<s>
EDNS	B-Protocol
Client	I-Protocol
Subnet	I-Protocol
(	O
ECS	O
)	O
is	O
an	O
option	O
in	O
the	O
Extension	B-Protocol
Mechanisms	I-Protocol
for	I-Protocol
DNS	I-Protocol
that	O
allows	O
a	O
recursive	O
DNS	O
resolver	O
to	O
specify	O
the	O
subnetwork	B-Protocol
for	O
the	O
host	O
or	O
client	O
on	O
whose	O
behalf	O
it	O
is	O
making	O
a	O
DNS	O
query	O
.	O
</s>
<s>
This	O
is	O
generally	O
intended	O
to	O
help	O
speed	O
up	O
the	O
delivery	O
of	O
data	O
from	O
content	B-Operating_System
delivery	I-Operating_System
networks	I-Operating_System
,	O
by	O
allowing	O
better	O
use	O
of	O
DNS-based	O
load	B-Application
balancing	I-Application
to	O
select	O
a	O
service	O
address	O
near	O
the	O
client	O
when	O
the	O
client	O
computer	O
is	O
not	O
necessarily	O
near	O
the	O
recursive	O
resolver	O
.	O
</s>
<s>
When	O
an	O
authoritative	O
name	O
server	O
receives	O
a	O
DNS	O
query	O
,	O
it	O
takes	O
advantage	O
of	O
ECS	O
DNS	B-Protocol
extension	I-Protocol
to	O
resolve	O
the	O
hostname	B-Protocol
to	O
a	O
CDN	O
which	O
is	O
geolocationally	O
near	O
to	O
the	O
client	O
IP	O
's	O
subnet	B-Protocol
,	O
hence	O
the	O
client	O
makes	O
further	O
requests	O
to	O
a	O
nearby	O
CDN	O
,	O
thereby	O
reducing	O
latency	O
.	O
</s>
<s>
The	O
EDNS	B-Protocol
client	I-Protocol
subnet	I-Protocol
mechanism	O
is	O
specified	O
in	O
.	O
</s>
<s>
The	O
owner	O
of	O
self-serve	O
web	O
archiving	O
tool	O
Archive.today	O
has	O
expressed	O
concern	O
over	O
Cloudflare	B-Protocol
1.1.1.1	I-Protocol
not	O
passing	O
the	O
contents	O
of	O
this	O
field	O
on	O
to	O
the	O
authoritative	O
DNS	O
server	O
for	O
Archive.today	O
,	O
and	O
has	O
in	O
response	O
configured	O
the	O
site	O
's	O
resolver	O
to	O
consider	O
Cloudflare	B-Application
DNS	O
requests	O
invalid	O
—	O
effectively	O
blocking	O
1.1.1.1	B-Protocol
from	O
resolving	O
the	O
website	O
DNS	O
records	O
.	O
</s>
<s>
The	O
owner	O
of	O
the	O
site	O
believes	O
1.1.1.1	B-Protocol
too	O
often	O
routes	O
recursive	O
DNS	O
requests	O
in	O
a	O
non-geographically-optimal	O
way	O
,	O
causing	O
poorer	O
connectivity	O
than	O
if	O
the	O
feature	O
was	O
available	O
at	O
all	O
times	O
.	O
</s>
<s>
Cloudflare	B-Application
CEO	O
Matthew	B-Application
Prince	I-Application
cited	O
privacy	O
concerns	O
as	O
reason	O
for	O
1.1.1.1	B-Protocol
to	O
not	O
support	O
ECS	O
.	O
</s>
