commendations for textual presentation has been defined in RFC 4291 [4] and RFC 5952 [18]. The uniform textual representations are also needed to simplify machine-based IPv6 textual address parsing functions, such as those that work with log files. The preferred format for presenting an IPv6 is where represents a 16-bit value in hexadecimal format using lowercase characters. The 16 bit value of each X is presented without leading zeros. Furthermore, in the case of the address having 32 or more consecutive zero bits, the zero bit sequence can be abbreviated with a syntax : In the case of an address having multiple series of zeros, the : : must be used where it makes the most difference (compresses the address the most). Below are examples of legitimate address presentations: 2001: db8 : : a 2001: db8 a :0:0 Here we list a few examples of address presentations that are not legitimate according to RFC 5952, even if they are otherwise unambiguous: 2001 0db8 : 1 - leading zeroes must not be shown 2001 db8 :0:0:0:a:: - the compression syntax of : : should be used to compress the longest sequence of 16-bit fields of zeros 2001 DB: : A - uppercase letters should not be used A special textual addressing format has been defined for IPv6 addresses that are carrying IPv4 address in the lowest 32 bits. The address format for such addresses is d. d, where d's are presenting an IPv4 address [4]. An example address could be: 64: ff9b : 192 0 2 [13]. When an IPv6 address needs to be shown with a port number, brackets '[' and ']' should be used to make the address unambiguous. Without brackets it would be impossible to determine whether the last digit is a port number or part of the IPv6 address, as Introduction to IPv6 illustrated here: 2001 db8 80. A correct use of brackets makes the distinction clear: [2001 db8 a] : 80. Textual Presentation of IPv6 Prefix Each IPv6 address logically consists of a prefix and an IID, as described in Section 3.1. The prefix length is presented in the notation familiar to the IPv4 Classless Inter-D