DAC Instructions for use

DAC information is provided in two forms, each are independent of the other with an entirely separate quota. A ‘Real Time’ query is optimised for speed and as such does not provide registration status information. A ‘Time Delay’ query includes registration status information, but each query incurs a small delay of 100ms.


The DAC service is available by making a TCP connection to dac.nic.uk.  Once connected the connection remains open allowing multiple queries to be sent to it, with new requests able to be submitted even before a response is received.  The DAC will respond in turn to each request with a line of text terminated by a carriage return and line feed pair.

The DAC is designed for long standing connections, as such to discourage repeated disconnection and reconnection we apply a delay of 3 seconds for each new DAC connection.  Up to 4 simultaneous connections are available for Real Time access and a further 4 for Time Delay access.  If the maximum number of connections is exceeded, the oldest will be dropped.

The IP addresses used to access the DAC must be registered with us through your online service account.  For both Real Time and Time delay access, up to 4 IP addresses can be added for each service

If connection attempts are made from unauthorised IP addresses the DAC will reply with ‘IP address a.b.c.d is not registered. Closing…’

On the occasions where the DAC thread servicing this connection cannot connect to our database, the DAC will return ‘Error accessing database. Closing…’

Connection details and acceptable use limits for both types of DAC query are as follows:

Real Time Time Delay
Server dac.nic.uk dac.nic.uk
Port 3043 2043
Connection Delay 3000 ms 3000 ms
Query Delay 0 ms 100 ms
4 4
Registered IP Addresses 4 4
24 Hour Quota 432,000 5 x Number of domains on your tag,
plus 200 x Your tag’s highest monthly registration figure in the past 12 months(to a maximum of 3,000,000)
Maximum Queries over 60 seconds 1000 (recalculated every 5 seconds) 1000 or
3 x 24 Hour Quota / 1440 if the 24 Hour Quota is greater than 432,000
(recalculated every 5 seconds)

This policy includes our standard anti-avoidance clause.


Once connected to the DAC, requests must consist of just the command followed by a carriage return and line feed pair.

The values of the fields returned are shown in the DAC field table below.

To query a domain name:


Where domain-name is the full domain name you wish to query.

The DAC system can respond in the following ways:

Real Time Queries: Domain,Registered,Detagged,Created,Expiry,Tag
Time Delay Queries: Domain,Registered,Detagged,Suspended,Created,Expiry,Status,Tag
Unregistered Domains: Domain,Registered
Acceptable Use Blocks: Domain,Registered,Delay

Following an acceptable use block, the connection will continue to accept queries, but will not respond until the stated time delay expires.

To distinguish from a domain query, all other commands start with the # symbol.  The format of the responses are the same for both the Real Time and Time Delay services.

To close the connection cleanly:


To return the number of queries made:


Response: #usage,C,60,Usage60,86400,Usage24

To return the number of queries that can be made:


Response: #limits,C,60,Limits60,86400,Limits24

DAC Fields

The various fields used for the DAC’s responses to both the Real Time and Time Delay services are shown below.

Real Time Time Delay
Domain The domain name supplied The domain name supplied
Registered Y – Registered
N – Not registered
B – Quota limit block
Y – Registered
N – Available
B – Quota limit block
E – Not within this registry
I – Syntax error
R – Rules prevent registration
Detagged Y
Suspended Y
Status 0 – No Created or Expiry Date
2 – Registered until expiry date
4 – Renewal required
7 – No longer required
Tag Current tag or DETAGGED Current tag or DETAGGED
Delay Number of seconds until the block is lifted Number of seconds until the block is lifted
Usage60 Queries made over the last 60 seconds Queries made within the last 60 seconds
Usage24 Queries made over the last 24 hours Queries made within the last 24 hours
Limit60 Queries possible over a 60 second period Queries possible over a 60 second period
Limit24 Queries possible over a 24 hour period Queries possible over a 24 hour period

DAC testbed

The DAC testbed runs against the beta database used for the EPP testbed.  The testbed is accessed is the same way as the live DAC system, replacing the server name with testbed-dac.nominet.org.uk.

There is no requirement to register to use the DAC testbed.

Minerva House, Edmund Halley Road, Oxford Science Park, OX4 4DQ, United Kingdom