why /8 announments are bad...

[bmanning () karoshi com]

> 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