# File lib/Dnsruby/zone_transfer.rb, line 220
    def compare_serial(s1, s2)
      if s1 == s2
        return 0
      end
      if s1 < s2 and (s2 - s1) < (2**31)
        return 1
      end
      if s1 > s2 and (s1 - s2) > (2**31)
        return 1
      end
      if s1 < s2 and (s2 - s1) > (2**31)
        return -1
      end
      if s1 > s2 and (s1 - s2) < (2**31)
        return -1
      end
      return 0
    end