But, with the expanded space, there is an issue of how to transition
to the larger numbers. This is a software problem as much as
anything.
Indeed, there is a software issue here which does not
seem to have been carefully considered.
Until all software understands the bigger numbers, people
will want to continue using the 16-bit ones.
The IESG message talked about numbers from 65536 to some
big number. Here suddenly, we see a reference to some
number of bits.
Meanwhile, to encourage the migration to 4-byte ASNs, the RIRs have
Now there is a reference to some number of bytes. What is going
on here? Is this a question of moving the maximum number
from 65535 to something much larger or is it a matter of
creating new notation to reflect the details of the BGP
protocol change?
Some people have been pushing to make the internal details
of the BGP protocol externally visible even though the new
ASNs are defined in such a way that any 32-bit numbers which
happen to be equal to a 16-bit number are treated as if they
were the old 16-bit number. In other words, if you were allocated
64999 as a 16-bit ASN, you have the right to use 64999 as a
32-bit ASN.
Because of this, some people are demanding that a new notation
be developed to place a punctuation character, either a dot
or a colon, between the two 16-bit segments or between the
2nd and the 3rd byte, if you want to count bytes. Using this
system, there can be no such thing as AS 65536 as was stated
in the IESG message. Instead, that 32 bit quantity will be
referred to as 1.0 or 1:0.
On the NANOG list it has already been pointed out that a lot
of network management software cannot handle such notation and
in some cases, 1.0 could be interpreted as the IP address
1.0.0.0. It has been confirmed that one widely used PERL
library interprets x.y as IP address x.0.0.y.
Because of this I think it would be useful for the IETF
to publish a draft defining the notation for AS numbers
so that we can either keep it simple or, if a new notation
is to be used, then publicly state the issues of software
which needs to be changed. Such a draft should really come
from the WG which extended the AS number in the first
place.
--Michael Dillon
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