"Introduction A single IPv6 address can be text represented in many ways. Examples are shown below. 2001:db8:0:0:1:0:0:1 2001:0db8:0:0:1:0:0:1 2001:db8::1:0:0:1 2001:db8::0:1:0:0:1 2001:0db8::1:0:0:1 2001:db8:0:0:1::1 2001:db8:0000:0:1::1 2001:DB8:0:0:1::1 All of the above examples represent the same IPv6 address. This flexibility has caused many problems for operators@ systems engineers@ and customers. The problems are noted in Section 3. A canonical representation format to avoid problems is introduced in Section 4. Requirements Language The key words ""MUST""@ ""MUST NOT""@ ""REQUIRED""@ ""SHALL""@ ""SHALL NOT""@ ""SHOULD""@ ""SHOULD NOT""@ ""RECOMMENDED""@ ""MAY""@ and ""OPTIONAL"" in this document are to be interpreted as described in [RFC2119]."