why /8 announments are bad...

Wed Feb 26 15:50:23 UTC 2003

> 
> In return, would Covad please consider performing some meaningful form of 
> route
> aggregation or other measures to reduce the amount of noise that is being
> passed across the global routing tables that originates from Covad?
> 
> http://www.cidr-report.org/cgi-bin/as-report?as=AS18566&view=4637
> 
> suggests that Covad could withdraw some 483 BGP routing table entries,
> reducing the total number of entires originated by Covad from 490
> to an equivalent set of 8 aggregate routes.


	perhaps this is not the time/place to raise the point,
	but I'm coming to the conclusion that there is increasing
	pushback to -NOT- announce space that is not in active use.

	So-called "dark" space, i.e. the unused interstitial gaps
	in delegated space that is the the product of sparse delegation
	techniques, is perhaps more of a hazzard, esp. wrt. spam/traffic
	generation than might have been considered in the past. think
	forged source addresses...

	if this is a rational line of argument, then two tactics present
	themselves:  1) announce the individual, more specifics. this 
	has the effect of further bloating the routing table, incuring 
	the rath of the self-appointed routing table police (so watch out
	Covad, don't do what Telstra did... :)  2) keep my number of 
	routing table entries consistant by "grooming" back my sparse 
	delegations into more homogenous groups, e.g.  renumber folks in 
	the four /28s spread across the /19 into a single /26 - then 
	withdraw the /19 and announce the /26 in its place.

	the number of routing table entries remains consistant and the
	number of possible entries for forged source addresses is
	dramatically reduced.  Of course this will require a major rethink/
	rewrite of most ISPs engineering practice/operating procedures,
	as it will be much more common to see legitimate, long prefixs in 
	the routing system.
	
	as usual, YMMV.

--bill