Hello Narad

A 4 byte AS number is represented by 32 bits. For AS numbers less than 65536, these numbers are simply represented as numbers ranging from 1 to 655356. For larger numbers, ASdot represents them as two 16 bit numbers separated by a dot. So for example:

- An AS number of
`00000000 00000000 00000000 11111111`

is

- 256 in decimal
- 256 in Asdot
- 0.256 in Asdot+

- An AS number of
`00000000 00000000 11111111 11111111`

is

- 65535 in decimal
- 65535 in Asdot
- 0.65535 in Asdot+

- An AS number of
`00000000 00000001 11111111 11111111`

is

- 131071 in decimal
- 1.65535 in Asdot
- 1.65535 in Asdot+

So if the two leftmost octets are zeros, then Asdot is the same as decimal. If however there is even a single “1” in any of the two leftmost octets, Asdot will revert to Asdot+.

I hope this has been helpful!

Laz