If you have nothing to hide

bdragon at gweep.net bdragon at gweep.net
Mon Aug 5 22:46:59 UTC 2002


> 
> 
> 
> > Validation of routing policy to ensure others aren't abusing you (pointing
> > default, for example). As for orders of magnitude, once an IP option is
> > in a packet, the damage is essentially done, otherwise looking up the
> > path to an address in the options is no more impactive than looking up the
> > address in the original destination field. 
> 
> Well, no.  Not really.
> First off, following the 80/20 rule (or in this case 99.x/(100-99.x)
> rule) says that hardware implementations which get optioned packets
> punt them to software.  This is at every hop.
> 
> Second, the IP source route is a stack of IP addresses, which must be
> modified at every hop.  This implies not just software forwarding, but
> also significantly more work than an IP lookup.

As I said, once the option is in the packet, the damage is done.
If the performance sucks for the person using the source-routing, who
cares, assuming packets without IP options are forwarded without
delay.

If I'm not mistaken, most (if not all) vendors still punt the
packets with source-routing options to software, even if they end
up dropping the packet due to administrative decision.

> eric




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