<s>
In	O
wired	O
computer	B-Architecture
networking	I-Architecture
,	O
including	O
the	O
Internet	O
,	O
a	O
hop	B-Protocol
occurs	O
when	O
a	O
packet	O
is	O
passed	O
from	O
one	O
network	B-Protocol
segment	I-Protocol
to	O
the	O
next	O
.	O
</s>
<s>
Data	O
packets	O
pass	O
through	O
routers	B-Protocol
as	O
they	O
travel	O
between	O
source	O
and	O
destination	O
.	O
</s>
<s>
The	O
hop	B-Protocol
count	I-Protocol
refers	O
to	O
the	O
number	O
of	O
network	O
devices	O
through	O
which	O
data	O
passes	O
from	O
source	O
to	O
destination	O
(	O
depending	O
on	O
routing	B-Protocol
protocol	I-Protocol
,	O
this	O
may	O
include	O
the	O
source/destination	O
,	O
that	O
is	O
,	O
the	O
first	O
hop	B-Protocol
is	O
counted	O
as	O
hop	B-Protocol
0	O
or	O
hop	B-Protocol
1	O
)	O
.	O
</s>
<s>
Since	O
store	B-Protocol
and	I-Protocol
forward	I-Protocol
and	O
other	O
latencies	O
are	O
incurred	O
through	O
each	O
hop	B-Protocol
,	O
a	O
large	O
number	O
of	O
hops	B-Protocol
between	O
source	O
and	O
destination	O
implies	O
lower	O
real-time	B-General_Concept
performance	O
.	O
</s>
<s>
In	O
wired	O
networks	O
,	O
the	O
hop	B-Protocol
count	I-Protocol
refers	O
to	O
the	O
number	O
of	O
networks	O
or	O
network	O
devices	O
through	O
which	O
data	O
passes	O
between	O
source	O
and	O
destination	O
(	O
depending	O
on	O
routing	B-Protocol
protocol	I-Protocol
,	O
this	O
may	O
include	O
the	O
source/destination	O
,	O
that	O
is	O
,	O
the	O
first	O
hop	B-Protocol
is	O
counted	O
as	O
hop	B-Protocol
0	O
or	O
hop	B-Protocol
1	O
)	O
.	O
</s>
<s>
Thus	O
,	O
hop	B-Protocol
count	I-Protocol
is	O
a	O
rough	O
measure	O
of	O
distance	O
between	O
two	O
hosts	O
.	O
</s>
<s>
For	O
a	O
routing	B-Protocol
protocol	I-Protocol
using	O
1-origin	O
hop	B-Protocol
counts	I-Protocol
(	O
such	O
as	O
RIP	O
)	O
,	O
a	O
hop	B-Protocol
count	I-Protocol
of	O
n	O
means	O
that	O
n	O
networks	O
separate	O
the	O
source	O
host	O
from	O
the	O
destination	O
host	O
.	O
</s>
<s>
Other	O
protocols	O
such	O
as	O
DHCP	O
use	O
the	O
term	O
"	O
hop	B-Protocol
"	O
to	O
refer	O
to	O
the	O
number	O
of	O
times	O
a	O
message	O
has	O
been	O
forwarded	O
.	O
</s>
<s>
On	O
a	O
layer	B-Application
3	I-Application
network	O
such	O
as	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	O
)	O
,	O
each	O
router	B-Protocol
along	O
the	O
data	O
path	O
constitutes	O
a	O
hop	B-Protocol
.	O
</s>
<s>
By	O
itself	O
,	O
this	O
metric	O
is	O
,	O
however	O
,	O
not	O
useful	O
for	O
determining	O
the	O
optimum	O
network	O
path	O
,	O
as	O
it	O
does	O
not	O
take	O
into	O
consideration	O
the	O
speed	O
,	O
load	O
,	O
reliability	O
,	O
or	O
latency	O
of	O
any	O
particular	O
hop	B-Protocol
,	O
but	O
merely	O
the	O
total	O
count	O
.	O
</s>
<s>
Nevertheless	O
,	O
some	O
routing	B-Protocol
protocols	I-Protocol
,	O
such	O
as	O
Routing	B-Protocol
Information	I-Protocol
Protocol	I-Protocol
(	O
RIP	O
)	O
,	O
use	O
hop	B-Protocol
count	I-Protocol
as	O
their	O
sole	O
metric	O
.	O
</s>
<s>
Each	O
time	O
a	O
router	B-Protocol
receives	O
a	O
packet	O
,	O
it	O
modifies	O
the	O
packet	O
,	O
decrementing	O
the	O
time	B-Protocol
to	I-Protocol
live	I-Protocol
(	O
TTL	O
)	O
.	O
</s>
<s>
The	O
router	B-Protocol
discards	O
any	O
packets	O
received	O
with	O
a	O
zero	O
TTL	O
value	O
.	O
</s>
<s>
This	O
prevents	O
packets	O
from	O
endlessly	O
bouncing	O
around	O
the	O
network	O
in	O
the	O
event	O
of	O
routing	B-Protocol
errors	O
.	O
</s>
<s>
Routers	B-Protocol
are	O
capable	O
of	O
managing	O
hop	B-Protocol
counts	I-Protocol
,	O
but	O
other	O
types	O
of	O
network	O
devices	O
(	O
e.g.	O
</s>
<s>
Ethernet	B-Protocol
hubs	I-Protocol
and	O
bridges	B-Protocol
)	O
are	O
not	O
.	O
</s>
<s>
Known	O
as	O
time	B-Protocol
to	I-Protocol
live	I-Protocol
(	O
TTL	O
)	O
in	O
IPv4	B-Protocol
,	O
and	O
hop	B-Protocol
limit	I-Protocol
in	O
IPv6	B-Protocol
,	O
this	O
field	O
specifies	O
a	O
limit	O
on	O
the	O
number	O
of	O
hops	B-Protocol
a	O
packet	O
is	O
allowed	O
before	O
being	O
discarded	O
.	O
</s>
<s>
Routers	B-Protocol
modify	O
IP	O
packets	O
as	O
they	O
are	O
forwarded	O
,	O
decrementing	O
the	O
respective	O
TTL	O
or	O
hop	B-Protocol
limit	I-Protocol
fields	O
.	O
</s>
<s>
Routers	B-Protocol
do	O
not	O
forward	O
packets	O
with	O
a	O
resultant	O
field	O
of	O
0	O
or	O
less	O
.	O
</s>
<s>
When	O
configuring	O
network	O
devices	O
the	O
hop	B-Protocol
may	O
refer	O
to	O
next	O
hop	B-Protocol
.	O
</s>
<s>
Next	O
hop	B-Protocol
is	O
the	O
next	O
gateway	O
to	O
which	O
packets	O
should	O
be	O
forwarded	O
along	O
the	O
path	O
to	O
their	O
final	O
destination	O
.	O
</s>
<s>
A	O
routing	B-Protocol
table	I-Protocol
usually	O
contains	O
the	O
IP	B-Protocol
address	I-Protocol
of	O
a	O
destination	O
network	O
and	O
the	O
IP	B-Protocol
address	I-Protocol
of	O
the	O
next	O
gateway	O
along	O
the	O
path	O
to	O
the	O
final	O
network	O
destination	O
.	O
</s>
<s>
By	O
only	O
storing	O
next-hop	O
information	O
,	O
next-hop	O
routing	B-Protocol
or	O
next-hop	O
forwarding	O
reduces	O
the	O
size	O
of	O
routing	B-Protocol
tables	I-Protocol
.	O
</s>
<s>
It	O
is	O
also	O
key	O
to	O
know	O
that	O
the	O
next	O
hops	B-Protocol
listed	O
in	O
a	O
routing	B-Protocol
table	I-Protocol
are	O
on	O
networks	O
to	O
which	O
the	O
gateway	O
is	O
directly	O
connected	O
.	O
</s>
<s>
The	O
traceroute	B-Protocol
command	O
can	O
be	O
used	O
to	O
measure	O
the	O
number	O
of	O
router	B-Protocol
hops	B-Protocol
from	O
one	O
host	O
to	O
another	O
.	O
</s>
<s>
Hop	B-Protocol
counts	I-Protocol
are	O
often	O
useful	O
to	O
find	O
faults	O
in	O
a	O
network	O
or	O
to	O
discover	O
if	O
routing	B-Protocol
is	O
indeed	O
correct	O
.	O
</s>
<s>
In	O
a	O
wireless	B-General_Concept
ad	I-General_Concept
hoc	I-General_Concept
network	I-General_Concept
,	O
commonly	O
,	O
every	O
participating	O
node	O
is	O
also	O
acting	O
as	O
a	O
router	B-Protocol
.	O
</s>
<s>
This	O
means	O
that	O
the	O
terms	O
"	O
hop	B-Protocol
"	O
and	O
"	O
hop	B-Protocol
count	I-Protocol
"	O
are	O
often	O
the	O
subject	O
of	O
confusion	O
.	O
</s>
<s>
Often	O
,	O
the	O
sending	O
node	O
is	O
simply	O
counted	O
as	O
the	O
first	O
hop	B-Protocol
,	O
thus	O
yielding	O
the	O
same	O
number	O
for	O
"	O
hops	B-Protocol
"	O
for	O
both	O
interpretations	O
of	O
"	O
hop	B-Protocol
"	O
as	O
"	O
traversed	O
routers	B-Protocol
"	O
and	O
"	O
jumps	O
from	O
node	O
to	O
node	O
"	O
.	O
</s>
<s>
For	O
example	O
,	O
RFC	O
6130	O
defines	O
a	O
"	O
1-hop	O
neighbor	O
"	O
as	O
any	O
other	O
node	O
that	O
is	O
directly	O
reachable	O
via	O
the	O
wireless	O
interface	O
.	O
</s>
