RFC 1035, "Domain names - implementation and specification", November 1987

Note: This RFC has been updated by RFC 1101, RFC 1183, RFC 1348, RFC 1876, RFC 1982, RFC 1995, RFC 1996, RFC 2065, RFC 2136, RFC 2181, RFC 2137, RFC 2308, RFC 2535, RFC 2673, RFC 2845, RFC 3425, RFC 3658, RFC 4033, RFC 4034, RFC 4035, RFC 4343, RFC 5936, RFC 5966, RFC 6604, RFC 7766, RFC 8482, RFC 8490, RFC 8767, RFC 9619

Errata ID: 8101
Status: Reported
Type: Technical
Publication Format(s) : TEXT
Reported By: Vishal Sharma
Date Reported: 2024-09-13

Section 4.1.2 says:

QNAME           a domain name represented as a sequence of labels, where
                each label consists of a length octet followed by that
                number of octets.  The domain name terminates with the
                zero length octet for the null label of the root.  Note
                that this field may be an odd number of octets; no
                padding is used.

It should say:

QNAME           a domain name represented as a sequence of labels, where
                each label consists of a length octet followed by that
                number of octets.  The domain name terminates with the
                zero length octet for the null label of the root.  Note
                that this field may be an odd number of octets; no
                padding is used.

                For example:
                - example.com is encoded as \x07example\x03com\x00 (in hex: 
                  07 65 78 61 6d 70 6c 65 03 63 6f 6d 00).
                  - \x07example is the first label:
                    - \x07 is a single byte that indicates the length of the 
                      label (7 characters).
                    - example is the content of the label.
                  - \x03com is the second label:
                    - \x03 is a single byte that indicates the length of the 
                      label (3 characters).
                    - com is the content of the label.
                  - \x00 is the null byte that terminates the domain name.

Notes:

To better understand the QNAME field in DNS queries, it's helpful to know how domain names are encoded. The QNAME field represents domain names as a series of labels, where each label starts with a byte indicating its length, followed by the label's content. The entire domain name ends with a null byte (\x00). For instance, example.com is encoded as \x07example\x03com\x00, where \x07 indicates the length of the first label example, \x03 indicates the length of the second label com, and \x00 marks the end of the domain name. This encoding format allows DNS servers to correctly interpret and process domain names in queries and responses.

Adding an example improves the understanding of QNAME field in DNS Question Section

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