<s>
A	O
routing	B-Protocol
protocol	I-Protocol
specifies	O
how	O
routers	B-Protocol
communicate	O
with	O
each	O
other	O
to	O
distribute	O
information	O
that	O
enables	O
them	O
to	O
select	O
routes	O
between	O
nodes	B-Protocol
on	O
a	O
computer	B-Architecture
network	I-Architecture
.	O
</s>
<s>
Routers	B-Protocol
perform	O
the	O
traffic	O
directing	O
functions	O
on	O
the	O
Internet	O
;	O
data	B-Protocol
packets	I-Protocol
are	O
forwarded	O
through	O
the	O
networks	O
of	O
the	O
internet	O
from	O
router	B-Protocol
to	O
router	B-Protocol
until	O
they	O
reach	O
their	O
destination	O
computer	O
.	O
</s>
<s>
Routing	B-Protocol
algorithms	I-Protocol
determine	O
the	O
specific	O
choice	O
of	O
route	O
.	O
</s>
<s>
Each	O
router	B-Protocol
has	O
a	O
prior	O
knowledge	O
only	O
of	O
networks	O
attached	O
to	O
it	O
directly	O
.	O
</s>
<s>
A	O
routing	B-Protocol
protocol	I-Protocol
shares	O
this	O
information	O
first	O
among	O
immediate	O
neighbors	O
,	O
and	O
then	O
throughout	O
the	O
network	O
.	O
</s>
<s>
This	O
way	O
,	O
routers	B-Protocol
gain	O
knowledge	O
of	O
the	O
topology	B-Architecture
of	I-Architecture
the	I-Architecture
network	I-Architecture
.	O
</s>
<s>
The	O
ability	O
of	O
routing	B-Protocol
protocols	I-Protocol
to	O
dynamically	O
adjust	O
to	O
changing	O
conditions	O
such	O
as	O
disabled	O
connections	O
and	O
components	O
and	O
route	O
data	O
around	O
obstructions	O
is	O
what	O
gives	O
the	O
Internet	O
its	O
fault	B-General_Concept
tolerance	I-General_Concept
and	O
high	O
availability	O
.	O
</s>
<s>
The	O
specific	O
characteristics	O
of	O
routing	B-Protocol
protocols	I-Protocol
include	O
the	O
manner	O
in	O
which	O
they	O
avoid	O
routing	B-Protocol
loops	O
,	O
the	O
manner	O
in	O
which	O
they	O
select	O
preferred	O
routes	O
,	O
using	O
information	O
about	O
hop	O
costs	O
,	O
the	O
time	O
they	O
require	O
to	O
reach	O
routing	B-Protocol
convergence	I-Protocol
,	O
their	O
scalability	B-Architecture
,	O
and	O
other	O
factors	O
such	O
as	O
relay	O
multiplexing	O
and	O
cloud	O
access	O
framework	O
parameters	O
.	O
</s>
<s>
This	O
has	O
the	O
added	O
benefit	O
of	O
preventing	O
issues	O
with	O
routing	B-Protocol
protocol	I-Protocol
loops	O
.	O
</s>
<s>
Many	O
routing	B-Protocol
protocols	I-Protocol
are	O
defined	O
in	O
technical	O
standards	O
documents	O
called	O
RFCs	O
.	O
</s>
<s>
Although	O
there	O
are	O
many	O
types	O
of	O
routing	B-Protocol
protocols	I-Protocol
,	O
three	O
major	O
classes	O
are	O
in	O
widespread	O
use	O
on	O
IP	B-Protocol
networks	I-Protocol
:	O
</s>
<s>
Interior	B-Protocol
gateway	I-Protocol
protocols	I-Protocol
type	O
2	O
,	O
distance-vector	B-Protocol
routing	I-Protocol
protocols	I-Protocol
,	O
such	O
as	O
Routing	B-Protocol
Information	I-Protocol
Protocol	I-Protocol
,	O
RIPv2	O
,	O
IGRP	B-Protocol
.	O
</s>
<s>
Exterior	B-Protocol
gateway	I-Protocol
protocols	I-Protocol
are	O
routing	B-Protocol
protocols	I-Protocol
used	O
on	O
the	O
Internet	O
for	O
exchanging	O
routing	B-Protocol
information	I-Protocol
between	O
Autonomous	B-Architecture
Systems	I-Architecture
,	O
such	O
as	O
Border	B-Protocol
Gateway	I-Protocol
Protocol	I-Protocol
(	O
BGP	B-Protocol
)	O
,	O
a	O
path-vector	B-Protocol
routing	I-Protocol
protocol	I-Protocol
.	O
</s>
<s>
Exterior	B-Protocol
gateway	I-Protocol
protocols	I-Protocol
should	O
not	O
be	O
confused	O
with	O
Exterior	B-Protocol
Gateway	I-Protocol
Protocol	I-Protocol
(	O
EGP	O
)	O
,	O
an	O
obsolete	O
routing	B-Protocol
protocol	I-Protocol
.	O
</s>
<s>
Routing	B-Protocol
protocols	I-Protocol
,	O
according	O
to	O
the	O
OSI	O
routing	B-Protocol
framework	O
,	O
are	O
layer	O
management	O
protocols	O
for	O
the	O
network	B-Application
layer	I-Application
,	O
regardless	O
of	O
their	O
transport	O
mechanism	O
:	O
</s>
<s>
Open	B-Protocol
Shortest	I-Protocol
Path	I-Protocol
First	I-Protocol
(	O
OSPF	B-Protocol
)	O
is	O
encapsulated	O
in	O
IP	O
,	O
but	O
runs	O
only	O
on	O
the	O
IPv4	B-Protocol
subnet	O
,	O
while	O
the	O
IPv6	B-Protocol
version	O
runs	O
on	O
the	O
link	O
using	O
only	O
link-local	O
addressing	O
.	O
</s>
<s>
IGRP	B-Protocol
,	O
and	O
EIGRP	B-Protocol
are	O
directly	O
encapsulated	O
in	O
IP	O
.	O
</s>
<s>
EIGRP	B-Protocol
uses	O
its	O
own	O
reliable	O
transmission	O
mechanism	O
,	O
while	O
IGRP	B-Protocol
assumed	O
an	O
unreliable	O
transport	O
.	O
</s>
<s>
Routing	B-Protocol
Information	I-Protocol
Protocol	I-Protocol
(	O
RIP	O
)	O
runs	O
over	O
the	O
User	B-Protocol
Datagram	I-Protocol
Protocol	I-Protocol
(	O
UDP	O
)	O
.	O
</s>
<s>
BGP	B-Protocol
runs	O
over	O
the	O
Transmission	B-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
TCP	O
)	O
.	O
</s>
<s>
Interior	B-Protocol
gateway	I-Protocol
protocols	I-Protocol
(	O
IGPs	O
)	O
exchange	O
routing	B-Protocol
information	I-Protocol
within	O
a	O
single	O
routing	B-Protocol
domain	I-Protocol
.	O
</s>
<s>
Exterior	B-Protocol
gateway	I-Protocol
protocols	I-Protocol
exchange	O
routing	B-Protocol
information	I-Protocol
between	O
autonomous	B-Architecture
systems	I-Architecture
.	O
</s>
<s>
Many	O
software	O
implementations	O
exist	O
for	O
most	O
of	O
the	O
common	O
routing	B-Protocol
protocols	I-Protocol
.	O
</s>
<s>
Examples	O
of	O
open-source	O
applications	O
are	O
Bird	B-Protocol
Internet	I-Protocol
routing	I-Protocol
daemon	I-Protocol
,	O
Quagga	B-Protocol
,	O
GNU	B-Application
Zebra	I-Application
,	O
OpenBGPD	B-Application
,	O
OpenOSPFD	B-Application
,	O
and	O
XORP	B-Protocol
.	O
</s>
<s>
Some	O
network	O
certification	O
courses	O
distinguish	O
between	O
routing	B-Protocol
protocols	I-Protocol
and	O
routed	B-Protocol
protocols	I-Protocol
.	O
</s>
<s>
A	O
routed	B-Protocol
protocol	O
is	O
used	O
to	O
deliver	O
application	O
traffic	O
.	O
</s>
<s>
It	O
provides	O
appropriate	O
addressing	O
information	O
in	O
its	O
internet	B-Protocol
layer	I-Protocol
or	O
network	B-Application
layer	I-Application
to	O
allow	O
a	O
packet	B-Protocol
to	O
be	O
forwarded	O
from	O
one	O
network	O
to	O
another	O
.	O
</s>
<s>
Examples	O
of	O
routed	B-Protocol
protocols	I-Protocol
are	O
the	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	O
)	O
and	O
Internetwork	B-Protocol
Packet	I-Protocol
Exchange	I-Protocol
(	O
IPX	B-Protocol
)	O
.	O
</s>
