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why /8 announments are bad...
From: bmanning () karoshi com
Date: Wed, 26 Feb 2003 07:50:23 -0800 (PST)

In return, would Covad please consider performing some meaningful form of 
aggregation or other measures to reduce the amount of noise that is being
passed across the global routing tables that originates from Covad?


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.


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