>
Lacking	O
reliability	O
,	O
UDP	O
applications	O
may	O
encounter	O
some	O
packet	B-Protocol
loss	O
,	O
reordering	O
,	O
errors	O
or	O
duplication	O
.	O
</s>
<s>
If	O
using	O
UDP	O
,	O
the	O
end-user	O
applications	O
must	O
provide	O
any	O
necessary	O
handshaking	B-Protocol
such	O
as	O
real-time	O
confirmation	O
that	O
the	O
message	O
has	O
been	O
received	O
.	O
</s>
<s>
Applications	O
,	O
such	O
as	O
TFTP	B-Device
,	O
may	O
add	O
rudimentary	O
reliability	O
mechanisms	O
into	O
the	O
application	O
layer	O
as	O
needed	O
.	O
</s>
<s>
If	O
an	O
application	O
requires	O
a	O
high	O
degree	O
of	O
reliability	O
,	O
a	O
protocol	O
such	O
as	O
the	O
Transmission	B-Protocol
Control	I-Protocol
Protocol	I-Protocol
may	O
be	O
used	O
instead	O
.	O
</s>
<s>
Streaming	O
media	O
,	O
real-time	O
multiplayer	O
games	O
and	O
voice	B-Application
over	I-Application
IP	I-Application
(	O
VoIP	B-Application
)	O
are	O
examples	O
of	O
applications	O
that	O
often	O
use	O
UDP	O
.	O
</s>
<s>
In	O
these	O
particular	O
applications	O
,	O
loss	O
of	O
packets	B-Protocol
is	O
not	O
usually	O
a	O
fatal	O
problem	O
.	O
</s>
<s>
In	O
VoIP	B-Application
,	O
for	O
example	O
,	O
latency	O
and	O
jitter	O
are	O
the	O
primary	O
concerns	O
.	O
</s>
<s>
The	O
use	O
of	O
TCP	B-Protocol
would	O
cause	O
jitter	O
if	O
any	O
packets	B-Protocol
were	O
lost	O
as	O
TCP	B-Protocol
does	O
not	O
provide	O
subsequent	O
data	O
to	O
the	O
application	O
while	O
it	O
is	O
requesting	O
re-sending	O
of	O
the	O
missing	O
data	O
.	O
</s>
<s>
Numerous	O
key	O
Internet	O
applications	O
use	O
UDP	O
,	O
including	O
:	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
,	O
the	O
Simple	B-Protocol
Network	I-Protocol
Management	I-Protocol
Protocol	I-Protocol
(	O
SNMP	B-Protocol
)	O
,	O
the	O
Routing	B-Protocol
Information	I-Protocol
Protocol	I-Protocol
(	O
RIP	O
)	O
and	O
the	O
Dynamic	B-Protocol
Host	I-Protocol
Configuration	I-Protocol
Protocol	I-Protocol
(	O
DHCP	B-Protocol
)	O
.	O
</s>
<s>
Real-time	O
video	O
and	O
audio	O
streaming	O
protocols	O
are	O
designed	O
to	O
handle	O
occasional	O
lost	O
packets	B-Protocol
,	O
so	O
only	O
slight	O
degradation	O
in	O
quality	O
occurs	O
,	O
rather	O
than	O
large	O
delays	O
if	O
lost	O
packets	B-Protocol
were	O
retransmitted	O
.	O
</s>
<s>
Because	O
both	O
TCP	B-Protocol
and	O
UDP	O
run	O
over	O
the	O
same	O
network	O
,	O
in	O
the	O
mid-2000s	O
a	O
few	O
businesses	O
found	O
that	O
an	O
increase	O
of	O
UDP	O
traffic	O
from	O
these	O
real-time	B-General_Concept
applications	I-General_Concept
slightly	O
hindered	O
the	O
performance	O
of	O
applications	O
using	O
TCP	B-Protocol
such	O
as	O
point	O
of	O
sale	O
,	O
accounting	B-Application
,	O
and	O
database	B-Application
systems	I-Application
(	O
when	O
TCP	B-Protocol
detects	O
packet	B-Protocol
loss	O
,	O
it	O
will	O
throttle	O
back	O
its	O
data	O
rate	O
usage	O
)	O
.	O
</s>
<s>
Some	O
VPN	B-Application
systems	O
such	O
as	O
OpenVPN	B-Language
may	O
use	O
UDP	O
and	O
perform	O
error	O
checking	O
at	O
the	O
application	O
level	O
while	O
implementing	O
reliable	O
connections	O
.	O
</s>
<s>
QUIC	B-Protocol
is	O
a	O
transport	B-Architecture
protocol	I-Architecture
built	O
on	O
top	O
of	O
UDP	O
.	O
</s>
<s>
QUIC	B-Protocol
provides	O
a	O
reliable	O
and	O
secure	O
connection	O
.	O
</s>
<s>
HTTP/3	B-Protocol
uses	O
QUIC	B-Protocol
as	O
opposed	O
to	O
earlier	O
versions	O
of	O
HTTPS	B-Protocol
which	O
use	O
a	O
combination	O
of	O
TCP	B-Protocol
and	O
TLS	B-Protocol
to	O
ensure	O
reliability	O
and	O
security	O
respectively	O
.	O
</s>
<s>
This	O
means	O
that	O
HTTP/3	B-Protocol
uses	O
a	O
single	O
handshake	B-Protocol
to	O
set	O
up	O
a	O
connection	O
,	O
rather	O
than	O
having	O
two	O
separate	O
handshakes	B-Protocol
for	O
TCP	B-Protocol
and	O
TLS	B-Protocol
,	O
meaning	O
the	O
overall	O
time	O
to	O
establish	O
a	O
connection	O
is	O
reduced	O
.	O
</s>
<s>
Transmission	B-Protocol
Control	I-Protocol
Protocol	I-Protocol
is	O
a	O
connection-oriented	O
protocol	O
and	O
requires	O
handshaking	B-Protocol
to	O
set	O
up	O
end-to-end	O
communications	O
.	O
</s>
<s>
Reliable	O
–	O
TCP	B-Protocol
manages	O
message	O
acknowledgment	O
,	O
retransmission	B-Protocol
and	O
timeouts	O
.	O
</s>
<s>
In	O
TCP	B-Protocol
,	O
there	O
's	O
either	O
no	O
missing	O
data	O
,	O
or	O
,	O
in	O
case	O
of	O
multiple	O
timeouts	O
,	O
the	O
connection	O
is	O
dropped	O
.	O
</s>
<s>
When	O
data	O
segments	O
arrive	O
in	O
the	O
wrong	O
order	O
,	O
TCP	B-Protocol
buffers	O
the	O
out-of-order	O
data	O
until	O
all	O
data	O
can	O
be	O
properly	O
re-ordered	O
and	O
delivered	O
to	O
the	O
application	O
.	O
</s>
<s>
Heavyweight	O
–	O
TCP	B-Protocol
requires	O
three	O
packets	B-Protocol
to	O
set	O
up	O
a	O
socket	O
connection	O
before	O
any	O
user	O
data	O
can	O
be	O
sent	O
.	O
</s>
<s>
TCP	B-Protocol
handles	O
reliability	O
and	O
congestion	O
control	O
.	O
</s>
<s>
Streaming	O
–	O
Data	O
is	O
read	O
as	O
a	O
byte	B-Application
stream	O
,	O
no	O
distinguishing	O
indications	O
are	O
transmitted	O
to	O
signal	O
message	O
(	O
segment	O
)	O
boundaries	O
.	O
</s>
<s>
User	B-Protocol
Datagram	I-Protocol
Protocol	I-Protocol
is	O
a	O
simpler	O
message-based	O
connectionless	B-Protocol
protocol	I-Protocol
.	O
</s>
<s>
Connectionless	B-Protocol
protocols	I-Protocol
do	O
not	O
set	O
up	O
a	O
dedicated	O
end-to-end	O
connection	O
.	O
</s>
<s>
Unreliable	B-Protocol
–	O
When	O
a	O
UDP	O
message	O
is	O
sent	O
,	O
it	O
cannot	O
be	O
known	O
if	O
it	O
will	O
reach	O
its	O
destination	O
;	O
it	O
could	O
get	O
lost	O
along	O
the	O
way	O
.	O
</s>
<s>
There	O
is	O
no	O
concept	O
of	O
acknowledgment	O
,	O
retransmission	B-Protocol
,	O
or	O
timeout	O
.	O
</s>
<s>
It	O
is	O
a	O
very	O
simple	O
transport	B-Architecture
layer	I-Architecture
designed	O
on	O
top	O
of	O
IP	O
.	O
</s>
<s>
Datagrams	B-Protocol
–	O
Packets	B-Protocol
are	O
sent	O
individually	O
and	O
are	O
checked	O
for	O
integrity	O
on	O
arrival	O
.	O
</s>
<s>
Packets	B-Protocol
have	O
definite	O
boundaries	O
which	O
are	O
honored	O
upon	O
receipt	O
;	O
a	O
read	O
operation	O
at	O
the	O
receiver	O
socket	O
will	O
yield	O
an	O
entire	O
message	O
as	O
it	O
was	O
originally	O
sent	O
.	O
</s>
<s>
Broadcasts	O
–	O
being	O
connectionless	B-Protocol
,	O
UDP	O
can	O
broadcast	O
-	O
sent	O
packets	B-Protocol
can	O
be	O
addressed	O
to	O
be	O
receivable	O
by	O
all	O
devices	O
on	O
the	O
subnet	O
.	O
</s>
<s>
Multicast	O
–	O
a	O
multicast	O
mode	O
of	O
operation	O
is	O
supported	O
whereby	O
a	O
single	O
datagram	B-Protocol
packet	B-Protocol
can	O
be	O
automatically	O
routed	O
without	O
duplication	O
to	O
a	O
group	O
of	O
subscribers	O
.	O
</s>
