Nc - No Compression

Nc - No Compression

This modifier disables DNS compression in the response, overriding any DNS compression settings specified in the configuration file.

This modifier is compatible with and can be combined with any other existing feature or modifier.

Category: Packet manipulation

Format

*.nc.*

This module has no parameters.

Examples

In this example, we use the basic always feature which always resolves to an IP address. Additionally, we request to disable DNS compression for the response:

# dig always.nc.yourdomain.com @127.0.0.1

; <<>> DiG 9.18.10-2-Debian <<>> always.nc.yourdomain.com @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50368
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;always.nc.yourdomain.com.	IN	A

;; ANSWER SECTION:
always.nc.yourdomain.com. 60	IN	A	2.3.4.5

;; Query time: 3 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Tue Oct 22 00:07:02 +04 2024
;; MSG SIZE  rcvd: 82

Download PCAP File

We can see that with compression disabled, the response is 82 bytes long.


Similar to the previous example, but in this case we request to enable DNS compression for the response using the fc modifier:

# dig always.fc.yourdomain.com @127.0.0.1

; <<>> DiG 9.18.10-2-Debian <<>> always.fc.yourdomain.com @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15206
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;always.fc.yourdomain.com.	IN	A

;; ANSWER SECTION:
always.fc.yourdomain.com. 60	IN	A	2.3.4.5

;; Query time: 3 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Tue Oct 22 00:07:03 +04 2024
;; MSG SIZE  rcvd: 58

Download PCAP File

We can see that with compression enabled, the response is 58 bytes long.


In this example, we use the size feature to fit as many A records as possible within 300-byte size limit. Additionally, we request to disable DNS compression for the response:

# dig size.300.nc.yourdomain.com @127.0.0.1

; <<>> DiG 9.18.10-2-Debian <<>> size.300.nc.yourdomain.com @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6481
;; flags: qr aa; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;size.300.nc.yourdomain.com.	IN	A

;; ANSWER SECTION:
size.300.nc.yourdomain.com. 60	IN	A	127.0.0.96
size.300.nc.yourdomain.com. 60	IN	A	127.0.0.111
size.300.nc.yourdomain.com. 60	IN	A	127.0.0.8
size.300.nc.yourdomain.com. 60	IN	A	127.0.0.161
size.300.nc.yourdomain.com. 60	IN	A	127.0.0.115
size.300.nc.yourdomain.com. 60	IN	A	127.0.0.67

;; Query time: 3 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Tue Oct 22 00:07:05 +04 2024
;; MSG SIZE  rcvd: 296

Download PCAP File

With compression disabled, we can only fit six (6) A records within the 300-byte limit.


Similar to the previous example, but in this case we request to enable DNS compression for the response:

# dig size.300.fc.yourdomain.com @127.0.0.1

; <<>> DiG 9.18.10-2-Debian <<>> size.300.fc.yourdomain.com @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 25884
;; flags: qr aa; QUERY: 1, ANSWER: 16, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;size.300.fc.yourdomain.com.	IN	A

;; ANSWER SECTION:
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.9
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.12
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.38
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.233
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.39
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.156
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.52
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.60
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.69
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.122
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.30
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.87
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.75
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.102
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.214
size.300.fc.yourdomain.com. 60	IN	A	127.0.0.215

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Tue Oct 22 00:07:06 +04 2024
;; MSG SIZE  rcvd: 300

Download PCAP File

With compression enabled, we can fit sixteen (16) A records within the same 300-byte limit.


From the same category

See also


Go back to catalogue.