Incoming SSDP UDP 1900 filtering

Mon Mar 25 16:54:45 UTC 2019

"It seems your position is 'i don't know how ACL
works on my platforms and i don't trust myself to write ACL, so i
should not do them',"

That is not my position at all, but thanks.

On Mon, Mar 25, 2019 at 12:43 PM Saku Ytti <saku at ytti.fi> wrote:

> Hey Tom,
>
> > If your edge ingress ACLs are not 100% in sync all the time, you will
> inevitably have Really Weird Stuff happen that will end up taking forever
> to diagnose.
>
> You may at some cases have hard to troubleshoot issues, which is true
> for everything, even when perfectly configured, because software is
> not perfect. However choosing to do iACL is still something many
> networks choose to do, because the upside is worth the complexity to
> them.
>
> > Packet filtering is more computationally taxing than just routing is.
> Your edge equipment is likely going to be built for maximum routing
> efficiency. Trying to bite off too much filtering there increases your risk
> of legit traffic being tossed on the floor.
>
> Depends on implementation, on some implementations it is zero-cost on
> some it is not. On most implementations it's very cheap, particularly
> compared to say uRPF. It seems your position is 'i don't know how ACL
> works on my platforms and i don't trust myself to write ACL, so i
> should not do them', which is perfectly valid position under those
> constrains, but other networks have other constrains under which it is
> no longer valid proposal to omit doing iACL.
>
> I would encourage networks to continue deploying iACL and consider it
> BCP. iACL removes attack surface and protects you from host of known
> and unknown SIRT issues.
>
> --
>   ++ytti
>
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