The prefix boundary must fall within one of the IP address' four bytes,
and this is the only byte that must be converted into binary. Prefix
lengths less than 8 require the first byte to be examined in binary;
the remaining three bytes of the address are ignored since they lie
completely beyond the address prefix. Likewise, prefix lengths between
8 and 16 require a binary decomposition on the second byte; the first
byte matches exactly and the last two bytes are ignored. Prefix lengths
from 16 to 24 fall within the third byte, so the first two bytes match
exactly and the last one is ignored. The final case, prefix lengths
greater than 24 exactly match the first three bytes and require the
fourth to be broken down into ones and zeros.
For example, upon seeing the address prefix 208.130.28/22,
you can immediately know that the first two bytes of any matching
address must be 208.130, and the fourth byte can be anything.
Only the third byte must be studied in detail.