SDN Internet Router (sir)

Matthew Walster matthew at
Sat Jan 7 13:40:37 UTC 2023

On Sat, 7 Jan 2023, 20:52 Masataka Ohta, <mohta at>

> Matthew Walster wrote:
> > No... It's action based. You can send it a different route, you can
> > replicate it, you can drop it, you can mutate it...
> Replication is a poor alternative for multicast.

You conveniently ignore things like IDS, port mirroring, things like that.

For other actions, why, do you think, they are performed?
> Just for fun? Or to differentiate treatment of some packets,
> that is, prioritization?

No. There are far more actions than for prioritisation.

What if you want to make sure certain classes of traffic do not flow over a
link, because it is unencrypted and/or sensitive, but you're happy to send
as much TLS wrapped data as you like?

What if you want to sample some flows in an ERSPAN like mechanism?

What if you want to urgently drop a set of flows based on a known DDOS

> You can send it to a
> > different destination for stateful filtering when it doesn't match an
> > expected pattern!
> Unless pattern is as simple as having certain port number,
> stateful filtering almost always needs all packets including
> those matching expected pattern, I'm afraid.

Or a certain set of IP addresses. Policy based routing.

> SDN is not just QoS routing, please stop saying that.
> See above.
> > Nope, not true. Had 1000 routes, only 100 available in FIB. So you filter
> > to the top 50 doing traffic and default route the rest of the traffic.
> Less
> > entries.
> If default route is acceptable, just rely on it along with
> 50 non default routes with plain IP routers.

That's what OP is suggesting. That's what SIR is. Classifying prefixes by
traffic and only keeping the ones with the highest volume of traffic,
discarding the rest, relying on the default route to infill.

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