Mean announcement delay.
This represents the average time, expressed in days, between the allocation and the announcement of a prefix, considering only those prefixes that at the time of measurement had already been announced.
The field ‘Total Lengh’which is part of the IPv4 header, is not found in the IPv6 header. Its function was to count the size of the packet payload plus the size of a variable lenght header. As the IPv6 header has a fixed size, the presence of this field is unnecessary.