<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: arial,helvetica,sans-serif; font-size: 10pt; color: #000000'><font face="arial, helvetica, sans-serif"><span style="font-size: 10pt;">"</span><span style="font-size: 13.3333px;">With plain IP routers?"</span></font><div><font face="arial, helvetica, sans-serif"><span style="font-size: 13.3333px;"><br></span></font></div><div><font face="arial, helvetica, sans-serif"><span style="font-size: 13.3333px;">Yes, or, well, relatively plain, depending on the implementation.</span></font></div><div><font face="arial, helvetica, sans-serif"><span style="font-size: 13.3333px;"><br></span></font></div><div><font face="arial, helvetica, sans-serif"><span style="font-size: 13.3333px;">The originally linked project used Arista.<br></span></font><div><br><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 10pt;"><span name="x"></span><br style="color:rgb( 0 , 0 , 0 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style="color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12pt; font-weight: normal; font-style: normal; text-decoration: none;"><b>From: </b>"Masataka Ohta" <mohta@necom830.hpcl.titech.ac.jp><br><b>To: </b>"Matthew Walster" <matthew@walster.org><br><b>Cc: </b>"nanog list" <nanog@nanog.org><br><b>Sent: </b>Saturday, January 7, 2023 8:44:59 AM<br><b>Subject: </b>Re: SDN Internet Router (sir)<br><br>Matthew Walster wrote:<br><br>>>> No... It's action based. You can send it a different route, you can<br>>>> replicate it, you can drop it, you can mutate it...<br>>><br>>> Replication is a poor alternative for multicast.<br><br>> You conveniently ignore things like IDS, port mirroring, things like that.<br><br>Wrong. Instead, you conveniently ignore that such forwarding<br>requires a link between an SDN router and a monitoring device<br>have the same or larger MTU than an incoming link of the SDN<br>router, which means the router and the monitoring device must<br>be tightly coupled effectively to be a single device.<br><br>Sometimes, packet loss possibility between them often requires<br>they must actually be the same device.<br><br>> No. There are far more actions than for prioritisation.<br><br>Just for fun? I'm afraid I already mentioned so.<br><br>> What if you want to make sure certain classes of traffic do not flow over a<br>> link, because it is unencrypted and/or sensitive, but you're happy to send<br>> as much TLS wrapped data as you like?<br><br>You are wrongly assuming TLS wrapped packets can be identified<br>packet by packet, as I wrote:<br><br> >> Unless pattern is as simple as having certain port number,<br> >> stateful filtering almost always needs all packets including<br> >> those matching expected pattern, I'm afraid.<br><br>So?<br><br>> What if you want to sample some flows in an ERSPAN like mechanism?<br><br>See above for MTU issues.<br><br>> What if you want to urgently drop a set of flows based on a known DDOS<br>> signature?<br><br>Urgently? Even though a DDOS signature is known in advance?<br><br>Why?<br><br>>> Unless pattern is as simple as having certain port number,<br>>> stateful filtering almost always needs all packets including<br>>> those matching expected pattern, I'm afraid.<br>>><br>> <br>> Or a certain set of IP addresses. Policy based routing.<br><br>That's even simpler than port number to be treated by<br>having or not having proper routing table entries.<br><br>>> If default route is acceptable, just rely on it along with<br>>> 50 non default routes with plain IP routers.<br><br>> That's what OP is suggesting.<br><br>With plain IP routers?<br><br>> That's what SIR is. Classifying prefixes by<br>> traffic and only keeping the ones with the highest volume of traffic,<br>> discarding the rest, relying on the default route to infill.<br><br>Given the connectionless nature of the Internet, route change based<br>on volume of traffic averaged over certain period of time is rather<br>harmful than useful.<br><br> Masataka Ohta<br></div><br></div></div></div></body></html>