<s>
An	O
administrative	B-Protocol
domain	I-Protocol
is	O
a	O
service	O
provider	O
holding	O
a	O
security	O
repository	B-Protocol
permitting	O
to	O
easily	O
authenticate	O
and	O
authorize	O
clients	B-Protocol
with	O
credentials	O
.	O
</s>
<s>
This	O
concept	O
is	O
captured	O
by	O
the	O
'	O
AdminDomain	O
 '	O
class	O
of	O
the	O
GLUE	O
information	B-Application
model	I-Application
.	O
</s>
<s>
An	O
administrative	B-Protocol
domain	I-Protocol
is	O
mainly	O
used	O
in	O
intranet	O
environments	O
.	O
</s>
<s>
It	O
may	O
be	O
implemented	O
as	O
a	O
collection	O
of	O
hosts	O
and	O
routers	B-Protocol
,	O
and	O
the	O
interconnecting	O
network(s )	O
,	O
managed	O
by	O
a	O
single	O
administrative	O
authority	O
.	O
</s>
<s>
Interoperation	O
between	O
different	O
administrative	B-Protocol
domains	I-Protocol
having	O
different	O
security	O
repositories	O
,	O
different	O
security	O
software	O
or	O
different	O
security	O
policies	O
is	O
notoriously	O
difficult	O
.	O
</s>
<s>
Therefore	O
,	O
administrative	B-Protocol
domains	I-Protocol
wishing	O
ad	O
hoc	O
interoperation	O
or	O
full	O
interoperability	O
have	O
to	O
build	O
a	O
federation	O
.	O
</s>
