<s>
DNS	B-Protocol
Long-Lived	I-Protocol
Queries	I-Protocol
is	O
a	O
mechanism	O
that	O
allows	O
DNS	B-Application
clients	O
to	O
learn	O
about	O
changes	O
to	O
DNS	B-Application
data	O
without	O
polling	B-General_Concept
.	O
</s>
<s>
DNS	B-Application
LLQ	O
is	O
currently	O
used	O
by	O
Apple	O
Inc.	O
'	O
s	O
Back	B-Operating_System
To	I-Operating_System
My	I-Operating_System
Mac	I-Operating_System
(	O
BTMM	O
)	O
service	O
to	O
track	O
changes	O
in	O
the	O
IP	O
addresses	O
of	O
BTMM	O
servers	O
and	O
clients	O
.	O
</s>
<s>
DNS	B-Application
LLQ	O
has	O
also	O
been	O
proposed	O
as	O
a	O
solution	O
for	O
doing	O
DNS-Based	O
Service	O
Discovery	O
(	O
DNS-SD	O
)	O
on	O
routed	O
networks	O
,	O
using	O
long-lived	O
TCP/IP	B-Protocol
connections	O
.	O
</s>
<s>
DNS-SD	O
is	O
a	O
mechanism	O
for	O
identifying	O
services	O
on	O
the	O
local	O
network	O
.	O
</s>
<s>
DNS-SD	O
is	O
typically	O
used	O
to	O
present	O
names	O
of	O
services	O
(	O
for	O
example	O
,	O
printers	O
or	O
file	O
servers	O
)	O
in	O
user	O
interfaces	O
.	O
</s>
<s>
DNS	B-Protocol
Long-Lived	I-Protocol
Queries	I-Protocol
(	O
DNS-LLQ	O
)	O
can	O
be	O
used	O
for	O
DNS-SD	O
to	O
allow	O
new	O
services	O
to	O
appear	O
automatically	O
in	O
an	O
active	O
user	O
interface	O
without	O
requiring	O
frequent	O
polling	B-General_Concept
.	O
</s>
<s>
DNS-LLQ	O
is	O
being	O
proposed	O
in	O
the	O
IETF	O
DNSSD	O
working	O
group	O
as	O
one	O
option	O
for	O
providing	O
service	O
discovery	O
in	O
these	O
routed	O
networks	O
.	O
</s>
<s>
Although	O
DNS	B-Application
LLQ	O
over	O
TCP/IP	B-Protocol
has	O
not	O
been	O
standardized	O
,	O
it	O
is	O
in	O
use	O
in	O
Apple	O
Inc.	O
'	O
s	O
current	O
mDNS	B-Protocol
implementation	O
.	O
</s>
<s>
DNS	B-Application
LLQ	O
is	O
initiated	O
by	O
a	O
client	O
resolver	O
that	O
wishes	O
to	O
track	O
one	O
or	O
more	O
names	O
in	O
the	O
DNS	B-Application
.	O
</s>
