Re: Why does Sprint have address filters again?

[Karl Denninger <karl () mcs net>]

On Mon, Jun 01, 1998 at 12:36:19AM -0700, Patrick W. Gilmore wrote:
> At 06:57 PM 5/31/98 -0500, Karl Denninger wrote:
>
> > > Second Q: How many AS numbers are available in total?
> >
> > Currently an ASN is a 16-bit number.
>
> And a whole lot (~1/2) are reserved to IANA.  Specifically:
>
>   32768-64511    IANA-RSVD
>   64512-65535    IANA-RSVD2
>
> You can find this on ftp://rs.arin.net/netinfo/asn.txt (even if it hasn't
> been February ;).
>
> The second block is the one you have to worry about since those numbers are
> used for things like BGP confederations.  I believe the first block could
> be allocated to the general public, but you'd have to check with someone
> more cluefull to be sure.

Well, other than the definition of an ASN as a "short" in router software
and BGP4, there's no *reason* an ASN has to be a short integer.

That is, it wouldn't be difficult *at all* to define BGP4.1 in which an ASN
was either defined as a "long" or as a "numeric string of arbitrary length".

Its not like an ASN is in the header of an IP packet (where field lengths
are limited) you know.

I suspect the first "reserved" block is due to suspected buggy
implementations that defined an ASN as a *signed* short.  Obviously that's
not an issue any longer, or the internal "reserved" numbers wouldn't work.

--
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