<s>
In	O
computer	O
network	O
protocol	O
design	O
,	O
inter-server	B-Protocol
communication	O
is	O
an	O
extension	O
of	O
the	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
model	I-Operating_System
in	O
which	O
data	O
are	O
exchanged	O
directly	O
between	O
servers	O
.	O
</s>
<s>
In	O
some	O
fields	O
server-to-server	B-Protocol
(	O
S2S	O
)	O
is	O
used	O
as	O
an	O
alternative	O
,	O
and	O
the	O
term	O
inter-domain	B-Architecture
can	O
in	O
some	O
cases	O
be	O
used	O
interchangeably	O
.	O
</s>
<s>
Protocols	O
that	O
have	O
inter-server	B-Protocol
functions	O
as	O
well	O
as	O
the	O
regular	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
communications	O
include	O
the	O
following	O
:	O
</s>
<s>
The	O
domain	B-Protocol
name	I-Protocol
system	I-Protocol
(	O
DNS	B-Protocol
)	O
,	O
which	O
uses	O
an	O
inter-server	B-Protocol
protocol	O
for	O
zone	B-Protocol
transfers	I-Protocol
;	O
</s>
<s>
The	O
Dynamic	B-Protocol
Host	I-Protocol
Configuration	I-Protocol
Protocol	I-Protocol
(	O
DHCP	B-Protocol
)	O
;	O
</s>
<s>
FXP	B-Protocol
,	O
allowing	O
file	O
transfer	O
directly	O
between	O
FTP	B-Protocol
servers	O
;	O
</s>
<s>
The	O
Inter-Asterisk	B-Protocol
eXchange	I-Protocol
(	O
IAX	B-Protocol
)	O
;	O
</s>
<s>
The	O
IRC	B-Protocol
,	O
an	O
Internet	B-Protocol
chat	I-Protocol
system	O
with	O
an	O
inter-server	B-Protocol
protocol	O
allowing	O
clients	O
to	O
be	O
distributed	O
across	O
many	O
servers	O
;	O
</s>
<s>
The	O
Network	B-Protocol
News	I-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
NNTP	B-Protocol
)	O
;	O
</s>
<s>
The	O
Protocol	O
for	O
SYnchronous	B-Protocol
Conferencing	I-Protocol
(	O
PSYC	O
)	O
;	O
</s>
<s>
SIP	B-Application
,	O
a	O
signaling	O
protocol	O
commonly	O
used	O
for	O
Voice	B-Application
over	I-Application
IP	I-Application
;	O
</s>
<s>
SILC	B-Protocol
,	O
a	O
secure	O
Internet	O
conferencing	B-Protocol
protocol	O
;	O
</s>
<s>
The	O
Extensible	B-Protocol
Messaging	I-Protocol
and	I-Protocol
Presence	I-Protocol
Protocol	I-Protocol
(	O
XMPP	B-Protocol
,	O
formerly	O
named	O
Jabber	B-Protocol
)	O
.	O
</s>
<s>
ActivityPub	B-Operating_System
a	O
client/server	B-Operating_System
API	B-Application
for	O
creating	O
,	O
updating	O
and	O
deleting	O
content	O
,	O
as	O
well	O
as	O
a	O
federated	O
server-to-server	B-Protocol
API	B-Application
for	O
delivering	O
notifications	O
and	O
content	O
.	O
</s>
