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  • From: Sean Doran
  • Date: Sat Sep 23 18:26:17 1995

After much discussion with many different people,
including some at registries, I have modified our
filter-list to accept /19s in the block.

The change will take effect upon the next clearing of
exterior BGP sessions with our various neighbours.

Note that there will be no further relaxtion of
the /19 limit, and that the principal reasoning
behind the change from /18 to /19 for this block
is as follows:

	-- a miscommunication between me and various
	   registries several months ago which led
	   to registries and perhaps some providers
	   handing out some /19s that they honesty
	   expected would pass through the filters;
	   the fact that they did, to some extent,
	   due to the minor implementation glitch
	   on this side, exacerbated the problem.

	-- several people have aggregated long prefixes
	   into /19s (thank you) and find that they
	   cannot reasonably do further aggregation
	   to /18s due to various allocation policies.

This change increases the number of prefixes AS1239 will
route towards by 129, all of which are /19s, and many of
which can and should be aggregated into even shorter

Note that this will not help anyone who is announcing
anything longer than a 19-bit prefix in the
range, nor anyone who is expecting to be able to
announce /19s in -

At this time, I don't intend to have AS1239 routers accept
/19s in those blocks from its external peers, nor do
I expect to increase the maximum length of the prefixes
accepted from beyond that which registries
were allocating as part of their slow-start scheme
with the expectation that /19s probably were short 
enough that they would stay routable everywhere.

- --
Sean Doran <>