[ppml] Fw: ":" - Re: Proposed Policy: 4-Byte AS Number Policy Proposal

Fri Dec 16 14:15:07 UTC 2005

On Thu, 15 Dec 2005, Owen DeLong wrote:

> Actually, for actual implementation, there are subtle differences between
> AS 0x0002 ans AS 0x00000002.  True, they are the same AS in 16 and 32 bit
> representation, and, for allocation policy, they are the same, but, in
> actual router guts, there are limited circumstances where you might actually
> care which one you are talking about.

The metadata in this case is per BGP session, not per AS as implied by the
original post.  They are still logically equivalent.

Further, the least error-prone way to implement BGP that can work in both 2
and 4 byte AS representations is to go completely 4-byte internally on the
router, and treat the 2-byte sessions as a backwards compatibility case.
In such an implementation, there is also no such thing as a "2-byte AS",
because all ASs are represented in 4 bytes.

-- 
-- Todd Vierling <tv at duh.org> <tv at pobox.com> <todd at vierling.name>