Who does source address validation? (was Re: what's that smell?)

Tue Oct 8 19:17:46 UTC 2002

On Tue, 8 Oct 2002, John M. Brown wrote:

> It seems to reason that if people started filtering RFC-1918 on
> their edge, we would see a noticable amount of traffic go away.

> Simulation models I've been running show that an average of 12 to 18 percent
> of a providers traffic would disappear if they filtered RFC-1918 sourced
> packets.

That is hard very to believe, unless you are referring to the load on the
root nameservers. Since they obviously don't receive a reply, these
resolvers will keep coming back.

> In addition to the bandwidth savings, there is also a support cost
> reduction and together, I believe backbone providers can see this
> on the bottom line of their balance sheets.

> We have to start someplace.  There is no magic answer for all cases.

> RFC-1918 is easy to admin, and easy to deploy, in relative terms compared
> to uRPF or similar methods.

uRPF is easier: one configuration command per interface. A filter for RFC
1918 space is also one configuration command per interface, and some
command to create the filter.

> For large and small alike it can be a positive marketing tool, if properly
> implemented.

Sure. "We can't be bothered to do proper filtering, but since filter
0.39% of what we should, we are cool."